Transportation influences on wetland diversity

Transportation systems have been critical to the development of most societies. These systems form large networks and require large areas of land. Over the passage of time most transportation systems will continue to expand and technological advances will lead to new forms of transportation. Thus, our understanding of their effects on the environment and the best way to build, reconstruct, maintain, and mitigate these systems needs to be a priority. This presentation will focus on roadbed transportation systems and their effects on wetlands. The presentation will look at their direct and indirect influences on wetlands. Direct impacts from filling wetlands have been well documented for many land uses. Many existing transportation corridors developed from what were early trails and passages. These early routes often followed waterways due to the ease of travel. Even with passage of time many new transportation corridors have been built along waterways and in valley bottoms to take advantage of gentle grades. Most wetlands also are found in these landscape positions, thus transportation systems can contribute a higher rate of direct losses from filling per area of development. Further, wildlife mortality, pollutant runoff, and vegetation management are examples of other direct influences these corridors have on wetlands adjacent to them. Indirect impacts have not been well documented and further research is necessary. A wide array of factors such as ditching, design criteria, change to drainage patterns, fill effects, soil compaction, bridge location, culvert invert elevations, traffic patterns, and pollutant spills have influences on wetlands. Further, these factors influences depend on certain parameters of the adjacent wetlands such as soil type, hydrologic regime, depth to bedrock, water chemistry, plant community, and flow patterns. Some resulting indirect influences include changes in plant communities, species richness, water chemistry, wildlife habits, sediment transport, hydrologic changes, and increase of invasive plant species. This presentation will consider these effects resulting from transportation construction, maintenance, design, and policies (past, present, and future) that have and will influence future wetland diversity. An overview of key literature, and personal experience will be presented