THE ROLE OF PESTICIDES IN AMPHIBIAN DECLINE

Amphibians are disappearing faster than any other group of vertebrates, and their decline is driven by multiple, often interacting threats. Habitat loss, pollution, climate change, and disease all contribute. Together, they can push these animals even closer to the brink of extinction. Our latest study explored the link between pesticides and disease, showing that pesticides may add extra stress to already threatened amphibians.

Painted Frog, Discoglossus Pictus (© Eduardo Fernández Meléndez

For our study, we focused on painted frogs and wanted to see how two common stressors, an agricultural herbicide, 2,4-D, and the fungal pathogen Batrachochytrium dendrobatidis (Bd), affect their health when they occur together. Bd is infamous for its role in global amphibian declines, but not all strains are equally dangerous. In our study, we exposed young frogs to two different strains: one highly virulent and a local strain considered much milder. Without exposure to the herbicide, the virulent strain slowed growth and weakened the frogs, while the milder strain caused more frequent infections but had only minor effects on their health.

However, the picture changed when chemical stress was introduced. Tadpoles exposed to 2,4-D just before metamorphosis became smaller froglets, and when this exposure was combined with the mild fungal strain, the resulting harm was as severe as that caused by the virulent strain alone.

The study shows how subtle interactions between pollutants and pathogens can magnify risks in unexpected ways. Even “low-risk” infections can become serious when paired with everyday agricultural chemicals. By revealing these hidden risks, our work can help guide more effective conservation strategies to protect vulnerable species.

Do you want to learn more about this study? Check out the full scientific article here!