Assisted Colonization: A Question of Focal Units and Recipient Localities

Assisted colonization as an adaptation strategy to conserve or restore biodiversity in the face of climate change deservedly evokes controversy. Assisted colonization is perceived by some as a last option for conserving endangered species and by others as a risky and unwise management effort due to current gaps of knowledge. Based on the pros and cons of the recent debate, we show that the current discussion mainly focuses on the assisted colonization of rare and endangered species beyond their natural range of distribution. We suggest that a more useful approach for the conservation of endangered species could occur by focusing on the relevant foundation or keystone species, which ensure ecosystem integrity for a multitude of dependent species by governing the habitat structure and microclimate of the site. Examples of foundation species include dominant tree species in forests or dominant corals in coral reefs. For a given conservation or restoration need (e.g. conservation of rare species), we recommend the assisted colonization of pre-adapted ecotypes of the relevant foundation species from climates similar to future expectations for the target site. This approach could lead to climate-safe habitats for endangered species with minimal adverse effects on recipient ecosystems.