Effects of Railroad Land Grant Development on Riparian Communities of Greater Yellowstone
The partitioning of railroad land grant properties to housing developments, timber companies, mining operations, oil and gas developments, farms and ranchlands has not only fragmented lowland riparian communities, but fundamentally changed their behavior. From alterations in stream flow (flood plain restrictions) to loss of vegetation (either from mechanical removal or reduced soil moisture storage), riparian communities in the Greater Yellowstone ecosystem, and the wildlife dependent upon them, are at risk.
Riparian communities are the most productive land. Comprising only 5% of the total area in Greater Yellowstone (
see maps ), riparian communities manage to yield more than 30% of the total productivity. They play an important role in the stream dynamics, wildlife ecology, and biodiversity of the region (Naiman et al 1993). Unfortunately, because riparian areas are so rich,they are highly valued for development. Housing development, more than any other land use in Greater Yellowstone, has impacted riparian communities the most. Development has increased by 60% over the past twenty years (McMillion, 2001).Primarily occurring in the rich river bottoms (floodplains) where the topography is relatively flat, settlements have quickly claimed access to rivers. These same areas are important to wildlife as migration routes. Development on flood plains restricts the home ranges of larger mammals and removes the forage and cover needed by wildlife. Neotropical birds such as
the yellow warbler are in danger of loosing critical nesting habitat from development in riparian corridors. Bald eagles, endangered cutthroat trout, most mammals, amphibians, and some reptiles are dependent on thriving riparian communities for their basic survival.
Besides the directly displacing wildlife, development on floodplains leads to floodplain control. Floodplain control is accomplished in several ways, through bank stabilization, removal of vegetation along river banks, levees and dikes. Among these solutions, bank stabilization is the most common and the most detrimental to river ecology.
The most apparent impact of large-scale bank stabilization on river ecology is that it robs the river of its ability to migrate within its floodplain. Plant composition, habitat structure, and productivity are determined by the timing duration, and extent of flooding (Manci, 1989) . Deprived of this most basic function, a river cannot curve new channels, deposit fresh alluvium, transport spawning gravels, and build new island systems. A river that cannot replenish its floodplain, cannot support its vegetation. Riparian vegetation acts as a natural buffer against floods, slowing down peak flows and channeling deposits, which allow for recruitment. High spring flows enhancing recruitment may occur onlyevery 5 to 10 years, resulting inspaced age classes of woody riparian species (
National Research Council, 2002 ). The slowing of streamflow allows time for water to absorbed into the ground replacing vital groundwater supplies. When stream flow is accelerated by restricted channels (riprap), soil moisture storage is severely impacted. Groundwater retention is a vital resource for vegetation development and replenishing stream levels during the dry summer months when wildlife needs water most.Manci, Karen M.1989. Riparian ecosystem creation and restoration: A literature summary.U.S. Fish and Wildlife Service Biological Report 189(20):1-59.Jamestown, ND:Northern Prairie Wildlife Research Center Home Page
(Version 16JUL97).Naiman , R.J., H. Decamps, M. Pollock. 1993. The role of riparian corridors on regional biodiversity. Ecological Applications. 3(2): 209-212.
National Research Council, 2002. Ecological Dynamics on Yellowstone’s Northern Range, a National Academy of ScienceReport. Committee on Ungulate Management in Yellowstone National Park, Board on Environmental Studies and Toxicology, Division on Earth and Life Studies. National Academy Press, Washington, D.C. pp. 49 — 59.
McMillion, Scott. 2001. Housing growth in Yellowstone Floodplain. Bozeman Daily Chronicle. Bozeman, MT.