Restoring Forest Landscapes in the Face of Climate Change

Jennifer Biringer and Lara J. Hansen

Key Points to Retain

Climate change increases the need for restoration, both to help forest systems to manage existing changes and to buffer them against likely changes in the future by increasing areas of natural, healthy forest systems.

Care needs to be taken to avoid oversim-plistic reliance on forests for carbon sequestration, and attempts at restoration to increase carbon storage must be assessed carefully to judge their true worth.

Tools such as vulnerability analyses can help to design effective restoration strategies, which are likely to include reduction of fragmentation, increasing connectivity, development of effective buffer zones, and maintenance of genetic diversity.

1. Background and

Explanation of the Issue

Climate change is arguably the greatest contemporary threat to biodiversity. It is already affecting ecosystems of all kinds and these impacts are expected to become more dramatic as the climate continues to change due to anthropogenic greenhouse gas emissions into the atmosphere, mostly from fossil fuel combustion. While restoration is made more diffi cult by climate change, it can conversely be seen as a possible adaptive management approach for enhancing the resilience of ecosystems to these changes.

Climate change will result in added physical and biological stresses to forest ecosystems, including drought, heat, increased evapotranspiration, altered seasonality of hydrology, pests, disease, and competition; the strength and type of effect will depend on the location. Such stresses will compound existing nonclimatic threats to forest biodiversity, including overhar-vesting,invasive species,pollution,and land conversion. This will result in forest ecosystems changing in composition and location. Therefore, in order to increase the potential for success, it will be necessary to consider these changes when designing restoration projects.

On the other hand, restoration projects can also be viewed as a key aspect of enhancing ecosystem resilience to climate change. Human development has resulted in habitat loss, fragmentation, and degradation. A first step in increasing resilience to the effects of climate change is enhancing or protecting the ecosystem's natural ability to respond to stress and change. Research suggests that this is best achieved with "healthy" and intact systems as a starting point, which can draw on their own internal diversity to have natural adaptation or acclimation potential,48 and therefore greater resilience. Any restoration activities that enhance the ecological health of a system can

48 Kumaraguru and Beamish, 1981;McLusky et al, 1986.

thus be seen as creating or increasing the potential buffering capacity against negative impacts of climate change. It should be mentioned that there are obvious limits to the rate and extent of change that even a robust system can tolerate. As a result it is only prudent to conduct restoration for enhancing resilience in tandem with efforts to reduce greenhouse gas emissions, the root cause of climate change.

For many with a forestry background, carbon dioxide sequestration might seem a concomitant advantage to restoration projects, which can aid in reduction of atmospheric concentrations of greenhouse gases.While forests do hold carbon, and their loss does release carbon, their long-term capacity to act as a reliable sink in the face of climate change, especially for effective mitigation, is not a foolproof strategy (for more on carbon sequestration projects, see "Carbon Knowledge Projects and Forest Landscape Restoration"). Where restoration is promoted with a focus on capturing carbon, an analysis of climate change impacts should be integrated into project planning to determine whether there really are net sequestration benefits. Increased incidence of forest fires as a result of warming and drying trends, for example, could outweigh any efforts to reduce carbon emissions. Case studies of successful resilience-building efforts are not yet plentiful, due to relatively recent revelations about the scale and impact that climate change will have on ecosystems. However, the global temperature has risen 0.7°C as atmospheric concentrations have risen49 and extinctions and large-scale ecosystem changes are expected. A number of forest types are already being negatively impacted, including tropical montane cloud forests, dry forests, and forests in the boreal zone, and climate-related extinctions are already thought to have occurred, for example amongst amphibians. Along the coasts, the rising sea level is increasing the vulnerability of mangroves. Restoration as a means to ensure healthy ecosystem structure and function will have a large part to play in adapting ecosystems to these broad-scale changes. See Box 5.1 for more in-depth exploration of these topics.

49 Hansen et al, 2003.

2. Example: Mangrove

Restoration as an Adaptive Management Strategy

Mangroves provide a concrete example of how restoration can be used as a tool to help enhance resistance and resilience to climate change. Mangroves are clearly vulnerable to rising sea levels, which will change sediment dynamics, cause erosion, and change salinity levels. The rate of sediment buildup, which is the backbone of mangrove survival, is expected to take place at only half the pace of sea-level rise in many places, and mangrove survival will therefore require active restoration. Another aspect of mangroves that makes them an ideal testing ground for restoration is their relative ecological simplicity. Furthermore, the relationship between human and ecological vulnerability to climate change is relatively clear. Low-lying coastal areas, particularly those in tropical Africa, South Asia, and the South Pacific, are predicted to experience among the most severe consequences of global climate change.50 As these are among the most populous areas across the globe, the livelihoods of many coastal communities that depend on mangrove resources for wood and shrimp farming, will be increasingly tied to their vulnerability to climate change.

Mangrove restoration can do much to limit or delay the negative effects of climate change on associated human and natural communities. Mangroves play an integral role in coastal ecosystems as the interface among terrestrial, freshwater, and marine systems. They are extensively developed on sedimentary shorelines such as deltas, where sediment supply determines their ability to keep up with sea-level rise. They afford protection from dynamic marine processes to both terrestrial and estu-arine systems, preventing erosion and chaotic mixing. They also act locally to filter water. Mangrove forests protect sea grass beds and coral reefs from deposition of suspended matter that is transported seaward by rivers and

50 IPCC, 2001.

Box 5.1. Framework for Understanding Intersection of Resilience-Building and Forest

Restoration and Protection

1. Protection: For some forests protection alone will not increase resilience to climate change. Many tropical montane cloud forests provide a case in point. Australia's Wet Tropics World Heritage Area is expected to experience a 50% reduction in habitat with warming of 1 degree Celsius, which will leave amphibians and other cool-adapted species no upland migration options as conditions become warmer and drier.

2. Sequestration via restoration: Many examples exist where the planting of trees stores carbon but is not coordinated with conservation or resilience-raising advantages. Nonnative trees, such as Eucalyptus, are often planted solely for the carbon benefit, though the planting may cause degradation of the landscape, and thus not provide a buffer against climate change.

3. Resilience/adaptation: Restoration is but one of the many types of management options that increase resilience. For example, actions that respond to changing dynamics such as insect infestations and changing fire patterns are aspects of good forestry that will receive special attention with the advent of climate change. Activities that increase the efficiency of resource use will also increase resilience. In Cameroon, mangroves are being aided by increasing the efficiency of wood-burning stoves so that 75 percent less mangrove wood is needed for cooking, thereby increasing the resilience of the system by reducing harvest levels. Such actions decrease degradation of the mangrove and raise the probability that it will be equipped to respond to the effects of climate change.

4. Sequestration and resilience/adaptation: Restoration and resilience go hand in hand when the impacts of climate change are taken into account in project planning. Whether passive or active restoration, activities target those areas that will be more suitable to climate change, and encourage use of species that will be hardier under new climatic conditions (successful seed dispersers, for example).

5. Intersection of protection, sequestration, and resilience/adaptation: Creating buffer zones through restoration can increase the resilience of protected areas to the impacts of climate change while at the same time sequestering carbon. This scenario is similar to the one above, except that restoration is focussed on increasing the resilience of protected areas by expanding boundaries to increase suitable habitat under changing climatic conditions.

6. Protection and adaptation: Protection can lead to increased resilience to the impacts of climate change, where suitable habitat is intact, and the expansion of boundaries is possible to accommodate species' needs with a changing climate. A successful protected area system includes identification and conservation of mature forest stands, functional groups and keystone species, and climate refugia.

provide nursery habitat for many fish species. Deteriorating water quality and coastal degradation are anticipated to be magnified by climate change. Globally, however, many mangrove systems have already been degraded and destroyed. Loss of these buffering systems precludes any protection they might afford. This has been recognised for some time, and many individual projects have attempted to rebuild mangrove systems. However, in the past, the emphasis of mangrove restoration projects has been on planting trees, and this has led to poor survival rates, such as in West Bengal, India, where survival rates in some projects were reported as low as less than 2 percent.51

New approaches are therefore required. In addition, simply restoring a mangrove where it has been degraded will not necessarily be enough in the face of climate change. Restoration in an environment where the climate is rapidly changing will require taking into account a few additional elements as opposed to restoration in a stable context. Before starting a restoration programme, two additional steps are required: (1) assess the cause of mangrove loss and evaluate how to remove those causes if possible; and (2) take into account the added complexity relating to how climate change will affect the system: in this case primarily through sea-level rise.

A large-scale mangrove restoration effort in Vietnam has demonstrated that this approach to mangrove management can benefit local resource users and enhance protection from storm surge and sea-level rise.52 The restoration project in this region has planted more than 18,000 hectares of mangrove along 100 kilometres of coastline. In addition to creating a more stable coastline capable of surviving changing marine conditions, harvestable marine resources are also increasing in number.

Understanding the hydrology (both frequency and duration of tidal flooding) is the single most important factor in designing successful mangrove restoration projects.53 Incorporating projections of sea-level rise into

51 Sanyal, 1998.

53 Lewis and Streever, 2000.

project design will be necessary so that mangroves are planted or are allowed to colonise naturally or regenerate (this takes 15 to 30 years where stresses leading to degradation are no longer present) in areas that will be more hospitable in the future. If the shoreline is moving, for instance, mangroves may need to be restored some distance from their original location.

3. Outline of Tools

This section offers a framework for integrating knowledge about climate change to forest managers who are considering restoration. It is based on an understanding of how adaptation (in this case to climate change) needs to be integrated with both restoration and protection, as outlined in Box 5.1 above.

3.1 Vulnerability Analysis

To understand how climate change will affect an existing forest system, an analysis of the vulnerability of the defined area can be undertaken. As a first stop, climate change impacts on the major forest types are presented in WWF's Buying Time: A User's Manual for Building Resistance and Resilience to Climate Change in Natural Systems,54 with examples from many different regions collected from the literature. For more specific information on a particular site, a literature search may identify whether a vulnerability analysis has been made of the project area in question.

If limited information on climate change impacts exists for the selected site, a vulnerability analysis can be commissioned to feed into project design activities. An expert conversant in climate change science as well as biological science for the region can piece together a picture of regional vulnerability that will help to guide project activities so that they can take account of likely alterations in environmental conditions as the climate changes. At a large

54 Hansen et al, 2003 (available on www.panda.org).

scale, major shifts in biome types can be projected by combining biogeography models such as the Holdridge Life Zone Classification Model with general circulation models (GCMs) that project changes under a doubled CO2 scenario. Biogeochemistry models simulate the gain, loss, and internal cycling of carbon, nutrients, and water-impact of changes in temperature, precipitation, soil moisture, and other climatic factors that give clues to ecosystem productivity. Dynamic global vegetation models integrate biogeochemical processes with dynamic changes in vegetation composition and distribution. Studies on particular species comparing present trends with paleo-ecological data also provide indications for how species will adapt to climate change.55

A vulnerability analysis can help to assess what systems or aspects of the systems have greater resilience and resistance to climate change impacts. This type of information can help to identify sites that have greater long-term potential as ecosystem "refugia" from climate change impacts. Some refugia exist due to their unique situational characteristics, but their resilience could be enhanced by management and restoration.

3.2 Restoration as a Resilience/ Adaptation Strategy

After completing a vulnerability analysis to determine how a forest system may be impacted by changing climatic conditions, the next step is to look at the range of adaptation options available in order to promote resilience. An effective vulnerability analysis will determine which components of the system— species or functions, for example—will be most vulnerable to change, together with consideration of which parts of the system are crucial for ecosystem health. An array of options pertinent to adapting forests to climate change are available, both to apply to forest communities at high risk from climate change impacts as well as for those whose protection should be prioritised given existing resilience. Long-term

55 Hansen et al, 2001.

resilience of species will be enabled where natural adaptation processes such as migration, selection, and change in structure are allowed to take place due to sufficient connectivity and habitat size within the landscape.

Restoration can provide a series of critical interventions to reduce climate change im-pacts.56 Basic tenets of restoration for adaptation include working on a larger scale to increase the amount of available options for ecosystems, inclusion of corridors for connectivity between sites, inclusion of buffers, and provision of heterogeneity within the restoration approach. Key approaches are as follows:

Reduce fragmentation and provide connectivity: Noss57 provides an overview of the negative effects of ecosystem fragmentation, which are abundantly documented worldwide. "Edge effects" threaten the microclimate and stability of a forest as the ratio of edge to interior habitat increases. Eventually, the ability of a forest to withstand debilitating impacts is broken. Fragmentation of forest ecosystems also contributes to a loss of biodiversity as exotic, weedy species with high dispersal capacities are favoured and many native species are inhibited by isolation. Restoration strategies should therefore often focus first on those areas where intervention can connect existing forest fragments into a more coherent whole. Provide buffer zones and flexibility of land uses: The fixed boundaries of protected areas are not well suited to a dynamic environment unless individual areas are extremely large. With changing climate, buffer zones might provide suitable conditions for species if conditions inside reserves become unsuitable.58 Buffer zones increase the patch size of the interior of the protected area and overlapping buffers provide migratory possibilities for some species.59 Buffer zones should ideally be large, and managers of protected areas and surrounding lands must demonstrate considerable flexibility by adjusting

56 Biringer, 2003;Noss, 2001.

57 Noss, 2000.

58 Noss, 2000.

59 Sekula, 2000.

land management activities across the landscape in response to changing habitat suitability. A specific case for a buffer zone surrounding tropical montane cloud forests can be made based on research that shows that the upwind effects to deforestation of lowland forests causes the cloud base to rise.60 Restoring forest around protected areas, for example to supply timber through continuous cover forestry, or for nontimber forest products, watershed protection, or as recreational areas, could help maintain the quality of the protected area in the face of climate change.

Maintain genetic diversity and promote ecosystem health via restoration: Adaptation to climate change via selection of resilient species depends on genetic variation. Efforts to maintain genetic diversity should be applied, particularly in degraded landscapes or within populations of commercially important trees (where genetic diversity is often low due to selective harvesting). In such places where genetic diversity has been reduced, restoration, especially using seed sources from lower elevations or latitudes, can play a vital role in maintaining ecosystem resilience.61 Hogg and Schwarz62 suggest that assisted regeneration could be used in southern boreal forests in Canada where drier conditions may decrease natural regeneration of conifer species. Similarly, genotypes of beach pine forests in British Columbia may need assistance in redistributing across the landscape in order to maintain long-term productivity.63 In addition, species that are known to be more resilient to impacts in a given landscape can be specifically selected for replanting. For example, trees with thick bark can be planted in areas prone to fire to increase tree survival during increased frequency and severity of fires.64

60 Lawton et al, 2001.

61 Noss, 2000.

62 Hogg and Schwarz, 1997.

63 Rehfeldt et al, 1999.

64 Dale et al, 2001.

4. Future Needs

Documentation of the role restoration plays in building resilience to climate change is in its infancy. Although field projects are beginning to test restoration as a resilience-building tool, we are far from definitive guidance. Unfortunately, this is the nature of the practice of conservation; decisions based on best knowledge need to be made now while we continue to gather more information. Otherwise, opportunities will be lost.

To meet these needs we propose additional field projects to test, confirm, and develop restoration's role in building resilience to climate change. This needs to be conducted across different forest types with as much replication as possible. A strong monitoring component is necessary for any such project, especially given the complex relationships between species' structure, composition, and functioning on which climate change is unfolding. The results of monitoring will also enable lessons to be drawn from resilience-building efforts, and to compare these with similar "control" landscapes or other resilience-building projects in different regions with similar habitat type.

Ideally, resilience-building management strategies will serve as another layer in a comprehensive forest management plan that has as its objective the overall health of the forest ecosystem. For example, many WWF eco-regional visions are adding vulnerability to climate change as another component that will drive conservation decisions. Such anticipatory resilience-building plans take climate change into account during the planning process, and will better ensure synergies with other management priorities. A number of scientific, governmental institutions and nongovernmental organisations (NGO) are acquiring expertise in the area of climate change impacts and adaptation/resilience. It will be fruitful to seek partnerships with these institutions at the beginning of any restoration project to analyse climate impacts and proposed restoration activities.

References

Biringer, J. 2003. Forest ecosystems threatened by climate change: promoting long-term forest resilience. In: Hansen, L.J., Biringer, J.L., and Hoffman, J.R. eds. Buying Time: A User's Manual for Building Resistance and Resilience to Climate Change in Natural Systems.WWF,Washington, pp. 41-69. (Also online at www.panda.org/climate/ pa_manual)

Dale, V., Joynce, L., McNurlty, S., et al. 2001. Climate change and forest disturbances. Bioscience 51(9): 723-734.

Hansen, A., Neilson, R., Dale, V., et al. 2001. Global change in forests: responses of species, communities, and Biomes. Bioscience 51(9):765-779.

Hansen, L.J., Biringer, J.L., and Hoffman, J.R. eds. 2003. Buying Time: A User's Manual for Building Resistance and Resilience to Climate Change in Natural Systems. WWF, Washington, 242 pages. (Also online at www.panda.org/climate/pa_ manual.)

Hogg, E., and Schwarz, A. 1997. Regeneration of planted conifers across climatic moisture gradients on the Canadian prairies: implications for distribution and climate change. Journal of Biogeogra-phy 24:527-534.

Intergovernmental Panel on Climate Change (IPCC). 2001. Impacts, Adaptations and Vulnera-bility.Working Group II,Third Assessment Report. Cambridge University Press, Cambridge, UK, 1032 pages.

Kumaraguru A.K., and Beamish, F.W.H. 1981. Lethal toxicity of permethrin (NRDC 143) to rainbow trout, Salmo gairdneri, in relation to body weight and water temperature. Water Research 15:503505.

Lawton, R., Nair, U., Pielke, R., and Welch, R. 2001. Climate impact of tropical lowland deforestation on nearby montane cloud forests. Science 294 (5542):584-587.

Lewis, R., and Streever, B. 2000. Restoration of mangrove habitat. WRP Technical Notes Collection

(ERDC TN-WRP-VN-RS-3.2), U.S. Army Engineer Research and Development Center, Vicks-burg, MS. www.wes.army.mil/el/wrp.

McLusky, D.S., Bryant, V., and Campbell, R. 1986. The effects of temperature and salinity on the tox-icity of heavy metals to the marine and estuarine invertebrates. Oceanography and Marine Biology Annual Review 24:481-520.

Noss, 2000. Managing forests for resistance and resilience to climate change: a report to World Wildlife Fund U.S., 53 pages.

Noss, R. 2001. Beyond Kyoto: forest management in a time of rapid climate change. Conservation Biology 15(3):578-590.

Rehfeldt G.,Ying, C., Spittlehouse D., and Hamilton, D., Jr. 1999. Genetic response to climate in Pinus contorta: niche breadth, climate change and reforestation. Ecological Monographs 69(3):375-407.

Sanyal, P. 1998. Rehabilitation of degraded mangrove forests of the Sunderbans of India. Programme of the International Workshop on the Rehabilitation of Degraded Coastal Systems. Phuket Marine Biological Center, Phuket, Thailand, January 19-24, p. 25.

Sekula, J. 2000. Circumpolar boreal forests and climate change: impacts and managerial responses. An unpublished discussion paper prepared jointly by the IUCN Temperate and Boreal Forest Programme and the IUCN Global Initiative on Climate Change.

Tri, N.H., Adger, W.N., and Kelly, P.M. 1998. Natural resource management in mitigating climate impacts: the example of mangrove restoration in Vietnam. Global Environmental Change 8(1): 49-61.

Additional Reading

Krankina, O., Dixon, R., Kirilenko, A., and Kobak, K. 1997. Global climate change adaptation: examples from Russian boreal forests. Climatic Change 36(1-2):197-215.

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