Roads through rainforests: measuring biodiversity impacts of infrastructure in the tropics

Abstract

Across the globe, a vast network of roads accompanies and aids anthropogenic activity, with wide ranging impacts on species and ecosystems. This road network is expanding at a rapid rate, particularly across the biodiverse tropical region. This thesis explores how roads are aecting species in the tropical region at a variety of spatial scales, using both meta-analyses of existing data and collecting empirical evidence. The impact of roads on the richness and abundance of invertebrate and vertebrate species across tropical regions was explored using meta-analysis (Chapter 2). Further meta-analysis investigated variation in road response for one group particularly sensitive to road impacts, mammals, using life history traits as predictors of abundance changes (Chapter 3). The eect of roads on mammal species is further explored in two case studies from dierent contexts of roads in tropical forests. Camera traps sampled mammal communities across accessibility gradients created by distance to roads and human population centres, across three sites in Brunei Darussalam (Chapter 4) and within a logging concession in Gabon (Chapter 5). Analysis revealed substantial declines in species, which varied depending on characteristics of the species, the roads, and the landscapes they were in. Results indicates that large mammals with specialised diets, carnivores in particular, are at risk of abundance declines as road networks expand. Distance to roads was an important predictor of species habitat use based on hierarchical multi-species occupancy models of data from Brunei. In Gabon, distance to village explained variation in both species richness and encounter rate. Overall, the thesis suggests that the expanding road network is a real cause for conservation concern. The eect of road related access to landscapes for hunting in particular needs to be controlled to prevent species from going extinct and meet targets for both sustainable development and biodiversity conservation.