Carrington, C.M.S.

Abstract - The Lesser Antilles is part of the Caribbean biodiversity hotspot and a priorityfor conservation of its flora is its endemic taxa. Using data from herbarium specimen labels, we recently carried out a preliminary conservation assessment of the 263 seed plant taxa unique to these islands, reporting that 70% of them are potentially threatened. In an effort to make conservation recommendations for the threatened species, we have further analyzed the specimen data for patterns in their distribution. We found that just over 1⁄3 of the region’s endemics are restricted to a single island, and the majority of these are only found at a single location, whereas the others are found at multiple sites on each island. Diversity of regional endemics appears to be associated with larger islands, and while there appears to be a loose correlation between areas of high diversity of regional endemics and local endemism, there are a number of isolated centers of local endemism scattered across the island chain that may be of particular conservation concern. We also detected a relationship between diversity and elevation, with a peak in the number of endemic species occurred at mid- elevations (400–800 m). This correlation translates to a relationship between endemism and habitat type, with elevated numbers of endemics found in rainforest and elfin woodland, both communities that typically occur at mid- to high elevations, respectively. The high-est proportion of threatened taxa is found in restricted and fragmented communities (elfin woodland, summit-herb vegetation, river bank, and moist forest) and the lowest proportion is found in the largest, most contiguous community (rainforest). Focused conservation ac-tion should occur in these important areas where plant endemism is locally high and habitat types are restricted and fragmented.

The Lesser Antilles is part of the Caribbean biodiversity hotspot and a priority for conservation of its flora is its endemic taxa. Using data from herbarium specimen labels, we recently carried out a preliminary conservation assessment of the 263 seed plant taxa unique to these islands, reporting that 70% of them are potentially threatened. In an effort to make conservation recommendations for the threatened species, we have further analyzed the specimen data for patterns in their distribution. We found that just over ⅓ of the region’s endemics are restricted to a single island, and the majority of these are only found at a single location, whereas the others are found at multiple sites on each island. Diversity of regional endemics appears to be associated with larger islands, and while there appears to be a loose correlation between areas of high diversity of regional endemics and local endemism, there are a number of isolated centers of local endemism scattered across the island chain that may be of particular conservation concern. We also detected a relationship between diversity and elevation, with a peak in the number of endemic species occurred at midelevations (400–800 m). This correlation translates to a relationship between endemism and habitat type, with elevated numbers of endemics found in rainforest and elfin woodland, both communities that typically occur at mid- to high elevations, respectively. The highest proportion of threatened taxa is found in restricted and fragmented communities (elfin woodland, summit-herb vegetation, river bank, and moist forest) and the lowest proportion is found in the largest, most contiguous community (rainforest). Focused conservation action should occur in these important areas where plant endemism is locally high and habitat types are restricted and fragmented.

Satellite image-based mapping of tropical forests is vital to conservation planning. Standard methods for automated image classification, however, limit classification detail in complex tropical landscapes. In this study, we test an approach to Landsat image interpretation on four islands of the Lesser Antilles, including Grenada and St. Kitts, Nevis and St. Eustatius, testing a more detailed classification than earlier work in the latter three islands. Secondly, we estimate the extents of land cover and protected forest by formation for five islands and ask how land cover has changed over the second half of the 20th century. The image interpretation approach combines image mosaics and ancillary geographic data, classifying the resulting set of raster data with decision tree software. Cloud-free image mosaics for one or two seasons were created by applying regression tree normalization to scene dates that could fill cloudy areas in a base scene. Such mosaics are also known as cloud-filled, cloud-minimized or cloud-cleared imagery, mosaics, or composites. The approach accurately distinguished several classes that more standard methods would confuse; the seamless mosaics aided reference data collection; and the multiseason imagery allowed us to separate drought deciduous forests and woodlands from semi-deciduous ones. Cultivated land areas declined 60 to 100 percent from about 1945 to 2000 on several islands. Meanwhile, forest cover has increased 50 to 950%. This trend will likely continue where sugar cane cultivation has dominated. Like the island of Puerto Rico, most higher-elevation forest formations are protected in formal or informal reserves. Also similarly, lowland forests, which are drier forest types on these islands, are not well represented in reserves. Former cultivated lands in lowland areas could provide lands for new reserves of drier forest types. The land-use history of these islands may provide insight for planners in countries currently considering lowland forest clearing for agriculture.