Do local environmental policies, land use planning, and fragmentation within lake catchments affect lake water clarity?

摘要

Michigan has 11,037 inland lakes, 3,288 miles of Great Lakes shoreline, and 36,000 miles of streams (Michigan Department of Environmental Quality (MDEQ) 2009). These freshwater aquatic resources require diligent management to preserve and protect both their quality and quantity. Federal, state and local governments share responsibility for setting policy and implementing management. However, land use planning decisions are primarily made at the local level of government throughout the United States. My research aimed to understand how local (government) environmental regulations affect inland lake water quality, as measured by water clarity. My questions were: 1) is water clarity negatively impacted by fragmentation (i.e. multiple jurisdictions within one lake catchment)?, and 2) does local land use and environmental policy have a positive effect on inland lake water clarity? I expected that lake water clarity would be better in unfragmented catchments and catchments with stronger local land use and environmental policies than in fragmented catchments with weak environmental policies. I answered these questions by examining 420 lakes and their corresponding local regulations in southwest Michigan, which is an area that is dominated by agriculture and urban land use. I sent a survey to local jurisdictions to gather local policy information. I used GIS to combine land use/cover and landscape characteristics with policy data at the township scale. I used ANOVA and multiple regressions to analyze the relationships between water clarity and policy while controlling for land use/cover and landscape factors. I found that water clarity was negatively affected by fragmentation (the number of townships within a lake catchment). However, once local environmental policy was included in the regression, fragmentation was no longer significant. I also found that some specific policies had a positive effect on water clarity. The complex and dynamic interactions between land use and water quality make it difficult to evaluate the sole effects of policy on water quality, which could be a reason why little scholarly research has been completed on the direct policy to water quality links.