Wetlands
September 16, 2020
One of my first, and favorite, courses I took in graduate school was simply titled Wetlands. The course examined, wetland ecology, human impact on wetlands, and contemporary conservation/remediation efforts, among other things. A project in the class tasked students with identifying a specific wetland for research. Some students chose wetlands around the globe, in far away places like Cambodia or Botswana. However, a good portion of the class chose to focus on local wetlands in or around Philadelphia, including John Heinz National Wildlife Refuge, Bartram’s Garden, Pennypack Creek wetland, and the Morris Arboretum restoration wetland.
I chose to investigate a wetland located in Chadds Ford, PA under the protection of the Brandywine Conservancy. Resting along a bank of the Brandywine River this wetland is considered a swamp or marsh because it contains both woody and herbaceous plant species. Likewise, portions of the wetland are flooded nearly year-round. The Wetland is easily accessible, even in times of inundation, with a built boardwalk extending through the area. It is a nice place to view different bird species as well as diverse vegetation including Black Willow (Salix nigra), Sycamore (Platanus occidentalis), Pin Oak (Quercus palustris), Arrowwood (Viburnum dentatum), Silky Dogwood (Cornus amomum), and Spice Bush (Lindera benzoin).
Unfortunately, this wetland in Chadds Ford receives most of its inflow as road runoff from highway U.S. Route 1, causing eutrophication in the waters. Eutrophication is a response to high nutrient levels in the water. It depletes oxygen, making it difficult for vegetation and the wildlife dependent on that vegetation to thrive in the wetland. Seasonal flooding of the Brandywine river, resulting in sedimentation, is another source of inflow for this wetland. This sedimentation is causing the wetland to gradually fill in with soil and debris. One day the wetland may be completely filled in, creating a meadow. Neither of these two disturbances are positive impacts on the wetland.
Wetlands have historically been seen as negative places, swamps where mosquitos and diseases breed or where unfamiliar things lurk in murky waters. In reality they are quite the opposite. Wetlands are rich ecosystems supporting a slew of vegetation and wildlife. Their functions are numerous. They act as important buffers between land and water, protecting farms and communities from rising floods. They are natural filters, cleaning the water as it flows through the diverse biota inherent in a healthy wetland. In certain places wetlands even serve as the staging grounds for sustainable food production, such as rice fields.
However, the perception of wetlands as stinky, dirty places has led many humans to treat them poorly. Waste and toxic dumping often occurs in wetland areas. Worse yet, people have been known to completely drain wetland areas to facilitate development or agriculture. More than half of the wetlands that once existed in the U.S. are now destroyed or heavily disturbed. New Orleans comes to mind. Wetlands once lined the Mississippi Delta protecting the shore from erosion and keeping flood waters off the land. Now, development and agricultural runoff into the Mississippi River has depleted the wetlands so events like Hurricane Katrina and the Deepwater Horizon BP oil blowout have far greater impacts on the land and people of the region.
Wetland restoration and wetland construction are ways of bringing back these important ecosystems. These actions also serve as cost-effective green infrastructure solutions to many development issues including water quality and supply problems, storm surge protection, and stormwater runoff management. Of course, conserving and preserving the remaining natural wetlands is the best thing we can do for ourselves and the diverse biota inhabiting these areas.