9.2: Atmosphere and Climate Regulation - Biology

9.2: Atmosphere and Climate Regulation - Biology

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Life on earth plays a critical role in regulating the earth's physical, chemical, and geological properties, from influencing the chemical composition of the atmosphere to modifying climate.

About 3.5 billion years ago, early life forms (principally cyanobacteria) helped create an oxygenated atmosphere through photosynthesis, taking up carbon dioxide from the atmosphere and releasing oxygen (Schopf 1983; Van Valen 1971). Over time, these organisms altered the composition of the atmosphere, increasing oxygen levels, and paved the way for organisms that use oxygen as an energy source (aerobic respiration), forming an atmosphere similar to that existing today.

Carbon cycles on the planet between the land, atmosphere, and oceans through a combination of physical, chemical, geological, and biological processes (IPCC 2001). One key way biodiversity influences the composition of the earth's atmosphere is through its role in carbon cycling in the oceans, the largest reservoir for carbon on the planet (Gruber and Sarmiento, in press). In turn, the atmospheric composition of carbon influences climate. Phytoplankton (or microscopic marine plants) play a central role in regulating atmospheric chemistry by transforming carbon dioxide into organic matter during photosynthesis. This carbon-laden organic matter settles either directly or indirectly (after it has been consumed) in the deep ocean, where it stays for centuries, or even thousands of years, acting as the major reservoir for carbon on the planet. In addition, carbon also reaches the deep ocean through another biological process -- the formation of calcium carbonate, the primary component of the shells in two groups of marine organisms coccolithophorids (a phytoplankton) and foraminifera (a single celled, shelled organism that is abundant in many marine environments). When these organisms die, their shells sink to the bottom or dissolve in the water column. This movement of carbon through the oceans removes excess carbon from the atmosphere and regulates the earth's climate.

Over the last century, humans have changed the atmosphere's composition by releasing large amounts of carbon dioxide. This excess carbon dioxide, along with other 'greenhouse' gases, is believed to be heating up our atmosphere and changing the world's climate, leading to 'global warming'. There has been much debate about how natural processes, such as the cycling of carbon through phytoplankton in the oceans, will respond to these changes. Will phytoplankton productivity increase and thereby absorb the extra carbon from the atmosphere? Recent studies suggest that natural processes may slow the rate of increase of carbon dioxide in the atmosphere, but it is doubtful that either the earth's oceans or its forests can absorb the entirety of the extra carbon released by human activity (Falkowski et al. 2000).

9.2: Atmosphere and Climate Regulation - Biology

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Nutrient Uptake by Plants

Several elements obtained from soil are considered essential for plant growth. Macronutrients, including C, H, O, N, P, K, Ca, Mg, and S, are needed by plants in significant quantities. C, H, and O are mainly obtained from the atmosphere or from rainwater. These three elements are the main components of most organic compounds, such as proteins, lipids, carbohydrates, and nucleic acids. The other six elements (N, P, K, Ca, Mg, and S) are obtained by plant roots from the soil and are variously used for protein synthesis, chlorophyll synthesis, energy transfer, cell division, enzyme reactions, and homeostasis (the process regulating the conditions within an organism).

Micronutrients are essential elements that are needed only in small quantities, but can still be limiting to plant growth since these nutrients are not so abundant in nature. Micronutrients include iron (Fe), manganese (Mn), boron (B), molybdenum (Mo), chlorine (Cl), zinc (Zn), and copper (Cu). There are some other elements that tend to aid plant growth but are not absolutely essential.

Micronutrients and macronutrients are desirable in particular concentrations and can be detrimental to plant growth when concentrations in soil solution are either too low (limiting) or too high (toxicity). Mineral nutrients are useful to plants only if they are in an extractable form in soil solutions, such as a dissolved ion rather than in solid mineral. Many nutrients move through the soil and into the root system as a result of concentration gradients, moving by diffusion from high to low concentrations. However, some nutrients are selectively absorbed by the root membranes, enabling concentrations to become higher inside the plant than in the soil.


Essentials of Environmental Science by Kamala Doršner is licensed under CC BY 4.0. Modified from the original by Matthew R. Fisher.

Five Reasons the Earth’s Climate Depends on Forests

“The Intergovernmental Panel on Climate Change (IPCC) will issue a new report soon on the impacts of 1.5°C of global warming. Limiting average temperature rise to 1.5°C requires both drastic reduction of carbon dioxide (CO2) emissions and removing excess carbon dioxide from the atmosphere. While high-tech carbon dioxide removal solutions are under development, the “natural technology” of forests is currently the only proven means of removing and storing atmospheric CO2 at a scale that can meaningfully contribute to achieving carbon balance.

In advance of the IPCC report, we highlight five often overlooked reasons why limiting global warming requires protecting and sustainably managing the forests we have, and restoring the forests we’ve lost.

1. The world’s forests contain more carbon than exploitable oil, gas, and coal deposits, hence avoiding forest carbon emissions is just as urgent as halting fossil fuel use. Recent research suggests that, in order to have a chance of limiting warming to 1.5°C, we cannot emit more than about 750 billion tons of CO2 in the coming century[i]. The carbon in readily exploitable fossil reserves could release 2.7 trillion tons[ii] of CO2 up to 2100. By comparison, forests store enough carbon to release over 3 trillion tons[iii] of CO2 if destroyed. And climate change itself makes forests more vulnerable, including to uncontrollable wildfires.

2. Forests currently remove around a quarter of the CO2 humans add to the atmosphere, keeping climate change from getting even worse. By destroying forests, we not only emit carbon dioxide but also lose the role forests play, through photosynthesis, in taking carbon dioxide out of the atmosphere. Of the 39 billion tons of CO2 that we emit into the atmosphere each year, 28%[iv] is removed on land (mostly by forests), and around a quarter by oceans. The remainder stays in the atmosphere. Maintaining and improving the management of existing forests is a critical part of climate change mitigation, with substantial additional benefits, including reducing air pollution, buffering against flooding, and conserving biodiversity.

3. Achieving the 1.5°C goal also requires massive forest restoration to remove excess carbon dioxide from the atmosphere. Reforestation and improving forest management together have large potential to remove CO2 from the atmosphere. These “natural climate solutions” could provide 18%[v] of cost-effective mitigation through 2030.

4. Bioenergy is not the primary solution[vi]. Achieving significant amounts of carbon dioxide removal through use of wood for energy and capturing the resulting carbon in geological reservoirs requires technology that is untested at large scale. In some areas, such as high carbon tropical forests and peatlands—both of which continuously remove carbon from the atmosphere—conservation is the best option. Climate benefits could also come from increased use of sustainably produced wood in longer-lived products, such as buildings, where timber can store carbon and substitute energy-intensive materials like concrete and steel.

5. Tropical forests cool the air around them and the entire planet, as well as creating the rainfall essential for growing food in their regions and beyond[vii]. Standing forests pull moisture out of the ground and release water vapor to the atmosphere, regulating local, regional and global precipitation patterns and acting as a natural air conditioner[viii]. In contrast, cutting down tropical forests increases local surface temperatures by up to 3°C[ix]. These “climate regulation” effects of tropical forests make their conservation essential to protect food and water security.

In sum, we must protect and maintain healthy forests to avoid dangerous climate change and to ensure the world’s forests continue to provide services critical for the well-being of the planet and ourselves. The natural technology forests provide underpins economic growth but, like crumbling infrastructure, we’ve allowed forests to be degraded, even as we know that deferring maintenance and repair only increases the costs and the risk of disaster. In responding to the IPCC report, our message as scientists is simple: Our planet’s future climate is inextricably tied to the future of its forests.”


1. Paulo Artaxo, Physics Department, University of São Paulo

2. Gregory Asner, Department of Global Ecology, Carnegie Institution for Science and US National Academy of Sciences

3. Mercedes Bustamante, Ecology Department, University of Brasilia and Brazilian Academy of Sciences

4. Stephen Carpenter, Center for Limnology, University of Wisconsin-Madison

5. Philippe Ciais, Laboratoire des Sciences du Climat et de l’Environnement, Centre d’Etudes Orme des Merisiers

6. James Clark, Nicholas School of the Environment, Duke University

7. Michael Coe, Woods Hole Research Center

8. Gretchen C. Daily, Department of Biology and Woods Institute, Stanford University and US National Academy of Sciences

9. Eric Davidson, University of Maryland Center for Environmental Science and President of the American Geophysical Union

10. Ruth S. DeFries, Department of Ecology, Evolution and Environmental Biology, Columbia University and US National Academy of Sciences

11. Karlheinz Erb, University of Natural Resources and Life Sciences, Vienna (BOKU)

12. Nina Fedoroff, Department of Biology, Penn State University

13. David R. Foster, Harvard University

14. James N. Galloway, Department of Environmental Sciences, University of Virginia

15. Holly Gibbs, Center for Sustainability and the Global Environment, University of Wisconsin-Madison

17. Matthew C. Hansen, Department of Geographical Sciences, University of Maryland

18. George Homberger, Vanderbilt Institute for Energy and Environment

19. Richard Houghton, Woods Hole Research Center

20. Jo House, Cabot Institute for the Environment and Department of Geographical Sciences, University of Bristol.

21. Robert Howarth, Department of Ecology and Evolutionary Biology, Cornell University

22. Daniel Janzen, Department of Biology, University of Pennsylvania and US National Academy of Sciences

23. Carlos Joly, Institute of Biology, University of Campinas

25. William F. Laurance, College of Science and Engineering, James Cook University

26. Deborah Lawrence, Department of Environmental Sciences, University of Virginia

27. Katharine Mach, Stanford University Earth System Science

28. Jose Marengo, National Centre for Monitoring and Early Warning and Natural Disasters (CEMADEN, Brazil)

29. William R. Moomaw, Global Development and Environment Institute, Tufts University and Board Chair, Woods Hole Research Center

30. Jerry Melillo, Marine Biological Laboratory, University of Chicago

31. Carlos Nobre, Institute of Advanced Studies, University of São Paulo and US Academy of Sciences

32. Fabio Scarano, Institute of Biology, Federal University of Rio de Janeiro, and Brazilian Foundation for Sustainable Development (FBDS)

33. Herman H. Shugart, Department of Environmental Sciences, University of Virginia

34. Pete Smith, FRS, FRSE, University of Aberdeen, United Kingdom

35. Britaldo Soares Filho, Institute of Geosciences, Federal University of Minas Gerais

36. John W. Terborgh, Nicholas School of the Environment, Duke University

37. G. David Tilman, College of Biological Sciences, University of Minnesota

38. Adalberto Luis Val, Brazilian National Institute for Research of the Amazon (INPA)

39. Louis Verchot, International Center for Tropical Agriculture (CIAT)

40. Richard Waring, Department of Forest Ecosystems and Society, Oregon State University

The views expressed are those of the signatories as individuals and may not be regarded as stating an official position of their respective institutions.

[i] Millar, R. J., Fuglestvedt, J. S., Friedlingstein, P., Rogelj, J., Grubb, M. J., Matthews, H. D., … & Allen, M. R. (2017). Emission budgets and pathways consistent with limiting warming to 1.5 C. Nature Geoscience, 10(10), 741. Goodwin, P., Katavouta, A., Roussenov, V. M., Foster, G. L., Rohling, E. J., & Williams, R. G. (2018). Pathways to 1.5 C and 2 C warming based on observational and geological constraints. Nature Geoscience, 11(2), 102. Tokarska, K. B., & Gillett, N. P. (2018). Cumulative carbon emissions budgets consistent with 1.5° C global warming. Nature Climate Change, 8(4), 296. These recent sources use different statistical methods and base years, all resulting in median estimates of 200-208 GtC remaining for a 50-66% probability of 1.5° C.

[ii] Heede, Richard and Naomi Oreskes (2016). Potential emissions of CO2 and methane from proved reserves of fossil fuels: An alternative analysis. Global Environmental Change 36 (2016) 12-20.

[iii] Pan, Y., Birdsey, R.A., Fang, J., Houghton, R., Kauppi, P.E., Kurz, W.A., Phillips, O.L., Shvidenko, A., et al. (2011). A large and persistent carbon sink in the world’s forests. Science 333, 988–993 Pan, Y., Birdsey, R.A., Phillips, O.L., Jackson, R.B. (2013). The structure, distribution, and bio mass of the world’s forests. Annu. Rev. Ecol. Evol. Syst. 44, 593–622.

[iv] Le Quéré, C. et al (2018). Global carbon budget 2017. Earth System Science Data, 10, 405-448.

[v] Calculated from Griscom et al (2017). Natural climate solutions (Supplementary Information). Proc. Natl. Acad. Sci. U. S. A., 114, 11645–11650, doi:10.1073/pnas.1710465114. Categories included in the 18% mitigation potential (from the cost-constrained 2°C scenario) include reforestation, natural forest management, improved plantations, mangrove restoration, peatland restoration (assuming much of this was or is forested), trees in cropland and biochar. All natural climate solutions are assumed to ramp up at the same rate.

[vi] Field, C. and Mach, K. (2017). Rightsizing carbon dioxide removal: Betting the future on planetary-scale carbon dioxide removal from the atmosphere is risky. Science, VOL 356 ISSUE 6339 Heck, V., Gerten, D., Lucht, W. and Popp, A., 2018. Biomass-based negative emissions difficult to reconcile with planetary boundaries. Nature Climate Change, p.1 Anderson, K. and Peters, G. (2016). The trouble with negative emissions. Science, Vol. 354, Issue 6309 Turner, P.A., Mach, K.J., Lobell, D.B. et al. (2018). The global overlap of bioenergy and carbon sequestration potential. Climatic Change (2018) 148: 1.

[vii] Lawrence, D. and Vandecar, K., 2015. Effects of tropical deforestation on climate and agriculture. Nature Climate Change, 5(1), p.27.

[viii] Ellison et al (2017). Trees, forests and water: Cool insights for a hot world. Global Environmental Change, Vol. 43, Pages 51-61.


The term conservation biology and its conception as a new field originated with the convening of "The First International Conference on Research in Conservation Biology" held at the University of California, San Diego in La Jolla, California in 1978 led by American biologists Bruce A. Wilcox and Michael E. Soulé with a group of leading university and zoo researchers and conservationists including Kurt Benirschke, Sir Otto Frankel, Thomas Lovejoy, and Jared Diamond. The meeting was prompted by the concern over tropical deforestation, disappearing species, eroding genetic diversity within species. [8] The conference and proceedings that resulted [2] sought to initiate the bridging of a gap between theory in ecology and evolutionary genetics on the one hand and conservation policy and practice on the other. [9] Conservation biology and the concept of biological diversity (biodiversity) emerged together, helping crystallize the modern era of conservation science and policy. The inherent multidisciplinary basis for conservation biology has led to new subdisciplines including conservation social science, conservation behavior and conservation physiology. [10] It stimulated further development of conservation genetics which Otto Frankel had originated first but is now often considered a subdiscipline as well.

The rapid decline of established biological systems around the world means that conservation biology is often referred to as a "Discipline with a deadline". [11] Conservation biology is tied closely to ecology in researching the population ecology (dispersal, migration, demographics, effective population size, inbreeding depression, and minimum population viability) of rare or endangered species. [12] [13] Conservation biology is concerned with phenomena that affect the maintenance, loss, and restoration of biodiversity and the science of sustaining evolutionary processes that engender genetic, population, species, and ecosystem diversity. [5] [6] [7] [13] The concern stems from estimates suggesting that up to 50% of all species on the planet will disappear within the next 50 years, [14] which has contributed to poverty, starvation, and will reset the course of evolution on this planet. [15] [16]

Conservation biologists research and educate on the trends and process of biodiversity loss, species extinctions, and the negative effect these are having on our capabilities to sustain the well-being of human society. Conservation biologists work in the field and office, in government, universities, non-profit organizations and industry. The topics of their research are diverse, because this is an interdisciplinary network with professional alliances in the biological as well as social sciences. Those dedicated to the cause and profession advocate for a global response to the current biodiversity crisis based on morals, ethics, and scientific reason. Organizations and citizens are responding to the biodiversity crisis through conservation action plans that direct research, monitoring, and education programs that engage concerns at local through global scales. [4] [5] [6] [7]

Natural resource conservation Edit

Conscious efforts to conserve and protect global biodiversity are a recent phenomenon. [7] [18] Natural resource conservation, however, has a history that extends prior to the age of conservation. Resource ethics grew out of necessity through direct relations with nature. Regulation or communal restraint became necessary to prevent selfish motives from taking more than could be locally sustained, therefore compromising the long-term supply for the rest of the community. [7] This social dilemma with respect to natural resource management is often called the "Tragedy of the Commons". [19] [20]

From this principle, conservation biologists can trace communal resource based ethics throughout cultures as a solution to communal resource conflict. [7] For example, the Alaskan Tlingit peoples and the Haida of the Pacific Northwest had resource boundaries, rules, and restrictions among clans with respect to the fishing of sockeye salmon. These rules were guided by clan elders who knew lifelong details of each river and stream they managed. [7] [21] There are numerous examples in history where cultures have followed rules, rituals, and organized practice with respect to communal natural resource management. [22] [23]

The Mauryan emperor Ashoka around 250 B.C. issued edicts restricting the slaughter of animals and certain kinds of birds, as well as opened veterinary clinics.

Conservation ethics are also found in early religious and philosophical writings. There are examples in the Tao, Shinto, Hindu, Islamic and Buddhist traditions. [7] [24] In Greek philosophy, Plato lamented about pasture land degradation: "What is left now is, so to say, the skeleton of a body wasted by disease the rich, soft soil has been carried off and only the bare framework of the district left." [25] In the bible, through Moses, God commanded to let the land rest from cultivation every seventh year. [7] [26] Before the 18th century, however, much of European culture considered it a pagan view to admire nature. Wilderness was denigrated while agricultural development was praised. [27] However, as early as AD 680 a wildlife sanctuary was founded on the Farne Islands by St Cuthbert in response to his religious beliefs. [7]

Early naturalists Edit

Natural history was a major preoccupation in the 18th century, with grand expeditions and the opening of popular public displays in Europe and North America. By 1900 there were 150 natural history museums in Germany, 250 in Great Britain, 250 in the United States, and 300 in France. [28] Preservationist or conservationist sentiments are a development of the late 18th to early 20th centuries.

Before Charles Darwin set sail on HMS Beagle, most people in the world, including Darwin, believed in special creation and that all species were unchanged. [29] George-Louis Leclerc was one of the first naturalist that questioned this belief. He proposed in his 44 volume natural history book that species evolve due to environmental influences. [29] Erasmus Darwin was also a naturalist who also suggested that species evolved. Erasmus Darwin noted that some species have vestigial structures which are anatomical structures that have no apparent function in the species currently but would have been useful for the species' ancestors. [29] The thinking of these early 18th century naturalists helped to change the mindset and thinking of the early 19th century naturalists.

By the early 19th century biogeography was ignited through the efforts of Alexander von Humboldt, Charles Lyell and Charles Darwin. [30] The 19th-century fascination with natural history engendered a fervor to be the first to collect rare specimens with the goal of doing so before they became extinct by other such collectors. [27] [28] Although the work of many 18th and 19th century naturalists were to inspire nature enthusiasts and conservation organizations, their writings, by modern standards, showed insensitivity towards conservation as they would kill hundreds of specimens for their collections. [28]

Conservation movement Edit

The modern roots of conservation biology can be found in the late 18th-century Enlightenment period particularly in England and Scotland. [27] [31] A number of thinkers, among them notably Lord Monboddo, [31] described the importance of "preserving nature" much of this early emphasis had its origins in Christian theology.

Scientific conservation principles were first practically applied to the forests of British India. The conservation ethic that began to evolve included three core principles: that human activity damaged the environment, that there was a civic duty to maintain the environment for future generations, and that scientific, empirically based methods should be applied to ensure this duty was carried out. Sir James Ranald Martin was prominent in promoting this ideology, publishing many medico-topographical reports that demonstrated the scale of damage wrought through large-scale deforestation and desiccation, and lobbying extensively for the institutionalization of forest conservation activities in British India through the establishment of Forest Departments. [32]

The Madras Board of Revenue started local conservation efforts in 1842, headed by Alexander Gibson, a professional botanist who systematically adopted a forest conservation program based on scientific principles. This was the first case of state conservation management of forests in the world. [33] Governor-General Lord Dalhousie introduced the first permanent and large-scale forest conservation program in the world in 1855, a model that soon spread to other colonies, as well the United States, [34] [35] [36] where Yellowstone National Park was opened in 1872 as the world's first national park. [37]

The term conservation came into widespread use in the late 19th century and referred to the management, mainly for economic reasons, of such natural resources as timber, fish, game, topsoil, pastureland, and minerals. In addition it referred to the preservation of forests (forestry), wildlife (wildlife refuge), parkland, wilderness, and watersheds. This period also saw the passage of the first conservation legislation and the establishment of the first nature conservation societies. The Sea Birds Preservation Act of 1869 was passed in Britain as the first nature protection law in the world [38] after extensive lobbying from the Association for the Protection of Seabirds [39] and the respected ornithologist Alfred Newton. [40] Newton was also instrumental in the passage of the first Game laws from 1872, which protected animals during their breeding season so as to prevent the stock from being brought close to extinction. [41]

One of the first conservation societies was the Royal Society for the Protection of Birds, founded in 1889 in Manchester [42] as a protest group campaigning against the use of great crested grebe and kittiwake skins and feathers in fur clothing. Originally known as "the Plumage League", [43] the group gained popularity and eventually amalgamated with the Fur and Feather League in Croydon, and formed the RSPB. [44] The National Trust formed in 1895 with the manifesto to ". promote the permanent preservation, for the benefit of the nation, of lands, . to preserve (so far practicable) their natural aspect." In May 1912, a month after the Titanic sank, banker and expert naturalist Charles Rothschild held a meeting at the Natural History Museum in London to discuss his idea for a new organisation to save the best places for wildlife in the British Isles. This meeting led to the formation of the Society for the Promotion of Nature Reserves, which later became the Wildlife Trusts.

In the United States, the Forest Reserve Act of 1891 gave the President power to set aside forest reserves from the land in the public domain. John Muir founded the Sierra Club in 1892, and the New York Zoological Society was set up in 1895. A series of national forests and preserves were established by Theodore Roosevelt from 1901 to 1909. [45] [46] The 1916 National Parks Act, included a 'use without impairment' clause, sought by John Muir, which eventually resulted in the removal of a proposal to build a dam in Dinosaur National Monument in 1959. [47]

In the 20th century, Canadian civil servants, including Charles Gordon Hewitt [48] and James Harkin spearheaded the movement toward wildlife conservation. [49]

In the 21st century professional conservation officiers begun to collaborate with indigenous communities for protecting wildlife in Canada. [50]

Global conservation efforts Edit

In the mid-20th century, efforts arose to target individual species for conservation, notably efforts in big cat conservation in South America led by the New York Zoological Society. [51] In the early 20th century the New York Zoological Society was instrumental in developing concepts of establishing preserves for particular species and conducting the necessary conservation studies to determine the suitability of locations that are most appropriate as conservation priorities the work of Henry Fairfield Osborn Jr., Carl E. Akeley, Archie Carr and his son Archie Carr III is notable in this era. [52] [53] [ citation needed ] Akeley for example, having led expeditions to the Virunga Mountains and observed the mountain gorilla in the wild, became convinced that the species and the area were conservation priorities. He was instrumental in persuading Albert I of Belgium to act in defense of the mountain gorilla and establish Albert National Park (since renamed Virunga National Park) in what is now Democratic Republic of Congo. [54]

By the 1970s, led primarily by work in the United States under the Endangered Species Act [55] along with the Species at Risk Act (SARA) of Canada, Biodiversity Action Plans developed in Australia, Sweden, the United Kingdom, hundreds of species specific protection plans ensued. Notably the United Nations acted to conserve sites of outstanding cultural or natural importance to the common heritage of mankind. The programme was adopted by the General Conference of UNESCO in 1972. As of 2006, a total of 830 sites are listed: 644 cultural, 162 natural. The first country to pursue aggressive biological conservation through national legislation was the United States, which passed back to back legislation in the Endangered Species Act [56] (1966) and National Environmental Policy Act (1970), [57] which together injected major funding and protection measures to large-scale habitat protection and threatened species research. Other conservation developments, however, have taken hold throughout the world. India, for example, passed the Wildlife Protection Act of 1972. [58]

In 1980, a significant development was the emergence of the urban conservation movement. A local organization was established in Birmingham, UK, a development followed in rapid succession in cities across the UK, then overseas. Although perceived as a grassroots movement, its early development was driven by academic research into urban wildlife. Initially perceived as radical, the movement's view of conservation being inextricably linked with other human activity has now become mainstream in conservation thought. Considerable research effort is now directed at urban conservation biology. The Society for Conservation Biology originated in 1985. [7] : 2

By 1992, most of the countries of the world had become committed to the principles of conservation of biological diversity with the Convention on Biological Diversity [59] subsequently many countries began programmes of Biodiversity Action Plans to identify and conserve threatened species within their borders, as well as protect associated habitats. The late 1990s saw increasing professionalism in the sector, with the maturing of organisations such as the Institute of Ecology and Environmental Management and the Society for the Environment.

Since 2000, the concept of landscape scale conservation has risen to prominence, with less emphasis being given to single-species or even single-habitat focused actions. Instead an ecosystem approach is advocated by most mainstream conservationists, although concerns have been expressed by those working to protect some high-profile species.

Ecology has clarified the workings of the biosphere i.e., the complex interrelationships among humans, other species, and the physical environment. The burgeoning human population and associated agriculture, industry, and the ensuing pollution, have demonstrated how easily ecological relationships can be disrupted. [60]

The last word in ignorance is the man who says of an animal or plant: "What good is it?" If the land mechanism as a whole is good, then every part is good, whether we understand it or not. If the biota, in the course of aeons, has built something we like but do not understand, then who but a fool would discard seemingly useless parts? To keep every cog and wheel is the first precaution of intelligent tinkering.

Measuring extinction rates Edit

Extinction rates are measured in a variety of ways. Conservation biologists measure and apply statistical measures of fossil records, [1] [61] rates of habitat loss, and a multitude of other variables such as loss of biodiversity as a function of the rate of habitat loss and site occupancy [62] to obtain such estimates. [63] The Theory of Island Biogeography [64] is possibly the most significant contribution toward the scientific understanding of both the process and how to measure the rate of species extinction. The current background extinction rate is estimated to be one species every few years. [65] Actual extinction rates are estimated to be orders of magnitudes higher. [66]

The measure of ongoing species loss is made more complex by the fact that most of the Earth's species have not been described or evaluated. Estimates vary greatly on how many species actually exist (estimated range: 3,600,000-111,700,000) [67] to how many have received a species binomial (estimated range: 1.5-8 million). [67] Less than 1% of all species that have been described beyond simply noting its existence. [67] From these figures, the IUCN reports that 23% of vertebrates, 5% of invertebrates and 70% of plants that have been evaluated are designated as endangered or threatened. [68] [69] Better knowledge is being constructed by The Plant List for actual numbers of species.

Systematic conservation planning Edit

Systematic conservation planning is an effective way to seek and identify efficient and effective types of reserve design to capture or sustain the highest priority biodiversity values and to work with communities in support of local ecosystems. Margules and Pressey identify six interlinked stages in the systematic planning approach: [70]

  1. Compile data on the biodiversity of the planning region
  2. Identify conservation goals for the planning region
  3. Review existing conservation areas
  4. Select additional conservation areas
  5. Implement conservation actions
  6. Maintain the required values of conservation areas

Conservation biologists regularly prepare detailed conservation plans for grant proposals or to effectively coordinate their plan of action and to identify best management practices (e.g. [71] ). Systematic strategies generally employ the services of Geographic Information Systems to assist in the decision making process. The SLOSS debate is often considered in planning.

Conservation physiology: a mechanistic approach to conservation Edit

Conservation physiology was defined by Steven J. Cooke and colleagues as: 'An integrative scientific discipline applying physiological concepts, tools, and knowledge to characterizing biological diversity and its ecological implications understanding and predicting how organisms, populations, and ecosystems respond to environmental change and stressors and solving conservation problems across the broad range of taxa (i.e. including microbes, plants, and animals). Physiology is considered in the broadest possible terms to include functional and mechanistic responses at all scales, and conservation includes the development and refinement of strategies to rebuild populations, restore ecosystems, inform conservation policy, generate decision-support tools, and manage natural resources.' [10] Conservation physiology is particularly relevant to practitioners in that it has the potential to generate cause-and-effect relationships and reveal the factors that contribute to population declines.

Conservation biology as a profession Edit

The Society for Conservation Biology is a global community of conservation professionals dedicated to advancing the science and practice of conserving biodiversity. Conservation biology as a discipline reaches beyond biology, into subjects such as philosophy, law, economics, humanities, arts, anthropology, and education. [5] [6] Within biology, conservation genetics and evolution are immense fields unto themselves, but these disciplines are of prime importance to the practice and profession of conservation biology.

Conservationists introduce bias when they support policies using qualitative description, such as habitat degradation, or healthy ecosystems. Conservation biologists advocate for reasoned and sensible management of natural resources and do so with a disclosed combination of science, reason, logic, and values in their conservation management plans. [5] This sort of advocacy is similar to the medical profession advocating for healthy lifestyle options, both are beneficial to human well-being yet remain scientific in their approach.

There is a movement in conservation biology suggesting a new form of leadership is needed to mobilize conservation biology into a more effective discipline that is able to communicate the full scope of the problem to society at large. [72] The movement proposes an adaptive leadership approach that parallels an adaptive management approach. The concept is based on a new philosophy or leadership theory steering away from historical notions of power, authority, and dominance. Adaptive conservation leadership is reflective and more equitable as it applies to any member of society who can mobilize others toward meaningful change using communication techniques that are inspiring, purposeful, and collegial. Adaptive conservation leadership and mentoring programs are being implemented by conservation biologists through organizations such as the Aldo Leopold Leadership Program. [73]

Approaches Edit

Conservation may be classified as either in-situ conservation, which is protecting an endangered species in its natural habitat, or ex-situ conservation, which occurs outside the natural habitat. [74] In-situ conservation involves protecting or restoring the habitat. Ex-situ conservation, on the other hand, involves protection outside of an organism's natural habitat, such as on reservations or in gene banks, in circumstances where viable populations may not be present in the natural habitat. [74]

Also, non-interference may be used, which is termed a preservationist method. Preservationists advocate for giving areas of nature and species a protected existence that halts interference from the humans. [5] In this regard, conservationists differ from preservationists in the social dimension, as conservation biology engages society and seeks equitable solutions for both society and ecosystems. Some preservationists emphasize the potential of biodiversity in a world without humans.

Ethics and values Edit

Conservation biologists are interdisciplinary researchers that practice ethics in the biological and social sciences. Chan states [75] that conservationists must advocate for biodiversity and can do so in a scientifically ethical manner by not promoting simultaneous advocacy against other competing values.

A conservationist may be inspired by the resource conservation ethic, [7] : 15 which seeks to identify what measures will deliver "the greatest good for the greatest number of people for the longest time." [5] : 13 In contrast, some conservation biologists argue that nature has an intrinsic value that is independent of anthropocentric usefulness or utilitarianism. [7] : 3,12,16–17 Intrinsic value advocates that a gene, or species, be valued because they have a utility for the ecosystems they sustain. Aldo Leopold was a classical thinker and writer on such conservation ethics whose philosophy, ethics and writings are still valued and revisited by modern conservation biologists. [7] : 16–17

Conservation priorities Edit

The International Union for the Conservation of Nature (IUCN) International Union for Conservation of Nature has organized a global assortment of scientists and research stations across the planet to monitor the changing state of nature in an effort to tackle the extinction crisis. The IUCN provides annual updates on the status of species conservation through its Red List. [76] The IUCN Red List serves as an international conservation tool to identify those species most in need of conservation attention and by providing a global index on the status of biodiversity. [77] More than the dramatic rates of species loss, however, conservation scientists note that the sixth mass extinction is a biodiversity crisis requiring far more action than a priority focus on rare, endemic or endangered species. Concerns for biodiversity loss covers a broader conservation mandate that looks at ecological processes, such as migration, and a holistic examination of biodiversity at levels beyond the species, including genetic, population and ecosystem diversity. [78] Extensive, systematic, and rapid rates of biodiversity loss threatens the sustained well-being of humanity by limiting supply of ecosystem services that are otherwise regenerated by the complex and evolving holistic network of genetic and ecosystem diversity. While the conservation status of species is employed extensively in conservation management, [77] some scientists highlight that it is the common species that are the primary source of exploitation and habitat alteration by humanity. Moreover, common species are often undervalued despite their role as the primary source of ecosystem services. [79] [80]

While most in the community of conservation science "stress the importance" of sustaining biodiversity, [81] there is debate on how to prioritize genes, species, or ecosystems, which are all components of biodiversity (e.g. Bowen, 1999). While the predominant approach to date has been to focus efforts on endangered species by conserving biodiversity hotspots, some scientists (e.g) [82] and conservation organizations, such as the Nature Conservancy, argue that it is more cost-effective, logical, and socially relevant to invest in biodiversity coldspots. [83] The costs of discovering, naming, and mapping out the distribution of every species, they argue, is an ill-advised conservation venture. They reason it is better to understand the significance of the ecological roles of species. [78]

Biodiversity hotspots and coldspots are a way of recognizing that the spatial concentration of genes, species, and ecosystems is not uniformly distributed on the Earth's surface. For example, "[. ] 44% of all species of vascular plants and 35% of all species in four vertebrate groups are confined to 25 hotspots comprising only 1.4% of the land surface of the Earth." [84]

Those arguing in favor of setting priorities for coldspots point out that there are other measures to consider beyond biodiversity. They point out that emphasizing hotspots downplays the importance of the social and ecological connections to vast areas of the Earth's ecosystems where biomass, not biodiversity, reigns supreme. [85] It is estimated that 36% of the Earth's surface, encompassing 38.9% of the worlds vertebrates, lacks the endemic species to qualify as biodiversity hotspot. [86] Moreover, measures show that maximizing protections for biodiversity does not capture ecosystem services any better than targeting randomly chosen regions. [87] Population level biodiversity (mostly in coldspots) are disappearing at a rate that is ten times that at the species level. [82] [88] The level of importance in addressing biomass versus endemism as a concern for conservation biology is highlighted in literature measuring the level of threat to global ecosystem carbon stocks that do not necessarily reside in areas of endemism. [89] [90] A hotspot priority approach [91] would not invest so heavily in places such as steppes, the Serengeti, the Arctic, or taiga. These areas contribute a great abundance of population (not species) level biodiversity [88] and ecosystem services, including cultural value and planetary nutrient cycling. [83]

Summary of 2006 IUCN Red List categories

Those in favor of the hotspot approach point out that species are irreplaceable components of the global ecosystem, they are concentrated in places that are most threatened, and should therefore receive maximal strategic protections. [92] The IUCN Red List categories, which appear on Wikipedia species articles, is an example of the hotspot conservation approach in action species that are not rare or endemic are listed the least concern and their Wikipedia articles tend to be ranked low on the importance scale. [ dubious – discuss ] This is a hotspot approach because the priority is set to target species level concerns over population level or biomass. [88] [ failed verification ] Species richness and genetic biodiversity contributes to and engenders ecosystem stability, ecosystem processes, evolutionary adaptability, and biomass. [93] Both sides agree, however, that conserving biodiversity is necessary to reduce the extinction rate and identify an inherent value in nature the debate hinges on how to prioritize limited conservation resources in the most cost-effective way.

Economic values and natural capital Edit

Conservation biologists have started to collaborate with leading global economists to determine how to measure the wealth and services of nature and to make these values apparent in global market transactions. [94] This system of accounting is called natural capital and would, for example, register the value of an ecosystem before it is cleared to make way for development. [95] The WWF publishes its Living Planet Report and provides a global index of biodiversity by monitoring approximately 5,000 populations in 1,686 species of vertebrate (mammals, birds, fish, reptiles, and amphibians) and report on the trends in much the same way that the stock market is tracked. [96]

This method of measuring the global economic benefit of nature has been endorsed by the G8+5 leaders and the European Commission. [94] Nature sustains many ecosystem services [97] that benefit humanity. [98] Many of the Earth's ecosystem services are public goods without a market and therefore no price or value. [94] When the stock market registers a financial crisis, traders on Wall Street are not in the business of trading stocks for much of the planet's living natural capital stored in ecosystems. There is no natural stock market with investment portfolios into sea horses, amphibians, insects, and other creatures that provide a sustainable supply of ecosystem services that are valuable to society. [98] The ecological footprint of society has exceeded the bio-regenerative capacity limits of the planet's ecosystems by about 30 percent, which is the same percentage of vertebrate populations that have registered decline from 1970 through 2005. [96]

The inherent natural economy plays an essential role in sustaining humanity, [99] including the regulation of global atmospheric chemistry, pollinating crops, pest control, [100] cycling soil nutrients, purifying our water supply, [101] supplying medicines and health benefits, [102] and unquantifiable quality of life improvements. There is a relationship, a correlation, between markets and natural capital, and social income inequity and biodiversity loss. This means that there are greater rates of biodiversity loss in places where the inequity of wealth is greatest [103]

Although a direct market comparison of natural capital is likely insufficient in terms of human value, one measure of ecosystem services suggests the contribution amounts to trillions of dollars yearly. [104] [105] [106] [107] For example, one segment of North American forests has been assigned an annual value of 250 billion dollars [108] as another example, honey-bee pollination is estimated to provide between 10 and 18 billion dollars of value yearly. [109] The value of ecosystem services on one New Zealand island has been imputed to be as great as the GDP of that region. [110] This planetary wealth is being lost at an incredible rate as the demands of human society is exceeding the bio-regenerative capacity of the Earth. While biodiversity and ecosystems are resilient, the danger of losing them is that humans cannot recreate many ecosystem functions through technological innovation.

Strategic species concepts Edit

Keystone species Edit

Some species, called a keystone species form a central supporting hub unique to their ecosystem. [111] The loss of such a species results in a collapse in ecosystem function, as well as the loss of coexisting species. [5] Keystone species are usually predators due to their ability to control the population of prey in their ecosystem. [111] The importance of a keystone species was shown by the extinction of the Steller's sea cow (Hydrodamalis gigas) through its interaction with sea otters, sea urchins, and kelp. Kelp beds grow and form nurseries in shallow waters to shelter creatures that support the food chain. Sea urchins feed on kelp, while sea otters feed on sea urchins. With the rapid decline of sea otters due to overhunting, sea urchin populations grazed unrestricted on the kelp beds and the ecosystem collapsed. Left unchecked, the urchins destroyed the shallow water kelp communities that supported the Steller's sea cow's diet and hastened their demise. [112] The sea otter was thought to be a keystone species because the coexistence of many ecological associates in the kelp beds relied upon otters for their survival. However this was later questioned by Turvey and Risley, [113] who showed that hunting alone would have driven the Steller's sea cow extinct.

Indicator species Edit

An indicator species has a narrow set of ecological requirements, therefore they become useful targets for observing the health of an ecosystem. Some animals, such as amphibians with their semi-permeable skin and linkages to wetlands, have an acute sensitivity to environmental harm and thus may serve as a miner's canary. Indicator species are monitored in an effort to capture environmental degradation through pollution or some other link to proximate human activities. [5] Monitoring an indicator species is a measure to determine if there is a significant environmental impact that can serve to advise or modify practice, such as through different forest silviculture treatments and management scenarios, or to measure the degree of harm that a pesticide may impart on the health of an ecosystem.

Government regulators, consultants, or NGOs regularly monitor indicator species, however, there are limitations coupled with many practical considerations that must be followed for the approach to be effective. [114] It is generally recommended that multiple indicators (genes, populations, species, communities, and landscape) be monitored for effective conservation measurement that prevents harm to the complex, and often unpredictable, response from ecosystem dynamics (Noss, 1997 [115] : 88–89 ).

Umbrella and flagship species Edit

An example of an umbrella species is the monarch butterfly, because of its lengthy migrations and aesthetic value. The monarch migrates across North America, covering multiple ecosystems and so requires a large area to exist. Any protections afforded to the monarch butterfly will at the same time umbrella many other species and habitats. An umbrella species is often used as flagship species, which are species, such as the giant panda, the blue whale, the tiger, the mountain gorilla and the monarch butterfly, that capture the public's attention and attract support for conservation measures. [5] Paradoxically, however, conservation bias towards flagship species sometimes threatens other species of chief concern. [116]

Conservation biologists study trends and process from the paleontological past to the ecological present as they gain an understanding of the context related to species extinction. [1] It is generally accepted that there have been five major global mass extinctions that register in Earth's history. These include: the Ordovician (440 mya), Devonian (370 mya), Permian–Triassic (245 mya), Triassic–Jurassic (200 mya), and Cretaceous–Paleogene extinction event (66 mya) extinction spasms. Within the last 10,000 years, human influence over the Earth's ecosystems has been so extensive that scientists have difficulty estimating the number of species lost [117] that is to say the rates of deforestation, reef destruction, wetland draining and other human acts are proceeding much faster than human assessment of species. The latest Living Planet Report by the World Wide Fund for Nature estimates that we have exceeded the bio-regenerative capacity of the planet, requiring 1.6 Earths to support the demands placed on our natural resources. [118]

Holocene extinction Edit

Conservation biologists are dealing with and have published evidence from all corners of the planet indicating that humanity may be causing the sixth and fastest planetary extinction event. [119] [120] [121] It has been suggested that an unprecedented number of species is becoming extinct in what is known as the Holocene extinction event. [122] The global extinction rate may be approximately 1,000 times higher than the natural background extinction rate. [123] It is estimated that two-thirds of all mammal genera and one-half of all mammal species weighing at least 44 kilograms (97 lb) have gone extinct in the last 50,000 years. [113] [124] [125] [126] The Global Amphibian Assessment [127] reports that amphibians are declining on a global scale faster than any other vertebrate group, with over 32% of all surviving species being threatened with extinction. The surviving populations are in continual decline in 43% of those that are threatened. Since the mid-1980s the actual rates of extinction have exceeded 211 times rates measured from the fossil record. [128] However, "The current amphibian extinction rate may range from 25,039 to 45,474 times the background extinction rate for amphibians." [128] The global extinction trend occurs in every major vertebrate group that is being monitored. For example, 23% of all mammals and 12% of all birds are Red Listed by the International Union for Conservation of Nature (IUCN), meaning they too are threatened with extinction. Even though extinction is natural, the decline in species is happening at such an incredible rate that evolution can simply not match, therefore, leading to the greatest continual mass extinction on Earth. [129] Humans have dominated the planet and our high consumption of resources, along with the pollution generated is affecting the environments in which other species live. [129] [130] There are a wide variety of species that humans are working to protect such as the Hawaiian Crow and the Whooping Crane of Texas. [131] People can also take action on preserving species by advocating and voting for global and national policies that improve climate, under the concepts of climate mitigation and climate restoration. The Earth's oceans demand particular attention as climate change continues to alter pH levels, making it uninhabitable for organisms with shells which dissolve as a result. [123]

Status of oceans and reefs Edit

Global assessments of coral reefs of the world continue to report drastic and rapid rates of decline. By 2000, 27% of the world's coral reef ecosystems had effectively collapsed. The largest period of decline occurred in a dramatic "bleaching" event in 1998, where approximately 16% of all the coral reefs in the world disappeared in less than a year. Coral bleaching is caused by a mixture of environmental stresses, including increases in ocean temperatures and acidity, causing both the release of symbiotic algae and death of corals. [132] Decline and extinction risk in coral reef biodiversity has risen dramatically in the past ten years. The loss of coral reefs, which are predicted to go extinct in the next century, threatens the balance of global biodiversity, will have huge economic impacts, and endangers food security for hundreds of millions of people. [133] Conservation biology plays an important role in international agreements covering the world's oceans [132] (and other issues pertaining to biodiversity [134] ).

The oceans are threatened by acidification due to an increase in CO2 levels. This is a most serious threat to societies relying heavily upon oceanic natural resources. A concern is that the majority of all marine species will not be able to evolve or acclimate in response to the changes in the ocean chemistry. [135]

The prospects of averting mass extinction seems unlikely when "[. ] 90% of all of the large (average approximately ≥50 kg), open ocean tuna, billfishes, and sharks in the ocean" [16] are reportedly gone. Given the scientific review of current trends, the ocean is predicted to have few surviving multi-cellular organisms with only microbes left to dominate marine ecosystems. [16]

Groups other than vertebrates Edit

Serious concerns also being raised about taxonomic groups that do not receive the same degree of social attention or attract funds as the vertebrates. These include fungal (including lichen-forming species), [136] invertebrate (particularly insect [14] [137] [138] ) and plant communities where the vast majority of biodiversity is represented. Conservation of fungi and conservation of insects, in particular, are both of pivotal importance for conservation biology. As mycorrhizal symbionts, and as decomposers and recyclers, fungi are essential for sustainability of forests. [136] The value of insects in the biosphere is enormous because they outnumber all other living groups in measure of species richness. The greatest bulk of biomass on land is found in plants, which is sustained by insect relations. This great ecological value of insects is countered by a society that often reacts negatively toward these aesthetically 'unpleasant' creatures. [139] [140]

One area of concern in the insect world that has caught the public eye is the mysterious case of missing honey bees (Apis mellifera). Honey bees provide an indispensable ecological services through their acts of pollination supporting a huge variety of agriculture crops. The use of honey and wax have become vastly used throughout the world. [141] The sudden disappearance of bees leaving empty hives or colony collapse disorder (CCD) is not uncommon. However, in 16-month period from 2006 through 2007, 29% of 577 beekeepers across the United States reported CCD losses in up to 76% of their colonies. This sudden demographic loss in bee numbers is placing a strain on the agricultural sector. The cause behind the massive declines is puzzling scientists. Pests, pesticides, and global warming are all being considered as possible causes. [142] [143]

Another highlight that links conservation biology to insects, forests, and climate change is the mountain pine beetle (Dendroctonus ponderosae) epidemic of British Columbia, Canada, which has infested 470,000 km 2 (180,000 sq mi) of forested land since 1999. [89] An action plan has been prepared by the Government of British Columbia to address this problem. [144] [145]

This impact [pine beetle epidemic] converted the forest from a small net carbon sink to a large net carbon source both during and immediately after the outbreak. In the worst year, the impacts resulting from the beetle outbreak in British Columbia were equivalent to 75% of the average annual direct forest fire emissions from all of Canada during 1959–1999.

Conservation biology of parasites Edit

A large proportion of parasite species are threatened by extinction. A few of them are being eradicated as pests of humans or domestic animals, however, most of them are harmless. Threats include the decline or fragmentation of host populations, or the extinction of host species.

Threats to biodiversity Edit

Today, many threats to Biodiversity exist. An acronym that can be used to express the top threats of present-day H.I.P.P.O stands for Habitat Loss, Invasive Species, Pollution, Human Population, and Overharvesting. [146] The primary threats to biodiversity are habitat destruction (such as deforestation, agricultural expansion, urban development), and overexploitation (such as wildlife trade). [117] [147] [148] [149] [150] [151] Habitat fragmentation also poses challenges, because the global network of protected areas only covers 11.5% of the Earth's surface. [152] A significant consequence of fragmentation and lack of linked protected areas is the reduction of animal migration on a global scale. Considering that billions of tonnes of biomass are responsible for nutrient cycling across the earth, the reduction of migration is a serious matter for conservation biology. [153] [154]

However, human activities need not necessarily cause irreparable harm to the biosphere. With conservation management and planning for biodiversity at all levels, from genes to ecosystems, there are examples where humans mutually coexist in a sustainable way with nature. [155] Even with the current threats to biodiversity there are ways we can improve the current condition and start anew.

Settled enough: Climate science, skepticism and prudence

Science is an edifice that is never finished. It is expanded, remodeled and strengthened continually by the efforts of a global community of scientists numbering in the many millions.

New gaps and uncertainties become evident even as old ones are filled and narrowed. And, sometimes, long-established understandings are overturned by unexpected new discoveries. Einstein’s relativity and Wegener’s continental drift are famous examples.

Skepticism about scientific claims — challenging them, testing them, testing them again when better tools become available — is a feature of the scientific process, not a bug. Accordingly, science should never be said to be completely “settled.”

At the same time, respect for healthy skepticism must be tempered by recognition that revolutions overturning central aspects of previous scientific understandings are extremely rare. The likelihood that the current, central understandings in any given scientific domain will be overturned declines with the diversity and robustness of the evidence supporting those understandings, including especially the extent of critical scrutiny, testing and retesting the supporting evidence has already received.

In the case of the current, central scientific understandings about global climate change, the supporting evidence is both immense and consistent, deriving from the intersection of:

  • Basic principles of physics, chemistry and biology
  • Millions of direct observations over the past 150 years
  • Inferences about natural influences on climate over much longer periods gleaned from studies of ice cores, fossil corals and pollens, ocean sediments and tree rings
  • Models ranging from “back of the envelope” calculations to simulations running on the fastest supercomputers

Because of the huge potential importance of this evidence for policy and for human well-being on the largest scale, moreover, its details and its conclusions have been scrutinized and re-scrutinized to a staggering degree. The reviewers have included armies of specialists in university departments of atmospheric and ocean science, governmental agencies, national laboratories, independent think tanks and professional societies all around the world. They have also included national academies of science in virtually every country that has one, the World Meteorological Organization and the multi-thousand-member scientific teams that have been convened continuously by the Intergovernmental Panel on Climate Change (IPCC) since its inception in 1988.

The body of climate science that has survived this extraordinary vetting has yielded five key conclusions recognized by competent climate scientists around the world as true beyond any reasonable doubt:

  1. Earth’s climate has been changing over the past century and more at a pace now far beyond what can be explained by natural variability.
  2. The main cause of the observed changes in this period has been the buildup in the atmosphere of global concentrations of carbon dioxide and other heat-trapping gases emitted by human activities, principally the combustion of fossil fuels but also, importantly, deforestation and agriculture.
  3. These human-caused changes in climate are already causing harm to life, health, property, economies and ecosystems, with stronger heat waves, downpours, floods, droughts and wildfires more of the most powerful storms worse smog and allergies accelerating sea-level rise and major impacts on ecosystem dynamics affecting pests, pathogens and valued species.
  4. The growth of these impacts cannot be stopped quickly, even assuming rapid emission reductions going forward, because of built-in time lags in Earth’s climate system, although the harm done to human well-being can be ameliorated in many cases by adaptation measures.
  5. The cost of the needed adaptation measures, as well as the future harm to human well-being from climate-change impacts that adaptation cannot fully abate, will be much smaller if human society moves promptly toward reducing global emissions of heat-trapping gases to near zero by 2050 than if it does not.

It is also almost certainly true, although this conclusion rests on findings not only from natural science but also from engineering and economic analyses, that the costs of adequate emission-reduction and adaptation efforts, over time, will be much smaller than the costs of damages arising from failure to make those investments.

These were the conclusions that underpinned the U.S. Climate Action Plan announced by President Obama in June 2013. And they were the conclusions, made even more robust by the continuing growth of climate-related damages in the ensuing years, that motivated 195 countries to sign the Paris Agreement in December 2015. The science was rightly considered “settled enough”, for those purposes, in both cases.

Why? Because the robustness of these conclusions was not in any way undermined, even then, by remaining uncertainties in climate science about, for example, how natural climate variability interacts with human-caused changes to shape regional weather patterns, or how aspects of cloud physics might influence the pace of future climate change, or just how fast sea level will rise in this century and subsequent ones.

The key conclusions are even stronger today, bolstered by observations since 2015 showing that the impacts of human-caused climate change are, for the most part, growing worse even faster than had been expected. These are the realities driving President Biden Joe BidenCriminal justice group urges clemency for offenders released to home confinement during pandemic Progressive poll: Majority supports passing Biden agenda through reconciliation Transportation moves to ban airline ticket sales to Belarus amid arrest of opposition journalist MORE ’s fully justified proposals for addressing the climate-change challenge.

A recent book by Steve Koonin, undersecretary of energy during President Obama’s first term, “Unsettled? What Climate Science Tells Us, What It Doesn’t, and Why It Matters,” revisits a number of the well-known uncertainties and argues that we know too little to support current policy proposals. He gets many of the relevant details wrong but, worse, wildly understates the robustness of the fundamental propositions that, I’ve noted here, are entirely adequate as the foundation for the climate policies that Biden and other world leaders are now proposing. and more.

Predictably, Koonin’s views have been receiving a warm welcome from the usual defenders of climate-change complacency at Fox News and the Wall Street Journal editorial page. But his is not the healthy, informed skepticism on which all science flourishes. It is, rather, a mish-mash of seemingly cherry-picked data and apparent misunderstandings of current climate science. And its propagation is a menace to public understanding and prudent policymaking.


According to the World Bank (World Bank data on agricultural land), nearly 40% of the terrestrial environment is devoted to agriculture. This proportion is predicted to increase, leading to substantial changes in soil cycling of carbon, nitrogen and phosphorus, among other nutrients. Furthermore, these changes are associated with a marked loss of biodiversity 206 , including of microorganisms 207 . There is increasing interest in using plant-associated and animal-associated microorganisms to increase agricultural sustainability and mitigate the effects of climate change on food production, but doing so requires a better understanding of how climate change will affect microorganisms.

Microorganisms affect climate change

Methanogens produce methane in natural and artificial anaerobic environments (sediments, water-saturated soils such as rice paddies, gastrointestinal tracts of animals (particularly ruminants), wastewater facilities and biogas facilities), in addition to the anthropogenic methane production associated with fossil fuels 208 (Fig. 2). The main sinks for CH4 are atmospheric oxidation and microbial oxidation in soils, sediments and water 208 . Atmospheric CH4 levels have risen sharply in recent years (2014–2017) but the reasons are unclear so far, although they involve increased emissions from methanogens and/or fossil fuel industries and/or reduced atmospheric CH4 oxidation, thereby posing a major threat to controlling climate warming 209 .

Agricultural practices influence microbial communities in specific ways. Land usage (for example, plant type) and sources of pollution (for example, fertilizers) perturb microbial community composition and function, thereby altering natural cycles of carbon, nitrogen and phosphorus transformations. Methanogens produce substantial quantities of methane directly from ruminant animals (for example, cattle, sheep and goats) and saturated soils with anaerobic conditions (for example, rice paddies and constructed wetlands). Human activities that cause a reduction in microbial diversity also reduce the capacity for microorganisms to support plant growth.

Rice feeds half of the global population 210 , and rice paddies contribute

20% of agricultural CH4 emissions despite covering only

10% of arable land. Anthropogenic climate change is predicted to double CH4 emissions from rice production by the end of the century 210 . Ruminant animals are the largest single source of anthropogenic CH4 emissions, with a 19–48 times larger carbon footprint for ruminant meat production than plant-based high-protein foods 211 . Even the production of meat from non-ruminant animals (such as pigs, poultry and fish) produces 3–10 times more CH4 than high-protein plant foods 211 .

The combustion of fossil fuels and the use of fertilizers has greatly increased the environmental availability of nitrogen, perturbing global biogeochemical processes and threatening ecosystem sustainability 212,213 . Agriculture is the largest emitter of the potent greenhouse gas N2O, which is released by microbial oxidation and reduction of nitrogen 214 . The enzyme N2O reductase in rhizobacteria (in root nodules) and other soil microorganisms can also convert N2O to N2 (not a greenhouse gas). Climate change perturbs the rate at which microbial nitrogen transformations occur (decomposition, mineralization, nitrification, denitrification and fixation) and release N2O (ref. 213 ). There is an urgent need to learn about the effects of climate change and other human activities on microbial transformations of nitrogen compounds.

Climate change affects microorganisms

Crop farming ranges from extensively managed (small inputs of labour, fertilizer and capital) to intensively managed (large inputs). Increasing temperature and drought strongly affect the ability to grow crops 215 . Fungal-based soil food webs are common in extensively managed farming (for example, grasslands) and are better able to adapt to drought than bacterial-based food webs, which are common in intensive systems (for example, wheat) 216,217 . A global assessment of topsoil found that soil fungi and bacteria occupy specific niches and respond differently to precipitation and soil pH, indicating that climate change would have differential impacts on their abundance, diversity and functions 218 . Aridity, which is predicted to increase owing to climate change, reduces bacterial and fungal diversity and abundance in global drylands 219 . Reducing soil microbial diversity reduces the overall functional potential of microbial communities, thereby limiting their capacity to support plant growth 173 .

The combined effects of climate change and eutrophication caused by fertilizers can have major, potentially unpredictable effects on microbial competitiveness. For example, nutrient enrichment typically favours harmful algal blooms, but a different outcome was observed in the relatively deep Lake Zurich 220 . Reducing phosphorus inputs from fertilizers reduced eukaryotic phytoplankton blooms but increased the nitrogen-to-phosphorus ratio and thus the non-nitrogen-fixing cyanobacterium Planktothrix rubescens became dominant 220 . In the absence of effective predation, annual mixing has an important role in controlling cyanobacterial populations. However, warming increased thermal stratification and reduced mixing, thereby facilitating the persistence of the toxic cyanobacteria 220 .

Carbon Dioxide Emissions

Chemical Formula: CO2
Lifetime in Atmosphere: See below 1
Global Warming Potential (100-year): 1

Carbon dioxide (CO2) is the primary greenhouse gas emitted through human activities. In 2019, CO2 accounted for about 80 percent of all U.S. greenhouse gas emissions from human activities. Carbon dioxide is naturally present in the atmosphere as part of the Earth's carbon cycle (the natural circulation of carbon among the atmosphere, oceans, soil, plants, and animals). Human activities are altering the carbon cycle–both by adding more CO2 to the atmosphere, and by influencing the ability of natural sinks, like forests and soils, to remove and store CO2 from the atmosphere. While CO2 emissions come from a variety of natural sources, human-related emissions are responsible for the increase that has occurred in the atmosphere since the industrial revolution. 2

Note: All emission estimates from the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990&ndash2019 (excludes land sector).

Larger image to save or print The main human activity that emits CO2 is the combustion of fossil fuels (coal, natural gas, and oil) for energy and transportation, although certain industrial processes and land-use changes also emit CO2. The main sources of CO2 emissions in the United States are described below.

    . The combustion of fossil fuels such as gasoline and diesel to transport people and goods was the largest source of CO2 emissions in 2019, accounting for about 35 percent of total U.S. CO2 emissions and 28 percent of total U.S. greenhouse gas emissions. This category includes transportation sources such as highway and passenger vehicles, air travel, marine transportation, and rail. . Electricity is a significant source of energy in the United States and is used to power homes, business, and industry. In 2019, the combustion of fossil fuels to generate electricity was the second largest source of CO2 emissions in the nation, accounting for about 31 percent of total U.S. CO2 emissions and 24 percent of total U.S. greenhouse gas emissions. The types of fossil fuel used to generate electricity emit different amounts of CO2. To produce a given amount of electricity, burning coal will produce more CO2 than natural gas or oil. . Many industrial processes emit CO2 through fossil fuel consumption. Several processes also produce CO2 emissions through chemical reactions that do not involve combustion, and examples include the production of mineral products such as cement, the production of metals such as iron and steel, and the production of chemicals. Fossil fuel combustion from various industrial processes accounted for about 16 percent of total U.S. CO2 emissions and 13 percent of total U.S. greenhouse gas emissions in 2019. Many industrial processes also use electricity and therefore indirectly result in CO2 emissions from electricity generation.

Carbon dioxide is constantly being exchanged among the atmosphere, ocean, and land surface as it is both produced and absorbed by many microorganisms, plants, and animals. However, emissions and removal of CO2 by these natural processes tend to balance, absent anthropogenic impacts. Since the Industrial Revolution began around 1750, human activities have contributed substantially to climate change by adding CO2 and other heat-trapping gases to the atmosphere.

In the United States, since 1990, the management of forests and other land (e.g., cropland, grasslands, etc.) has acted as a net sink of CO2, which means that more CO2 is removed from the atmosphere, and stored in plants and trees, than is emitted. This carbon sink offset is about 12 percent of total emissions in 2019 and is discussed in more detail in the Land Use, Land-Use Change, and Forestry section.

To find out more about the role of CO2 in warming the atmosphere and its sources, visit the Climate Change Indicators page.

Emissions and Trends

Carbon dioxide emissions in the United States increased by about 3 percent between 1990 and 2019. Since the combustion of fossil fuel is the largest source of greenhouse gas emissions in the United States, changes in emissions from fossil fuel combustion have historically been the dominant factor affecting total U.S. emission trends. Changes in CO2 emissions from fossil fuel combustion are influenced by many long-term and short-term factors, including population growth, economic growth, changing energy prices, new technologies, changing behavior, and seasonal temperatures. Between 1990 and 2019, the increase in CO2 emissions corresponded with increased energy use by an expanding economy and population, including overall growth in emissions from increased demand for travel.

Note: All emission estimates from the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990&ndash2019.

Reducing Carbon Dioxide Emissions

The most effective way to reduce CO2 emissions is to reduce fossil fuel consumption. Many strategies for reducing CO2 emissions from energy are cross-cutting and apply to homes, businesses, industry, and transportation.

EPA is taking common sense regulatory actions to reduce greenhouse gas emissions.

Improving the insulation of buildings, traveling in more fuel-efficient vehicles, and using more efficient electrical appliances are all ways to reduce energy use, and thus CO2 emissions.

  • See EPA's ENERGY STAR® programExit for more information on energy-efficient appliances.
  • See EPA's and DOE's siteExit for more information on fuel-efficient vehicles.
  • Learn about EPA's motor vehicle standards that improve vehicle efficiency and save drivers money.

Reducing personal energy use by turning off lights and electronics when not in use reduces electricity demand. Reducing distance traveled in vehicles reduces petroleum consumption. Both are ways to reduce energy CO2 emissions through conservation.

Learn more about What You Can Do at Home, at School, in the Office, and on the Road to save energy and reduce your carbon footprint.

Producing more energy from renewable sources and using fuels with lower carbon contents are ways to reduce carbon emissions.

Carbon dioxide capture and sequestration is a set of technologies that can potentially greatly reduce CO2 emissions from new and existing coal- and gas-fired power plants, industrial processes, and other stationary sources of CO2. For example, capturing CO2 from the stacks of a coal-fired power plant before it enters the atmosphere, transporting the CO2 via pipeline, and injecting the CO2 deep underground at a carefully selected and suitable subsurface geologic formation, such as a nearby abandoned oil field, where it is securely stored.

1 Atmospheric CO2 is part of the global carbon cycle, and therefore its fate is a complex function of geochemical and biological processes. Some of the excess carbon dioxide will be absorbed quickly (for example, by the ocean surface), but some will remain in the atmosphere for thousands of years, due in part to the very slow process by which carbon is transferred to ocean sediments.

2 IPCC (2013). Climate Change 2013: The Physical Science Basis. Exit Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. [Stocker, T. F., D. Qin, G.-K. Plattner, M. Tignor, S. K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P. M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 1585 pp.

INSIDER: Why Burning Trees for Energy Harms the Climate

Trees are renewable, so why not let them count under the proposed revisions to the EU renewable energy target? Here we answer this and other questions to demonstrate why burning trees for energy is not inherently climate-friendly.

What is the EU renewable energy target and its relevance to trees?

The European Union (EU) Renewable Energy Directive establishes an overall policy for advancing the use of energy from renewable sources in the EU. The current framework requires the EU to meet at least 20 percent of its total energy needs with renewables by 2020. Wood is currently the largest contributor to this renewable energy target, accounting for as much as 45 percent of all renewable energy consumed. Much of the forest biomass currently used consists of industrial and harvest residues and traditional fuelwood. However, these sources are nearing full exploitation and further demand for wood for bioenergy will likely come from additional tree harvesting. Even now, Europe is importing wood pellets from U.S. and Canadian forests. Proposals currently under discussion by the European Parliament for a revised Renewable Energy Directive would increase the share of renewable energy in the EU&rsquos total energy mix from 20 percent to at least 27 percent, and possibly 30&ndash35 percent, by 2030. This proposal would likely increase demand to turn trees into energy as EU countries seek ways to meet these more ambitious renewable energy targets.

Why aren&rsquot trees a climate-friendly energy source?

There is a common perception that burning trees to generate heat or electricity should be considered “zero emissions” or “carbon neutral” because the carbon dioxide (CO2) released during burning is either recaptured by photosynthesis as trees regrow, or the CO2 already sequestered by trees cancels out the emissions. The reality, however, is more complex for the following reasons:

  • When burned, trees generate more CO2 emissions per unit of energy generated than fossil fuels. An oft overlooked fact is that burning wood emits more CO2 than fossil fuels per megawatt-hour (MWh) of electricity generated or per unit of heat generated. For example, per data from Laganière et al. (2017), smokestack CO2 emissions from combusting wood for heat can be 2.5 times higher than those of natural gas and 30 percent higher than those of coal per unit of generated energy. In terms of electricity generation, smokestack emissions from combusting wood can be more than three times higher than those of natural gas, and 1.5 times those of coal per MWh.
  • There is a carbon sequestration opportunity cost. Harvesting trees for energy releases carbon that would otherwise have remained stored in the forest. It also forgoes future carbon sequestration that otherwise would have occurred had the trees been allowed to continue growing.
  • The re-sequestration of the released carbon back into biomass is not instantaneous. It takes a long time for the CO2 emissions from burning trees to be re-absorbed in new additional biomass.

Because of the combination of these factors, it takes a long time before the CO2 absorbed by additional tree regrowth offsets the increase in CO2 emissions associated with burning wood for energy (relative to the emissions generated by burning fossil fuels to yield an equivalent amount of energy). As a result, the increase in atmospheric CO2 emissions from burning trees for energy persists for many years. This delay before atmospheric CO2 benefits are achieved is referred to as carbon payback time&mdash”when preharvest carbon levels are reached (absolute carbon balance)”&mdashor as time to carbon parity&mdash”when comparing carbon levels to a reference case [such as when fossil fuels are burned and the trees remain growing] (relative C balance).” The payback time varies according to where trees are grown, type of energy generation facility, and type of fossil fuel being replaced, among other factors. In the case of mature forests, there may never be a complete payback, if the replanted forest is regularly harvested.

How long are carbon payback periods?

Several studies indicate that the carbon payback periods can be on the order of decades to more than a century, varying by forest type and the fossil fuel being compared against. Payback periods in this range are summarized by the European Joint Research Centre (2014), which draws from a half-dozen studies covering temperate and boreal forests from Europe, Canada, and the United States. Another example is Laganière et al. (2017), which analyzed carbon payback periods for various bioenergy feedstocks sourced from Canadian forests relative to coal-, oil-, and natural gas-fired power and heat generation. Figure 1 summarizes their results, with each black bar indicating the number of years that bioenergy results in increased CO2 levels in the atmosphere relative to the fossil fuel alternative.

Figure 1. Carbon Payback Periods for Bioenergy from Canadian Forests

Black = period with net carbon losses
Yellow = possible additional payback times depending on various management choices
Green = period with net carbon gains
* That otherwise would have been burned or left to decompose

Source: Laganière et al. 2017. “Range and Uncertainties in Estimating Delays in Greenhouse Gas Mitigation Potential of Forest Bioenergy Sourced from Canadian Forests.” Global Change Biology Bioenergy 9 (2): 358&ndash69.

Among other studies coming to similar conclusions, Mitchell et al. (2012) analyzed an even broader set of forests and harvesting regimes and found most options to have payback times of more than 100 years, with the fastest payback times for a limited number of forest types and management regimes being at least 30 years. The science office of the Department of Energy & Climate Change in the United Kingdom had similar findings.

Why does the time delay to carbon payback matter?

Burning biomass for energy releases a big “pulse” of CO2 into the atmosphere relative to what would otherwise have been emitted if the power generator had continued to use fossil fuels. But the world needs to dramatically reduce greenhouse gas emissions over the coming three decades and peak global emissions as soon as possible, if it is to stay below a 2°C temperature rise relative to pre-industrial levels, let alone below a 1.5°C rise. There is a significant environmental cost to delaying greenhouse gas emission reductions, as recognized by the fifth assessment report of the Intergovernmental Panel on Climate Change. Now is not the time to increase atmospheric CO2 concentrations over decadal or century timescales.

But won&rsquot trees that are already growing elsewhere re-absorb the CO2 released from harvesting and burning trees, “offsetting” the emissions?

No. Those trees growing elsewhere would have grown anyway in the counterfactual situation where fossil energy was burned instead of wood. Thus, their absorption of CO2 is not “additional” and cannot be counted as an offset for absorbing the CO2 released by burning trees for energy.

But haven&rsquot trees used for bioenergy already absorbed CO2, so their emissions are not “new”?

Some people argue that it is okay to cut down and burn trees because the trees have already absorbed carbon from the atmosphere during their growing phase. In other words, they argue that burning trees for energy should be credited for the carbon that the same trees absorbed when they grew. However, as far as the atmosphere is concerned, the carbon stored by trees is in the trees, and not in the atmosphere. Cutting down and burning the trees converts this carbon into CO2, increasing the concentration of CO2 in the atmosphere. Meeting global temperature goals requires keeping the carbon sequestered in trees for as long as possible.

Are there any tree-based feedstocks that could be beneficial from an atmospheric CO2 perspective?

Some sources of bioenergy have shorter carbon payback periods. These include various forms of tree-based residues and wastes, including forest slash left over after harvest, black liquor from paper making, unused sawdust, and urban wood waste.

Have others arrived at similar conclusions?

Yes. A U.S. Environmental Protection Agency Science Advisory Board concluded in 2012 that bioenergy is not inherently “carbon neutral” in the near term. Support for this conclusion was expressed in a letter from more than 90 leading U.S. scientists. A European Environment Agency Scientific Committee came to a similar conclusion when giving advice on greenhouse gas accounting in relation to bioenergy. A number of other papers have found that burning stem wood increases CO2 emissions for at least decades, including the following:

    “Using Ecosystem CO2 Measurements to Estimate the Timing and Magnitude of Greenhouse Gas Mitigation Potential of Forest Bioenergy.” Global Change Biology Bioenergy 5 (1): 67&ndash72. “The Impacts of the Demand for Woody Biomass for Power and Heat on Climate and Forests.” London: Chatham House: The Royal Institute of International Affairs. “Harvesting in Boreal Forests and the Biofuel Carbon Debt.” Climatic Change 112 (2): 415&ndash28. “Regional Carbon Dioxide Implications of Forest Bioenergy Production.” Nature Climate Change 1: 419&ndash-23. “Forest Bioenergy or Forest Carbon? Assessing Trade-offs in Greenhouse Gas Mitigation with Wood-based Fuels.” Environmental Science & Technology 45: 789&ndash95. “Forest Debt and Carbon Sequestration Parity in Forest Bioenergy Production.” Global Change Biology Bioenergy 4 (6): 818&ndash27. “Life Cycle Impacts of Biomass Electricity in 2020.” London: UK Department of Energy & Climate Change. “Biomass Sustainability and Carbon Policy Study.” Brunswick, ME: Manomet Center for Conservation Sciences. “Is Woody Bioenergy Carbon Neutral? A Comparative Assessment of Emissions from Consumption of Woody Bioenergy and Fossil Fuel.” Global Change Biology Bioenergy 4 (6): 761&ndash72.

What should the EU do with the revised Renewable Energy Directive?

First, the EU should pass an amendment to the Renewable Energy Directive to limit the definition of renewable biomass from forests to residues and wastes. The current sustainability criteria for bioenergy proposed by the European Commission do not ensure that use of bioenergy results in CO2 reduction benefits over fossil fuel alternatives in climate-relevant timescales. Second, the EU should phase out subsidies and incentives for the use of stemwood and stumps. Tree-based wastes and residues should benefit from subsidies or incentives only if they have no major alternative uses. In practice, the quantity of biomass that results in CO2 benefits for the atmosphere is likely to be limited relative to the total demand for renewable energy.

The enhanced EU renewable energy target should instead be met by increased investments in wind, solar, and other zero-emitting energy sources with unambiguous climate benefits. And efforts to increase energy efficiency should be strengthened.

If the EU does not restrict biomass to genuinely CO2-friendly feedstocks, other countries will likely adopt similarly lax regulations that allow trees to be used as renewable energy sources&mdashwith significant negative consequences for forests and climate.

Climate changes and photosynthesis

This paper is a review. According to the latest data issued by the UN, global warming causes danger to human health and well-being, as well as to animals and plants. As global warming is mainly caused by anthropogenic activities, it was considered that emission of the so-called greenhouse gases should be reduced and in some cases even prohibited. Plants are more easily exposed to biological damage than any other living organisms. The paper deals with the biochemical measures that will increase plants' biological potential, in particular, their photosynthetic and energy opportunities and, therefore, will contribute to drought resistance and will prevent increase of carbon dioxide concentrations in the atmosphere.

Solar energy is environmentally friendly and its conversion to energy of chemical substances is carried out only by photosynthesis – effective mechanism characteristic of plants. However, microorganism photosynthesis occurs more frequently than higher plant photosynthesis. More than half of photosynthesis taking place on the earth surface occurs in single-celled organisms, especially algae, in particular, diatomic organisms.

Watch the video: 210016 Gr11 Life Science: The Atmosphere and Climate Change (September 2022).


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