Working with multiple collaborators in Congo and Gabon, we quantify forest structure and composition and monitor changes associated with human activities. We are interested in both basic and applied questions relating to Central African forests. Why are they less species rich and higher in biomass than their Amazon counterparts? How do human activities (logging, hunting, industrial agriculture) affect forests? Are there management actions that can mitigate the impact of human activities on forests and their inhabitants? Can we detect changes in phenology, forest composition, or structure as a result of climate change?
We are answering these questions via several projects.
Gabon National Resource Inventory
National forest inventories are one of the key elements of forest monitoring systems, but most tropical countries lack such inventories, which are expensive and time-consuming to establish and maintain. In 2012, we worked with the Government of Gabon and a multinational scientific team (USFS, UCLA, Leeds Univ.) to create a National Resource Inventory (NRI) to measure the country's biological resources, with an initial focus on carbon stocks. The NRI consists of a countrywide network of forest plots located in a stratified, random design. By combining field data with remote sensing data, particularly LiDAR, we are quantifying the country's carbon stocks. We are in the process of using this exceptional dataset to calculate different carbon pools, including soil carbon, coarse woody debris, and aboveground biomass, as well as determine the environmental variables that drive variation in carbon densities. The NRI is being grown to a network of 500 permanent field plots to monitor carbon flux in the future. (See summary here.)
Effect of land use on forest carbon
Due to their lack of development, many Central African countries have low deforestation rates and high forest cover. In the last decade, however, these countries have built infrastructure and invited in foreign investors as steps towards growing and diversifying their economies. Extractive industries, including timber production, mining, palm oil agriculture, and rubber plantations are now on the rise. The challenge is for Central African governments to avoid going the way of West Africa and Southeast Asia by regulating companies to reduce biodiversity loss and carbon emissions to a minimum. In Gabon we link science to policy by asking questions such as: can palm oil production in tropical forest be compatible with no-net emission pledges? and where and how should agriculture take place to minimize environmental damage?
Combining field data and LiDAR, we worked with OLAM-Gabon and the Gabon Parks Agency to quantify the CO2 emissions from palm oil agriculture in Gabon to find that there is little opportunity for palm production to meet zero-net carbon emissions. During summer 2015, we are starting a second project to investigate the carbon and biodiversity losses from palm oil agriculture.
While deforestation from agriculture is relatively easy to detect, estimating carbon losses from selective logging has proven a more difficult task. In collaboration with Sassan Saatchi (UCLA/JPL), we are pairing field measurements with aerial LiDAR in Gabon to test new methods of measuring forest degradation. The USAID SilvaCarbon program is supporting this project.
Forest diversity and biomass: Sangha Plot Network
In 2005, Connie Clark, David Harris (Edinburgh Botanical Gardens) and I set up the Sangha Plot Network -- a system of 30 1-ha plots that straddle a gradient of selective logging and hunting. Since then, we have followed the survival and growth of more than 11,000 individual trees. Our preliminary results suggest that even 30 years after timber harvest, logged forest still contain significantly lower biomass than undisturbed forest. We are now evaluating the relationship between forest productivity and species diversity as well as linking rates of forest growth with selective logging disturbance.