School of Geography and the Environment

Examining the effect of recent drought in Amazonia

The drought which affected the Amazon in 2005 was extreme, recorded as the most intense dry period since weather records began in the mid 20 th Century. With its problems, comes the unique opportunity to evaluate the impacts and the response of biodiversity to extreme conditions, which may be synonymous to future climates in a warming world.

Described as the ‘global centre of tree diversity', and containing between a quarter and a third of the worlds biodiversity, the Amazon is a vital component of the biosphere. In the last 25 years biomass and forest growth rates have been rising, possibly resulting in a moderate carbon sink, but this may be under threat from climate change. This study aims to use the recent drought to examine how these tropical humid systems respond to intense drought, assess their recovery, and possible subsequent decline.

Amazonian climates usually have no dry season, and are expected to be unlikely to adapt to even modest seasonal drought. Therefore, impacts are likely to exist at many levels, as shown by earlier studies. They are expected to include:

• Increases in rates of mortality
• Increased litterfall
• Changes in rates of leaf production and leaf loss
• Physiological effects of drought stress: inhibition of photosynthesis

Project Objectives

The research will take place throughout much of 2006, with field work between January and April. The main objectives of the project will be to produce the following outputs:

• Map the spatial and temporal extent of the drought and its forest canopy using field researchers in the region
• Impact of the drought on tree-level ecological indicators
• Impact of the drought on stand-level ecological indicators (biomass, growth, mortality, mode of mortality, composition)
• Quantify drought responses and recovery of ecosystem processes (tree growth, litter-fall, leaf area index and root turnover)