On their way to north, species need habitat

Species that have expanded their range northwards are disproportionately found in protected areas in the UK, state Thomas et al. in the paper we discussed in our journal club on September 14th, 2012. This is an encouraging observation to complement the concerning findings that climate change is a threat in protected areas.

The most important conclusion of the study is between the lines: when climatic conditions allow species to expand their range, species need habitat to colonize. The UK landscape is highly fragmented, and protected areas have maintained islands of particular habitats. It is a pity that Thomas et al. do not describe the distribution of different habitats in their study area. Nor do we know whether the species were previously found disproportionately from protected areas.

Another important conclusion was that species composition in protected areas is expected to change. The world is full of protected area designation schemes. Some of them are more focused on ecosystems, others designate sites based on the occurrence of species of conservation interest. Such species-oriented schemes should be revised to ensure that they can account for community turnover in sites.

Thomas et al. focused on species that have expanded their range. What about species that did not expand? Bioclimatic envelope models provide a tool for constructing comparisons between expected and observed range expansions and exploring the differences in species habitat associations and traits. Are there links to past population trends? Dispersal ability? Particular habitats underrepresented in the protected area network? Identifying such discrepancies could help planning the protected area network in such a way that it would become even more effective in enabling species to colonize new sites in their northward-shifting climate envelope.

Thomas et al. 2012. Protected areas facilitate species’ range expansions. PNAS 109: 14063-14068.

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