Findlay, Scott and Josée Bourdages. 2000. Response time of wetland biodiversity to road construction on adjacent lands. Conservation Biology 14(1):86-94.
RELEVANT TO: ROADS/OFF-ROAD VEHICLES
INVASIVE SPECIES
VEGETATION AND WILDLIFE
MONITORING/ADAPTIVE MANAGEMENT
DESCRIPTION
This scientific article discusses the impacts of road construction and higher road densities on numerous taxa. The authors use modeling to predict changes over a period of four decades in various taxa using both historical and current road densities adjacent to wetlands in Canada. The model is compared to previously-measured species richness of wetlands birds, herptiles and plants as a function of wetland area and road densities.
MAJOR FINDINGS
Perhaps the most important finding is that many negative environmental impacts are unnoticeable for many years, sometimes decades. The model that best fits wetlands species richness measurements was the model that took into account past densities of roads rather than current densities of roads. This means declines in biodiversity may not be observable for decades after road construction.
Road construction may result in significant loss of biodiversity at both local and regional scales due to effects that have been documented in numerous scientific studies, such as:
- Restricted movement between populations
- Increased mortality
- Habitat fragmentation and edge effects
- Invasion by exotic species
- Increased human access to wildlife habitats
The above effects are all expected to increase local extinction rates or decrease local recolonization rates.
Populations of susceptible species are expected to decline gradually after road construction, as opposed to immediate loss of species.
Through modeling, the authors determine:
- Lags in wetland biodiversity loss in response to road construction
- The proportion of variation in herptile and bird richness explained by road densities increased significantly when past densities were substituted for more current densities in multiple regression models.
- For vascular plants, birds, and herptiles, there were significant negative effects of historical road densities when the most current densities were controlled statistically.
"For wetland plants, our results suggest that in fact, species loss may not even be detectable until several decades after road construction. For birds and herptiles [i.e., reptiles and amphibians], in contrast, species loss is detectable within <8 years on average. But even for these taxa, our results suggest that the full effects of road construction on species richness may not be evident for decades" (p. 91).
Such lags in response to changes in human caused stress have important implications for retention of biodiversity, land use management, and environmental impact estimates.
QUESTIONS RAISED FOR THE THREE FORESTS
- What baseline and long-term monitoring of biodiversity exists on these Three Forests in relation to roads, livestock, ORV use in or near wet meadows or other wetlands, cross-country snowmobile use, etc.?
- Have you documented impacts from any particular project or activity ten years or more after the project or activity was begun?
RELEVANCE TO FOREST MANAGEMENT
- Baseline and long-term monitoring are essential when changes are made in human disturbance in the Forest, e.g., a road is constructed or closed; an exclosure is established; an aspen stand is logged.
- Transportation analysis should start with a "blank map," with only those roads and routes remaining open that are necessary for reasonable access; are ecologically sound; and avoid wetlands, wet meadows, and riparian areas.
- The potential for long-term impacts of an ecosystem must be included in the decision process for new road construction.
- All roads/routes must be closed unless posted open; no motorized travel should occur outside of roads/routes.