Newsletter:20070428/Balancing waterways
From EcoReality
Balancing Waterways and Wetlands
Any vegetated area immediately adjacent to a watercourse is called a “riparian area”. These zones are unique in their ecological structure – often hosting a more diverse array of plants, including herbaceous grasses and forbs, shrubs and trees than the surrounding landscape. As a function of the high moisture content, the soils in a riparian area differ in nutrients and structure from the surrounding soils; the plant community in these zones is highly sought after by herbivorous and omnivorous animals (including vertebrates, insects and invertebrates alike) for food and shelter. This unique habitat is a common ground for bird nesting, mating and breeding, for ungulates and other large mammals to drink and bathe, and of course for the aquatic wildlife which is wholly dependent on the watery environment itself for survival. Vegetation in the riparian area directly affects water temperature and provides a stable environment needed by fish. Maintaining the vegetation within twenty-five feet of the shoreline is important to maintain healthy fish populations in fish-bearing streams. Riparian zones are ecologically invaluable to combat habitat loss, the number one threat to wildlife, and they also act as travel corridors between increasingly segmented habitats.
In addition to the key role that riparian areas play in maintaining habitat and preserving biodiversity, they also have functional physical and chemical roles in the ecosystem or agroecosystem such as: helping to reduce floods, stabilizing streambanks, and controlling and reducing the effects of nonpoint-source pollution are among some of their notable ecological functions. Nonpoint-source pollution can include chemicals (fossil fuels, pesticides, fertilizers), and sediment from the surrounding watershed.
When managing landscapes with the many facets of riparian area health as criteria for management, one must also consider the width of the riparian area in relation to how the adjacent land is being used, and the slope of the land. The width of a riparian area is measured from the top of the stream bank, back. A larger riparian buffer may be needed in certain cases (such as high-turnover cropping zones with bare soil part of the year) to filter out fertilizers, herbicides and sediment before runoff enters the stream and before the stream hits the lake or ocean. A buffer strip in this case may consist of maintaining a grass strip between the field and stream. If the goal is diverse wildlife habitat, you may wish to encourage certain plant species (known to be food and/or shelter for particular wildlife in your area) and the width of the riparian area must be managed to accommodate the type of wildlife you hope to attract.
Land use for agriculture (even small scale hobby farms, gardens and hayfields) is considered as a source of non-point source pollution, and riparian areas can help buffer and reduce the effects of non-point source pollution on downstream wildlife and fish populations. Non-point source pollution can also take the form of sedimentation (which affects dissolved oxygen levels in aquatic environments and can severely alter the aquatic ecology) and highly concentrated nutrients (from fertilization) causing eutrophication or “dead zones” in lakes and oceans. Protecting riparian areas is not only crucial for land management in a permaculture design, but it also demonstrates to an increasingly urbanized population that the ecological services provided by healthy waterways in natural ecosystems, as well as in agroecosystems such as row crops, hay fields or cattle ranches, are worth more than their agricultural profit margin might indicate if they were to be cleared and/or watercourses shifted to serve conventional ‘economic agricultural needs’.
