Azara Blog: Decline in leaves might be behind decline in amphibians in Costa Rica

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Date published: 2007/04/18

The BBC says:

A decline in the amount of leaves on the ground could be behind the rapid demise of frog species, a study of a rainforest in Costa Rica has suggested.

Until now, the prime suspect for the amphibians' population crash was a deadly fungal infection.

By studying data over a 35-year period, researchers found that lizards, which were not susceptible to the infection, had also declined by a similar rate.
The international team of scientists examined data of amphibian and common reptile populations in La Selva, a protected area of rainforest in Costa Rica.

Between 1970 and 2005, the data showed that the number of amphibians had declined by about 75%, which supported the idea that frogs were being wiped out by the chytrid fungus.

However, the data also showed a similar fall in the area's reptiles, which were not susceptible to the fungus.

Over the same period, the data showed that there had been a 75% reduction in the density of leaves falling to the ground from the rainforest's canopy.

Leaf litter provides a vital habitat, offering food and shelter, for the amphibians and lizards.

The team, from Florida International University, the University of Costa Rica and San Diego State University, suggested shifts in the area's climate had led to a decline in the habitat needed to sustain the creatures.

"The increasingly warm and wet conditions of the past two decades could negatively influence standing litter mass by affecting rates of litterfall or litter decomposition," the authors wrote.

It sounds halfway plausible but so doesn't the idea that the problem for frogs is the fungal infection. Basically, ecosystems are complex, and models and theories are sometimes just hopelessly incomplete and naive, and it's also sometimes difficult to figure out what is a cause and what is an effect.

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