Amazon's Low Salt Content Keeps Carbon Emissions at Bay

Christine Dell'Amore
National Geographic News
November 4, 2009

Supposedly the most robust of the world's rain forests, the Amazon jungle suffers from "chronic malnutrition" due to a lack of salt, according to the lead scientist behind a new study.

And that might not be a bad thing, because the carbon build-up spurred by lack of salt in some forests may be keeping our atmosphere cooler.

Decomposers—life-forms that munch on dead plants—don't get enough of the vital mineral, which deep in the rain forest comes primarily from mammal urine.

That lack of salt keeps decomposer numbers in check, while plants, which don't need salt, flourish, piling up carbon on the forest floor when they die.

"The tropics is a place for happy plants and less happy" decomposers, said study leader Michael Kaspari, a zoologist at the University of Oklahoma.

When researchers sprinkled a salt solution in the Peruvian Amazon, plant-eaters such as termites and bacteria sprung to life and quickly devoured the detritus.

"We were terribly surprised to find how fast a little bit of sodium in the ecosystem starts [the process of] breaking down accumulated litter," Kaspari said.

Recycling dead matter keeps forests more productive and moves carbon more quickly through the environment—one of the most crucial cycles of life. But decomposition releases carbon dioxide, a potent greenhouse gas that contributes to global warming.

To better predict how much greenhouse gas might be released in the future, scientists are struggling to find any unknown carbon stores. "I suspect," Kaspari said, "some of that missing carbon may be lying around in tropical rain forests."

Just Add Salt

Salt hunger is innate in most animals, and previous studies have shown that landlocked animals and insects particularly crave salt.

In additon to mammal urine, hurricanes bring salt to inland environments—though rarely—by blowing seawater thousands of kilometers from the coasts.

Continued on Next Page >>


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