Reduced availability of habitat structures in urban landscapes: Implications for policy and practice

Over half the world's population resides in cities, with increasing trends towards urbanisation expected to continue globally over the next 50 years. Urban landscapes will be more ecologically sustainable where key habitat structures (e.g. trees, shrubs and woody debris) that support multiple taxa are maintained. Yet, there is little empirical data on the extent to which habitat structures have been modified in urban landscapes. Obtaining these data is a necessary first step towards reducing the ecological impacts of urbanisation. This is because urban practitioners can use this information to formulate more targeted management policies and conservation strategies that seek to better maintain and perpetuate habitat structures in urban landscapes. We compared the availability of multiple habitat structures in urban greenspace, agricultural land, and semi-natural reserves in Canberra, southeastern Australia. In urban greenspace, the density and/or probability of occurrence of trees, seedlings, dead trees, hollow-bearing trees, hollows, logs and native ground and mid-storey vegetation were significantly lower compared with reserves, but comparable with agricultural land. Our results highlight an urgent need for improved habitat protection policies, management strategies, and on-the-ground conservation actions that aim to retain and restore key habitat structures in urban landscapes. To achieve this requires innovative strategies that balance socio-economic priorities and biodiversity conservation. We propose three strategies that can be practically implemented in cities worldwide including: (1) establishing dedicated conservation areas; (2) spatially zoning habitat structures hazardous to humans within existing urban greenspaces, and (3) educating key stakeholders about the importance of habitat structures within urban environments.