October 21, 2008
Amphibian Losses Cut Ecosystem Productivity

Some wonder whether loss of species diversity has costs. Here's an example such a cost. The loss of frogs to the global spread of a killer fungus causes streams to produce less biomass.

Athens, Ga. – Streams that once sang with the croaks, chirps and ribbits of dozens of frog species have gone silent. They’re victims of a fungus that’s decimating amphibian populations worldwide.

Such catastrophic declines have been documented for more than a decade, but until recently scientists knew little about how the loss of frogs alters the larger ecosystem. A University of Georgia study that is the first to comprehensively examine an ecosystem before and after an amphibian population decline has found that tadpoles play a key role keeping the algae at the base of the food chain productive.

“Many things that live in the stream depend on algae as a base food resource,” said lead author Scott Connelly, a doctoral student who will graduate in December from the UGA Odum School of Ecology. “And we found that the system was more productive when the tadpoles were there.

The results, which appear in the early online edition of the journal Ecosystems, demonstrate how the grazing activities of tadpoles help keep a stream healthy. The researchers found that while the amount of algae in the stream was more than 250 percent greater after the amphibian population decline, the algae were less productive at turning sunlight and nutrients into food for other members of the ecosystem. Without tadpoles swimming along the streambed and stirring up the bottom, the amount of sediment in the stream increased by nearly 150 percent, blocking out sunlight that algae need to grow.

Which species losses due to human activity will cut into the amount of biomass produced by ecosystems? We are going to find out.

Share |      Randall Parker, 2008 October 21 09:32 PM  Trends Extinction

David Govett said at October 22, 2008 12:48 AM:

In a decade or so, we'll be able to bioengineer dozens of species of amphibians, some able to glow in the dark or croak rap songs. Don't sweat it now.

James Bowery said at October 22, 2008 9:41 AM:

Amen, David! The hidden agenda here is, of course, xenophobia and the ecology of exclusion. As covered by Carl Zimmer, author of "Parasite Rex", in his articles in "Discover" magazine, global panmixia of species is beneficial to global ecosystems according to "scholars". The spread of the Xenopus frog as a carrier of the Chytrid fungus throughout the world is simply another example of beneficial diversity being resisted by fearful nativists clinging desperately to their ecological niches as we approach a post-autotrophic world.

Mthson said at October 23, 2008 12:10 PM:

The deeper our understanding of all the necessary inputs for human agriculture (e.g. bees), including any deriving from the broader ecosystem, the less need there is for undomesticated biomass.

Humans can get their natural beauty need met by trees and farms.

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