Tropical reforestation more effective than temperate afforestation for slowing global warming.
Rainforest tree in Panama. Photo by: Rhett A. Butler.
Preserving forest cover and reforesting cleared areas in the tropics will more effectively reduce temperatures than planting trees across temperate croplands, argues a new paper published in Nature Geoscience.
Using computer models, Vivek Arora and Alvaro Montenegro estimate that converting all the world’s croplands to forests would reduce global temperatures in 2100 by only 0.45°C, a fraction of this rise forecast by scientists based on current emissions trajectories. The authors say their results indicate the importance of reducing greenhouse emissions rather than relying on afforestation in temperate regions.
“Afforestation is not a substitute for reduced greenhouse-gas emissions,” they write.
But the authors find that reforestation in the tropics has a disproportionate cooling effect relative to tree planting efforts away from the Equator, but not because of carbon sequestration. Forests in far northern and southern regions absorb more sunlight than croplands, causing local warming. Meanwhile heat absorption by tropical forests is offset by increased water transpiration, which has a cooling effect.
The net of this means that afforestation in tropical areas is about three times more effective at reducing warming than afforestation in temperate zones.
Arora and Montenegro therefore conclude that protecting and expanding tropical forests is an especially worthwhile approach to helping mitigate climate change.
“Avoided deforestation and continued afforestation in the tropics are effective forest management strategies from a climate perspective.”
Vivek K. Arora and Alvaro Montenegro. Small temperature benefits provided by realistic afforestation efforts. Nature Geoscience PUBLISHED ONLINE: 19 JUNE 2011 | DOI: 10.1038/NGEO1182
(11/12/2009) A new report states that boreal forests store nearly twice as much carbon as tropical forests per hectare: a fact which researchers say should make the conservation of boreal forests as important as tropical in climate change negotiations. The report from the Canadian Boreal Initiative and the Boreal Songbird Initiative, entitled “The Carbon the World Forgot”, estimates that the boreal forest—which survives in massive swathes across Alaska, Canada, Northern Europe, and Russia—stores 22 percent of all carbon on the earth’s land surface. According to the study the boreal contains 703 gigatons of carbon, while the world’s tropical forests contain 375 gigatons.
(08/12/2009) Boreal forests in some of the world’s wealthiest countries are being rapidly destroyed by human activities — including mining, logging, and purposely-set fires — report researchers writing in Trends in Ecology and Evolution.
(01/03/2008) North American forests are storing less carbon due to warmer autumns, reports a study published in the journal Nature by an international team of researchers.
(10/31/2007) Forest fires in the boreal forests of Canada are an important source of greenhouse gas emissions reports a new study published in the journal Nature.
(08/10/2007) Carbon sequestration projects in temperate regions — already facing doubts by scientists — were dealt another blow by Duke University-led research that found pine tree stands grown under elevated carbon dioxide conditions only store significant amounts of carbon when they receive sufficient amounts of water and nutrients.
(12/05/2005) Growing a forest might sound like a good idea to combat global warming, since trees draw carbon dioxide from the air and release cool water from their leaves. But they also absorb sunlight, warming the air in the process. According to a new study from the Carnegie Institution's Department of Global Ecology and Lawrence Livermore National Laboratory, planting forests at certain latitudes could make the Earth warmer.