Tiffany Harvey

Curriculum Vitae: 

Harvey_CV.pdf

Riparian corridors of the desert southwest constitute a small percentage of the landscape, yet they support a high diversity and high densities of avian species.  These ribbons of green in the otherwise brown landscape are used by birds both as migratory stopover sites and also as breeding habitat for many species, providing water, shade, and lush habitat for food and cover from predators.  However, altered hydrologic conditions, cattle grazing, and invasive species have put these habitats at risk.   The most prominent invader is tamarisk (Tamarix spp.), or "saltcedar," a taxa of introduced ornamental plants that began invading the riparian systems in the west in the late 1800s.  Much debate exists over what the management strategy of tamarisk should be, but the plant is generally viewed as unsuitable habitat for birds.  When a river system is already subject to other stresses, the spread of tamarisk can be so severe that seas of it can occur without any native vegetation.

Damage to these riparian systems has already led to a decrease in populations of many avian species that rely on riparian habitat for any or all parts of the year.  For instance, while the Southwestern Willow Flycatcher winters in lush tropical forests in Central America, this species comes north to the rivers and washes of the desert Southwest only to breed.  This species is now listed as Endangered.  Many other species that are obligated to use these rivers during the breeding season are also showing signs of decline.

My thesis work includes exploring how varying densities of tamarisk, Tamarix ramosissima, affect what birds are found breeding in the area on the upper San Pedro River.  I am also investigating whether remotely-sensed characteristics of the physical landscape can be used to spatially model riparian breeding bird communities by applying a GIS model based on NDVI (Normalized Difference Vegetation Index) and looking for correlations between remotely-sensed measurements, bird community structure, and the actual vegetation occurring at sites along the San Pedro River.  A better understanding of how breeding birds respond to the invasion of tamarisk and whether these patterns can be mapped on a large scale using remote sensing will hopefully have a role in the management and protection of these very important ecosystems.