"This proposal directly addresses one of the great challenges in Earth system science: how will the terrestrial biosphere respond to global atmospheric change and, more specifically, how does the biodiversity of the biosphere moderate or affect that response? This proposal focuses on tropical forests. We are currently unable to understand how tropical forests will respond to climate change because there is (i) a data-deficit: we simply do not have the data to understand the relationship between tropical forest diversity and ecosystem science; and (ii) a theory-deficit: we have not developed an adequate and quantitative theoretical framework to relate functional biodiversity to ecosystem function. This proposal will directly address both these deficits.Firstly, I will build a unique global tropical ecosystems monitoring network (GEM), that will measure in comprehensive detail the structure, productivity and metabolism of 47 tropical forest sites over a globally synchronous 2.5 year period. In addition, I will develop a large dataset of functional diversity by collecting functional traits of leaves and wood.Secondly, the theory deficit will be addressed by drawing on the recent development of a novel mathematical formalism that links biodiversity to ecosystem function. This formalism focuses on the distribution of traits within an ecosystem, links this distribution to ecosystem function, and develops predictions of how the shape of the distribution is controlled by environment, biological interactions and previous states of the ecosystem. I will further develop this theory, test its predictions against my unique field data, and ultimately use it to develop a new biodiversity-focussed way of representing tropical forests in ecosystem and Earth system models. This new approach used to answer questions such as: how does the functional diversity of tropical forests affect their resilience to climate change, and how will this diversity respond to atmospheric change?"