Research focus
My research focuses on understanding how global change drivers impact biodiversity in the tropics. To do this, I take advantage of field-based studies, experiments, molecular biology and statistical tools to gain new insights into how humans are reshaping the world's ecosystems. Currently, most of my work is based in Costa Rica.
Below I describe some of my current research projects
Below I describe some of my current research projects
Current Projects
Spatiotemporal community dynamics under land use change
Humans are fundamentally restructuring ecological communities. However, our understanding of how these communities respond to global change drivers is often limited to short-term studies and space-for-time substitutions. To overcome some of these limitations, I am exploring the temporal dynamics of avian communities using 17+ years of population monitoring data in 44 sites that span a land use change gradient across 4 regions of Costa Rica. In particular, this project aims to understand how trends in species richness may hide the degree to which intensively managed landscapes change through time.
Interactive effects of human land use and climate change on population dynamics
Shifting climatic conditions are affecting habitats globally, often with negative impacts on biodiversity, especially in the tropics, where species have limited ranges and have evolved in fairly aseasonal climatic conditions. Although climate change may not yet be a primary driver of species extinctions, it responsible for the reshaping of ecological communities and driving species range shifts. Indeed, many of the contemporary impacts of changing climate on biodiversity are likely to manifest through alterations of population-level processes long before local extinctions occur. The effects of climate change on species populations do not occur in isolation, but interact with other global change drivers. Notably, the impact of climate change on can be strongly mediated by land use context. The conversion of forest to agriculture has been repeatedly shown to alter biodiversity, often with dramatic declines in species richness and abundance with increasing land use intensity. While it is well established that these global change drivers interact, most work has analyzed these factors in isolation.
Using high-resolution climate data in combination with long-term datasets, we are using hierarchal models to understand both the individual and interactive effects of land use and climate change on population size in bird communities. Early results suggest that land use intensity greatly exacerbates the impact of climate on population size.
How does land use change restructure interactions between trophic levels?
The conversion of natural habitat for agricultural production is the greatest contemporary threat to biodiversity in the tropics. While extensive work has described how human land use change alters biological communities within a given trophic level, much less work has explored how interactions between trophic groups responds to increasing habitat disturbance. In this project, we are using extensive field sampling of avian and arthropod communities in combination with DNA metabarcoding of avian fecal samples to identify how use of arthropods changes with increasing land use intensity. We are combining this information with remotely sensed measurements of landscape complexity to understand how both biotic and abiotic gradients restructure trophic interactions. In addition, describing how resource use changes with increasing land intensity has potential to shed light on why some species are able to colonize and persist in human-dominated landscapes while other species are driven to local extinction.
Does fragment size mediate the strength of trophic cascades driven by invasive rats in Hawaiian Kipuka?
Invasive species are driving global scale changes to biodiversity and ecosystems. While the individual effects of invasive species have been well-demonstrated, it is increasingly clear that interactions between global change drivers may produce qualitatively different outcomes for biodiversity. Tropical islands are particularly susceptible to invasive species, with invasions often resulting in species extinctions and alterations to how these ecosystems are structured and function. Coupled with pressures imposed by invasive species on native biota is the high rate and severity of land use change and fragmentation of island habitats. This modification can alter the impact of invasive species by limiting invasive species population size or by altering the functional affects in invaded systems.
In Hawaii, the introduction of rats Rattus rattus and R. exulans has driven large shifts to the structure of endemic communities. With few large mammals on Hawaii, rats may act as top predators, and as such their presence may have cascading effects on other trophic levels. While the presence of rats has been shown to create trophic cascades, it is unclear if habitat size mediates the impact rats have on plant communities. Given the widespread distribution of rats and habitat fragmentation, understanding their interaction may help guide the management of invasive species.
Humans are fundamentally restructuring ecological communities. However, our understanding of how these communities respond to global change drivers is often limited to short-term studies and space-for-time substitutions. To overcome some of these limitations, I am exploring the temporal dynamics of avian communities using 17+ years of population monitoring data in 44 sites that span a land use change gradient across 4 regions of Costa Rica. In particular, this project aims to understand how trends in species richness may hide the degree to which intensively managed landscapes change through time.
Interactive effects of human land use and climate change on population dynamics
Shifting climatic conditions are affecting habitats globally, often with negative impacts on biodiversity, especially in the tropics, where species have limited ranges and have evolved in fairly aseasonal climatic conditions. Although climate change may not yet be a primary driver of species extinctions, it responsible for the reshaping of ecological communities and driving species range shifts. Indeed, many of the contemporary impacts of changing climate on biodiversity are likely to manifest through alterations of population-level processes long before local extinctions occur. The effects of climate change on species populations do not occur in isolation, but interact with other global change drivers. Notably, the impact of climate change on can be strongly mediated by land use context. The conversion of forest to agriculture has been repeatedly shown to alter biodiversity, often with dramatic declines in species richness and abundance with increasing land use intensity. While it is well established that these global change drivers interact, most work has analyzed these factors in isolation.
Using high-resolution climate data in combination with long-term datasets, we are using hierarchal models to understand both the individual and interactive effects of land use and climate change on population size in bird communities. Early results suggest that land use intensity greatly exacerbates the impact of climate on population size.
How does land use change restructure interactions between trophic levels?
The conversion of natural habitat for agricultural production is the greatest contemporary threat to biodiversity in the tropics. While extensive work has described how human land use change alters biological communities within a given trophic level, much less work has explored how interactions between trophic groups responds to increasing habitat disturbance. In this project, we are using extensive field sampling of avian and arthropod communities in combination with DNA metabarcoding of avian fecal samples to identify how use of arthropods changes with increasing land use intensity. We are combining this information with remotely sensed measurements of landscape complexity to understand how both biotic and abiotic gradients restructure trophic interactions. In addition, describing how resource use changes with increasing land intensity has potential to shed light on why some species are able to colonize and persist in human-dominated landscapes while other species are driven to local extinction.
Does fragment size mediate the strength of trophic cascades driven by invasive rats in Hawaiian Kipuka?
Invasive species are driving global scale changes to biodiversity and ecosystems. While the individual effects of invasive species have been well-demonstrated, it is increasingly clear that interactions between global change drivers may produce qualitatively different outcomes for biodiversity. Tropical islands are particularly susceptible to invasive species, with invasions often resulting in species extinctions and alterations to how these ecosystems are structured and function. Coupled with pressures imposed by invasive species on native biota is the high rate and severity of land use change and fragmentation of island habitats. This modification can alter the impact of invasive species by limiting invasive species population size or by altering the functional affects in invaded systems.
In Hawaii, the introduction of rats Rattus rattus and R. exulans has driven large shifts to the structure of endemic communities. With few large mammals on Hawaii, rats may act as top predators, and as such their presence may have cascading effects on other trophic levels. While the presence of rats has been shown to create trophic cascades, it is unclear if habitat size mediates the impact rats have on plant communities. Given the widespread distribution of rats and habitat fragmentation, understanding their interaction may help guide the management of invasive species.