Endangered Frogs See ‘Population Explosion’ After 422 Ponds Were Built in Switzerland

All of Switzerland’s threatened frog species’ populations ‘exploded’ when scientists began a simple pond-building campaign.

Particular among the web-footed beneficiaries were the European tree frog, whose numbers have quadrupled since 1999, as have the numbers of areas they can be found.

While protection laws in the Swiss canton of Aargau for their suite of frog, newt, and toad species were strong, scientists wanted to see if habitat restoration could kick start their continually-declining numbers.

In 1999, in coordination with the Aargau government, non-profits, volunteers, and landholders, a 20-year program of building 422 ponds across five regions of Aargau was started.

Most frogs need small ponds that naturally develop off the sides of the bends in slowly meandering rivers, features that have rapidly disappeared in Switzerland’s high road/railway density and intensively managed farmland.

Of the eight endangered species, 52% increased their regional populations and 32% were stabilized.

“Habitat loss is one of the main problems, and just by addressing that we could see the difference it made, and begin the recovery of these species,” lead author of the study Dr. Helen Moor told BBC News. “The key message is that it pays to do something, even if it feels overwhelming.”

One of the species that had a particularly strong rebound was the European tree frog. This tiny frog can travel as much as a couple of miles in search of habitat to lay its eggs.

Frogs need new ponds to migrate to, as predator species eventually make their way into existing ponds to pray on their tadpoles. What few ponds existed before the project were often occupied by these predators.

The scientists believe that this simple action of pond building can be used to help restore amphibian populations in human-dominated landscapes.