Characterization of the Ashepoo-Combahee-Edisto (ACE) Basin, South Carolina
An ecosystem is defined as "a set of organisms (community) living in an area, their physical environment, and the interactions between them" (Daily 1997). Although it has not always been clearly recognized, humans are completely dependent on the ecosystems in which they live. Humans have been dependent on the ACE Basin ecosystem for over 6,000 years. The many processes that integrate energy and nutrients flowing through the ACE Basin ecosystem provide its human inhabitants a variety of services. Besides providing food and shelter, the ecosystem provides waste treatment (by way of carbon dioxide consumption, oxygen production, and breakdown of sewage), a water filtration system (by the soil), recreational opportunities, and a basis for economic development. Some of these services, such as food production, are readily apparent and have a market value. In the ACE Basin, commercial fishing is an important means of food production. Likewise, both agriculture and forestry products are produced in the ACE Basin and have a market value. Less apparent services include biological and chemical processes, such as the transfer of energy through the food chain, that operate in order to produce the fish or agricultural products (Peterson and Lubchenco 1997; Odum 1997). These services are generally taken for granted; yet they may be severely impacted by land use and pollution. Remove any one of these "services" and the character and function of the other components can be compromised.
Coastal areas, such as the ACE Basin, located between the open ocean and upland areas, have a high diversity of habitats and microhabitats, supporting diverse and abundant communities of plants and animals. As habitats are modified, ecological processes in these habitats also change and some of these changes may be significant. One of the greatest threats to habitat diversity in the ACE Basin is the conversion of existing habitats to structurally and biologically simpler habitats such as agricultural fields, pine plantations, and urban or residential areas. In addition to the direct loss of habitat, the resulting fragmentation of the remaining forested and wetland areas results in decreased species diversity. As a consequence of fragmentation in the ACE Basin, ecotones where the vegetative communities previously graded slowly from wetland to upland forest have been changed to sharper boundaries between wetland areas and what are now agricultural fields or suburban developments.
Other threats to the ACE Basin ecosystem occur as a result of human disturbance of the natural transfer of energy and trophic structure, which can alter the carrying capacity of the ecosystem. In addition, the current global economy is consuming more energy than is renewable over the long term, and humans are heavily dependent on nonrenewable fossil fuels and nuclear energy. Energy use at the local level of the ACE Basin is no exception. Millions of dollars in fuel, fertilizer, and pesticides are used to increase the production of agricultural products well beyond natural levels. When fossil fuels become expensive and scarce, it will be difficult to maintain the current production levels on ACE Basin farms. In order to limit the impact humans have on the ACE Basin ecosystem, appropriate management decisions must be made at the federal, state, and local government levels as well as by individual property owners and residents of the ACE Basin.