Special Section Essay

Climate Change, Connectivity, and ConservationSuccessLEE HANNAHConservation International, 2011 Crystal Drive, Arlington, VA 22202, U.S.A., andBren School of Environmental Science and Management, University of California Santa Barbara, CA 93106, U.S.A.,email l.hannah@conservation.org

Ten years ago in the pages of Conservation Biology,Whitten et al. (2001) asked whether writing about con-servation biology served as displacement behavior forbiologists. Their point was that extensive destruction offorests in Southeast Asia coincided with a surge in publi-cations about conservation in the region (Whitten et al.2001). Were biologists writing papers because they hadlost the real conservation battle? The same question ap-plies today to climate change. Is studying climate-changebiology a kind of displacement behavior for conservationprofessionals? Is our professional community writing somuch about climate change because we have been im-potent in addressing habitat loss, the real alpha male ofmodern conservation?

It is a challenge to address future threats without al-lowing them to distract all attention from current action.Although each of us needs to reflect on our motivationsand effectiveness, the scientific basis for action can bemore objectively evaluated. Scientists have been explor-ing climate-change biology for approximately the sameamount of time that Conservation Biology has been pub-lished. The seminal papers of Peters and others (e.g.,Peters & Darling 1985) appeared as this journal was gain-ing prominence, and soon articles from these authorsappeared in these pages. It now can be asked whetherthe 25 years of literature provides a sound foundation toinform action.

Here the case will be made that conservation pro-fessionals now have the necessary knowledge to ad-dress climate change and habitat loss in an integratedway. Action needs to be taken quickly to avoid thethreshold at which habitat loss forecloses our optionsto address climate change. Rapid, informed action andclear priorities can ensure that climate-change biol-ogy provides for endurance of our immediate con-servation gains and is not an outlet for displacementbehavior.

Action in Response to Climate Change

The past decade and a half yielded a strong literature onconservation planning in the face of climate change. Re-cent reviews point to many elements that climate changebiologists agree should be part of any conservation re-sponse to climate change: new protected areas, connec-tivity, adaptive management, managed relocation, andex situ conservation (Heller & Zavaleta 2009; Mawdsleyet al. 2009). These elements can now be implementedand the experience from that action used to refine theoryand practice, iteratively improving our practical abilities.

Establishment of protected areas, a leading conser-vation tool before climate change gained attention, isalso an effective measure in response to climate change(Hannah et al. 2007). The placement of new protectedareas can anticipate climate change, substantially improv-ing the probability that species and ecosystem functionswill be maintained in reserves. Where protected areas aretoo small to encompass species and ecosystem functions,connectivity between present and future populations isrequired. Populations, rather than protected areas, arethe key elements to be connected, as is explored below.

Where natural processes are more extensive than in-dividual protected areas, adaptive management can fa-cilitate range shifts (Hansen et al. 2003). Coordinationacross management units is critical. Species may needto be relocated to persist given the very rapid pace ofhuman-induced climate change (McLachlan et al. 2007).For instance, where agricultural or urban land or a topo-graphic barrier interrupts a range shift, artificial move-ment of the species or its propagules may be warranted(Hoegh-Guldberg et al. 2008). When all else fails, ex situmeasures, including captive breeding and gene banking,may be necessary to preserve species and their genetic in-formation. Gene and seed banks that expressly considerclimate change are already being established.

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1140 Climate Change and Connectivity

Protected areas and connectivity are the most impor-tant of these elements to implement because these re-sponses have the potential to conserve the greatest num-ber of species and ecosystems. By the time a species orecosystem needs managed relocation or ex situ manage-ment, the potential for other types of action to conservethem is very limited. Connectivity is perhaps the mostmisunderstood of these essential tools.

Concepts of Connectivity

Connectivity is one of the most difficult concepts to ap-ply to current practice because confusion exists in theliterature about what needs to be connected. Multipleconcepts of connectivity are used, often without defini-tion. Connectivity for different purposes and at differentscales is sometimes confounded.

Concepts of connectivity as a response to climatechange began to emerge with the first publications onclimate change and biological diversity. Peters and Dar-ling (1985) and Peters and Lovejoy (1992) recognizedthat species ranges shift in response to climate, whereasprotected areas are fixed in space. Species ranges as char-acterized in these early concepts were monolithic (i.e.,large, continuous areas in which the species was presenteverywhere and beyond which it was absent). Thesewere representations of the extent of occurrence, therough equivalent of a species’ range map in a field guide.To communicate the point that species ranges wouldshift as human-driven climate change accelerates theserepresentations were sufficient.

But when a conservation strategy needs to be devel-oped, a much more nuanced view is needed, that ofarea of occupancy (habitat patches occupied by individ-ual populations within the extent of occurrence). Theseare the populations that will be established or extirpatedfor climate change and that will collectively determinewhether the species persists or becomes extinct.

The early concepts of range shifts seemed consistentwith emphasizing connectivity among protected areas. Aspecies was either inside or outside a protected area, andif it moved out it would need to be protected at all stepsalong its travels until it was again in a protected site. Alinear corridor between two protected areas seemed alogical mechanism for capturing this dynamic.

A more nuanced view emphasizes populations. Mostspecies exist in multiple populations within a protectedarea, as well as outside. As climate changes, some ofthese populations may increase in size while others de-crease, and each population will represent a larger orsmaller proportion of the total abundance of the species.Populations have a probability of extirpation and also aprobability of colonization or recolonization as a functionof the ability of propagules or individuals to move (Davis& Shaw 2001).

Connectivity in response to climate change can also beconceptually confused with connectivity among popula-tions of large mammals or the ability of large mammalsto disperse or migrate. Much of mainstream connectiv-ity planning is focused on movements of large mam-mals among protected areas, a critical process as naturalland cover becomes increasingly fragmented (Beier et al.2008). Because large mammals frequently move acrosslarge areas, ensuring their ability to disperse often meanscreating connections between protected areas.

But connectivity for large mammals is not the sameas ensuring connectivity for climate change. Connect-ing populations in time is a finer-resolution phenomenonthan connecting protected areas in space. Conservationplans that mix these different concepts very often con-fuse purposes and scales of connectivity.

Assessing Connectivity

Connections among populations as climate changes canbe simulated with simple species distribution models(SDMs) and with population models that are comple-mented by empirical evidence. SDMs constructed formultiple time steps (e.g., decades) can simulate connec-tions among climatically suitable habitat patches (e.g.,grid cells) through time (Phillips et al. 2008). Connectinghabitat in all time steps is one way to connect popula-tions as climate changes. Finding efficient connectionsfor multiple species then suggests priorities for conser-vation (Williams et al. 2005). Several software packages(e.g., Network Flow, Zonation) can directly derive or ap-proximate such solutions. Population models can be usedto explore connectivity more fully. For example, popula-tion models can incorporate SDM outputs to define habi-tat quality or carrying capacity through time (Keith et al.2008).

Often the most efficient model solution is to connecthabitat over a few square kilometers, as opposed to tensor hundreds of square kilometers. For example, severalLeucadendron (conebush species) in South Africa cur-rently have sizable populations in West Coast NationalPark and smaller populations near the Cederberg Wilder-ness. In SDM simulations, relative abundances reverse asclimate changes, with the populations in the Cederbergexpanding and populations in West Coast National Parkcontracting. Bridging these protected areas with a cor-ridor would be very difficult. West Coast National Parkand the Cederberg are separated by about 200 km oflargely agricultural land. However, connecting presentand future populations at the Cederberg could be accom-plished within a few square kilometers or tens of squarekilometers. Conserving small populations now would al-low them to expand into the protected area as climatechanges. In this case, modeling supports the idea that

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population-level linkages will be effective. Contractualconservation (easements) or the expansion of the pro-tected area could help ensure that populations near theCederberg would survive to expand and populate thereserve as climate changes.

The Land-Use Change Threshold

In the real world, there is a race between this emergingunderstanding of responses to climate change on the onehand and ongoing habitat loss on the other. The forcesof land-use change are closing out our conservation op-tions for dealing with climate change. If we wait decadesfor certain knowledge of climate-change effects, land-usechange will have already dictated the conservation land-scape, and the scope for adapting to climate change willbe minimal.

Conversely, if we act now, we will have to act inthe face of considerable uncertainty. Dealing intelligentlywith uncertainty in a landscape with considerable spaceto make choices seems our best option. Acting intelli-gently will therefore require taking some risks and con-vincing society and policy makers that risks are worthtaking. The alternative is letting uncertainty become anexcuse for inaction. This is no more reasonable in climate-change adaptation than it is in international policy onmitigation.

The real-world challenge is to act before the thresholdarrives. There is a window, in some places a very nar-row window, in which to maximize the probability thatpopulations can persist as climate changes. Habitat loss isslamming the window shut in some places, and once it isshut, there will be little choice of location for protectedareas or connections among habitat patches.

I’m writing this essay in Madagascar, and nowhere isthe threshold advancing more rapidly. After a coup d’etatin March 2009, living conditions here have deterioratedin both urban and rural areas. Illegal logging and wildlifetrade have surpassed tourism as the nation’s fastest grow-ing economic sectors. Containers of illegal wood takenfrom national parks leave the country regularly. Conser-vationists in the field have been threatened and assaultedby illegal loggers. Illicit wildlife trade is at record high lev-els, even though the price in the field for an endangeredtortoise or lemur may be as low as US$1.

The U.S. government has discontinued its supportfor the environment in Madagascar after over 20years and nearly $150 million of investment. Thisleaves KfW, the German infrastructure fund, and theWorld Bank as the leading funders of new invest-ments in the national parks. These lenders are un-likely mainstays of conservation funding in a regionthat remains one of the highest global conservationpriorities.

If the acceleration of forest loss and wildlife trade cur-rently taking place in Madagascar cannot be stopped,there is no point in planning responses to climate changein the country. Forests dissected by logging and emptyof lemurs that disperse seeds will not be able to sup-port shifts in the ranges of species in response to climatechange. The location of particular climate attributes willmove at spatial extents far greater than that of any for-est remnants that persist. Here habitat loss will pass thethreshold long before species respond to climate change.

An improved political situation with emphasis on goodgovernance needs support from the United States, Eu-rope, and elsewhere. Human development and respectfor laws must be sufficient to reverse the current lossesof habitat or there will be no wildlife populations to pro-tect. In Madagascar, as in many other parts of the world,that message has to be conveyed by conservation pro-fessionals and their allies even as we find responses toclimate change.

Converging Forces, Integrated Response

Society now has sufficient understanding to act as cli-mate changes. There are well-accepted suites of actionsto be pursued. There is understanding that society willhave to act intelligently in the face of uncertainty, or haveno latitude for action. There is much to be learned. Theelements of responses to climate change are not prescrip-tions; they are realms of action that must be tested andrefined in the real world. There must be rapid movementalong this learning curve so that responses precede theundesirable effects of climate change.

Equally urgent is the need to recognize the speed atwhich thresholds are approaching. In Europe and theUnited States, loss of natural habitats has slowed and insome cases is reversing. In much of the tropics, habitatloss continues unabated. Madagascar is an extreme ex-ample, but not, unfortunately, the only one.

Clearly, climate change needs to be understood at thesame time habitat losses need to be halted or reversed.Yet a search of the recent peer-reviewed literature re-veals that over the past year, over 2600 articles haveappeared that address climate change and conservationstrategies, while less than 50 have addressed whetherfunding for global conservation efforts is adequate or thetargets of the Convention on Biological Diversity havebeen reached.

Climate change is more complex than habitat loss. Ad-equate funding and achievement of Convention on Bi-ological Diversity targets are relatively straightforward,but fundamentally important to what conservation pro-fessionals do and how successful we are in the near term.So, we may be justified in studying and writing about cli-mate change. Responses to climate change will determine

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whether long-term conservation is successful. But if wedo not also write about and secure the resources to avoidthe land-use change threshold, we will ultimately be writ-ing to ourselves, grooming each other, while the alphamales have dominion in Madagascar, Southeast Asia, andelsewhere.

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