Land use change, stream connectivity, and the health of freshwater ecosystems in the Amazon’s agricultural frontier

Marcia Macedo, Columbia University, mnm2115@columbia.edu (Presenter)
Ruth DeFries, Columbia University, rd2402@columbia.edu
Michael Coe, Woods Hole Research Center, mtcoe@whrc.org

Over the last decade the southern Amazon has been one of the most active deforestation frontiers on the planet. As agricultural land uses become more prevalent in the landscape, stream ecosystems may become degraded through several mechanisms, including fragmentation of the stream network by impoundments, changes in the amount of light and nutrient inputs from riparian areas, and alterations to both the quality and quantity of water flowing within streams. This project takes a multi-scale approach to evaluate some of these impacts in the headwaters of the Xingu Basin. At the landscape scale, we combine data from moderate and high resolution sensors (MODIS, ASTER, and Landsat 5) to characterize land use history, as well as the distribution of impoundments and riparian forests. At the microwatershed scale, we use field data collected in 12 catchments dominated by pasture, soy croplands, and forest to evaluate the local impacts of these land uses on stream ecosystems. Landscape scale results reveal a stream network that is highly fragmented and increasingly dominated by agricultural land uses, with important consequences for headwater streams. Streams draining pasture catchments were characterized by warmer (27.3°C) mean diel temperatures than those draining forest (24.5°C) and soy (26.3°C) catchments. Furthermore, the mean diel temperature range of pasture and soy streams was twice that of forest streams, indicating that agricultural catchments have greater variability and more extreme daily maximum temperatures than forested catchments. Together with changes in connectivity, such increases in temperature can exert a strong influence on the quality and distribution of stream habitat, thus negatively impacting stream biota and the overall integrity of aquatic ecosystems. Preliminary models suggest that these impacts could be substantially mitigated through improved land use practices, including the preservation and restoration of riparian areas and management of impoundments in the landscape.

Presentation Type:  Poster

Session:  Global Change Impact & Vulnerability   (Tue 11:30 AM)

Associated Project(s): 

• DeFries, Ruth: Tropical Deforestation and the Land-Water Interface: Linking Land Use, Stream Connectivity, and the Health of Freshwater Fish Communities ...details

Poster Location ID: 226