We are studying how land-use decisions affect the health of an area’s ecosystem. We are building models that show the consequences of land-use choices on the Chesapeake Bay health and local economies. The project is designed to provide area-specific consequences of land-use scenarios, so that decision-makers can compare impacts and determine which land-use plan best enhances a community’s overall interests and goals.
Why We Care
The health of the Chesapeake Bay is directly linked to population growth and land use in the watershed. Since 1950, the population of the watershed has nearly doubled to nearly 17 million and will grow another 20 percent by 2030. More forests, farms, and other lands will be transformed into subdivisions, shopping centers, or parking lots. This urban growth increases hypoxia, contaminants, disease-causing organisms, and invasive species in the Bay and its tributaries. Incrementally, the landscape and the way-of-life of millions people living in the watershed are affected. Moreover, up to $60 billion in fishing, tourism, property, and shipping activities are at stake.
There is a need to educate communities about the profound consequences of each of their land-use choices. What is lost when a new shopping center or youth center is built? Are those losses offset by what is gained? While we’ve long known that the way we use land influences the health of the Bay, we cannot yet quantify for a planning committee or commissioner how a specific land-use proposal under consideration will affect, for example, their local swimming and fishing interests. Our project is a step in this direction.
What We Are Finding
Early results of our six watershed model measurements have shown, as expected, that the agricultural-dominated Corsica watershed has elevated nutrients and turbidity. However, it is not suffering from oxygen problems commonly associated with eutrophication. Relative to the other rivers, the Corsica has a lot of fish and high fish species diversity. The surprise was that these fish are not healthy—all measures of fish health (disease prevalence, parasite burden, weight at length, etc.) were poor. Conversely, the developed Magothy River has low nutrients, but severe seasonal oxygen problems and elevated sediment contaminants. Fish are less abundant and less diverse, but generally healthy. The forested Rhode River also has fewer fish than the Corsica, but fish are healthy, nutrients in the river are low, and oxygen levels are good. These results highlight the trade-offs that exist in ecosystem based management and will serve as the basis for ecosystem response modeling.
What We Are Doing
In Phase 1, we are comparing estuarine conditions across different landscapes (e.g., forested, agricultural, urban) to understand how land use affects ecosystem health. In Phase 2, we are packaging our findings into decision-making tools that illustrate the resulting trade-offs among incremental development, Chesapeake Bay health, and local economies.
We are measuring the same parameters in six watersheds as models: the agriculture-dominated Corsica and Sassafras Rivers, the urban-dominated Magothy and Middle Rivers, and the forest-dominated Rhode and Nanjemoy Rivers. We are building build two kinds of models: cumulative stressor models to identify and rank the severity threats to rivers and impact models to predict the consequences (system level response) of those threats. When coupled with research on valuing ecosystem services, these models lay the foundation for land use planning and prioritization of mitigation or restoration efforts. For the first time, we’ll be able to quantitatively answer questions about, for example, how developing 2 percent of a county’s forest affects its fish and water quality
To meet our goals, we are also developing better measures of ecosystem health to track change and predict how the environment will respond to land-use scenarios. Looking at cellular level, whole-animal, and community-level responses give us a more thorough understanding of what is happening and its ecological significance. We will sample across the entire food chain, including sediment, fish, oysters, bacteria, and smaller benthic animals, to understand how they respond to environmental stresses. By using a suite of indicators representing all of these levels and animals, we can more accurately and more quickly assess ecosystem health and pinpoint problems and communicate consequences.
In addition we are expanding the study to make sure that the models and conclusions drawn from studying these six watersheds can be generalized to the rest of the Bay. Does the size of the river or the salinity of the water affect the magnitude of the impact of the development? If we model development scenarios for the Magothy River, can we expect the same trade-offs to be found in developing the James River?
Getting this science into the hands of communities and decision-makers is equally important. We’ve started working with watershed groups (e.g., Maryland and Virginia’s coastal programs, The Nature Conservancy, River Keepers, the Chesapeake Bay Foundation) who are interested in using our findings to educate their constituencies, complement their monitoring, and develop science-based land use plans and policies. They are helping us identify the most important questions and teaching us how our information and tools can be incorporated into land-use planning and other coastal management discussions. These groups have also asked us to produce reports on the health of individual rivers in addition to our current reports on the health associated with a type of land use.