Professional Experience:

Research Interests:

Streams integrate the land uses and landscape attributes of the watersheds they drain. The aquatic organisms reflect the condition of the watershed and can be used to infer the "health" or condition of the stream. Disturbances or changing conditions in the watershed may reduce the water quality, habitat, or habitable space in the stream to the point where some organisms can no longer survive or there are not enough individuals in a population for long-term persistence.  An emerging area of study is to determine the extent to which this change is gradual and continuous or if it is rapid and abrupt as occurs when a catastrophic threshold is crossed.

I have extremely broad research interests ranging from aquatic to terrestrial, individuals through communities and ecosystems, and microhabitats to landscapes. Although my research is driven more by the question than the system, I often end up where I started - in cold water mountain streams. Most of my current focus is on conservation, restoration, and risk assessment of populations, communities, and the systems they inhabit. I am particularly interested in bridging the worlds of theory and application so that our research findings and theoretical advances are known to and used by natural resources practitioners for more efficient, effective, and responsible management, conservation, and use of our natural resources.

My current research revolves around three related areas: 1) How much is enough - population viability and space/habitat requirements; 2) Restoration and recovery of target species and the systems they inhabit; and 3) Ecosystem assessment/condition diagnostics.  My research group has a new, large effort (The ASTERS Project) aimed at exploring the concepts of thresholds, alternate ecosystem states, and resilience in streams.  You can read more about thresholds and alternate states in my research and others in a recent issue of Chesapeake Quarterly here.

Streams can function as one-dimensional environments for the fish and other aquatic organisms that live there. Any object or event [be it a non-native species such as this brown trout that can outcompete cutthroat trout (top left), physical barriers to movement such as road culverts (above right) or dams, or habitat degradation such as high sediment from erosion from practices in the watershed (bottom left above)] that can limit the distribution or movement of a species can effectively isolate populations and restrict them to small areas.

Some populations were naturally small or existed in isolated habitat fragments in dissected or disconnected landscapes. For a number of natural and not so natural causes, many populations are now faced with limited space and resources and are cut off from other populations. Generally, the smaller the population size, the greater the extinction risk because there are fewer individuals to recover from disturbances such as floods, droughts, or fires, and there is less genetic diversity to fend off inbreeding or allow for future adaptations to changing conditions. Similarly, the more variable the environment, the greater the extinction risk for a given population size. On a larger scale, spatially limited populations may not have all of the habitats necessary to fulfill their life history requirements (e.g., migratory species) or maintain the variation in life history strategies often found in fish populations. Simulation models indicate that the process of population extirpation may take many years or decades from the time a population becomes isolated, fragmented, or reduced in size. In my opinion, one of the greatest threats to fish and wildlife over the next few decades will be the loss of populations due to isolation and spatial limitations.

 

Current and Recent Research Projects:

• Inventory and monitoring protocols for water resources of National Capital Region parks (ended in 2005; National Park Service)

• Landscape determinants of population viability of the Delmarva fox squirrel (ended in 2004; US Fish and Wildlife Service)

 

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The views expressed on this web site are those of the author and do not necessarily reflect those of the University of Maryland Center for Environmental Science, the Appalachian Laboratory, or the Trustees of the University System of Maryland.

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