Assessing habitat protection regimes in Tanzania using AVHRR NDVI composites: Comparisons at different spatial and temporal scales

Abstract

Studies assessing temporal changes in vegetation using satellite imagery are complicated by: (1) high interseasonal and interannual variation in phenology that make vegetation comparisons difficult; (2) anthropogenic pressures on the habitats that vary by geographic region and habitat type; and (3) spatial resolution and processing characteristics of available satellite data that differ substantially. This paper addresses these concerns while examining the effects of various forms of protection on different habitat types in Tanzania. First, a long-term (1982-94) vegetation trend was calculated from monthly Normalized Difference Vegetation Index (NDVI) composites to reduce the effect of seasonal fluctuations. Second, we controlled for confounding variables such as habitat type, elevation, aspect and location as well as anthropogenic factors such as fires, roads and refugee camps. Finally, vegetation changes in protected areas and habitat types were examined in order to compare results produced by the different spatial and temporal data (8 km, 7.6 km and 1.1 km). While some results were consistent across spatial and temporal scales, many were not. We therefore recommend that, if possible, analyses of changes in vegetative health be conducted at more than one temporal and spatial scale before management recommendations are put forward.