How peri-urban areas can strengthen animal populations within cities: a modeling approach

We explore the extent to which inner-city fauna can be enhanced by source areas in peri-urban zones as a response to a decreasing quality and size of green habitats within cities. The objectives were to get a better understanding of the interaction between animal populations of urban and peri-urban areas, and the role of urban green structures within this relationship, and to find out the extent to which peri-urban areas can contribute to urban animal populations. We illustrate the idea of peri-urban support by using a simulation model for individual animal movement, applied in a particular case-study with butterflies as model species. Results show differences in accessibility of inner-city areas between model butterfly species that differ in mobility. The impact of peri-urban individuals on populations of inner-city habitats differed among several peri-urban source-scenarios: the enlargement of the inner-city butterfly population by peri-urban individuals was determined as 7¿36% for `moderate dispersers¿ and 19¿56% for `good dispersers¿. Results also show that well-connected habitat patches within existing urban green structures were more likely to be visited by peri-urban individuals than isolated habitat patches. We conclude that peri-urban nature areas, if large enough, can have a potentially positive influence on the presence of fauna in inner-city neighborhoods. In addition, results suggest that connectivity between inner-city and peri-urban habitat patches enhances contribution of peri-urban migrants to inner-city populations. By providing a range of different habitats, from inner-city up to peri-urban area, moderately mobile habitat specialists could better compete against the small set of successful habitat generalists that are increasing in urban environments all over the world.