Special Section Essay
Climate Change, Connectivity, and Conservation Success
Ten years ago in the pages of Conservation Biology, Whitten et al. (2001) asked whether writing about conservation biology served as displacement behavior for biologists. Their point was that extensive destruction of forests in Southeast Asia coincided with a surge in publications about conservation in the region (Whitten et al. 2001). Were biologists writing papers because they had lost the real conservation battle? The same question applies today to climate change. Is studying climate-change biology a kind of displacement behavior for conservation professionals? Is our professional community writing so much about climate change because we have been impotent in addressing habitat loss, the real alpha male of modern conservation?
It is a challenge to address future threats without allowing them to distract all attention from current action. Although each of us needs to reflect on our motivations and effectiveness, the scientific basis for action can be more objectively evaluated. Scientists have been exploring climate-change biology for approximately the same amount of time that Conservation Biology has been published. The seminal papers of Peters and others (e.g., Peters & Darling 1985) appeared as this journal was gaining prominence, and soon articles from these authors appeared in these pages. It now can be asked whether the 25 years of literature provides a sound foundation to inform action.
Here the case will be made that conservation professionals now have the necessary knowledge to address climate change and habitat loss in an integrated way. Action needs to be taken quickly to avoid the threshold at which habitat loss forecloses our options to address climate change. Rapid, informed action and clear priorities can ensure that climate-change biology provides for endurance of our immediate conservation gains and is not an outlet for displacement behavior.
Action in Response to Climate Change
The past decade and a half yielded a strong literature on conservation planning in the face of climate change. Recent reviews point to many elements that climate change biologists agree should be part of any conservation response to climate change: new protected areas, connectivity, adaptive management, managed relocation, and ex situ conservation (Heller & Zavaleta 2009; Mawdsley et al. 2009). These elements can now be implemented and the experience from that action used to refine theory and practice, iteratively improving our practical abilities.
Establishment of protected areas, a leading conservation tool before climate change gained attention, is also an effective measure in response to climate change (Hannah et al. 2007). The placement of new protected areas can anticipate climate change, substantially improving the probability that species and ecosystem functions will be maintained in reserves. Where protected areas are too small to encompass species and ecosystem functions, connectivity between present and future populations is required. Populations, rather than protected areas, are the key elements to be connected, as is explored below.
Where natural processes are more extensive than individual protected areas, adaptive management can facilitate range shifts (Hansen et al. 2003). Coordination across management units is critical. Species may need to be relocated to persist given the very rapid pace of human-induced climate change (McLachlan et al. 2007). For instance, where agricultural or urban land or a topographic barrier interrupts a range shift, artificial movement of the species or its propagules may be warranted (Hoegh-Guldberg et al. 2008). When all else fails, ex situ measures, including captive breeding and gene banking, may be necessary to preserve species and their genetic information. Gene and seed banks that expressly consider climate change are already being established.
Protected areas and connectivity are the most important of these elements to implement because these responses have the potential to conserve the greatest number of species and ecosystems. By the time a species or ecosystem needs managed relocation or ex situ management, the potential for other types of action to conserve them is very limited. Connectivity is perhaps the most misunderstood of these essential tools.
Concepts of Connectivity
Connectivity is one of the most difficult concepts to apply to current practice because confusion exists in the literature about what needs to be connected. Multiple concepts of connectivity are used, often without definition. Connectivity for different purposes and at different scales is sometimes confounded.
Concepts of connectivity as a response to climate change began to emerge with the first publications on climate change and biological diversity. Peters and Darling (1985) and Peters and Lovejoy (1992) recognized that species ranges shift in response to climate, whereas protected areas are fixed in space. Species ranges as characterized in these early concepts were monolithic (i.e., large, continuous areas in which the species was present everywhere and beyond which it was absent). These were representations of the extent of occurrence, the rough equivalent of a species’ range map in a field guide. To communicate the point that species ranges would shift as human-driven climate change accelerates these representations were sufficient.
But when a conservation strategy needs to be developed, a much more nuanced view is needed, that of area of occupancy (habitat patches occupied by individual populations within the extent of occurrence). These are the populations that will be established or extirpated for climate change and that will collectively determine whether the species persists or becomes extinct.
The early concepts of range shifts seemed consistent with emphasizing connectivity among protected areas. A species was either inside or outside a protected area, and if it moved out it would need to be protected at all steps along its travels until it was again in a protected site. A linear corridor between two protected areas seemed a logical mechanism for capturing this dynamic.
A more nuanced view emphasizes populations. Most species exist in multiple populations within a protected area, as well as outside. As climate changes, some of these populations may increase in size while others decrease, and each population will represent a larger or smaller proportion of the total abundance of the species. Populations have a probability of extirpation and also a probability of colonization or recolonization as a function of the ability of propagules or individuals to move (Davis & Shaw 2001).
Connectivity in response to climate change can also be conceptually confused with connectivity among populations of large mammals or the ability of large mammals to disperse or migrate. Much of mainstream connectivity planning is focused on movements of large mammals among protected areas, a critical process as natural land cover becomes increasingly fragmented (Beier et al. 2008). Because large mammals frequently move across large areas, ensuring their ability to disperse often means creating connections between protected areas.
But connectivity for large mammals is not the same as ensuring connectivity for climate change. Connecting populations in time is a finer-resolution phenomenon than connecting protected areas in space. Conservation plans that mix these different concepts very often confuse purposes and scales of connectivity.
Connections among populations as climate changes can be simulated with simple species distribution models (SDMs) and with population models that are complemented by empirical evidence. SDMs constructed for multiple time steps (e.g., decades) can simulate connections among climatically suitable habitat patches (e.g., grid cells) through time (Phillips et al. 2008). Connecting habitat in all time steps is one way to connect populations as climate changes. Finding efficient connections for multiple species then suggests priorities for conservation (Williams et al. 2005). Several software packages (e.g., Network Flow, Zonation) can directly derive or approximate such solutions. Population models can be used to explore connectivity more fully. For example, population models can incorporate SDM outputs to define habitat quality or carrying capacity through time (Keith et al. 2008).
Often the most efficient model solution is to connect habitat over a few square kilometers, as opposed to tens or hundreds of square kilometers. For example, several Leucadendron (conebush species) in South Africa currently have sizable populations in West Coast National Park and smaller populations near the Cederberg Wilderness. In SDM simulations, relative abundances reverse as climate changes, with the populations in the Cederberg expanding and populations in West Coast National Park contracting. Bridging these protected areas with a corridor would be very difficult. West Coast National Park and the Cederberg are separated by about 200 km of largely agricultural land. However, connecting present and future populations at the Cederberg could be accomplished within a few square kilometers or tens of square kilometers. Conserving small populations now would allow them to expand into the protected area as climate changes. In this case, modeling supports the idea that population-level linkages will be effective. Contractual conservation (easements) or the expansion of the protected area could help ensure that populations near the Cederberg would survive to expand and populate the reserve as climate changes.
The Land-Use Change Threshold
In the real world, there is a race between this emerging understanding of responses to climate change on the one hand and ongoing habitat loss on the other. The forces of land-use change are closing out our conservation options for dealing with climate change. If we wait decades for certain knowledge of climate-change effects, land-use change will have already dictated the conservation landscape, and the scope for adapting to climate change will be minimal.
Conversely, if we act now, we will have to act in the face of considerable uncertainty. Dealing intelligently with uncertainty in a landscape with considerable space to make choices seems our best option. Acting intelligently will therefore require taking some risks and convincing society and policy makers that risks are worth taking. The alternative is letting uncertainty become an excuse for inaction. This is no more reasonable in climate-change adaptation than it is in international policy on mitigation.
The real-world challenge is to act before the threshold arrives. There is a window, in some places a very narrow window, in which to maximize the probability that populations can persist as climate changes. Habitat loss is slamming the window shut in some places, and once it is shut, there will be little choice of location for protected areas or connections among habitat patches.
I’m writing this essay in Madagascar, and nowhere is the threshold advancing more rapidly. After a coup d’etat in March 2009, living conditions here have deteriorated in both urban and rural areas. Illegal logging and wildlife trade have surpassed tourism as the nation's fastest growing economic sectors. Containers of illegal wood taken from national parks leave the country regularly. Conservationists in the field have been threatened and assaulted by illegal loggers. Illicit wildlife trade is at record high levels, even though the price in the field for an endangered tortoise or lemur may be as low as US$1.
The U.S. government has discontinued its support for the environment in Madagascar after over 20 years and nearly $150 million of investment. This leaves KfW, the German infrastructure fund, and the World Bank as the leading funders of new investments in the national parks. These lenders are unlikely mainstays of conservation funding in a region that remains one of the highest global conservation priorities.
If the acceleration of forest loss and wildlife trade currently taking place in Madagascar cannot be stopped, there is no point in planning responses to climate change in the country. Forests dissected by logging and empty of lemurs that disperse seeds will not be able to support shifts in the ranges of species in response to climate change. The location of particular climate attributes will move at spatial extents far greater than that of any forest remnants that persist. Here habitat loss will pass the threshold long before species respond to climate change.
An improved political situation with emphasis on good governance needs support from the United States, Europe, and elsewhere. Human development and respect for laws must be sufficient to reverse the current losses of habitat or there will be no wildlife populations to protect. In Madagascar, as in many other parts of the world, that message has to be conveyed by conservation professionals and their allies even as we find responses to climate change.
Converging Forces, Integrated Response
Society now has sufficient understanding to act as climate changes. There are well-accepted suites of actions to be pursued. There is understanding that society will have to act intelligently in the face of uncertainty, or have no latitude for action. There is much to be learned. The elements of responses to climate change are not prescriptions; they are realms of action that must be tested and refined in the real world. There must be rapid movement along this learning curve so that responses precede the undesirable effects of climate change.
Equally urgent is the need to recognize the speed at which thresholds are approaching. In Europe and the United States, loss of natural habitats has slowed and in some cases is reversing. In much of the tropics, habitat loss continues unabated. Madagascar is an extreme example, but not, unfortunately, the only one.
Clearly, climate change needs to be understood at the same time habitat losses need to be halted or reversed. Yet a search of the recent peer-reviewed literature reveals that over the past year, over 2600 articles have appeared that address climate change and conservation strategies, while less than 50 have addressed whether funding for global conservation efforts is adequate or the targets of the Convention on Biological Diversity have been reached.
Climate change is more complex than habitat loss. Adequate funding and achievement of Convention on Biological Diversity targets are relatively straightforward, but fundamentally important to what conservation professionals do and how successful we are in the near term. So, we may be justified in studying and writing about climate change. Responses to climate change will determine whether long-term conservation is successful. But if we do not also write about and secure the resources to avoid the land-use change threshold, we will ultimately be writing to ourselves, grooming each other, while the alpha males have dominion in Madagascar, Southeast Asia, and elsewhere.