Habitat fragmentation. The Demon Among us.

In keeping with the topic of species extintion as a proxy for the impact of travel on the environment, it seems appropriate to explore the role of transport links, and specifically roads, on habitat fragmentation.



Habitat destruction leading to fragmentation is probably one of the most important causes of species decline across industrial area. Many species now depend on small habitat plots, and while the separation of these patches has often been a result of agriculture, Vos and Chardon (1998) investigated the role of extreme barriers such as roads.



Focussing on Dutch amphibians and specifically the Moor frog, a 40,000ha study area was examined, see fig. 1. Through counting calling males and egg clusters in moorland ponds, the impact of 4 types of road (motorways, roads over 7m, roads between 4 and 7m and small paved or pebbled roads) on frog distribution and fragmentation were examined.

Figure 1. Study Site. While it is tough to make out the specifics of the map, the level of roads and urbanised nature of the the site can be understood. This can help in finding other area for which this study could be representative; where else could the results of the study be useful? 

Through diving the area into 50x50m grids Vos and Chardon found frog distribution across 45% of the study site to be unaffected. For the majority of the area, however, pond occupation was markedly affected: only 73 of 109 moorland ponds were populated with Moor frogs.



The real strength of the study comes in its pursuit of rigour and trends across different species. In comparing the Moor frog results with the distribution of other amphibians such as the Tree and Pool frogs, Vos and Chardon showed road density to have an important negative effect on habitat fragmentation across many amphibians.


The thorough nature of the article continues into its discussion. While before in this blog I have critiqued authors’ inabilities to look at the implication of their conclusions, this study warrants no such criticism. Here there is a clear sense of what the results mean, and how it is important for us to remember that even minimal fragmentation can have widespread negative effects on multiple species. As urbanisation increases therefore, we must learn and understand that roads will become a greater problem than ever in the fragmentation of habitats, and unless monitored and planned the laying of roads will become one of the main contribotors to global environmental change.