from Science Daily by John J. Wiens.
Extinctions related to climate change have already happened in hundreds of plant and animal species around the world. New research, publishing on December 8th in the open-access journal PLOS Biology, shows that local extinctions have already occurred in 47% of the 976 plant and animal species studied.
Climate change is predicted to threaten many species with extinction, but determining how species will respond in the future is difficult. Dozens of studies have already demonstrated that species are shifting their geographic ranges over time as the climate warms, towards cooler habitats at higher elevations and latitudes. The new study, by Professor John J. Wiens from the University of Arizona, used these range-shift studies to show that local extinctions have already happened in the warmest parts of the ranges of more than 450 plant and animal species. This result is particularly striking because global warming has increased mean temperatures by less than 1 degree Celsius so far. These extinctions will almost certainly become much more widespread over time, because temperatures are predicted to increase by an additional 1 to 5 degrees in the next several decades. These local extinctions could also extend to species that humans depend on for food and resources.
The study also tested the frequency of local extinction across different regions, habitats, and groups of organisms. It found that local extinctions occurred in about half of the species surveyed across different habitats and taxonomic groups. However, the results showed that local extinctions varied by region and were almost twice as common among tropical species as among temperate species. This is important as the majority of plant and animal species live in the tropics. The results of this study contribute to our understanding of how plants and animals will respond to global climate change and highlight the need to slow and prevent further warming.
That scenario is likely to be played out repeatedly and at an accelerating rate as the world continues to warm, Stanford researchers say.
By 2100, climate change could cause up to 30 percent of land-bird species to go extinct worldwide, if the worst-case scenario comes to pass. Land birds constitute the vast majority of all bird species.
The stream of refugees will now include those fleeing from coasts to safer interiors – millions at a time when storms hit. Where they persist, coastal cities will become fortified islands. The world economy, too, will be threadbare. As direct losses, social instability and insurance payouts cascade through the system, the funds to support displaced people will be increasingly scarce. Sea levels will be rampaging upwards – in this temperature range, both poles are certain to melt, causing an eventual rise of 50 metres. “I am not suggesting it would be instantaneous. In fact it would take centuries, and probably millennia, to melt all of the Antarctic’s ice. But it could yield sea-level rises of a metre or so every 20 years – far beyond our capacity to adapt. Oxford would sit on one of many coastlines in a UK reduced to an archipelago of tiny islands.
More immediately, China is on a collision course with the planet. By 2030, if its people are consuming at the same rate as Americans, they will eat two-thirds of the entire global harvest and burn 100m barrels of oil a day, or 125% of current world output. That prospect alone contains all the ingredients of catastrophe. But it’s worse than that: “By the latter third of the 21st century, if global temperatures are more than three degrees higher than now, China’s agricultural production will crash. It will face the task of feeding 1.5bn much richer people – 200m more than now – on two thirds of current supplies.” For people throughout much of the world, starvation will be a regular threat; but it will not be the only one.
The summer will get longer still, as soaring temperatures reduce forests to tinderwood and cities to boiling morgues. Temperatures in the Home Counties could reach 45C – the sort of climate experienced today in Marrakech. Droughts will put the south-east of England on the global list of water-stressed areas, with farmers competing against cities for dwindling supplies from rivers and reservoirs.
Air-conditioning will be mandatory for anyone wanting to stay cool. This in turn will put ever more stress on energy systems, which could pour more greenhouse gases into the air if coal and gas-fired power stations ramp up their output, hydroelectric sources dwindle and renewables fail to take up the slack. The abandonment of the Mediterranean will send even more people north to “overcrowded refuges in the Baltic, Scandinavia and the British Isles.
Britain will have problems of its own. As flood plains are more regularly inundated, a general retreat out of high risk areas is likely. Millions of people will lose their lifetime investments in houses that become uninsurable and therefore unsaleable? The Lancashire/Humber corridor is expected to be among the worst affected regions, as are the Thames Valley, eastern Devon and towns around the already flood-prone Severn estuary like Monmouth and Bristol. The entire English coast from the Isle of Wight to Middlesbrough is classified as at ‘very high’ or ‘extreme’ risk, as is the whole of Cardigan Bay in Wales.
One of the most dangerous of all feedbacks will now be kicking in – the runaway thaw of permafrost. Scientists believe at least 500 billion tonnes of carbon are waiting to be released from the Arctic ice, though none yet has put a figure on what it will add to global warming. One degree? Two? Three? The pointers are ominous.
As with Amazon collapse and the carbon-cycle feedback in the three-degree world, stabilising global temperatures at four degrees above current levels may not be possible. If we reach three degrees, therefore, that leads inexorably to four degrees, which leads inexorably to five?
Chance of avoiding four degrees of global warming: poor if the rise reaches three degrees and triggers a runaway thaw of permafrost.
And the results suggest warming over 2C would have a bigger impact on marine biodiversity than we’ve seen in the last three million years.