Tropical forests hold more species of plant and animal than any other kind of terrestrial environment, and store large amounts of greenhouse gases in their trees and soils. Yet most of us are aware that they are also highly threatened by human activities, with media attention often focussing on deforestation - when forests are replaced with alternative land-uses, such as agriculture and cattle ranching. However, forests are also being modified in other ways, when trees are felled for the commercial extraction of timber, or when forest burn in abnormally dry years. These events are known as forest degradation, and affect a larger area of land than deforestation alone. The widespread nature of forest degradation means it is very important to understand whether these human-modified forests are performing similar roles as intact primary forests. How much carbon and nitrogen do they hold, and are these nutrients cycled between the leaves and the forest floor at similar rates as in primary forests? Can these ecosystem processes by predicted by characteristics of the vegetation itself (such as leaf shape and format, and the rate it carries out photosynthesis). And crucially, what are the implications of these changes for the future of these forests - are they able to resist additional modification? This project will answer these questions in two separate Brazilian biomes, the Atlantic Forests of Sao Paulo and the Amazon forests near the city of Santarem. The data we collect in two years of fieldwork will be used to improve our understanding of forest functioning, and can help develop computer simulations of forests. These simulations can then be used to examine how forests may respond to changes in climate, or other human impacts such as logging or fire. These forests are also crucial for biodiversity conservation, as many rare and endemic species are only found in landscapes where forests have already been heavily modified by humans. It is important to assess to what extent they help conserve these species, and what factors could be managed to improve their conservation value. Tropical forests hold a bewildering number of species, and so many of these species are yet to be described. It is therefore important to focus on groups of species which are well known, making birds and plants are two ideal species groups. The detailed work on forest functioning will take place in a limited number of forest plots, as we are limited by the many precise measures that need to be taken over time. In contrast, biodiversity is much quicker to sample, allowing us to examine much larger areas of around one million hectares in the Amazon and in the Atlantic Forest. As well as examining biodiversity in these landscapes, this project will also assess changes in species traits, which are characteristics that link species to the many tasks they perform in nature. By doing so, we will be able to examine the extent to which human-modified forests are losing key ecosystem processes, such as pollination from long-beaked hummingbirds, or the ability of trees to assimilate and store large quantities of carbon. This will provide us with a much better idea of how the many different kinds of human activity are affecting biodiversity, which is important if we are to design landscapes that help protect the many species of conservation concern. For too long, important scientific knowledge has remained locked away in learned journals, and has failed to inform and influence policies. We are determined not to let this happen with our research, as we believe it will produce important insights that can help us preserve the ecological stability of tropical forests and the biodiversity they contain. To facilitate these impacts, we will make every effort to disseminate our findings. These activities include producing a series of short films for YouTube, linking with local schools, and writing policy briefs.