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- Degradation of an abiotic ecological factor (for example, increase of temperature, less significant rainfalls)
- Increased pressures from predation
- Rise in the number of individuals (i.e. overpopulation)
Because of the impact of humans on the natural environment in the recent geological period, the term ecological crisis is often applied to environmental issues caused by human civilizations such as: the climate crisis, biodiversity loss and plastic pollution which have emerged as major global challenges during the first few decades of the 21st century.
Crises caused by abiotic factors
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.
Biodiversity loss includes the worldwide extinction of different species, as well as the local reduction or loss of species in a certain habitat, resulting in a loss of biological diversity. The latter phenomenon can be temporary or permanent, depending on whether the environmental degradation that leads to the loss is reversible through ecological restoration/ecological resilience or effectively permanent (e.g. through land loss). The current global extinction (frequently called the sixth mass extinction or Anthropocene extinction), has resulted in a biodiversity crisis being driven by human activities which push beyond the planetary boundaries and so far has proven irreversible.
Even though permanent global species loss is a more dramatic and tragic phenomenon than regional changes in species composition, even minor changes from a healthy stable state can have dramatic influence on the food web and the food chain insofar as reductions in only one species can adversely affect the entire chain (coextinction), leading to an overall reduction in biodiversity, possible alternative stable states of an ecosystem notwithstanding. Ecological effects of biodiversity are usually counteracted by its loss. Reduced biodiversity in particular leads to reduced ecosystem services and eventually poses an immediate danger for food security, but also can have more lasting public health consequences for humans.International environmental organizations have been campaigning to prevent biodiversity loss for decades, public health officials have integrated it into the One Health approach to public health practice, and increasingly preservation of biodiversity is part of international policy. For example, the UN Convention on Biological Diversity is focused on preventing biodiversity loss and proactive conservation of wild areas. The international commitment and goals for this work is currently embodied by Sustainable Development Goal 15 "Life on Land" and Sustainable Development Goal 14 "Life Below Water". However, the United Nations Environment Programme report on "Making Peace with Nature" released in 2020 found that most of these efforts had failed to meet their international goals.
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.
Examples of animal overpopulation caused by introduction of a foreign species abound.
- In the Argentine Patagonia, 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.
Some common examples of ecological crises are:
- Deforestation and desertification, with disappearance of many species.
- Extinction events
- The Exxon Valdez oil spill off the coast of Alaska in 1989
- Global warming related to the Greenhouse effect. Warming could involve flooding of the Asian deltas (see also eco refugees), multiplication of extreme weather phenomena and changes in the nature and quantity of the food resources (see Global warming and agriculture). See also international Kyoto Protocol.
- 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.
- Ozone layer depletion.
- Volcanic eruptions such as Mount St. Helens and the Tunguska and other impact events
- Coral reef depletion
- Acid rain
- Ground water depletion
- North Atlantic garbage patch
- Ecological collapse
- Global warming
- Human overpopulation
- Peak oil
- Collapse: How Societies Choose to Fail or Succeed
- "IPCC Special Report on Climate Change, Desertification, Land Degradation, Sustainable Land Management, Food Security, and Greenhouse gas fluxes in Terrestrial Ecosystems:Summary for Policymakers" (PDF).
- "Summary for Policymakers — Special Report on the Ocean and Cryosphere in a Changing Climate". Retrieved 2019-12-23.
- Mammola, Stefano; Goodacre, Sara L.; Isaia, Marco (January 2018). "Climate change may drive cave spiders to extinction". Ecography. 41 (1): 233–243. doi:10.1111/ecog.02902. hdl:2318/1623725. S2CID 55362100.
- Bradshaw CJ, Ehrlich PR, Beattie A, Ceballos G, Crist E, Diamond J, et al. (2021). "Underestimating the Challenges of Avoiding a Ghastly Future". Frontiers in Conservation Science. 1. doi:10.3389/fcosc.2020.615419.
- Ripple WJ, Wolf C, Newsome TM, Galetti M, Alamgir M, Crist E, Mahmoud MI, Laurance WF (13 November 2017). "World Scientists' Warning to Humanity: A Second Notice". BioScience. 67 (12): 1026–1028. doi:10.1093/biosci/bix125.
Moreover, we have unleashed a mass extinction event, the sixth in roughly 540 million years, wherein many current life forms could be annihilated or at least committed to extinction by the end of this century.
- Cardinale BJ, Duffy JE, Gonzalez A, Hooper DU, Perrings C, Venail P, et al. (June 2012). "Biodiversity loss and its impact on humanity" (PDF). Nature. 486 (7401): 59–67. Bibcode:2012Natur.486...59C. doi:10.1038/nature11148. PMID 22678280. S2CID 4333166.
...at the first Earth Summit, the vast majority of the world’s nations declared that human actions were dismantling the Earth’s ecosystems, eliminating genes, species and biological traits at an alarming rate. This observation led to the question of how such loss of biological diversity will alter the functioning of ecosystems and their ability to provide society with the goods and services needed to prosper.
- United Nations Environment Programme (2021). Making Peace with Nature: A scientific blueprint to tackle the climate, biodiversity and pollution emergencies. Nairobi: United Nations.
- "Global Warming Said Devastating Aquatic Ecosystems" by Brad Bohlander
- "Death of a Small Planet" by Murray Bookchin
- "The Ecological Crisis as Part of the Present Multidimensional Crisis and Inclusive Democracy" by Takis Fotopoulos, (International Journal of Inclusive Democracy, vol 3, no 3, June 2007)
- "Myths on the Ecological Crisis" by Takis Fotopoulos
- "Polar Bears Send an 'SOS'" by WWF
- The Paradox of Wealth: Capitalism and Ecological Destruction by John Bellamy Foster and Brett Clark
- "Utilisation Competitions over Ecological Resources - Uncovering the Social Nature of the Environmental Problem (in: Progress in Industrial Ecology – An International Journal, Vol. 8, No. 4, 2014, pp.237–256)" by Andreas Metzner-Szigeth