A new study shows that tropical vegetation contains 21 percent more carbon dioxide than previous similar studies had suggested.The study produced maps of carbon storage of forest, shrub lands, and savannas in the tropics of Africa, Asia and South America.
Published in the journal Nature Climate Change, the study was conducted by scientists from Woods Hole Research Center (WHRC), Boston University, and the University of Maryland who created the “wall-to-wall” map with a spatial resolution of 500 metres by 500 metres.
The results from this study, lead researchers believe that current models may overestimate the net flux of carbon into the atmosphere due to tropical vegetation loss by 11 to 12 percent, meaning that when vegetation is lost – deforestation – more carbon is being lost than previously anticipated.
In fact, the scientists estimated, for example, that tropical forests in America store 118 billion tons of carbon, a fifth more than had been previously indicated.
For countries who are trying to meet requirements under the United Nations Framework Convention on Climate Change (UNFCCC) and to participate in international schemes such as Reducing Emissions from Deforestation and Forest Degradation (REDD+), these studies with their refined findings allow for a more accurate estimate of the carbon being lost to deforestation.
“For the first time we were able to derive accurate estimates of carbon densities using satellite LiDAR observations in places that have never been measured,” said lead author Alessandro Baccini, an assistant scientist at WHRC. “This is like having a consistent, very dense pantropical forest inventory.”
“We worked closely with collaborators in 12 countries around the tropics to collect the field data needed to calibrate the satellite measurements and ensure relevance for their national reporting,” said co-author Nadine Laporte, a WHRC associate scientist, who coordinated field measurements in Africa.
“The paper is important for two reasons,” said co-author and WHRC senior scientist Richard A. Houghton. “First, it provides a high-resolution map of aboveground biomass density for the world’s tropical forests. Previous maps were of much coarser resolution and yielded wildly different estimates of both regional totals and spatial distribution. Second, the paper calculates a new estimate of carbon emissions from land-use change in the tropics.”
According to Woods Hole Research Center, the calculation of carbon emissions was done by “using the co-location of biomass density and deforestation to assign a more representative carbon density to the forests cleared. Previous estimates used ‘average’ biomass densities that may have biased emissions’ estimates. In short, the approach will lead to better tracking of changes in biomass density resulting from degradation and growth.”
“The study represents a major step forward in the effort to map the current state of global tropical biomass stocks,” commented Greg Asner, an ecologist at the Carnegie Institution for Science. “The 500m resolution of the map will help countries implement activities to improve forest management and to help fight climate change through reduced carbon emissions from deforestation.”
Global measurements of where carbon is accumulating and where it’s being lost will be used to better quantify how many carbon credits would be needed to reduce carbon emission under the UNFCCC and, when carbon is valued, to quantify financial rewards. As Richard A. Houghton said, “Your forest may be worth more if it’s accumulating more carbon than another forest.”
“Coupling the Lidar and field measurements is what makes this study and our map so unique, and powerful” notes study co-author and WHRC senior scientist Scott Goetz. “Without measurements from a satellite-based Lidar, a study of this nature would not have been possible. We need that capability going forward.”
Source: Woods Hole Research Center