Frogspawn study reveals climate change dangers

A study of thousands of records of when UK frogs spawn revealed the amphibians are closely adapted to local conditions - which could put them at risk as the climate changes.

More than 50,000 records of frogspawn, including contributions from the public and BBC Springwatch viewers, were used to see how common frogs responded to temperature across different parts of the UK.

Frogs spawn earlier in warmer years, which provides a longer period for tadpoles to develop, potentially reducing competition for food, and may reduce the chances of the offspring being eaten by newts.

Frogs in the warmer South West lay their spawn earlier on average than those in the colder north and east.

But the records from between 1998 and 2006 found that while all populations of frogs spawned earlier in warmer springs, those in the south do so several days earlier than northern frogs - even if they are experiencing the same temperatures on the same days.

The researchers, writing in a paper published in the Proceedings of the National Academy of Sciences, said the findings showed the frogs were genetically adapted to their local climatic conditions.

For example, frogs in more northern parts of the UK may not respond as quickly to a warmer spring as they are more likely to experience a cold snap, which would kill the spawn, than the south.

But because frogs are so adapted to their immediate environment they will not be able to deal with the changes in the local climate that global warming will bring, conservationists warned.

And the Woodland Trust, which manages the Nature's Calendar survey of observations from which the 50,000 records were drawn, said a wide range of UK wildlife could be facing the same problem.

The results indicate frogs have sufficient flexibility to respond to warmer temperatures by spawning up to seven days earlier on average.

But they would need to spawn on average 30 days earlier by the second half of this century to keep in step with predicted changes in temperature of up to 3C in the South East and 1.7C in the North West between 2050 and 2070.

The shortfall between their ability to bring forward their spawning time and the shift required by rising temperatures could be as much as 25 days in the south of the UK, the study said.

As a result frogs will have to evolve, which is unlikely given the short timescale over which temperatures are rising, or move north to find suitable conditions.

One of the paper's lead authors, Albert Phillimore from Imperial College London, said: "It is unlikely that frogs will be able to evolve sufficiently rapidly, so they will need to move northwards.

"All frog populations face a challenge but the most southerly populations are in the greatest predicament because the English Channel provides a total barrier to immigration from further south."

And Richard Smithers, senior conservation adviser for the Woodland Trust, said: "The average climate frogs will experience in their local environment will be quite different from that they are experiencing today - it will be like a climate from a lot further south."

He said frogs would need to move north to find conditions closer to what they are used to.

But he said: "To do that they have a huge challenge. Frogs are not good at dispersing and we have a really hostile landscape for wildlife so they will struggle to get there.

"This reinforces the message that conservationists are saying loudly at the moment - that we need to create landscapes which work for wildlife as well as people, across which wildlife can move and which at the same time produce the food we need."