New research has found the global collapse of frogs and other amphibians due to the amphibian chytrid fungus exacerbated malaria outbreaks in Costa Rica and Panama during the 1990s and 2000s, providing some evidence that preserving biodiversity and preventing species extinction helps protect human health.

“This is like a small building block showing that there could be unwanted human health consequences of amphibian collapses, and so we should really be trying to account for these impacts,” said Joakim Weill, an environmental economist at the University of California, Davis, who will present the results Tuesday, 8 December at AGU’s Fall Meeting 2020. “We really view this as an important first step leveraging this type of interdisciplinary work, trying to tease out the causal relationship between environmental change and human health.”

Chytrid fungal disease, which has played a role in the decline of more than 500 amphibian species over the past five decades and presumably caused extinctions of 90 species, traveled across Costa Rica and Panama from the early 1980s through the 2000s. Following this collapse of amphibian populations, both countries experienced large increases in malaria cases.

In the new study, researchers investigated whether malaria outbreaks were connected to amphibian declines because amphibians eat the mosquitoes that transmit malaria. They compared the timing and spatial extent of amphibian die-offs with malaria cases in Costa Rica and Panama at the county level from 1976 to 2016.

The researchers found a significant increase in malaria cases in these countries that started immediately after the amphibian die-offs began and peaked 5 to 6 years after. In 1980, there were fewer than 1,000 cases of malaria in the two countries, but cases began to rise in 1990 and peaked at about 7,000 in Costa Rica in the mid-1990s and 5,000 in Panama in the mid-2000s.

The findings show how preserving biodiversity can benefit humans as well as local ecosystems.

“We are able to find what really seems to be this striking causal relationship between amphibian declines and malaria,” Weill said. “It’s pretty incredible that we are finding anything in the first place, because these are events that occurred 40 years ago and the right people were in the right place to make observations about amphibian populations and human disease that we can use today to arrive at new insights.”