Promoting climate-driven forest migration through large-scale urban afforestation

Abstract

Abstract Anthropogenic climate warming is expected to shift the geographical distribution of forest trees worldwide. Urbanization-induced landscape fragmentation represents a considerable impediment to species’ range shifts. Large-scale afforestation is often suggested to be an effective measure to mitigate the negative impacts of landscape fragmentation. However, the effectiveness of afforestation on climate-driven forest migration has rarely been evaluated in urban environments. Here, we tested the effectiveness of two common afforestation strategies in promoting the migration of bird-dispersed tree species in Greater Manchester, UK: (A) planting trees in private gardens and roadsides and (B) establishing large woodlands in public lands. A modelling approach combining graph and circuit theory was used to assess the improvement in landscape connectivity after urban afforestation and to analyze how the two strategies promote the process of forest migration under climate change. Our results suggested that planting trees in gardens and streets could improve the spatial patterns of forest migration by forming stepping stones for the movement of birds across the urban matrix; establishing large woodlands in public areas could enhance the probability of forest migration between urban woodlands by providing population hubs. We found that the effectiveness of urban afforestation was strongly influenced by the spatial arrangement of trees and the physical characteristics of local bird species. The study offers new insight into the biodiversity benefits of urban landscapes, encourages tree-planting programs in urban environments, and calls for close cooperation between urban foresters, designers, and managers to cope with the changing climate.