Research

How Does Climate Change Affect Invasive Plants?

I use bioclimatic envelope modeling to project how invasive plant habitat could shift with climate change. This research is important for identifying areas at risk from invasive species before they become widespread and unmanageable. I have developed plant distribution models for several common invaders in the United States, including cheatgrass (Bromus tectorum), yellow starthistle (Centaurea solstitialis), leafy spurge (Euphorbia esula), kudzu (Pueraria montata), and cogongrass (Imperata cylindrica)

The image at left shows the distribution of cheatgrass climatic habitat.

How Will Climate Change Affect Subsistence Agriculture in South Africa?

The objective of this project is to assess how climate change will affect agricultural productivity in South Africa, and, in turn, how changes in agricultural productivity could threaten biodiversity conservation. I use time series of remotely sensed data to assess agricultural yield in emerging (subsistence) agriculture. I then use bioclimatic envelope modeling to assess the impacts of climate change on agricultural productivity, and project risk to neighboring areas with high conservation value.

The image at left shows a range of productivity (annual phenology) of corn in commercial and emerging agriculture in South Africa.

How Can Geospatial Analysis Aid Conservation Planning?

GIS analysis of remote-sensing derived maps creates a powerful tool for identifying potential drivers of change. I have used this type of integrated analysis to determine how land use influences cheatgrass invasion, how topography influences expansion of pinyon-juniper woodland, and how grazing affects ecosystem greenness. This research is useful for conservation planning because it provides a framework for assessing landscape scale risk from land use and species invasion.

The image at left shows how probability of cheatgrass occurrence increases with proximity to roads.

What Can Inter-annual Phenology Tell Us About Ecosystem Processes?

Time series of remotely sensed data have long been used to study land cover trends, but what are those trends actually measuring? As part of an effort by the National Phenology Network to better link satellite and ground measurements, I am working with scientists at Sevilleta Long Term Ecological Research Station to compare multi-temporal ASTER remote sensing data to contemporaneous field measurements during the 2007-2008 growing seasons.

The image at left shows a sample plot at Sevilleta where scientists are measuring community greenness.