(photo credit: DR)
Researchers at the Weizmann Institute of Science
in Rehovot recently made a surprising discovery about the abilities of
forests to combat global warming.
In an article published on Friday in the journal Science
Prof. Dan Yakir and Dr. Eyal Rotenberg of the Environmental Sciences
and Energy Research Department discuss their analysis of findings from
the Yatir Forest research station.
By looking at the other side of the equation, the two
researchers discovered that desertification was not necessarily all bad
- in fact, it may have retarded global warming by as much as 20%. The
desert reflects sunlight and releases infrared radiation, which has a
cooling effect. And in a world in which desertification is continuing
at a rate of about six million hectares a year, that news might have a
significant effect on how we estimate the rates and magnitude of
The Yatir Forest station sits on the edge of the Negev Desert,
a semi-arid zone. While forests are commonly believed to be excellent
"carbon sinks," sucking up the carbon dioxide in the atmosphere, which
is thought to contribute to global warming, the two scientists have
discovered other, potentially significant, opposing effects. While
forests do constitute good carbon sinks, semi-arid forests also absorb
and trap more of the sun's rays than surrounding shrub land, they
found, thus contributing to surface heating.
Semi-arid forests also transfer heat from the trees
into the surrounding air to stay cool, causing more surface warming as
well, the two found.
The Weizmann Institute has been operating the research station
for 10 years, as part of a worldwide project comprised of more than 400
stations and called FLUXNET, which investigates the relationship
between forests, the atmosphere and climate around the globe.
Yatir station is unique because it "is one of very few in the semi-arid
zone, which covers over 17 percent of the earth's land surface, and it
has the longest record of the processes taking place in semi-arid
forests," according to Yakir.
"Although the numbers vary with location and conditions," Yakir
said in a statement, "we now know it will take decades of forest growth
before the 'cooling' CO2 sequestration can overtake these opposing
"Overall, forests remain hugely important climate stabilizers
(not to mention the other ecological services they provide), but there
are tradeoffs, such as those between carbon sequestration and surface
radiation budgets, and we need to take these into consideration when
predicting the future," Yakir said.