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Health and Environmental Effects Research

Habitat Alteration

Most simply, a habitat is the place and conditions in which an organism lives. Habitats are defined by the physical characteristics of an environment and the interconnected living beings that derive their life-support from that environment. While it may be easy to understand that alterations to habit can threaten the well-being of organisms and species, quantifying the consequences of habitat alteration is a complex problem. The challenge lies in describing the relationship between organisms and their habitat in adequate and accurate enough detail to enable scientists to predict the effects of changes. This information is crucial to setting priorities for protection and restoration efforts.

Planned research under the topic of Habitat Alteration includes work to collect information about how changes in vegetated aquatic habitats affect species that are of particular concern because of their commercial, societal, or ecological value. Also under development are models that will link changes in a habitat to the responses of populations dependant on that habitat. Special emphasis is placed on evaluating how human activities and other stresses affect salmon, other native fish, and wildlife.

View information about the Implementation Plan for Habitat Alteration Research within the Aquatic Stressors PDF file (PDF, 197 pp, 3.21 MB, About PDF).


Wetland are

A wetland area with wildlife.

Vegetated Aquatic Habitats

Vegetated aquatic habitats are environments such as freshwater or estuarine wetlands, marshes, and seagrass beds. These environments are special because they are some of the most widespread and productive types of aquatic habitat. Many recreationally and commercially important fish, shellfish, and wildlife, as well as rare and endangered species, depend on vegetated aquatic habitats as sources of food, shelter, and nurseries. Aquatic vegetation also strongly influences substrate type and stability, wave and current energy, and water quality-all key factors that determine the suitability of a given environment to serve as a habitat for a given species.


The first step in understanding how populations respond to changes in their habitat is to chose specific species for study and to determine the ways these species are dependant upon a given habitat. Based on this understanding, scientists can assess the ways a population responds to alterations of its habitat. This data can subsequently be used to develop computer-based numerical models designed to quantitatively predict the effects of habitat alteration on a multitude of organisms and to extrapolate information from a well-studied area to another less well-studied area or to extend predictions to a larger spatial or temporal scale.

Native Fish

Observed declines in the number of salmon and other native fish in the Pacific Northwest and in the Great Lakes have spurred EPA scientists to research the factors responsible. This research includes examining how the management of upland within the watershed affects lacustrine and riverine habitats and takes into account the fact that fish migrate between water bodies at different times and at different stages of life.

Ducks in water

Ducks in their natural habitat.


EPA scientists are interested in developing and improving ways to assess the risks to wildlife populations that are posed by chemical and non-chemical stressors across large regions. An on-going case study and demonstration project is that of the common loon and its responses to mercury contamination and habitat alteration. Research activities within the loon project include the development of geospatial modeling methods to assess the relative effects of heterogeneously distributed stressors, including dietary methylmercury, habitat degradation, acidification, and human disturbance. Also under development are methods to identify spatial relationships among stressors, potential interactions among stressors, and the relative risks among potential stressors to populations of loons at varying spatial scales.

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