0423-1201-SDTDC: Riparian Restoration, Page 12

Riparian Restoration

CHAPTER 3: HOW RECREATION IMPACTS AFFECT KEY CHARACTERISTICS OF RIPARIAN ECOSYSTEMS (CONTINUED)

Habitat Edges

The edge of a stream or the transition from riparian ecosystem to upland forest creates a natural edge. See figure 44. Plant type and density vary on edges as compared to the interior, an area away from an edge. Trails and ever-expanding camp and picnic units or staging areas increase the exposure of the interior by creating new edges. Roads create their own edge effects and their impacts can be great. Longer roads potentially have a greater impact on the nearby environment. These edges are more open to disturbance by humans and to the influx of nonnative species, both plant and animal, by “…providing pathways for travel and by having newly disturbed areas to colonize in” (Falk 2000). They encourage nonnative wildlife species at the expense of native species that require interior habitat for nesting and shelter. The balance shifts, skewing the ecology.

Photo of a stream that cuts through an area densely vegetated by grasses and shrubs.
Figure 44—Stream edges.

Aquatic Ecosystems

Most aquatic ecosystems depend on adjacent riparian ecosystems for food, shelter, cover, and for maintaining proper water temperature. See figure 45. When riparian ecosystems lose structure, opportunities for erosion and sediment deposition into water bodies increase. See figure 46. Vehicle crossings and pollution from motorized equipment such as boats, jet skis, and gasoline generators used for recreational instream mining also impact the aquatic ecosystems.

Photo of a stream that cuts through a dense vegetation of trees and shrubs.
Figure 45—Aquatic ecosystem. Woody debris is present; trees
and shrubs overhang the bank, creating a microclimate that helps
keep the water temperature appropriate for that stream; insects
on the vegetation drop into the water to feed the fish; and the
banks are stabilized by the vegetation.

Photo of two people standing on a lakeshore with their boat. The shore is covered with dead woody debris.
Figure 46—Trampling and boat wakes are eroding this lakeshore.

Fish productivity is intricately linked to riparian plant composition. Plants provide shade to maintain proper water temperature and shelter fish. Many aquatic insect species spend a part of their life cycles on riparian vegetation before dropping into the water to be eaten by fish and other aquatic species. When riparian vegetation is missing from the water’s edge, much less food is available for fish and other aquatic species.