Ecological collapse

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 time scale. Ecological collapse can be considered as a consequence of ecosystem collapse on the biotic elements that depended on the original ecosystem. 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 time scale. Ecological collapse can be considered as a consequence of ecosystem collapse on the biotic elements that depended on the original ecosystem. 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. 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 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. Rainforest collapse refers to the actual past and theoretical future ecological collapse of rainforests. It may involve habitat fragmentation to the point where little rainforest biome is left, and rainforest species only survive in isolated refugia. Habitat fragmentation can be caused by roads. When humans start to cut down the trees for logging, secondary roads are created that will go unused after its primary use. Once abandoned, the plants of the rainforest will find it difficult to grow back in that area. Forest fragmentation also opens the path for illegal hunting. Species have a hard time finding a new place to settle in these fragments causing ecological collapse. This leads to extinction of many animals in the rainforest. In the Carboniferous period, coal forests, great tropical wetlands, extended over much of Euramerica (Europe and America). This land supported towering lycopsids which fragmented and collapsed abruptly. The collapse of the rainforests during the Carboniferous has been attributed to multiple causes, including climate change. Specifically, at this time climate became cooler and drier, conditions that are not favourable to the growth of rainforests and much of the biodiversity within them. This sudden collapse affected several large groups including lycopsids and amphibians. Reptiles prospered in the new environment due to adaptations that let them thrive in drier conditions.