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Monday, October 17, 2011

Animals shrinking in the heat: Sheep, deer, bird and reptile numbers falling due to global warming

By Tamara Cohen

Animals including sheep, deer, birds and reptiles are shrinking due to climate change, scientists have warned.

Researchers say warmer temperatures over the past few years have made some animals adapt to need less body fat to survive while others are struggling for food.

They expect the next few decades to see some types of mammals, fish and birds and plants get even smaller - and evolve into miniature versions of what we know today.

Shrinking: Soay sheep, found wild in the Scottish Highlands, are getting smaller

But they warn could have a major impact on humans who eat them and play havoc with the food chain forcing some creatures to become extinct.

Among the animals which have already started shrinking are Soay sheep, found in the Scottish highlands, which were shown in a study to have decreased in size by five per cent between 1985 and 2007 due to warmer winters.

Dr David Bickford from the National University of Singapore reviewed research showing creatures from deer to tortoises, gulls, goshawks and even polar bears have already shrunk over the past 50 years.

Dr Bickford said: ‘Consequences of this shrinking are not yet fully understood, but could have far-reaching consequences for biodiversity and humans alike.

‘Because recent climate change may be faster than past historical changes in climate, many organisms may not respond or adapt quickly enough... the species that can adapt are the species that will be affected by potential declines in body size.’

Threatened: The warming of polar bears' habitats seems to affect their size

Writing in the journal Nature, the researchers predict shrinking of certain species will accelerate during this century as temperatures could rise by as much as 7c by the year 2100.

Ecologists have known since the mid-19th century that colder climates contain larger animals because they have adapted to conserve more heat - known as Bergmann’s rule after the German biologist who first described it.

But the researchers say warmer and drier conditions have seen an increase in droughts which have shrunk some plants, and acidification of the ocean has affected the size of algae and plankton which are at the bottom of the food chain.

Experimental research had also shown that for every degree Celsius of warming, plants of various types shrank by between 3 and 17 per cent, up to 4 per cent in marine animals, and up to 22 per cent in fish.

The study warned that shrinking fish and crustaceans could adversely affect the nearly one billion people who eat them as their main source of protein.

There would also be an impact on crops from shrinking plants, as the population gets larger by 2050, the researchers wrote.

The findings mirrors the dramatic changes seen 55million years ago when temperatures rose by between 3 and 7 per cent and rainfall levels plummeted.

Fossil evidence from shows creatures such as insects, squirrels and woodrats shrunk or were wiped out. The researchers say today’s climate change is happening even faster.

Dr Bickford added: ‘Reduction in nutrients, food availability and water will probably have negative implications and are inter-related with climate change and shrinking organisms. Being able to predict change is critical in creating strategies that reduce negative effects.’

Grahame Madge, a naturalist at the Royal Society for Protection of Birds said: ‘This is what happened during previous changes in climate millions of years ago, but today animals are also up against changes to the landscape which have reduced their habitats.

‘What we have to bear in mind is that those who manage to evolve are the lucky ones, and many of them will be unable to and become extinct.’



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