My research focuses on understanding the drivers and ecological impacts of human activities, particularly agriculture and how these vary over time and in space.

Recent News

Successful first course on UAS for environmental monitoring

Last week I was in Italy to help teach a new course on UAS for Environmental Monitoring, which was organized by Salvatore Manfreda and Kelly Caylor, and run under the aegis of the University of Basilicata. Xurxo Gago from the Universitat de les Illes Balears provided instruction on multicopters and estimating crop water use from thermal imagery. We held classes in the ancient city of Matera (a remarkable place), while flight training and data collection practicals took place in farmland to the south near Metaponto. By the end of the week, 17 students successfully ran a data collection mission (using fixed-wing UAS from, processed the resulting imagery into orthomosaics and DEMs, and did some initial data analysis, including a comparison of leaf area index measurements made in the field, UAS-derived BNDVI, and Landsat-derived NDVI (Marc Mayes from Brown University found that Landsat 8 had imaged the area during that week, making a very nice comparison). The student presentations and lectures are available here.  We hope to run this course again next summer, so please watch this space if you are interested in learning how to use UAS to close the gap between field and spaceborne observations. Click here for some photos or video.


High Environmental Costs Relative To Benefits of Farming African Wet Savannas

Screenshot 2015-03-17 10.07.02My colleagues and I published a paper yesterday in Nature Climate Change that examines the environmental costs relative to the potential crop and biofuel production benefits of farming Africa's higher rainfall savannas.  We found that only 2-11% of these areas qualify as high benefit/low cost in terms of maize and soy yield potential relative to the carbon that would be released from land transformation, while only 1-3% of the land would produce biofuels that meet EU standards for greenhouse gas savings. We also found that this region has mammal and bird diversity similar to that tropical forests.  These findings suggest that African savannas cannot produce commodity crops or biofuel for global export without incurring significant environmental cost, and that new crop production in these areas should be prioritized for meeting the continent's rapidly growing food demand. We emphasize the need for more detailed, country-level analyses to identify the areas where food production can be maximized for the least ecological cost. Please follow the links below for more detail.

Article Press Op-ed1 Op-ed2

AAAS Session on New Earth Observing Methods

My Valentine's day this year was spent en route to San Jose, where I attended the AAAS meeting to convene a session on "Advances in Earth Observation: Enabling New Insights into Global Environmental Change", featuring Matt Hansen, Kelly Caylor, and Maggi Kelly. The goal of the session was to illustrate how new methods and hardware, such as advanced parallel processing, in-field environmental sensors, and data integration platforms, are starting to fill in the spatial and temporal gaps in our current abilities to observe ecological processes. We had a pretty nice turnout, despite the fact that we were scheduled for 8 am on Sunday morning!

October trip to Zambia

Screen Shot 2014-11-20 at 13.08.57I was in Zambia a few weeks ago, working with colleagues at the Zambia Agricultural Research Institute (ZARI) on new projects [1, 2, 3].  I spent part of my time setting up PulsePods (the fantastic tool being developed by my colleagues Adam Wolf, Kelly Caylor, Ben Siegfried, and Eric Wood) at a few trial sites, in preparation for larger scale deployments that will happen next year.  The pods provide in-field measurements, returned via cell phone SMS, of crop growth and micrometeorology, and will provide key data for scaling up model-derived crop yield estimates to crop to larger extents. Below are a few photos from deployments at ZARI and near Chirundu along the Zimbabwe border (and near the confluence of the Kafue and Zambezi Rivers),  with Sesele Sokotela and Stalin Sichinga of ZARI, and with Muke Mukelabai (and colleagues) at the Zambia Meteorological Department.

Trends in water availability for African maize, 1979-2010

We recently published a paper in Environmental Research Letters that examines changes in the water available for growing maize in sub-Saharan Africa between 1979 and 2010. We identified trends in rainfall, potential evapotranspiration (PET, which is the atmospheric demand for water), and the ratio of the two (also known as the aridity index), and also quantified the factors responsible for changing PET. You can follow the links below to several stories that provide a fuller overview of the findings.