Wetlands: Workhorses of the Landscape by Siobhan Fennessy, Associate Professor of Biology, was originally published in the BFEC newsletter, Vol. 13/No. 2, Spring 2009.
Once thought of as inhospitable and sinister landscapes, best to be drained, wetlands are now known as a one of the most biologically diverse and productive ecosystems on earth. They provide many ecological benefits, dating back to the Carboniferous Period when the swampy conditions of the time led to the production of the fossil fuels we use today.
They are often found in the transition zone where water meets the land. Because they are neither terrestrial nor truly aquatic ecosystems they share characteristics of both, making them extremely dynamic, with a rich abundance of species. They are typically shallowly to intermittently flooded lands where water affects all aspects of their function, including species diversity, soils and nutrient cycling.
Some wetland types, like ours at the BFEC, are flooded or saturated for only short periods during the year, making them difficult to identify in the dry season. Regardless of how wet they are, all wetlands have three things in common:
The term wetland includes a diversity of ecosystem types; for example, in Ohio we have marshes (including Lake Erie coastal marshes), bogs, fens and swamps. Marshes generally have standing water and are dominated by emergent herbaceous vegetation such as cattails and rushes. Swamps are dominated by trees and shrubs with little else, except water, in the understory. Bogs and fens accumulate peat, and in the case of bogs, it is often harvested for fuel or for use as peat moss in gardening. Their peat is strongly acidic (low pH) and very low in nutrients, hence they are home to a unique array of plant species that are carnivorous, including species sometimes grown as houseplants such as pitcher plants or venus flytraps that catch and digest insects as a way to acquire nutrients for their growth.
Wetlands are perhaps most prized for their “ecosystem services” that benefit both human and environmental health. They support a vast array of species, including many amphibians, waterfowl, fish and other wildlife that require wetlands for general habitat, breeding grounds or nursery areas. These wetland dependent species have become imperiled in many parts of the world as wetlands decline. Wetlands also perform functions such as water purification, flood regulation, carbon storage, coastal protection and recreational opportunities. Because of their natural ability to improve water quality they have been called the “kidneys of the landscape.”
Wetlands cover only about six percent of the land area of the earth, and of this area it has been estimated that nearly half have been lost due to human activities. Nearly 55 percent of the wetlands that were present in the U.S. at the time of settlement have been lost due to human actions such as drainage for agriculture and development. Losses approach 90 percent in some states, including Ohio. To counter this trend and reverse losses, wetlands are being restored or created at many locations around the world, including at the BFEC!
A large wetland exists adjacent to Wolf Run within the portion of the BFEC preserve that lies north of Route 229. It is a relatively uncommon wetland type, a “wet meadow slope wetland,” so called because its main source of water is groundwater that emerges at the bottom of a hill that borders it to the east. Water flows very slowly through the site, eventually joining Wolf Run. For many years cattle grazed the site, which is a common use of this type of wetland. In the fall of 2000 a fence was installed to keep the cattle out and allow the site to recover. Kenyon students have been active in monitoring the site since then to document changes.
As we anticipated, the plant community has rebounded to a remarkable degree. Where once there were about 10 plant species, and plenty of cow hoof prints, there are now over 50 plant species at the site.
Many of these are wetland dependent species, such as the swamp milkweed (Aesclepias incarnata, pictured here) and joe-pye weed (Eupatorium purpureum) with colorful, showy flowers. Others, such as the common rush (Juncus effusus) and Frank’s sedge (Carex frankii) are grasslike with very reduced flowers. There are even a few plants that are downright dangerous to any exposed skin, including rice-cut grass (Leersia oryzoides) and tear-thumb (Polygonum sagittatum). These have small hooks on their leaves and stems that can scratch the unsuspecting passerby, so it is a good idea to wear pants if you walk through this site in the summer. Our wetland is also home to insects, small animals and some amphibians, including sightings of spotted salamanders.
Students have also been active in research at the site. Early in the restoration process we established a series of wells (also known as 4 inch diameter PVC pipe) to measure groundwater levels in the wetland. The amount of water present is important because, as in all wetlands, hydrology is the “master variable” that controls a lot of what happens in the system.
Several students have worked on a project to study the role of this wetland in the global carbon cycle. Despite the limited extent of wetlands globally, they are estimated to contain approximately 20 percent of all the carbon in the terrestrial biosphere, thus they serve as an important storehouse of carbon. Kenyon students have investigated the uptake and release of carbon dioxide, an important greenhouse gas, from the soils at the site. Studying this wetland to determine how carbon moves through it will give us an indication of how restored wetlands change through time, and how our wetland is linked to the global carbon cycle!