Chemicals' role in frog deaths missed.

Posted by Tamara Tal at Aug 08, 2011 09:00 AM |

Sabri Ben-Achour's story for WAMU – Washington D.C.'s National Public Radio affiliate – highlights the role a fungus called chytrid plays in the intensifying amphibian die-offs and extinctions occurring globally. By some estimates, the fungus was associated with 94 out of 122 frog species extinctions since 1980.

While the article mentions that habitat loss and climate change are also significant drivers in amphibian population crashes, the author misses an additional point about chemicals in the environment. Some can weaken amphibians’ immune systems – and by some accounts – leave them less well-equipped to fight off infection.

Climate change, habitat loss, widespread environmental contamination and infectious disease are all are believed to contribute to global declines in amphibian populations. But the risk factors are often examined in isolation.

A study of northern leopard frog tadpoles infected with a parasite found the tadpoles only died when they were exposed to a second stressor – the pesticide atrazine. These findings backed up another study with the North American wood frog. An even earlier report found that leopard frogs exposed to environmentally realistic levels of six pesticides – atrazine, metribuzin, aldicarb, endosulfane, lindane and dieldrin – were far more likely to succumb to lung infection following exposure to a parasitic roundworm.

While there is no doubt that the chytrid fungus is killing frogs, the events that precipitate infection are not known. More and more research is placing at least some of the blame on the pervasive presence of chemicals in the environment.

Readers would benefit from a more critical evaluation of the varied factors that can influence the infections contributing to the disastrous worldwide crashes in amphibian populations.


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