The urban population is growing every year. This has an impact on biodiversity in the city. Biodiversity is particularly important in populated areas such as the city for providing ecosystem services such as pest regulation – think of the oak processionary, for example. Ecologists Juan Antonio Hernández-Agüero (Institute for Environmental Studies) and Bas Krijnen, who graduated from the Master’s in Environment and Resource Management, investigated which human factors influence the interaction between animal species in the city. They also wanted to know which actions can improve urban biodiversity.
The research, which was published in Wildlife Biology, is part of two projects supported by a Dobberke Grant and the Ecology Fund of the Royal Netherlands Academy of Arts and Sciences. The aim of these projects is using ‘green’ and ‘blue’ infrastructure – vegetation and water – to reduce human impact on biodiversity in Amsterdam. To do this, it is necessary to first investigate the main causes of biodiversity loss in the city.
Noise
According to the researchers, noise is the most important factor influencing bird behaviour. Birds tend to avoid noisy areas. As a result, there is less natural pest control near roads or railways. ‘That is a problem, because car and train traffic cannot be stopped immediately’, says Hernández-Agüero. But the researchers do see a role for noise barriers. ‘They have been used for a long time, and we show that they are more necessary than ever.’
The research also shows that impervious surfaces, artificial night light, high human population densities and local temperature increases (due to heating) all influence bird behaviour. These human influences increase bird activity during cold and dark periods, but have a negative effect during warmer and brighter periods.
Forty oaks
To conduct the study, the researchers placed artificial prey in forty English oaks at various locations in Amsterdam. They studied the marks that insectivorous birds left in these fake caterpillars. In addition, they used satellite information and ground data from the municipality of Amsterdam to calculate the presence of human influences such as noise and artificial night light.
