Research in the lab centers on understanding how the amount, arrangement, and identify of habitat in landscape influences the distribution and abundance of species. I am particularly interested in how coupled climate change-landscape interactions alter species distributions. My students and I conduct field work, do experiments, and develop geospatial models to understand species responses to climate and landscape change. Below are descriptions of some recent research projects the lab is involved in.
Habitat loss and fragmentation in Neotropical forests
I began working in a naturally-fragmented landscape in the southern Amazon Basin of Bolivia for my dissertation, and have continued to work in Bolivia ever since. My main research site in Bolivia occurs in a climate and biogeographic transition zone where the moist forests of the Amazon meet and intergrade with dry forests and savanna characteristic of the Cerrado and Chaco biomes to the south and east of the Amazon. At the El Refugio-Huanchaca field station in the Parque Nacional Noel Kempff Mercado, the forest-savanna transition is abrupt, and many forest islands of varying size and distance from the continuous forest are surrounded by seasonally-flooded savanna.
I surveyed amphibian and reptile populations throughout the landscape at El Refugio between 2002 and 2004. In contrast to most studies in terrestrial fragmented landscapes, I found that distance to continuous forest was a much stronger predictor of species richness than forest area. I suspect that the importance of geographic isolation in this system is a function of both ecological traits of the study organisms and landscape context.
From 2012-2013 I worked with a Bolivian student using field-based desiccation trials to measure interspecific variation in desiccation resistance in forest and savanna at El Refugio. We confirmed the importance of desiccation resistance as a predictor of species distributions among forest islands: desiccation-prone species are dispersal limited and do not occur on the most isolated forest islands in the landscape. I suspect that desiccation resistance is a key trait of amphibians that may determine responses to habitat loss, fragmentation, and climate change, and students in my lab continue to do lab and field work to understand the importance of this key trait.
I believe that landscape context also determines how species respond to habitat loss and fragmentation. A complex, heterogeneous matrix likely supplies resources (abiotic refugia, prey availability, reproductive sites) at greater rates than a homogeneous matrix. As a result, species distributions may be less affected by characteristics of habitat patches when surrounded by heterogeneous compared with homogenous matrix types. Similarly, patches surrounded by a structurally-similar, low-contrast matrix are probably more functionally connected than patches surrounded by a very dissimilar, high-contrast matrix. I am particularly interested in understanding how matrix heterogeneity and contrast interact to affect species distributions in landscapes using meta-analysis, geospatial modeling, experiments, and field surveys.
My students and I have recently begun work in a fragmented forest landscape at the Reserva El Silencio in the Magdalena River Valley of north central Colombia. At El Silencio, humans have driven the conversion of forest to pasture for cattle ranches, resulting in a landscape mosaic of primary and secondary forest, and pasture of different ages. We will be surveying vertebrate populations and communities in remnant forest and throughout the landscape to understand how habitat amount and fragmentation alter environmental conditions and species distributions in this anthropogenically-modified system.
Landscape and climate change effects on endangered vertebrates
I am involved with several ecological modeling projects designed to forecast species responses to changing climate and landscape structure in the United States. With colleagues from other universities, NGOs, and the federal government, we have developed GIS-enabled species distribution models and landscape connectivity models to provide support for large-scale conservation planning.
Key insights to emerge from our ecological modeling work include the importance of using a multi-model framework for both distribution and connectivity modeling, the identification of a key conservation corridor for vertebrates in the southeastern USA along the Cumberland Plateau ecoregion in Tennessee, and identification of Florida’s vertebrates most threatened by climate and landscape change. On going work in 2016-2017 will focus on integrating our results with other large-scale connectivity efforts and downscaling of model predictions to prioritize parcel-level conservation options.