By Erik German, GlobalPost, November 3, 2010
MUTUM, Brazil—A motorboat barreling through the night
up a shallow Amazon stream could only beat the odds for so long.
Just after 9 p.m., the aluminum canoe slammed to a
halt with the sound of a thunderclap. Passengers and cargo lurched into the
air. Shouts of surprise, profanity and a man-sized splash echoed in the dark.
A swift lesson on Newtonian physics and the risks of
night boating had been delivered by a large, semi-submerged tree.
The mishap demonstrated what everyone in this remote
corner of the Brazilian jungle had been saying for days. The world’s largest
rain forest was dangerously dry, and may well be drying out.
October marked the end of one of the worst Amazon
droughts on record—a period of tinder-dry forests, dusty cropland and rivers
falling to unprecedented lows. Streams are the highways of the deep jungle and
they’re also graveyards for dead trees, usually hidden safely under fathoms of
navigable water.
But not this year, and the drought’s significance
extends far beyond impeded boats.
While the region has seen dry spells before, locals
and experts say droughts have grown more frequent and severe. Scientists say
there’s mounting evidence the Amazon’s shifting weather may be caused by global
climate change.
Covering an area the size of the continental United
States, the Amazon holds 20 percent of Earth’s fresh water and generates a
fifth of its oxygen. With the planet’s climate increasingly threatened by
surging carbon emissions, the Amazon has been one of the few forces keeping
them in check. But the latest scientific evidence suggests the forest may be
unable to shield us from a hotter world.
“Every ecosystem has some point beyond which it can’t
go,” said Oliver Phillips, a tropical ecology professor at the University of
Leeds who has spent decades studying how forests react to changing weather.
“The concern now is that parts of the Amazon may be approaching that
threshold.”
Through photosynthesis, the rain forest absorbs 2
billion tons of atmospheric carbon dioxide each year. But the 2005 drought
caused a massive die-off of trees and inverted the process. Like a vacuum
cleaner expelling its dust, the Amazon released 3 billion tons of carbon
dioxide in 2005. All told, the drought caused an extra 5 billion tons of
heat-trapping gases to end up in the atmosphere—more than the combined annual
emissions of Europe and Japan.
It still remains to be seen whether the rain forest’s
ability to absorb greenhouse gases has been permanently harmed. “We can’t say
for sure—it could be happening now,” Phillips said. “Often you don’t know
you’ve passed a turning point until you’ve already passed it.”
Phillips said he’s worried about yet another drought
following so closely after the last. Along the edge of the forest in Peru and
Bolivia, there were more fires this year than any year on record, he said,
along with reports of substantial damage to plants in the normally wet
northwestern Amazon.
Asner said melting polar ice sheets aren’t the only
climate change sentinels out there. The world’s largest rain forest—drained,
drying, sometimes burning—is on the front lines, too, and just as threatened.
This year, one of the Amazon River’s biggest
tributaries, the Rio Negro, dropped 13 feet below its dry-season average—to the
lowest level on record. Channels in some areas have become little more than
winding belts of mud—leaving boats stranded and remote communities cut off from
supplies.
