|Shields Jr, Fletcher|
Submitted to: Journal of the American Water Resources Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/23/2006
Publication Date: 2/1/2006
Citation: Shields Jr, F.D., Langendoen, E.J., Doyle, M.W. 2006. Adapting existing models to examine effects of agricultural conservation programs on stream habitat quality. Journal of the American Water Resources Association. 42(1):25-33.
Interpretive Summary: Aquatic ecosystems are increasingly threatened by degradation associated with agriculture. The federal government is increasing funding for agricultural programs that provide incentives for farmers to take land out of cultivation, plant trees, establish buffers of natural vegetation along streams and watercourses, and other activities intended to protect the environment. However, the benefits of these expenditures have not been quantified. A recently initiated program seeks to estimate benefits using computer models, but these models focus primarily on water quality and have very limited capacity to simulate stream habitat quality. A preliminary assessment of the capabilities of these models was conducted, and an approach for deriving ecologically-meaningful information from the model outputs was outlined. This approach, if adopted, could assist administrators of agricultural conservation programs to achieve greater returns in ecological services for public funds invested.
Technical Abstract: Annual expenditures by the federal government in the US for agricultural conservation programs increased about 80% with passage of the 2002 Farm Bill. However, environmental benefits of these programs have not been quantified at the national level. A national project is underway to estimate the effect of conservation practices on environmental resources. However, watershed models designated for the aforementioned national project have minimal habitat assessment capability and even more limited links to ecological condition. Freshwater aquatic ecosystems face especially severe threats within agricultural landscapes, and assessments of ecological benefits should consider stream corridors and associated buffers. Major impairments to aquatic ecosystems in many watersheds consist of physical habitat degradation not water quality. This paper describes approaches for adding components to these models to allow rudimentary stream habitat quality assessments. At least five types of variables could be examined for ecological impact: stream flow, water temperature, stream bed material type, large woody debris, and hydraulic conditions at base flow. All of these variables are influenced by the presence, location and quality of buffers. Generation of ecological or habitat quality indices might provide a stepping stone between habitat evaluation and economic benefit quantification.