Extinction risk from global warming
The extinction risk of global warming is the risk of species becoming extinct due to the effects of global warming. This may be Earth's sixth major extinction, often called the Anthropocene or Holocene extinction.
Latest consensus on projections
The scientific consensus in the 2014 IPCC Fifth Assessment Report is that:
A large fraction of both terrestrial and freshwater species faces increased extinction risk under projected climate change during and beyond the 21st century, especially as climate change interacts with other stressors, such as habitat modification, over-exploitation, pollution, and invasive species. Extinction risk is increased under all RCP scenarios, with risk increasing with both magnitude and rate of climate change. Many species will be unable to track suitable climates under mid- and high-range rates of climate change during the 21st century. Lower rates of climate change will pose fewer problems.— IPCC, 2014
Extinction risks reported
In one study published in Nature in 2004, between 15 and 37% of 1103 endemic or near-endemic known plant and animal species will be "committed to extinction" by 2050. More properly, changes in habitat by 2050 will put them outside the survival range for the inhabitants, thus committing the species to extinction.
Other researchers, such as Thuiller et al., Araújo et al., Person et al., Buckley and Roughgarden, and Harte et al. have raised concern regarding uncertainty in Thomas et al.'s projections; some of these studies believe it is an overestimate, others believe the risk could be greater. Thomas et al. replied in Nature addressing criticisms and concluding "Although further investigation is needed into each of these areas, it is unlikely to result in substantially reduced estimates of extinction. Anthropogenic climate change seems set to generate very large numbers of species-level extinctions." On the other hand, Daniel Botkin et al. state "... global estimates of extinctions due to climate change (Thomas et al. 2004) may have greatly overestimated the probability of extinction..."
Mechanistic studies are documenting extinctions due to recent climate change: McLaughlin et al. documented two populations of Bay checkerspot butterfly being threatened by precipitation change. Parmesan states, "Few studies have been conducted at a scale that encompasses an entire species" and McLaughlin et al. agreed "few mechanistic studies have linked extinctions to recent climate change."
In 2008, the white lemuroid possum was reported to be the first known mammal species to be driven extinct by man-made global warming. However, these reports were based on a misunderstanding. One population of these possums in the mountain forests of North Queensland is severely threatened by climate change as the animals cannot survive extended temperatures over 30 °C. However, another population 100 kilometres south remains in good health.
According to research published in the January 4, 2012 Proceedings of the Royal Society B current climate models may be flawed because they overlook two important factors: the differences in how quickly species relocate and competition among species. According to the researchers, led by Mark C. Urban, an ecologist at the University of Connecticut, diversity decreased when they took these factors into account, and that new communities of organisms, which do not exist today, emerged. As a result the rate of extinctions may be higher than previously projected.
According to research published in the 30 May 2014 issue of Science, most known species have small ranges, and the numbers of small-ranged species are increasing quickly. They are geographically concentrated and are disproportionately likely to be threatened or already extinct. According to the research, current rates of extinction are three orders of magnitude higher than the background extinction rate, and future rates, which depend on many factors, are poised to increase. Although there has been rapid progress in developing protected areas, such efforts are not ecologically representative, nor do they optimally protect biodiversity. In the researchers' view, human activity tends to destroy critical habitats where species live, warms the planet, and tends to move species around the planet to places where they don’t belong and where they can come into conflict with human needs (e.g. causing species to become pests).
In 2016 the Bramble Cay melomys, which lived on a Great Barrier Reef island, was reported to probably be the first mammal to become extinct because of sea level rises due to human-made climate change.
Extinction risks of the Adelie penguin are being reported because of global warming. The Adelie penguin (Pygoscelis adeliae) species is declining and data analysis done on the breeding colonies is used to estimate and project future habitat and population sustainability in relation to warming sea temperatures. By 2060, one-third of the observed Adelie penguin colony along the West Antarctic Peninsula (WAP) will be in decline. The Adelie penguins are a circumpolar species, used to the ranges of Antarctic climate, and experiencing population decline. Climate model projections predict sanctuary for the species past 2099. The observed population is similarly proportional to the species-wide population (one-third of the observed population is equal to 20% of the species-wide population).
Sex ratios for sea turtles in the Caribbean are being affected because of global warming. Environmental data were collected from the annual rainfall and tide temperatures over the course of 200 years and showed an increase in air temperature (mean of 31.0 degree Celsius). These data were used to relate the decline of the sex ratios of sea turtles in the North East Caribbean and climate change. The species of sea turtles include Dermochelys coriacea, Chelonia myads, and Eretmochelys imbricata. Extinction is a risk for these species as the sex ratio is being afflicted causing a higher female to male ratio. Projections estimate the declining rate of male Chelonia myads as 2.4% hatchlings being male by 2030 and 0.4% by 2090.
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