The bird and the road

At least in the UK, the species diversity of birds decreases the closer they are to a road. After analyzing data on 75 bird species, Cambridge ornithologists came to this conclusion. It was discovered that migratory, rare, and small species tended to stay away from highways. More widespread species take their place, impoverishing the entire community. The authors of the article urge action to lessen the harm that highways cause to ecosystems.

The Earth’s surface is covered in highways that total more than 64 million kilometers. According to experts, this number will only rise in the future. This poses a major danger to biodiversity since roads contribute to noise and pollution, as well as the fatalities of animals hit by moving vehicles. Sadly, little research has been done on how the transportation network affects natural ecosystems. Furthermore, very few nations consider roads to be an environmental threat.

With 80% of the country located less than a kilometer from the closest freeway, the UK has one of the densest road networks in the world.

The researchers examined data on bird species diversity that were gathered in 2,033 one-square-kilometer plots by volunteers during national surveys between 2012 and 2014. These were contrasted in relation to other types of roadways that were five kilometers away. The scientists also considered other elements that might have had an impact on bird populations, such as the amount and proportion of arable land, the amount of forest cover, air temperature, and rainfall.

63% of the bird species were impacted by the presence of roads. In places with denser road networks, population density was 53% lower. However, this percentage increased to 81 percent when only major roadways remained in the research. The impact of being close to roadways was greatest on rare, tiny, and migratory species.

It’s interesting to note that certain birds stayed away from primary thoroughfares but thrived near secondary thoroughfares. This suggests that although certain species can thrive in borderline habitats that arise around roadways, the negative effects of noise and pollution near major highways outweigh the positive effects.

The variety of bird species decreased with distance from the road. The replacement of delicate, rare species like the Meadow Pipit (Anthus pratensis) by more widespread species that are tolerant of human presence, noise, and other detrimental factors, such as the common bullfinch (Pyrrhula pyrrhula), ensured that their overall abundance in the vicinity of the roads remained high. In other words, groups of poor, uniform birds have sprung up around the highways.

The ability of specific species to settle near roadways and changes in their population numbers across the nation were not linked, according to the authors. They explain this by pointing out that full bird counts did not start until the 1970s, and that in that time, less than 25% more of Britain's roadways have been built. It is possible that as early as the middle of the last century, the number of species unable to adjust to the presence of motorways began to fall.

Researchers are urging the creation of strategies that would lessen the damaging effects that highways have on the environment. The main issue here is noise pollution. Protected natural places should receive special consideration because, in the UK, 41% of them are located less than 700 meters from a road. The analysis' findings are crucial for nations where the road system is expanding quickly.