January 18, 2012
New study evaluates impact of land use activity in the Amazon basin
Highlights signs of transition to a disturbance-dominated regime
A new paper published today in Nature reveals that human land use activity has begun to change the regional water and energy cycles - the interplay of air coming in from the Atlantic Ocean, water transpiration by the forest, and solar radiation - of parts of the Amazon basin. In addition, it shows that ongoing interactions between deforestation, fire, and climate change have the potential to alter carbon storage, rainfall patterns and river discharge on an even larger basin-wide scale.
The research was led by the Woods Hole Research Center (WHRC). Lead scientist Eric Davidson (WHRC) and 13 Brazilian and US colleagues from universities, government and the NGOs, all of whom participated in the Large-Scale Biosphere-Atmosphere Experiment in the Amazon (LBA), produced a framework by which the connections among climate change, agricultural expansion, logging, and fire risk can be evaluated. The framework considers changes in greenhouse-gas emissions, and energy and water cycles. Using it they found signs of transition to a disturbance-dominated regime in the southern and eastern portions of the Amazon basin. Co-author Jennifer K. Balch adds: “One strong sign of a new disturbance regime is the high number of recent large-scale wildfires, which are a by-product of intentional fires in Brazil’s ‘arc of deforestation.’” These fires are frequent, occurring every few years, compared with every couple centuries in the past.
Why is this important? Humans have been part of the Amazon basin forest-river system for thousands of years, but the expansion and intensification of agriculture, logging and urban development, and their synergistic impacts are beginning to stress the natural integrity of the ecosystem. As co-author and professor of environmental physics at the University of Sao Paulo in Brazil, Paulo Artaxo says, “Tropical forests are big players in the global balance of climate and carbon, and the Amazon is the biggest of the lot.” Dr. Artaxo adds, “We wanted to build a scientific base from which to learn how the region could be developed sustainably.” Since the Amazon River produces about 20% of the world’s fresh water discharge and the Amazon forest holds about 100 billion tones of carbon (10 years’ worth of global fossil fuel emissions), it is important that economic development in the region proceed along sustainable paths that do not degrade the ecosystem services provided to local, regional and global communities by the forests and rivers of the region.
“The studies in this review, document changes in river flow, sedimentation in rivers, and lengthening of the dry season in the southern and eastern flanks of the Amazon Basin,” notes Dr. Davidson. “Whether similar changes are likely to occur in other parts of the basin will depend on the interplay of management decisions and the impacts of climate change during the next few years and decades.”
The project showed that the Amazon forest is resilient to considerable climatic variation from year to year, but that this resilience can be exceeded by severe or prolonged drought. The evidence points to a system in biophysical transition, highlighting the need for improved understanding of the trade-offs among land cover, carbon stocks, water resources, habitat conservation, human health, and economic development in future scenarios of climate change and land-use change.
Efforts in Brazil to curb deforestation have led to a significant decline in the clearing of forests in the Amazon basin, from nearly 28,000 km2 per year in 2004 to less than 7,000 km2 in 2010, but at the same time, the incidence of fire has not decreased, indicating continued risks for forest degradation through climate-fire interactions.
With Brazil poised to become a major economic power, the study emphasizes that improvements in scientific and technological capacity, and human resources will be required to guide and manage future sustainable development in the region.
The Woods Hole Research Center addresses the great issues for a healthy planet through science, education, and policy. We combine satellite remote sensing with field research to study, model, map, and monitor Earth's chemistry and ecology, and we use this knowledge to address the planet's great issues. We work around the Earth, from local to global scales, including the Amazon and Cerrado of South America, the Congo Basin and East Africa, the high latitudes of North America and northern Eurasia, and across the United States. We are unique in the depth of our science capability in combination with our commitment to the environment.
A Nature ‘World View’ article written by Dr. Paulo Artaxo about the LBA project can be found here: http://www.nature.com/news/break-down-boundaries-in-climate-research-1.9844
Following is a sample of the media coverage of this study:TG Daily: Amazon basin becoming carbon emitter
Mongabay.com: Deforestation, climate change threaten the ecological resilience of the Amazon rainforest
BBC (radio): Carbon emissions from Amazon forest
Listen to the Nature podcast "The Amazon basin in transition" (starts at 6:20):
Ian Vorster, Director of Communications,
Cattle-pasture fire burning through the night in Mato Grosso, Brazil, the southern Amazon. Image Credit: Jennifer K. Balch, 2006.
Smoke from a deforestation fire generating a pyrocumulous cloud in Mato Grosso, Brazil. Image Credit: Jennifer K. Balch, 2006.
Over 140,000 active fires were detected on a single day (08/23/2010) in this NASA MODIS image that spans 2500 km across southern Latin America, including Brazil, Bolivia, Argentina, Peru, Chile, and Paraguay (http://earthobservatory.nasa.gov/IOTD/view.php?id=45449). Image Credit: Jeff Schmaltz, MODIS Rapid Response Team at NASA GSFC.
A map of the study area with related information. A thick blue line demarcates the hydrologic Amazon basin; isopleths of mean daily precipitation during the driest months of the year in mm are overlain onto four land-cover classes. The arrow emphasizes the trend from continuously wet conditions in the northwest to long pronounced dry seasons in the southeast. The scientists had to consider this natural trend and related information in their study on the interactions between global climate, land use, fire, hydrology, ecology and human activity. Image Credit: Paul A. Lefebvre