Amazon's Low Salt Content Keeps Carbon Emissions at Bay

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For their experiment, Kaspari and colleagues added measured amounts of water to pairs of plots in an old-growth forest near Iquitos (map), Peru, about 1,242 miles (2,000 kilometers) from the ocean.

Every other day the team added salt and stream water to 35 of the plots, while another 35 received just stream water.

For each salted plot, the team used roughly the amount of sodium that's in a splash of monkey urine—apparently a common type of precipitation in the Amazon.

"If you work in a tropical rain forest long enough, you'll be buzz-bombed by a monkey," Kaspari added.

After 18 days "some of the scariest-looking termites I've ever seen" began swarming in the salted plots, increasing sevenfold in number, Kaspari said.

Ants—a common termite predator—increased twofold in number, Kaspari said.

Overall the leaf litter in the salty plots began disappearing 41 perecent faster than before, according to the study, which appears this week in the journal Proceedings of the National Academy of Sciences.

The new study reveals that salt can not only speed up decomposition, it can encourage population explosions in species higher up the food chain.

"What is new about it—and is actually pretty cool—is we had very little idea of how [salt] propagates in the ecosystem," said Carlos Martínez del Rio, a physiological ecologist at the Univeristy of Wyoming who was not involved in the research. "It's like a salt cascade."

The research was funded in part by a grant from the National Geographic Society's Committee for Research and Exploration. (The National Geographic Society owns National Geographic News.)

Salt in the Wound?

If hurricanes ramp up due to warming temperatures, as some scientists have suggested, inland ecosystems could get saltier.

Such a sodium jolt could in turn worsen climate change, Kaspari said.

"What happens if suddenly the Amazon gets all the sodium it wants?" Kaspari said.

"All this litter starts breaking down, and there's a heck of a lot more [of the greenhouse gas] CO2 in the atmosphere."

In that sense, Kaspari said, "the Amazon forest animals' loss is our gain."

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