An ecological or environmental crisis occurs when changes to the environment of a species or population destabilizes its continued survival. Some of the important causes include:
Climate change is starting to have major impacts on ecosystems. With global temperature rising, there is a decrease in snow-fall, and sea levels are rising. Ecosystems will change or evolve to cope with the increase in temperature. Consequently, many species are being driven out of their habitats.
Polar bears are being threatened. They need ice for hunting seals, their primary prey. However, the ice caps are melting, making their hunting periods shorter each year. As a result, the polar bears are not developing enough fat for the winter; therefore, they are not able to reproduce at a healthy rate.
Fresh water and wetland ecosystems are dealing with extreme effects of the increase of temperature. The climate change could be devastating to salmon and trout and to other aquatic life. The increase in temperature will disrupt the current life patterns of the salmon and trout. The cold-water fish will eventually leave their natural geographical range to live in cooler waters by migrating to higher elevations.
While many species have been able to adapt to the new conditions by moving their range further towards the poles, other species are not as fortunate. The option to move is not available for polar bears and for some aquatic life.
Predicated changes for Earth's biomes under two different climate change scenarios for 2081–2100. Top row is low emissions scenario, bottom row is high emissions scenario. Biomes are classified with Holdridge life zones system. A shift of 1 or 100% (darker colours) indicates that the region has fully moved into a completely different biome zone type.
Climate change is already now altering biomes, adversely affecting terrestrial and marine ecosystems.[2][3] Climate change represents long-term changes in temperature and average weather patterns.[4][5] This leads to a substantial increase in both the frequency and the intensity of extreme weather events.[6] As a region's climate changes, a change in its flora and fauna follows.[7] For instance, out of 4000 species analyzed by the IPCC Sixth Assessment Report, half were found to have shifted their distribution to higher latitudes or elevations in response to climate change.[8]
Furthermore, climate change may cause ecological disruption among interacting species, via changes in behaviour and phenology, or via climate niche mismatch.[9] For example, climate change can cause species to move in different directions, potentially disrupting their interactions with each other.[10][11]
Examples of effects on some biome types are provided in the following.[clarification needed][where?] Research into desertification is complex, and there is no single metric which can define all aspects. However, more intense climate change is still expected to increase the current extent of drylands on the Earth's continents. Most of the expansion will be seen over regions such as "southwest North America, the northern fringe of Africa, southern Africa, and Australia".[12]
Mountains cover approximately 25 percent of the Earth's surface and provide a home to more than one-tenth of the global human population. Changes in global climate pose a number of potential risks to mountain habitats.[13]
Boreal forests, also known as taiga, are warming at a faster rate than the global average,[14] leading to drier conditions in the Taiga, which leads to a whole host of subsequent impacts.[15] Climate change has a direct impact on the productivity of the boreal forest, as well as its health and regeneration.[15]
Almost no other ecosystem is as vulnerable to climate change as coral reefs. Updated 2022 estimates show that even at a global average increase of 1.5°C (2.7°F) over pre-industrial temperatures, only 0.2% of the world's coral reefs would still be able to withstand marine heatwaves, as opposed to 84% being able to do so now, with the figure dropping to 0% at 2°C (3.6°F) warming and beyond.[16][17]
Summary of major environmental-change categories that cause biodiversity loss. The data is expressed as a percentage of human-driven change (in red) relative to baseline (blue), as of 2021. Red indicates the percentage of the category that is damaged, lost, or otherwise affected, whereas blue indicates the percentage that is intact, remaining, or otherwise unaffected.
Climate change is another threat to global biodiversity.[32][33] For example, coral reefs—which are biodiversity hotspots—will be lost by the year 2100 if global warming continues at the current rate.[34][35] Still, it is the general habitat destruction (often for expansion of agriculture), not climate change, that is currently the bigger driver of biodiversity loss.[36][37] Invasive species and other disturbances have become more common in forests in the last several decades. These tend to be directly or indirectly connected to climate change and can cause a deterioration of forest ecosystems.[38][39]
Groups that care about the environment have been working for many years to stop the decrease in biodiversity. Nowadays, many global policies include activities to stop biodiversity loss. For example, the UN Convention on Biological Diversity aims to prevent biodiversity loss and to conserve wilderness areas. However, a 2020 United Nations Environment Programme report found that most of these efforts had failed to meet their goals.[40] For example, of the 20 biodiversity goals laid out by the Aichi Biodiversity Targets in 2010, only six were "partially achieved" by 2020.[41][42]
This ongoing global extinction is also called the holocene extinction or sixth mass extinction.
In the wilderness, the problem of animal overpopulation is solved by predators. Predators tend to look for signs of weakness in their prey, and therefore usually first eat the old or sick animals. This has the side effects of ensuring a strong stock among the survivors and controlling the population.
In the absence of predators, animal species are bound by the resources they can find in their environment, but this does not necessarily control overpopulation. In fact, an abundant supply of resources can produce a population boom that ends up with more individuals than the environment can support. In this case, starvation, thirst, and sometimes violent competition for scarce resources may effect a sharp reduction in population, and in a very short lapse, a population crash. Lemmings, as well as other less popular species of rodents, are known to have such cycles of rapid population growth and subsequent decrease.
In an ideal setting, when animal populations grow, so do the number of predators that feed on that particular animal. Animals that have birth defects or weak genes (such as the runt of the litter) also die off, unable to compete over food with stronger, healthier animals.
In reality, an animal that is not native to an environment may have advantages over the native ones, such being unsuitable for the local predators. If left uncontrolled, such an animal can quickly overpopulate and ultimately destroy its environment.
In the ArgentinePatagonia, for example, European species such as the trout and the deer were introduced into the local streams and forests, respectively, and quickly became a plague, competing with and sometimes driving away the local species of fish and ruminants.
In Australia, when rabbits were introduced (unwillingly) by European immigrants, they bred out of control and ate the plants that other native animals needed to survive. Farmers hunted the rabbits to reduce their population and prevent the damage the rabbits did to the crops. They also brought cats to guard against rabbits and rats. These cats created another problem, since they became predators of local species.
The nuclear meltdown at Chernobyl in 1986 caused the death of many people and animals from cancer, and caused mutations in a large number of animals and people. The area around the plant is now abandoned by humans because of the large amount of radiation generated by the meltdown. Twenty years after the accident, the animals have returned.[44]
↑ Parmesan, C., M.D. Morecroft, Y. Trisurat, R. Adrian, G.Z. Anshari, A. Arneth, Q. Gao, P. Gonzalez, R. Harris, J. Price, N. Stevens, and G.H. Talukdarr, 2022: Chapter 2: Terrestrial and Freshwater Ecosystems and Their Services. In Climate Change 2022: Impacts, Adaptation and Vulnerability [H.-O. Pörtner, D.C. Roberts, M. Tignor, E.S. Poloczanska, K. Mintenbeck, A. Alegría, M. Craig, S. Langsdorf, S. Löschke,V. Möller, A. Okem, B. Rama (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 257-260 |doi=10.1017/9781009325844.004
↑ Sales, L. P.; Rodrigues, L.; Masiero, R. (November 2020). "Climate change drives spatial mismatch and threatens the biotic interactions of the Brazil nut". Global Ecology and Biogeography. 30 (1): 117–127. doi:10.1111/geb.13200. S2CID228875365.
↑ Nogués-Bravoa D.; Araújoc M.B.; Erread M.P.; Martínez-Ricad J.P. (August–October 2007). "Exposure of global mountain systems to climate warming during the 21st Century". Global Environmental Change. 17 (3–4): 420–8. Bibcode:2007GEC....17..420N. doi:10.1016/j.gloenvcha.2006.11.007.
↑ Stokstad, Erik (6 May 2019). "Landmark analysis documents the alarming global decline of nature". Science. doi:10.1126/science.aax9287. For the first time at a global scale, the report has ranked the causes of damage. Topping the list, changes in land use—principally agriculture—that have destroyed habitat. Second, hunting and other kinds of exploitation. These are followed by climate change, pollution, and invasive species, which are being spread by trade and other activities. Climate change will likely overtake the other threats in the next decades, the authors note. Driving these threats are the growing human population, which has doubled since 1970 to 7.6 billion, and consumption. (Per capita of use of materials is up 15% over the past 5 decades.)
↑ Pimm SL, Jenkins CN, Abell R, Brooks TM, Gittleman JL, Joppa LN, Raven PH, Roberts CM, Sexton JO (May 2014). "The biodiversity of species and their rates of extinction, distribution, and protection". Science. 344 (6187) 1246752. doi:10.1126/science.1246752. PMID24876501. S2CID206552746. The overarching driver of species extinction is human population growth and increasing per capita consumption.
↑ Cafaro, Philip; Hansson, Pernilla; Götmark, Frank (August 2022). "Overpopulation is a major cause of biodiversity loss and smaller human populations are necessary to preserve what is left"(PDF). Biological Conservation. 272 109646. Bibcode:2022BCons.27209646C. doi:10.1016/j.biocon.2022.109646. ISSN0006-3207. S2CID250185617. Archived(PDF) from the original on December 8, 2023. Retrieved December 25, 2022. Conservation biologists standardly list five main direct drivers of biodiversity loss: habitat loss, overexploitation of species, pollution, invasive species, and climate change. The Global Assessment Report on Biodiversity and Ecosystem Services found that in recent decades habitat loss was the leading cause of terrestrial biodiversity loss, while overexploitation (overfishing) was the most important cause of marine losses (IPBES, 2019). All five direct drivers are important, on land and at sea, and all are made worse by larger and denser human populations.
↑ Crist, Eileen; Mora, Camilo; Engelman, Robert (21 April 2017). "The interaction of human population, food production, and biodiversity protection". Science. 356 (6335): 260–264. Bibcode:2017Sci...356..260C. doi:10.1126/science.aal2011. PMID28428391. S2CID12770178. Retrieved 2 January 2023. Research suggests that the scale of human population and the current pace of its growth contribute substantially to the loss of biological diversity. Although technological change and unequal consumption inextricably mingle with demographic impacts on the environment, the needs of all human beings—especially for food—imply that projected population growth will undermine protection of the natural world.
↑ Hughes, Alice C.; Tougeron, Kévin; Martin, Dominic A.; Menga, Filippo; Rosado, Bruno H. P.; Villasante, Sebastian; Madgulkar, Shweta; Gonçalves, Fernando; Geneletti, Davide; Diele-Viegas, Luisa Maria; Berger, Sebastian; Colla, Sheila R.; de Andrade Kamimura, Vitor; Caggiano, Holly; Melo, Felipe (2023-01-01). "Smaller human populations are neither a necessary nor sufficient condition for biodiversity conservation". Biological Conservation. 277 109841. Bibcode:2023BCons.27709841H. doi:10.1016/j.biocon.2022.109841. ISSN0006-3207. Through examining the drivers of biodiversity loss in highly biodiverse countries, we show that it is not population driving the loss of habitats, but rather the growth of commodities for export, particularly soybean and oil-palm, primarily for livestock feed or biofuel consumption in higher income economies.
↑ Finch, Deborah M.; Butler, Jack L.; Runyon, Justin B.; Fettig, Christopher J.; Kilkenny, Francis F.; Jose, Shibu; Frankel, Susan J.; Cushman, Samuel A.; Cobb, Richard C. (2021). "Effects of Climate Change on Invasive Species". In Poland, Therese M.; Patel-Weynand, Toral; Finch, Deborah M.; Miniat, Chelcy Ford (eds.). Invasive Species in Forests and Rangelands of the United States: A Comprehensive Science Synthesis for the United States Forest Sector. Cham: Springer International Publishing. pp.57–83. doi:10.1007/978-3-030-45367-1_4. ISBN978-3-030-45367-1. S2CID234260720.
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