Are Forests Breathing Easier? Thank City Dwellers

Urbanization and going back to nature seem like incompatible concepts, but there’s a body of evidence that says increasing migration to cities has definite environmental benefits.

An obvious one is that living close to, or even where you work takes cars off the road and reduces CO2 emissions.

Also, as people increasingly move to urban centers, pressure on global forests eases. Because forests double as the planet’s lungs, they are a natural and effective answer to sequestering carbon emissions. The more those particular lungs can hold, the better.

A study published last month by Science, suggests the world’s forests are doing better than anticipated, and the reason for that is traced to increased urban living.

The study, led by U.S. Forest Service researcher Yude Pan (and cited by The New York Times’ Green blog), found the world’s established forests absorb 2.4 billion tons of carbon dioxide each year, or about a third of the total released by burning fossil fuels.

Pan says the study is the most comprehensive analysis of the global carbon budget to date, showing that forests are a far more significant carbon sink than previously thought. At the same time, the report emphasizes the devastating effects of tropical deforestation and the need to protect trees that perform an enormous global service.

Of the three different types of forests studied — boreal, temperate and tropical — the paper shows that tropical forests are the most dynamic in capturing CO2. During the 17-year study period, from 1990 to 2007, an international team of researchers found that established tropical forests alone captured about 1.2 billion tons of CO2 a year, accounting for 55 percent of the total established carbon sink in forests.

Of the three different types of forests studied — boreal, temperate and tropical — tropical forests are the most dynamic in capturing CO2. During the 17-year study period, from 1990 to 2007, researchers found that established tropical forests alone captured about 1.2 billion tons of carbon dioxide a year, accounting for 55 percent of the total established carbon sink in forests.

Tropical deforestation in places like Indonesia and Brazil appears to be the only thing holding forests back from even greater sequestration--net deforestation.

Wait. Isn’t global deforestation getting worse? Perhaps not.

A report published last year by Hector Maletta, an economist at the Universidad del Salvador in Buenos Aires, says deforestation rates in Brazil’s Amazon rainforest have actually fallen by more than 75 percent off recent peak reached in 2004.

Maletta this week said, "The majority of deforestation nowadays is caused by subsistence farmers clearing land for subsistence crops, and some remaining clearing for cattle pasture by ranching agribusinesses; Brazilian deforestation is now concentrated in only one State (Pará), on which current forest protection is becoming focused.

“Besides deforestation for agricultural or logging purposes, another factor affecting carbon emission from forests is the use of wood and charcoal for cooking. This is rapidly diminishing in Brazil due to urbanization and especially due to increasing use of bottled natural gas in rural kitchens, as revealed in regular household surveys, and the same trend is observed in other countries covering parts of the Amazon basin such as Bolivia, Peru or Colombia.”

Deforestation in the Amazon will never stop entirely; but Maletta believes the net change will continue to shrink.

Scientists Joseph Wright and Helene Muller-Landau of the Smithsonian Tropical Research Institute suggest that secondary growth forests are expanding at a very brisk pace—for every acre of land deforested each year, more than 50 acres are waiting to take their place, according to the United Nations’ Food and Agriculture Organization 2005 “State of the World’s Forests” report.

Wright estimates that reforestation rates are more than double deforestation ones, meaning that the world’s forests may grow back faster than the need to chop them down.

And as Wright argues, the reasons for that are simple: migration and urbanization.

 

[Image Credit: Slash and burn by Jagubal, Flickr Creative Commons]