Dry forests of the Galápagos: a comparative assessment of a World Heritage Site

Abstract

Despite worldwide knowledge of the importance of the Galápagos archipelago, there is little comparative plot data from the forests in the dry regions. We examined patterns of woody plant (≥2.5cm diameter at breast height (DBH)) species richness and structure using Gentry’s transect method (0.1ha) on the three largest islands in the Galápagos. We identified the conservation status of woody plants within the dry forest region, assessed forest cover and change in the region, and compared field results to other tropical dry forests in the Pacific. Of the 22 species encountered (11 native, 11 endemic), there were no non-native species and only one threatened species. Isabela, Santa Cruz and San Cristóbal have similar overall levels of species, genera, family and liana richness per site, but significantly different tree species richness, density and tree height per transect. Geospatial databases identified 51 species (native 40%, endemic 60%) of woody plants (≥2.5cm DBH) within the dry forest region of the Galápagos and 13 species (10 from the genus Scalesia) on the IUCN Red List. There is an estimated 551.97km2 of dry forest in the Galápagos and there has been little change (<0.01%) in forest cover from 2000 to 2015. Dry forests of the Galápagos have similar levels of species richness to Hawaii and the Marquesas but contain lower densities, basal areas and tree heights than other dry forests in the Pacific. These dry forests appear to be the best preserved and protected tropical dry forest in the Pacific.