Deforestation and the spread of non-native species

Abstract

Over ninety percent of Madagascar’s original forests have been deforested, and the population of Madagascar has doubled in the past forty years, further exacerbating problems of local, unsustainable forest use. While research on Madagascar's endemic species is common, less information is known about its non-native species and the increasing effects they have on local biodiversity as the forest becomes more degraded. This study aimed to fill this gap in knowledge. We collected data on human forest use and the presence/absence of five non-native plant species: Mangifera indica, (cultivated) Albizia lebbeck (cultivated), Mucuna pruriens (non-cultivated), Lantana camara (non-cultivated), Tamarindus indica (origin unknown) in and around the periphery of the Ankarana National Park, northern Madagascar. Data was collected systematically along transects across three different forest types which ranged low to high human disturbance. We found that the presence of historically cultivated non-native species positively correlated with human disturbance. In contrast, historically non-cultivated species did not show this correlation to human disturbance levels. Our results indicate that anthropogenic modification of habitats could impacts the densities and spread of cultivated species. This study increases understanding of the negative effects that humans have on densities of non-native species in disturbed habitats, the effects of roads and human access points, and illustrates the importance of natural history knowledge of non-native species regarding their anthropogenic cultivation histories.