Vermont Water Resources & Lake Studies Center
Dr. Michael Coe seminar
April 12, 2013, noon, Johnson House, UVM
- By Elissa Schuett
The Vermont Water Center and Gund Institute will host
Dr. Michael T. Coe (http://www.whrc.org/about/cvs/mtcoe.html)
April 12, noon, Johnson House
"Feedbacks between deforestation, climate, and hydrology in the Amazon"
Deforestation in the Amazon causes important changes in the energy and water balance by changing how incoming precipitation and radiation are partitioned among sensible and latent heat fluxes. Pasturelands and croplands (e.g. soybeans and corn) generally have a higher albedo and decreased water demand, evapotranspiration, and atmospheric turbulence compared to the forests they replace. These differences in the water and energy balance work at a variety of time and space scales and the combined influences on regional hydrology are complex. Observations from micro (2) to meso (100s km2) and large (10,000 km2) spatial scales in the Amazon clearly show that deforestation reduces evapotranspiration and increases soil moisture and stream flow. These changes result from the reduced leaf area index, altered phenology, decreased root density and depth, and total water demand of the pasture and crops compared to the native vegetation. Global and meso-scale climate model studies indicate that once deforestation occurs on a very large scale (> several 100,000s km2), atmospheric feedbacks may reduce regional precipitation. Replacing forest with higher albedo, less water-demanding crops and pastures leads to reduced net surface radiation, decreased moisture convergence over the basin, decreased water recycling, and reduced precipitation. The south-southeastern Amazon region has been most affected by these changes because of the combination of large-scale historical deforestation and its geographic position in a climatological and ecological transition zone. Given the current distribution of protected lands in south-southeastern Amazon, mitigation of future ecological impacts of externally and regionally driven climate changes will depend heavily on leveraging existing policy mechanisms to strengthen the protection of forests on private lands.