Professor Simon Lewis

Profile

The main focus of my research is on the impacts and interactions of multiple anthropogenic global change phenomena and tropical forests. I am interested in better understanding how humans are impacting on the 'Earth System', specifically the tropical forest biome.

The main focus of my research is on the impacts and interactions of multiple anthropogenic global change phenomena and tropical forests. I am interested in better understanding how humans are impacting on the 'Earth System', specifically the tropical forest biome.

I have recently been developing an interest in African tropical forests, as over recent decades both data and theory about tropical forests generally (e.g. maintenance of diversity) have been heavily based on information from Latin American forest. However, approximately one quarter of the worlds tropical forest is in Africa, and they may differ substantially different from Latin American forests.

I also remain active in the field of my PhD, attempting to understand forest regeneration, and the impacts of habitat fragmentation on this.

Current Projects

2004-2009 Evaluating Functional and Biodiversity Changes Across Tropical Forests.

Funded of the Royal Society. The text below is reprinted from Royal Society 'Lay Summary' of project

Introduction

Both climate change and tropical deforestation have regularly been in the news for years. We know they are important issues, but they are often dealt with in isolation. This is largely true both in the wider media and within the scientific community. For example, remaining 'virgin' tropical forests are thought by many to be pristine environments. However, we now know that human impacts on the environment, such as rising air temperatures, affect even remote areas. Moreover, the 21st century will see these global environmental changes reach unprecedented levels: air temperatures will continue to rise, and atmospheric carbon dioxide concentrations will reach levels unprecedented over the past 20 million years. Alone, these global changes will change tropical forests, while in concert with other human impacts the implications are likely to be staggering: deforestation alone is predicted to cause the sixth mass extinction in evolutionary history. Indeed, scientists have called this period the Anthropocene: we are living through truly epoch-making times.

My research focuses on the impacts and interactions of multiple anthropogenic global change phenomena and tropical forests. A number of strands of recent research show that apparently undisturbed tropical forests have altered dramatically over recent decades: (1) they have become a net carbon sink, absorbing carbon and buffering the rate of climate change, (2) their tree populations have become much more dynamic, and I have recently shown (3) that these two trends have occurred simultaneously within the same forest stands, as forest productivity has increased. So far however, studies of long-term changes in tropical forests have investigated only stand-level properties: only the behaviour of all the trees together has been studied. These stand-level changes beg several questions: (1) are some tree species becoming more abundant at the expense of others? (2) What do these changes mean for critical ecosystem functions, such as how much carbon these forests store and hence their contribution to either slowing or accelerating the rate of climate change? (3) What drivers are causing such changes? Thus, the aims of this fellowship are to understand the recent, current, and likely future functional trajectory of the tropical forest biome, by conducting the first comprehensive investigation into changes in forest composition and function across the tropics.

Research Methods

I will tackle this ambitious agenda by: (1) using a unique resource of >200 long-term forest monitoring plots from across the tropics where each tree is identified and tracked over time by periodic re-measurement, which I have helped develop, and (2) by collecting and collating currently disparate data on individual species' effects on ecosystem functions, such as carbon storage. Firstly, I will assess where, when and by how much different taxa (species and higher groupings) have altered. Secondly, by assigning each stem in the plot monitoring database with a value for a functional trait, such as the amount of carbon that a species typically holds in its wood, and then assessing the spatial and temporal trends in these traits, I will be able to quantify the impacts of these changes on ecosystem functions, and the likely factor(s) driving these trends. The key barriers to this work have been the lack of plot data, poor understanding of species' ecological behaviour, and inconsistencies in tree nomenclature across the tropics. My recent work has already assembled the plot data needed, while collaborations with other experts (most of whom I already work with) will allow functional trait data to be collated. Finally, the nomenclature problems across space and time for >200,000 tree records, and >5,000 species in the plot database can be practically resolved for the first time, as new Internet tools available this year will allow complex searches across key herbaria worldwide. Hence the discovery of long-term compositional trends, using a variety of statistical techniques, will now be possible for the first time.

Wider Implications

The results from this research will be of great societal importance for two reasons. Firstly, will surviving tropical forests remain a carbon sink - currently equivalent to the fossil fuel emissions of entire European Union - or will rising temperatures and other changes cause them to become a source? Secondly, as tropical forests house more than half the world's species, the interactive balance of millions of plant and animal species is bound to change, even within the largest areas of forest. What does this mean for global biodiversity conservation? On the ground monitoring of forests, as this project proposes, to understand how, when and where changes in composition and carbon balance of tropical forests are occurring will provide essential information, possibly including early warnings of more radical changes. This will assist policy makers and wider civil society to make better-informed choices about the kind of future world we want to live in.

Previous Projects

• 2000-2003 'Changing Tropical Forest Dynamics: a critical evaluation of physical, chemical and biological drivers'.
  NERC funded (with O. Phillips & Y. Malhi).

No teaching at present.

Present Position

• Royal Society Research Fellow

Previous Posts

2001-2003

• Research Fellow, University of Leeds, Changing Tropical Forest Dynamics: a critical evaluation of physical, chemical and biological drivers. Natural Environment Research Council funded position.

2000-2001

• Research Fellow, University of Leeds, Changing Tropical Forest Dynamics: a critical evaluation of physical, chemical and biological drivers. Natural Environment Research Council funded position.

Qualifications and Education

1994-1998

• PhD Tropical Forest Ecology, Department of Plant Sciences, University of Cambridge. Joint with the Biological Dynamics of Forest Fragments Project, Brazil. Thesis title: Treefall gaps and regeneration: a comparison of continuous and fragmented forest in central Amazonia.

1990-1993

• BSc with First Class Honours in Ecology, University of Leeds.

• Lewis, S. L., Phillips, O.L., Baker, T.R., Lloyd, J., Malhi, Y. Tropical forests and atmospheric carbon dioxide: current knowledge and potential future scenarios. DEFRA 'Avoiding Dangerous Climate Change' international Symposium. Invited Speaker. Hadley Centre, Exeter, UK [Presented by Lewis]
• Phillips, O.L., Lewis, S.L., Malhi, Y. A general framework for testing hypotheses of drivers of ecological change in mature tropical forests. May 2004. NASA workshop on Amazon carbon dynamics. Invited speaker. New Orleans, Louisiana, U.S.A. [Presented by Phillips]
• Phillips, O.L., Baker, T., Malhi, Y., Lewis, S.L. Ecological changes in old-growth neotropical forests, at the October 2003 BIOMERGE Adapative Synthesis II workshop, Missouri Botanical Garden, St. Louis, Missouri, U.S.A. [Presented by Phillips]
• Lewis, S.L., Phillips, O.P., Malhi, Y. & 27 others. Impacts of global change on tropical forest dynamics, at the September 2003 British Ecological Society annual meeting, University of Manchester, U.K. [Presented by Lewis]
• Lewis, S.L., Phillips, O.P., Malhi, Y. & 27 others. Impacts of global change on tropical forest dynamics, at the July 2003 Association for Tropical Biology & Conservation international meeting, University of Aberdeen, Scotland. [Presented by Lewis]
• Lewis, S.L., Phillips, O., and Malhi, Y. August 2002. The What's driving global changes in tropical forests?: a framework for testing causal mechanisms, hypotheses, and some initial results. Association for Tropical Biology, STRI, Panama: Tropical Forests, Past, Present, Future. [Presented by Lewis]

Research groups and institutes

• Ecology and Global Change