Unhoppy News: Long-term decline in common toads

Unhoppy News: Long-term decline in common toads

Rare and endangered species are often the focus of conservation efforts, but common species that are in decline may nonetheless have a significant impact on ecosystems. Despite the ongoing global decline in amphibians, monitoring data on the abundance of widespread and common amphibians remains scarce.

Benedikt Schmidt from the University of Zurich and Silviu Petrovan from Froglife used citizen science data from the U.K. and Switzerland to assess long-term national and regional trends for one of Europe’s most abundant amphibian species, the common toad.

Their findings, published in PLOS ONE, show a surprisingly severe and long-term decline in both Swiss and U.K. populations, with implications for amphibian conservation. To learn more about the study and the significance of its results, I interviewed Dr. Schmidt via email.

Benedikt Schmidt März2013 297

When did you become interested in conservation biology, and what led you to study amphibians?

BS: Even as a boy I was interested in critters, and amphibians in particular – I feel lucky to have become a professional amphibian biologist. Witnessing amphibian habitat loss and local population extinctions and reading about the global amphibian decline led me to research the conservation biology of amphibians.

Why did you decide to study the common toad instead of a more endangered species?

BS: There is already a lot of research on rare species. This is good. However, we should also make sure that common species remain common as they have an important role in ecosystems. Therefore, it makes sense to study one of Europe’s commonest amphibian species. The many volunteers involved in toad patrols also show that this species has widespread public support.

Your study relied on data from toad patrol volunteers. Could you tell us about this conservation project? What, in your opinion, are the benefits of such citizen science?

BS: Toad patrols have been in place for decades in parts of Europe, and thousands of very dedicated volunteers go out during toad migration season every spring rescuing amphibians from road traffic. This action of removing amphibians from the danger of crossing roads is probably the first large-scale amphibian conservation measure undertaken by volunteers anywhere in the world. Saving the lives of amphibians in this way is probably the beginning of large-scale amphibian conservation action, at least in Western Europe. Our study shows that the data the toad patrollers provide can be used to identify robust long-term trends over decades and across large areas. This data simply does not exist from professional surveys; for this reason, citizen-led efforts are invaluable.

One key finding was that the common toad population has declined continuously and rapidly in the U.K. and Switzerland every decade since the 1980s. Were you surprised by this finding? Why do you think the decline has occurred?

BS: There have been suggestions in the past that toads are in trouble, but this is the first time we could use such massive datasets and demonstrate large-scale declines. We were surprised at the severity of the declines and also at the fact that Swiss and British declines seemed to start at the same time, around the mid-1980s. Our data cannot explain the declines, but we suspect there are multiple factors, including increased road traffic, habitat loss and degradation in farmland and the wider countryside, and potentially climate change and amphibian diseases.

What do you see as the next steps in conservation of amphibians like the common toad? What impact do you hope your study might have?

BS: We want to draw attention to the fact that conservation should not only focus on rare species: common species deserve more attention as they can be extremely important members of ecosystems. Now that we know toads are in serious decline, we can work to identify the exact causes and find realistic measures to protect them. For example, large populations should be recognized as important for biodiversity and should get protection in the U.K. planning system as they have in Switzerland. At popular road crossing sites we would promote measures such as road tunnels to protect migrating toads. Nature-friendly schemes, such as reduced pesticide use and agri-environment farming schemes, already include certain bird species, and should now also consider toads.


Research Article: Petrovan SO, Schmidt BR (2016) Volunteer Conservation Action Data Reveals Large-Scale and Long-Term Negative Population Trends of a Widespread Amphibian, the Common Toad (Bufo bufo). PLoS ONE 11(10): e0161943. doi:10.1371/journal.pone.0161943

Image CreditFrank Vassen, Flickr; Benedikt Schmidt


Beth works at PLOS as Journal Media Manager. She read Natural Sciences, specializing in Pathology, at the University of Cambridge before joining PLOS in 2013. She feels fortunate to be able to read and write about the exciting new research published by PLOS.

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