Refugia: keys to climate change management

Abstract

IntroductionRefugia are habitats that components of biodiversityretreat to, persist in and can potentially expand fromunder changing environmental conditions (Keppelet al., 2012), facilitating the survival of organisms dur-ing extreme climatic changes (Me´dail & Diadema,2009). They may thus maintain favourable climatic con-ditions now absent in the surrounding landscape. Thisis enabled by higher local heterogeneity of micro-climates and the decoupling of local from regionalclimates (Dobrowski, 2011; Keppel et al., 2012).Because refugia potentially safeguard the persistenceof components of biodiversity over millennia, they mayact as safe havens under projected anthropogenic cli-mate change (Me´dail & Diadema, 2009; Keppel et al.,2012). This capacity makes them critical components inclimate change management. As a result, the identifica-tion and protection of refugia has increased in priorityin conservation planning (Noss, 2001; Game et al.,2011). However, refugia are currently loosely definedand their study is often based on ad hoc, descriptivedata sources (Ashcroft, 2010). We therefore clarify theconcept of refugia and related terms. We then argue foran increased focus on understanding how refugia willrespond to climate change. In the context of rapidanthropogenic climate change, we suggest that thisfocus will lead to prioritization of conservation actionstowards those habitats offering the greatest potential assafe havens for biodiversity.What are refugia and what are not?Despite an exponential increase in the use of the termsrefugia and refuges in literature (Fig. 1), refugia are stillconfused with refuges, remnants and reserves. Most cur-rent uses of refugia are to places providing environmen-tal conditions not available in the surroundinglandscapeoverlongperiodsoftime(e.g.,Ashcroft,2010;Dobrowski,2011),withanincreasinginterestinidentify-ing future refugia under projected anthropogenic cli-matechange.However,thetermisalsousedtorefertoavariety of other concepts. For example, in Global ChangeBiology refugia have recently been used to refer totemporary shelter from predation or disturbance (e.g.,Ledger et al., 2011) and to remnant patches of suitablehabitat (e.g., Rittenhouse et al., 2010). The term refugiahas also been used in reference to reserves (see Fig. 1).While thetermrefugiahas onlyrecently beeneffectivelydefined (see Keppel et al., 2012), use of the other threeR-terms has long been widely established. We thereforeadvocatethecorrectuseoftherelevantjargon.Refuges are places that through structures or pro-cesses provide shelter from disturbances, predation,herbivory or competition. They are therefore defined aslocations providing spatial and/or temporal protectionor advantages in biotic interactions over ecological timeperiods (i.e., within the life span of the relevant organ-ism). Remnants are patches of suitable habitats for spe-cies intolerant of changed or modified landscapes thatprevail in landscapes highly modified by human popu-lations and resource exploitation. Reserves are areaslegally or customarily protected from particular anthro-pogenic activities and may vary in size from remnantsto portions of large ‘intact’ landscapes or so-calledwilderness areas.Refugia and anthropogenic climate changeWhile refuges, remnants and reserves continue toreceive considerable research attention, refugia are anarea of rapid recent growth (Fig. 1). The ability of refu-gia to locally mitigate the effects of regional climatechange is increasingly considered important for climatechange adaptation planning (Ashcroft, 2010; Gameet al., 2011). This is because they are potential safehavens for biota and may offer the only hope for in-situpersistence of poorly dispersed species. Protecting suchclimate change refugia could allow some species to