Oral Session - Assessing the Consequences of Landscape Change on Ecological and Hydrological Processes Chair(s): Semmens, Darius ¹, ¹ Department of Watershed Management, Tucson, AZ
Friday, April 2, 2004 3:00 PM - 4:20 PM Apollo Room 3

Landslides and their impact on landcover change in the mountains of Guatemala: Consequences for local and regional carbon budgets. Alvarez, Nora^*,1, Restrepo, Carla¹, ¹ Department of Biology, San Juan, PR, USA

ABSTRACT- Mountains represent <20% of the land surface, yet their rivers account for >47% of organic carbon discharged to the ocean. A combination of steep topography, heavy rains, and seismic activity results in landsliding, a process that may account for a large fraction of this carbon. Unlike deforestation, landsliding is a fast process that results in the removal of soil, weathered bedrock, and vegetation over extensive areas. Centered in the mountains of Guatemala impacted by Hurricane Mitch in 1998, we used LandsatTM imagery and landslide coverages from the USGS to identify and quantify the extent to which landslides transformed land cover. After applying an atmospheric correction to the images and removing pixels on slopes <15 derived from SRTM data we followed at two-step approach to classify the images. First, we classified landslides and landcover types using all TM spectral bands over a heterogenous (whole scene) versus homogenous (ecoregion) landscape. Second, we classified the same landscapes using a spectral composite of bands 1, 2 and NDVI. A visual inspection of the images, and the accuracy assessments revealed that the use of TM spectral bands (1-5, and 7) over ecoregions resulted in the best approach for identifying landslides (producer and user accuracies 85.92% and 81.33%, respectively). Estimates of landcover change resulting from landslides in combination with published figures on biomass were used to evaluate local and regional carbon budgets.

KEY WORDS: tropical, landslides, mountains, landcover change, carbon budgets