Ecological life zones of Saint Lucia

Aim The purpose of this study is to apply geographical information and arti ficial neural network (ANN) technologies in assessing ecosystem distributio n on the island of Saint Lucia, as well as to develop an improved ecologica l classification using Holdridge's system of natural life zones. Location Saint Lucia is a Caribbean island state located at 14 degreesN and 61 degreesW and of a land area of 616 km(2). Methods The main inputs for classifying life zones were a 25-m x 25-m digit al elevation model of Saint Lucia (DEM), mean annual temperature and annual total precipitation. The DEM was initially obtained by digitizing contour lines on a topographic map. Elevation-temperature regressions developed for Puerto Rico were used to generate point-estimates of mean temperature acro ss the island of Saint Lucia. A generalized (trained) ANN was employed to c reate an annual total rainfall surface for the island. The variables of lon gitude, latitude and elevation were used to construct the rainfall model. C omparison of predicted and observed total precipitation revealed that the A NN explained over 95% of variability exhibited in the observed data, within a standard error of estimate of 123 mm (similar to6% of the total precipit ation). Results Three complete and three transitional life zones were identified as occurring on Saint Lucia. Twelve per cent of the island was classified as tropical premontane moist/wet, 20% as tropical premontane wet, 6% as subtro pical dry/moist, 29% as subtropical moist, 26% as subtropical moist/ wet an d 7%, as subtropical wet. Conclusion Quality of life zone delineation depends on an objective applica tion of universally accepted criteria and available terrain analysis techno logies.