Our research proposal directly addresses the following scientific question which is a priority for this announcement: What are the consequences of climate and sea level changes and increased human activities on coastal regions? Our proposal focuses on mangrove wetlands, which are found primarily in the tropics and sub-tropics along coastlines or river deltas. Mangroves are part of a coastal biological complex that also includes seagrass beds, and coral reefs. Mangroves are highly specialized, salt-tolerant plants, which include trees, shrubs, ferns and palms. Mangroves are especially vulnerable to global changes because of potential variation of sea level and increased hurricane (severe storm) frequency and intensity in certain areas. However, human impact is the main threat on this ecosystem because of clearing and degradation to make way for shrimp farming, charcoal industries, run-off of chemicals from agricultural lands, or simply for urban expansion. We propose:
1. to generate enhanced SRTM elevation data to estimate vegetation height in wetlands dominated by mangroves by;
a. concurrent LIDAR mapping;
b.semi-empirical modeling of radar scattering in mangroves to correct for the height bias;
c. differential height measurements.
2. to estimate productivity within the complex mangrove mosaic, in the process improving our understanding of its underlying controls, and extend production models to regional scales.
3. to develop a landscape-scale understanding of recovery from disturbance, which is of course related to the innate productivity of the site.
The proposed methodology relies on SRTM (Shuttle Radar Topography Mission) interferometric radar data to estimate canopy height and upscaling of ecosystem models. Our approach uses LIDAR (Laser altimeter), AIRSAR and ground collected data to calibrate and validate SRTM products and also derive empirical scattering models for the land cover types found in mangrove forests. First, we will rebuild SRTM elevation data with ground truth data as well as adaptive filters to improve height accuracy on a regional scale. Then we will investigate two methods for canopy height determination: penetration estimate and differential height. The penetration estimate and models are mainly used to construct height bias look-up tables as a function of land cover. The differential height is computed as the interferometric elevation difference between the mangrove vegetation and over the water as an estimate of canopy height. The proximity of mangrove wetlands to coastal waters offers a unique opportunity to use this technique. The derived vegetation height models will be used in the MANGAL model to estimate mangrove productivity and also storm surge recovery on a regional scale. The SRTM and AIRSAR data is readily available at JPL, which is responsible for processing. Florida International University and the International Hurricane Center own a LIDAR instrument that we propose to fly for this investigation. The team from the University of Louisiana at Lafayette have developed the mangrove productivity models. The University of Queensland and CSIRO will investigate different applications of this new data.