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:
Degradation of an abiotic
ecological factor (for example, increase of temperature, less significant rainfalls)
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.
Climate change
{{Excerpt|Effects of climate change on biomes hshgdnsj }
Climate change is another threat to
global biodiversity.[14][15] For example,
coral reefs—which are biodiversity hotspots—will be lost by the year 2100 if global warming continues at the current rate.[16][17] Still, it is the general habitat destruction (often for expansion of agriculture), not climate change, that is currently the bigger driver of biodiversity loss.[18][19] 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.[20][21]
Deforestation also plays a large role in biodiversity loss. More than half of the worlds biodiversity is hosted in tropical rainforest.[22] Regions that are subjected to exponential loss of biodiversity are referred to as "hotspots", since 1988 the hotspots increased from 10 to 34, of the total 34 hotspots currently present, 16 of them are in tropical regions.[23] Researchers have noted that only 2.3% of the world is covered with biodiversity loss hotspots, even though only a small percentage of the world is covered in hotspots, it host a large fraction (50%) of vascular plant species.[24]
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.[25] For example, of the 20 biodiversity goals laid out by the
Aichi Biodiversity Targets in 2010, only six were "partially achieved" by 2020.[26][27]
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.[29]
^
abBradshaw, Corey J. A.; Ehrlich, Paul R.; Beattie, Andrew; Ceballos, Gerardo; Crist, Eileen; Diamond, Joan; Dirzo, Rodolfo; Ehrlich, Anne H.; Harte, John; Harte, Mary Ellen; Pyke, Graham; Raven, Peter H.; Ripple, William J.; Saltré, Frédérik; Turnbull, Christine; Wackernagel, Mathis; Blumstein, Daniel T. (2021).
"Underestimating the Challenges of Avoiding a Ghastly Future". Frontiers in Conservation Science. 1.
doi:10.3389/fcosc.2020.615419.
^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), Poland, Therese M.; Patel-Weynand, Toral; Finch, Deborah M.; Miniat, Chelcy Ford (eds.), "Effects of Climate Change on Invasive Species", 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,
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S2CID234260720