香港六合彩

The findings, published today in Nature, predict when and where there could be severe ecological disruption in the coming decades, and suggests that the first waves could already be happening.

The study鈥檚 lead author, Dr Alex Pigot (香港六合彩 Centre for Biodiversity & Environment Research): 鈥淲e found that climate change risks to biodiversity don鈥檛 increase gradually. Instead, as the climate warms, within a certain area most species will be able to cope for a while, before crossing a temperature threshold, when a large proportion of the species will suddenly face conditions they鈥檝e never experienced before.鈥�

鈥淚t鈥檚 not a slippery slope, but a series of cliff edges, hitting different areas at different times.鈥�

Dr Pigot and colleagues from the USA and South Africa were seeking to predict threats to biodiversity over the course of the 21^st century, rather than a single-year snapshot. They used climate model data from 1850 to 2005, and cross-referenced it with the geographic ranges of 30,652 species of birds, mammals, reptiles, amphibians, fish, and other animals and plants. The data was available for areas across the globe, divided up into 100 by 100 km square grid cells.

They used climate model projections for each year up to 2100 to predict when species in each grid cell will begin experiencing temperatures that are consistently higher than the organism has previously experienced across its geographic range, for a period of at least five years.

The study鈥檚 first author, Dr Christopher Trisos (African Climate and Development Initiative, University of Cape Town, and National Socio-Environment Synthesis Center 鈥� SESYNC, Maryland, USA), said: 鈥淭he historic temperature models, combined with species ranges, showed us the range of conditions that each organism can survive under, as far as we know.鈥�

鈥淥nce temperatures in a given area rise to levels that the species have never experienced, we would expect there to be extinctions, but not necessarily 鈥� we simply have no evidence of the ability of these species to persist after this point,鈥� he said.

The researchers found that in most ecological communities across the globe, a large proportion of the organisms will find themselves outside of their niche (comfort zone) within the same decade. Across all of the communities, on average 73% of the species facing unprecedented temperatures before 2100 will cross that threshold simultaneously.

The researchers predict that if global temperatures rise by 4掳C by 2100, under a 鈥渉igh emissions鈥� scenario* which the researchers say is plausible, at least 15% of communities across the globe, and potentially many more, will undergo an abrupt exposure event where more than one in five of their constituent species crosses the threshold beyond their niche limit within the same decade. Such an event could cause irreversible damage to the functioning of the ecosystem.

If warming is kept to 2掳颁 or less, potentially fewer than 2% of communities will face such exposure events, although the researchers caution that within that 2% includes some of the most biodiverse communities on the planet, such as coral reefs.

The researchers predict that such unprecedented temperature regimes will begin before 2030 in tropical oceans, and recent events such as mass bleaching of corals on the Great Barrier Reef suggest this is happening already. Higher latitudes and tropical forests are predicted to be at risk by 2050.

Dr Pigot said: 鈥淥ur findings highlight the urgent need for climate change mitigation, by immediately and drastically reducing emissions, which could help save thousands of species from extinction. Keeping global warming below 2掳颁 effectively 鈥榝lattens the curve鈥� of how this risk to biodiversity will accumulate over the century, providing more time for species and ecosystems to adapt to the changing climate 鈥� whether that鈥檚 by finding new habitats, changing their behaviour, or with the help of human-led conservation efforts.鈥�

Co-author Dr Cory Merow (University of Connecticut) said: 鈥淲e hope that our findings could serve as an early warning system, predicting which areas will be most at risk and when, that could help target conservation efforts and improve future model projections. It may be valuable to develop a ten-year monitoring programme 鈥� similar to what climate scientists do, but for biodiversity 鈥� which could be updated regularly based on what actually occurs.鈥�

The study was funded by the Royal Society, the National Science Foundation (USA) and the African Academy of Sciences.

Links

• 香港六合彩 Centre for Biodiversity & Environment Research
• 香港六合彩 Genetics, Evolution & Environment
• * The Intergovernmental Panel on Climate Change (IPCC) uses Representative Concentration Pathways (RCPs) that project the concentration of greenhouse gases, and resulting climate changes, based on scenarios with different emissions. This paper compares RCP2.6 (strong mitigation, with a reduction in emissions), RCP4.5 (moderate mitigation) and RCP8.5 (high emissions scenario, sometimes referred to as 鈥榖usiness as usual鈥�).
• Media coverage

Image

• Maps showing the percentage of species in each area that will face unprecented temperatures by the years listed, under the RCP8.5 high emissions scenario. Credit: Chris听Trisos, Cory Merow & Alex Pigot

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