This story first appeared in the SERC quarterly newsletter winter 2005/2006

Mapping It Out

When it comes to predicting, and ultimately protecting, healthy ecosystems, it's not just how much land is developed or how much is farmed that matters. It's where and how. According to studies by Donald Weller, Matthew Baker, Ryan King, and Thomas Jordan, the arrangement of different land uses and their relationships to one another and the topography all play an important role in predicting the impact of land use on aquatic systems.

It sounds like common sense: A forest between a farm and a stream will block or absorb more nutrient runoff than a forest that is not associated with a farm. However, many current methods of predicting the impacts of land use on streams don't factor in this type of information. Rather, they treat all streamside forests the same, whether or not they are downhill from a source of nutrient runoff.

"'The simple proportions of disturbed land cover types, such as cropland or developed land, in a watershed can be good predictors of aquatic conditions," Weller said, "'but focusing on source areas and how things are connected to the stream tells us more of what we want to know."

SERC researchers are developing models that account for spacial arrangement of landuse when determining landuse impact on ecosystem health. For instance, farmland that lies directly upstream from a watershed should represent a more significant impact on watershed health than farmland situated away from a watershed

Using Geographic Information Systems (GIS) to analyze data from contour maps, land cover maps and other sources, the researchers have developed new methods that factor in such things as the distance of various types of land use to the water, how topography affects the direction of runoff from disturbed areas, and amount of forest along the path of water flow between nutrient sources and streams. Their work provides potentially powerful tools for restoration and conservation management.

For more information or to reach Dr. Weller, please contact SERC science writer Kristen Minogue.