Are forest roads compromising the integrity of natural forest ecosystem?

Roads have always been considered the pioneer of human urbanization throughout the past few centuries. There is always a positive relationship between road network expansion and the economic development of a country as it enhances social connection as well as internal communication systems within a country. Constructions of roads, both paved and unpaved, is a common feature in different forest area around the world. These roads are used for different managerial and conservation activities around the forest coverage area. Besides, some roads are built to improve the communication between two areas through a forest patch situated in an area.

For instance, in Bangladesh, several road networks are built through the forest area; Lawachara National Park is one of the prime examples, which has a paved road, as well as, a railway road perforating through this valuable forest coverage connecting important areas in the region.

But nowadays, a growing concern has developed among the scientific community and nature conservationists over the impacts of these roads on the surrounding forest habitat. Changes in forest landscapes are one of the prime issues that are being influenced due to rapid urban development through road establishment through a forest. In addition to these, forest area is suffering from the edge effect, a consequence of the forest road construction in the forest, which is a relatively infamous issue when it comes to forest disturbance (Goosem, 2007).

Edge is an area between the boundary of two areas, and the edge effect occurs at the boundary of these two habitats, causing changes in the micro climatic condition of the boundary areas. As the edge effect in a forested area is promoted due to established roads, the surrounding vegetation composition and wildlife habitat is greatly affected due to this phenomenon. This situation gets even severe, as the edge effect is not limited to the boundary area and tends to spread across the interior forest. Due to this edge effect vegetation composition is changed, because the changes in the micro climatic habitat- a result of the edge effect- triggers this mechanism by favoring the establishment of exotic species and competing with the native species resulting in an eventual extinction of these native species. Besides, the road situated in a forest works as a seed dispersal corridor between two parts of the forest separated by the road. This results in an anomaly- increased plant diversity in the outer portion of the forest- which is closer to the forest road, compared to the inner one. This seed dispersal mechanism is carried out by vehicles moving through the road, movement small pollinators, as well as, large mammals, wind and rainwater runoff (Fallahchai et al., 2018). 

Animal movement behavior is largely influenced by the presence of roads in a continuous forest patch. Many animals use the outermost part of the forest that is close to the track as their habitat, movement corridor, feeding ground, or retreating due to fear of predation.

A Research by Kolb, 1984 stated that dog foxes used railways as their movement corridor in a forest. Many bird species prefer the forest edge as their habitat depending on the plant composition and movement corridor which contributes to dispersal (Asemani et al., 2013).

The width of the forest road plays an important role in the intensity of impact that is produced due to a road (Zhou et al., 2020). For instance, it takes a lot of time for the wildlife to cross a wide road resulting in more collision with vehicles, and the successful seed dispersal through different mediums, between forest patches separated by a road, will be hampered. This is why narrows roads such as forest trails are more harmonious to the forest ecosystem than wide paved roads.

As roads are an important part of the modernized world, it needs to be put into congruity with the forest ecosystem. Most of the negative impacts of forest roads on the wildlife are related to collision with passing vehicles while crossing. Some countries have already taken initiatives to mitigate wildlife mortality due to vehicle collisions. India is a perfect example, as it has recently built an underpass for wildlife crossing between two famous wildlife parks, Kanha and Pench. Sweden is another country that is concerned and taking initiatives regarding the effects of forest roads. Sweden has recently announced the establishment of series of wildlife bridges in busy roads through a forest area to reduce wildlife collision with vehicles.

Indeed, careful planning of building and managing the forest roads could be a way of minimizing the effect of roads partly but not wholly. Another way is to build the road in an environmentally friendly way, using environmentally friendly materials. To eradicate the effect completely, the necessity of building the corridor should be evaluated and alternatives should be considered. In case of revegetating the area that is prone to severe fragmentation, emphasis should be given to native species instead of exotic species to avoid habitat alteration and invasion.

Reference

Asemani, Y., Torabi, Z., Najafi, N., & Asemani, A. (2013). Impacts of Traffic Noise and Traffic Volume on Birds of Roadside Habitats. Life Science Journal, 10(SUPPL. 5), 502–504.

Fallahchai, M. M., Haghverdi, K., & Mojaddam, M. S. (2018). Ecological effects of forest roads on plant species diversity in Caspian forests of Iran. Acta Ecologica Sinica, 38(3), 255–261. https://doi.org/10.1016/j.chnaes.2017.08.002

Goosem, M. (2007). Fragmentation impacts caused by roads through rainforests. Current Science, 93.

Kolb, H. H. (1984). Factors Affecting the Movements of Dog Foxes in Edinburgh. The Journal of Applied Ecology, 21(1), 161. https://doi.org/10.2307/2403044

Zhou, T., Luo, X., Hou, Y., Xiang, Y., & Peng, S. (2020). Quantifying the effects of road width on roadside vegetation and soil conditions in forests. Landscape Ecology, 35(1), 69–81. https://doi.org/10.1007/s10980-019-00930-8