[Marxism] Deforestation and Drought

Louis Proyect lnp3 at panix.com
Sun Oct 11 20:01:10 MDT 2015

NY Times, Oct. 11 2015
Deforestation and Drought

LIKE California, much of Brazil is gripped by one of the worst droughts 
in its history. Huge reservoirs are bone dry and water has been rationed 
in São Paulo, a megacity of 20 million people; in Rio; and in many other 

Drought is usually thought of as a natural disaster beyond human 
control. But as researchers peer deeper into the Earth’s changing 
bioclimate — the vastly complex global interplay between living 
organisms and climatic forces — they are better appreciating the crucial 
role that deforestation plays.

Cutting down forests releases stored carbon dioxide, which traps heat 
and contributes to atmospheric warming. But forests also affect climate 
in other ways, by absorbing more solar energy than grasslands, for 
example, or releasing vast amounts of water vapor. Many experts believe 
that deforestation is taking place on such a large scale, especially in 
South America, that it has already significantly altered the world’s 
climate — even though its dynamics are not well understood.

“A lot of people are scrambling to make observations in the Amazon this 
year, with the expected big El Niño coming,” said Abigail L. S. Swann, 
an eco-climatologist at the University of Washington. “It’s expected to 
drive significant drought over the Amazon, which will change how much 
water trees have available.”

Humans have long settled in places where there is adequate and 
predictable precipitation, and large forests play a crucial role in 
generating dependable amounts of rainfall. Trees take up moisture from 
the soil and transpire it, lifting it into the atmosphere. A fully grown 
tree releases 1,000 liters of water vapor a day into the atmosphere: The 
entire Amazon rain forest sends up 20 billion tons a day.

The water vapor creates clouds, which are seeded with volatile gases 
like terpenes and isoprene, emitted by the trees naturally, to form 
rain. These water-rich banks of clouds travel long, wind-driven 
distances, a conveyor belt for the delivery of precipitation that 
scientists call flying rivers.

The sky-borne river over the Amazon carries more water than the Amazon 
River itself. It begins as moisture that builds over the Atlantic Ocean, 
and then flows westward over the emerald crown of the Amazon, where it 
picks up far more moisture. The laden clouds eventually bump up against 
the Andes and are steered south and then east, which means rain for 
Bolivia and Brazil.

One way forests may move water is known as “biotic pumping.” As water 
transpires into the atmosphere above the forest, the theory holds, it 
creates a low-pressure system that sucks in air surrounding it, 
eventually and continually pumping moisture inland from the ocean. 
Cutting down forests degrades these low-pressure systems, essentially 
turning off the pump. Large-scale deforestation is thus believed to be a 
major contributor to the extreme drought in Brazil.

Scientists have long known that vegetation has a profound effect on 
weather. In 1907, officials built a 2,000-mile-long fence across 
Australia to keep invasive rabbits from crossing from the wild outback 
into farms. On the side with native vegetation, rain clouds formed in 
the sky above, but the farm-field skies were clear. The “bunny-fence 
experiments” charted a decline in rainfall of 20 percent on the 
cultivated side. Researchers are still trying to explain why, but the 
leading theory is that the darker native plants absorb more heat and 
release it into the atmosphere, along with energy and water vapor to 
form clouds.

Today’s researchers mainly rely on computer modeling to understand the 
effects of deforestation, a difficult task because there are so many 
complex pathways through which trees control climate: precipitation, 
carbon storage, large clouds of complex chemical emissions and 
absorption of the sun’s energy.

“This area is a frontier,” said David Schimel, an eco-climatologist at 
NASA’s Jet Propulsion Laboratory and the author of “Climate and 
Ecosystems,” “but a frontier because it’s difficult, not because it’s 

In the last year alone some 2,000 square miles of the Amazon — roughly 
the size of Delaware — were lost to clearing, largely for planting 
soybeans and raising cattle. A growing number of scientists are warning 
that wide-scale deforestation — about 20 percent of the Amazon forest is 
gone already and nearly that much is degraded — may already be directing 
precipitation away from places long accustomed to it.

One Princeton study suggested that deforesting the Amazon could 
potentially contribute to drought in places as far away as California, 
while other research indicated that recent droughts in Texas and New 
Mexico might be linked to cutting in the Amazon. Despite the uncertainty 
embedded in these and other studies, “There’s lots of evidence that 
changing the water cycle in the Amazon would have global consequences,” 
Dr. Schimel said. “It’s a fairly robust notion.”

AND its impact could potentially accelerate. In a recent report, Antonio 
Donato Nobre, a veteran climatologist with Brazil’s National Institute 
for Space Research, warned that if just 40 percent of the Amazon region 
is deforested there could be an abrupt large-scale shift to grasslands, 
which could substantially alter global weather patterns “and cause a 
breakdown of the current climate system.” If deforestation continues, he 
has said, São Paulo will most likely “dry up.”

In the broadest sense, scientists say, forests represent a kind of 
ecological infrastructure that helps maintain comfortable living 
conditions on the planet, whether by taking up and holding carbon 
dioxide, cleaning water through their roots, preventing floods by 
stabilizing soil — or, in this case, by regulating climate.

Dr. Nobre and other climate experts are urging an immediate halt to 
deforestation, as well as large-scale planting of new forests, as a way 
to essentially nurse the Amazon back to full health and stabilize its 
pivotal role in climate.

Gordon Bonan, a scientist at the University Corporation for Atmospheric 
Research in Boulder, Colo., and the author of “Ecological Climatology,” 
said reducing deforestation and replanting forests should be priorities 
not just in Brazil but in North America and beyond for many reasons, 
including the health of climate systems. “The pace of change is far 
outpacing our understanding of what the change is doing,” he said, “and 
by the time we do understand it’s probably going to be too late.”

While it is true that vast tree planting, which reroutes groundwater on 
a huge scale and absorbs far more energy than an unforested landscape, 
can have complex and potentially negative effects, “On balance,” if done 
properly, “it’s a positive strategy for climate change,” he added.

Some people aren’t waiting for further research and are hoping to 
geoengineer local climates with new forests. Bishop Fredrick Shoo, the 
bishop elect of the Evangelical Lutheran Church in Tanzania, has been 
planting trees with 100,000 of his parishioners upwind of Mount 
Kilimanjaro for 12 years, in hopes of cooling the hot, dry winds that 
are melting the mountain’s glaciers. During that time, he estimates, 
they have planted 3.7 million trees.

“My hope is we’ll be able to restore the forests of Kilimanjaro and save 
the water sources of Kilimanjaro,” said Bishop Shoo, known as the tree 
bishop. “We have a moral obligation to take care of creation and to be 
sure coming generations have a good place to live.”

Jim Robbins is a frequent contributor to The New York Times and the 
author of “The Man Who Planted Trees.”

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