Researchers at the University of British Columbia believe that 71 per cent of wildlife overpasses in North America are too narrow.
Overpasses are bridges that allow bears and other animals to cross over busy highways roads, allowing these animals to live and breed across their normal habitat which, as the study proves, is an extremely important factor in biodiversity. Previous research indicates that a width of 50 metres and a width-to-length ratio of 0.8 is the recommended measurement for animals to feel comfortable when crossing.
Liam Brennan, a UBC environmental science student who was an author on the study, explained that wildlife overpasses are a part of a larger network with fencing and underpasses that are usually in association with human-wildlife vehicle collision mitigation projects.
As for the specific overpasses that were analyzed in the study itself using Google Earth, 120 total bridges around the world were found to be narrower than local guidelines.
“The study was broken into pieces with the first focused on the 120 around the world. On the second however, we specifically looked at 12 wildlife overpasses in western North America and did a more thorough analysis on the number of animals crossing,” Brennan said.
As for the adequate measurement, this is still an on-going discussion and, as Brennan puts it, there probably isn’t going to be a global consensus given the different terrains around the world. Brennan said that the adequate measurement will come down to multiple factors, where the overpass is located, what the goal of the project is going to be, and also which species are being looked at. Some require wider width than others so there really is no global consensus.
Brennan himself is a major advocate for overpasses as he considers them a win-win.
“They promote biodiversity and, with other measures like fencing, save animal and human lives.”