Globally, more people live in urban areas than in rural ones. Urbanisation is a selective force that is changing the composition of animal communities tremendously.
During the process of urbanisation some animal species will disappear from the newly urbanised habitat. For example, birds that feed on specific natural food sources will fly to other areas to search for food. Species that cannot move as fast as urbanisation is expanding will disappear.
Parallel to this other species, such as crows and doves, will move into the city or increase in density. Thus urbanisation also filters bird communities.
However, there is still a clear research gap in understanding the mechanisms and impact of urbanisation on wildlife. The unprecedented rate of current urbanisation poses a major threat to biodiversity. It presents one of the biggest environmental challenges of our time. Understanding exactly how urbanisation affects wildlife is crucial to help animals to survive in our vicinity.
Urbanisation leads to habitat fragmentation, where larger continuous habitats are divided into smaller unconnected patches. It also causes habitat loss, through an increase in roads and buildings that are not producing any biomass. This exposes wildlife to new man-made stress. Physiological and ecological constraints affect organisms directly, but also change host-parasite and predator-prey interactions.
Prolonged chronic physiological stress caused by air, noise and light pollution, or low food quality could affect susceptibility to parasites and disease. Animals’ body condition and immune function can be altered as a result.
The inability to remove the toxic compounds caused by traffic fumes and antigens like dust and parasites can have severe consequences. It can result in increased molecular damage, tissue dysfunction and disease-related mortality.
On the other hand, research from the UK has shown, that the popular pastime of feeding birds is significantly shaping garden bird communities. In the UK, where at least half of the population feeds birds in their yards, the populations of several species of garden birds have grown in number, and the diversity of species visiting feeders has also increased. It shows that increases in bird diversity at feeders are associated with increasing community evenness, as species previously rarely observed in gardens have increasingly exploited the growing variety of foods on offer over time. Urban areas of Britain are consequently nurturing growing populations of feeder-using bird species, while the populations of species that do not use feeders remain unchanged. The findings illustrate the on-going, gross impact people can have on bird community structure across large spatial scales.
(Extract from the article published on weforum.org by Petra Sumasgutner and Caroline Isaksson, and The composition of British bird communities is associated with long-term garden bird feeding’ by Kate E. Plummer, Kate Risely, Mike P. Toms & Gavin M. Siriwardena on nature.com )