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What Apocalypse? – Part 8

Ecological collapse refers to a situation where an ecosystem suffers a drastic, possibly permanent, reduction in carrying capacity for all organisms, often resulting in mass extinction. Usually, an ecological collapse is precipitated by a disastrous event occurring on a short timescale.

Ecosystems have the ability to rebound from a disruptive agent. The difference between collapse or a gentle rebound is determined by two factors—the toxicity of the introduced element and the resiliency of the original ecosystem.

Through natural selection, the planet’s species have continuously adapted to change through variation in their biological composition and distribution. Mathematically it can be demonstrated that greater numbers of different biological factors tend to dampen fluctuations in each of the individual factors.

Scientists can predict tipping points for ecological collapse. The most frequently used model for predicting food web collapse is called R50, which is a reliable measurement model for food web robustness.

Causes and examples
Although, there is no single cause for ecological collapse, attributing factors include asteroid impacts, extremely large volcanic eruptions, and abrupt climate change. The snowball effect of these attributing factors and ecological collapse are demonstrated within the fossil record. Prehistoric examples include the Carboniferous Rainforest Collapse, the Cretaceous–Paleogene extinction event, the Permian–Triassic extinction event, and other mass extinctions. For example, effects of climate change as a contributing factor towards ecological collapse are demonstrated in the Ordovician–Silurian extinction events. A possible cause of the Ordovician Extinction was global cooling which affected the habitats of marine life. Consequently, sea creatures such as trilobites, brachiopods, and graptolites became extinct. Furthermore, Karabonov and colleagues conducted a study to show how during the Last Glacial Maximum (LGM), alternations in the environment and climate led to an ecological collapse in Lake Baikal and Lake Hovsgol which then led to species evolution in these systems. The collapse of Hovsgol’s ecosystem during the LGM brought forth a new ecosystem, with limited biodiversity in species and low levels of endemism, in Hovsgol during the Holocene. Karabonov’s study also shows that ecological collapse during LGM in Lake Hovsgol led to higher levels of diversity and higher levels of endemism as a byproduct of evolution following the ecological collapse of the LGM. The Ordovician Extinction event and Lake Baikal and Hovsgol demonstrate two effects of ecological collapse on prehistoric environments.

Historic examples include the collapse of the Grand Banks cod in the early 1990s, attributed to overfishing.

Important pressures contributing to current and future ecological collapse include habitat loss, degradation, and fragmentation, overgrazing, overexploitation of ecosystems by humans, human industrial growth and overpopulation, climate change, ocean acidification, pollution, and invasive species.

 

Steven Sheeley

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Post Series: What Apocalypse

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