Mass observations of frogs spawning have sounded a warning bell not only for the future of the common frog but also for Britain’s wildlife more generally.

Frogs are so locally adapted that they may not be able to cope with even modest climate change, new research led by Imperial College London has found.

What’s true of frogs is likely to be true for many other poorly-dispersing species. Their only alternative will be to move and that is not an option unless there is swift action to create landscapes that work for wildlife as well as people.

These are the conclusions of a paper published in the Proceedings of the National Academy of Sciences. It analysed more than 50,000 UK observations of first frogspawn from 1998-2006 collated by Nature’s Calendar, a national survey coordinated by the Woodland Trust.

A unique approach to assessing local adaptation was developed. It compared how relationships between temperature and spawning dates vary across Britain with how they vary over time.

All populations spawn earlier in warmer years but southern populations do so several days earlier than northern ones even if they experience the same temperatures, a difference that can be attributed to natural selection. Indeed, it was discovered that this local adaptation is detectable between populations throughout Britain in neighbouring 150km grid squares; areas the size of an average English county.

Data on frogspawning was collected by the general public

The paper’s authors come from Imperial College London, the University of Edinburgh, the Max Planck Institute for Demographic Research in Germany, and the Woodland Trust.

Joint lead author Albert Phillimore, a Junior Research Fellow from the Division of Biology at Imperial College London, said “For frog populations to keep in step with medial projections of climate change for 2050-2070, they may need to spawn about 30 days earlier. Their current flexibility, however, may only enable them to spawn 7 days earlier. It’s 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.”

British frogs could be threatened by mild climate change

“Local adaptation has been assessed in relatively few species, as it has previously required logistically-challenging experiments”, said co-author, Richard Smithers, the Woodland Trust’s senior conservation adviser. “But like frogs, a great many other species are poor at dispersing and may be locally adapted.”

Jarrod Hadfield, joint lead author from the University of Edinburgh, added, “Our study demonstrates the great value of citizen science. The observations collected by the public have enabled us to gain important, if sobering insights, into the evolutionary challenges that frogs are likely to face”.

Article, Imperial College website, 20 April 2010, Lucy Goodchild

The latest update to the IUCN Red List of Threatened Species has been published today, revealing that the number of species threatened with extinction is growing. 47,677 species are on the list, of which 17,291 are at serious risk. This includes 21% of mammals, 30% of amphibians, 70% of plants and 35% of invertebrates. Amphibians are the group most seriously at risk, with 1,895 of 6,825 known species threatened with extinction. 484 of these species are ‘critically endangered’ and 754 are ‘endangered’. 39 species of amphibian are either ‘extinct’ or ‘extinct in the wild’.

Commenting on the report, Jane Smart, Director of the IUCN Biodiversity Conservation Group said: The latest analysis… shows that the 2010 target to reduce biodiversity loss will not be met…It’s time for governments to start getting serious about saving species and make sure it’s high on their agendas for next year, as we are rapidly running out of time.”

Source: BBC News

Access the BES and IEEM position statement on ‘Conserving and Managing Biodiversity Beyond 2010′

The global decline in frog populations has been attributed to an increase in infectious diseases. However findings in Nature reveal a link between parasitic infection and local interaction between phosphate fertilisers and herbicides.

The study focused on leopard frogs from wetlands in Minnesota, USA, and these frogs were examined for trematode larvae – a type of parasitic flatworm. Trematodes are known to cause kidney damage and occasionally deformities in amphibians. The researchers also looked for indicative signs of water pollution, by measuring the level of melanomacrophage liver cells, which are involved in amphibian immune response.

Of the many possible factors contributing to these ailments in the frogs, the strongest predictor of larval infection was the herbicide atrazine combined with high phosphate levels. High levels of the atrazine herbicide were correlated with low levels of melanomacrophage cells, indicating the herbicide suppressed the frogs’ immune response, increasing susceptibility to the trematodes.

A probable cause of the interaction was revealed, when the frogs were placed in tanks exposed to supposed environmental levels of these chemical in the U.S. Atrazine reduced phytoplankton growth, creating clearer water and higher levels of nutrients. This stimulated algal growth, which in turn encouraged gastropods. Gastropods play host to trematodes, acting as a vector to the amphibians. Since wetland birds are the primary host of trematode eggs, as the authors suggest, these must be present along with the elevated phosphate levels and herbicide for the interactive effect to take place.

The findings highlight problems in the European and American systems for registering chemicals. Although the chemicals have no direct effect on mortality independently, the combined effect results in this pollution-disease pathway and would not be identified under existing pollutant control tests.

Many European countries banned its use even before EU legislation withdrew support for its use in 2004, because of concerns over concentrations in groundwater. Atrazine is used widely across the world for corn and sorghum production. There is still some limited support for its use in European countries, although the UK, Ireland, Spain and Portugal no longer have any support for it.

Amphibians are becoming increasingly threatened across the globe, with many species expected to become extinct by 2050. Amphibian fungal infections, particularly Chytridiomycosis are on the rise across the globe, possibly exacerbated by climate change. Chytridiomycosis is thought to have originated in South Africa, although nobody is entirely certain where it began.

Adapted from the Science Environment Policy bulletin, Source: Rohr, J.R., Schotthoefer, A.M., Raffel, T.R., et al. (2008). Agrochemicals increase trematode infections in a declining amphibian species. Nature. 455: 1235-1240.