A Clearer Picture of Tropical Carbon
Tropical forests, alongside boreal forests and wetlands, are prime ecosystems for storing carbon. Now, researchers have created a new high-resolution map of carbon storage in tropical forests that could play an important role in effective forest management
By DYLAN WALSH | The New York Times | March 27, 2012
Woods Hole Research CenterAbove-ground biomass in southern Asia and Oceania, based on data gathered by laser satellite technology. Dark green indicates the highest potential for carbon storage.
Shades of russet, yellow and deep green between the tropics of Cancer and Capricorn circle the globe, providing the clearest picture yet of the world’s above-ground tropical biomass – essentially, plants and trees. The data are mapped at a resolution that is four times greater than any other previous measurements.
Researchers led by Alessandro Baccini at the nonprofit Woods Hole Research Center gathered two years of laser satellite, or Lidar, data to develop the image. “Lidar is very good at telling you how tall and how complex the vertical structure of the forest is,” said Dr. Baccini, an assistant researcher at the center. “If you know how tall trees are, and how many you have, then you’re very close to knowing what the carbon stock is,” he said.
More than 300 field visits across Latin America, Africa and Asia were used to confirm and calibrate the Lidar data on carbon stocks before the final measurements were projected onto an interactive map.
Both the map and the data are available online, fulfilling the goal of allowing any institution, researcher, policymaker or student to use the information.
The Indonesian government, for example, has expressed interest in using the maps to reduce the carbon footprint of the palm oil industry, which is responsible for widespread destruction of the country’s tropical forests through development of palm plantations.
The map “has tremendous potential for advocating changes in use policies,” said Peter Schlesinger, an expert in deforestation at Carbon Decisions International, a private forest management company. Governments, developers and forest managers can now consider a new dimension in land use planning: carbon sequestration potential.
The information might also encourage a new source of national revenue through the United Nations program on reducing emissions from deforestation and forest degradation, known as REDD, by highlighting the lands that would be most profitable to protect. REDD provides payments to developing countries for reducing such emissions.
Although he says he sees great potential in the project, Dr. Baccini also recognizes the limitations: the data are mapped in 500-square-meter (1.9-square-mile) plots, still quite coarse for genuinely effective management. “Deforestation often happens at a very, very small scale,” he said.
Mark Ashton, a forest ecologist at Yale University, agrees. “Degradation is very patchy and dynamic along the forest edges,” he said. Effective land management strategies sometimes require meter-by-meter sensitivity.
Such tight resolution will be impossible for Lidar to achieve in the foreseeable future, as neither the frequency of measurements nor the optic sensitivity of the satellites is adequate.
Additionally, no space-borne Lidar currently exists for the specific measurement of carbon density in biomass, Dr. Baccini said. He and his team were instead using the GLAS satellite operated by NASA, which was designed to measure ice-sheet topography and associated temporal changes; from this satellite they could only infer carbon density.
The maps’ exclusive focus on above-ground biomass is also problematic, Dr. Ashton said, because soil is a fundamental component of the carbon cycle. A recent study found that soil and roots might store more than 25 percent of the carbon in tropical forests.
Nonetheless, the potential of the maps has already been affirmed through the partnership in Indonesia, Dr. Baccini said. He also described collaborative work with indigenous groups in South America that were involved in the initial field measurements. The new quantitative understanding of forest cover is helping those groups “sit at the table with government and discuss policy in their land,” Dr. Baccini said.
The data used in the mapping were summarized in a January article in Nature Climate Change for which Dr. Baccini was the lead author.
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