Researchers studying the Amazon Basin have revealed unprecedented details about the size, age, and species of trees across the region by comparing satellite maps with hundreds of field plots.
The findings will help assess more accurately the amount of carbon each tree can store—a key factor in carbon offset schemes, in which trees are given a cash value according to their carbon content, and credits can be traded in exchange for preserving trees.
Existing satellite maps of the area have estimated trees’ carbon content based largely on their height, but don’t account for large regional variations in their shape and density.
The findings could help quantify the amount of carbon available to trade in forest areas. This in turn could help administer carbon offsetting more accurately, and improve understanding of how much carbon is stored in the world’s forests, which informs climate change forecasts.
“Satellites can’t see species, but species really matter for carbon. This is the big challenge for the next generation of satellite and field scientists, ” says Oliver Phillips, professor of geography at the University of Leeds.
“New satellites will be launched soon that will be more sensitive to forest structure and biomass, but we must ensure we have sufficient ecological ground data to correctly interpret and use them.”
‘Live fast, die young’
For the study, published in Global Ecology and Biogeography, scientists studied a database of thousands of tree species, taken from more than 400 hectare-sized plots across the nine countries of the Amazon Basin—Brazil, Bolivia, Colombia, Ecuador, French Guiana, Guyana, Peru, Suriname, and Venezuela. The survey was developed as part of a sister project, known as RAINFOR, involving more than 200 researchers across the region.
Forests in the basin’s northeast on average store twice as much carbon as those in the southwest, as a result of soil, climate, and species variation. The northeast has slow-growing, dense-wooded species, while the southwest is dominated by light-wooded trees with faster turnover. In these naturally dynamic, light-wooded forests the species simply can’t store as much carbon.
“Tree species and dynamics are mostly controlled by soil conditions, largely unseen from above”, says Carlos Quesada, RAINFOR soil scientist at the National Amazon Research Institution in Manaus, Brazil. “The younger, shallow soils of the western Amazon tend to restrict root growth—a case of live fast, die young.”
“Developing our understanding of this aspect of forests, in the Amazon and elsewhere, could be hugely important for our climate,” says lead author Ed Mitchard from the University of Edinburgh.
The Natural Environment Research Council funded the study.
Source: University of Leeds