Kaleidoscopic image revealing the biodiversity of the Amazon rainforest. Each color represents different chemical signatures, revealing information about biodiversity and growth rates. Photo courtesy of the Carnegie Airborne Observatory.
Severe drought conditions in 2010 appear to have substantially increased tree mortality in the Western Amazon, a region thought largely immune from the worst effects of changes occurring in other parts of the world’s largest rainforest, reported research presented last week at the fall meeting of the American Geophysical Union (AGU). The findings suggest that the Amazon may face higher-the-expected vulnerability to climate change, potentially undercutting its ability to help mitigate greenhouse gas emissions by absorbing carbon dioxide through faster growth.
The results are based on months of mapping using an advanced airplane-based system that reveals both the physical and chemical structure of a forest at extremely high resolution. The system — known as the Airborne Taxonomic Mapping System (AToMS) — was developed by a team led by Greg Asner of the Carnegie Institution.
According to Nature News, Asner found that the 2010 mega-drought triggered a 4 percent die-off in trees in the most affected area, a sharp increase over the normal rate.
“Limb loss increased as much as four-fold as the team flew into the epicenter of the drought, while the rate of downed trees increased by about 50 percent,” writes Jeff Tollefson. “But trees are big and take time to come down, which means the rate of downed trees will increase in the coming years.”
The findings, which are undergoing peer-review, suggest that the Amazon may be less resilient to climate change than other studies have predicted. Global warming is expected to increase the incidence of drought across much of the Amazon Basin, a prediction already coming to bear — since 2005 the region has experienced the two worst droughts on record.
The preliminary results come shortly after a study published in Nature warned that forests worldwide are vulnerable to elevated tree mortality due to drought stress. The research found that 70 percent of the tree species sampled are particularly vulnerable to reduction in water availability.
Two views of tropical forest canopy in Madre de Dios, Peru from the CAO. The lower kaleidoscopic image, taken in the Manu Biosphere Reserve, reveals biodiversity signals that are missed with the naked eye. Photos courtesy of the Carnegie Airborne Observatory.
Carnegie’s system uses powerful optical, chemical, and laser sensors to create high-resolution, three-dimensional maps of vegetation structure and plant communities. AToMS can capture detailed images of individual trees at a rate of 500,000 or more per minute.
RELATED STUDIES
- Asner, G.P., et al. High-resolution Mapping of Forest Carbon Stocks in the Colombian Amazon. Biogeosciences Discuss., 9, 2445-2479, 2012
- Mascaro, J. at al. Evaluating uncertainty in mapping forest carbon with airborne LiDAR. Remote Sensing of Environment (2011), doi:10.1016/j.rse.2011.07.019
- Asner, G.P., et al. (2011). A universal airborne LiDAR approach for tropical forest carbon mapping. Oecologia DOI 10.1007/s00442-011-2165-z
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