Restoration,

John P McCarty and Joy B Zedler Volume 2, The Earth system: biological and ecological dimensions of global environmental change, pp 532–539

Edited by

Professor Harold A Mooney and Dr Josep G Canadell

in Encyclopedia of Global Environmental Change (ISBN 0-471-97796-9)

Editor-in-Chief

Ted Munn

 John Wiley & Sons, Ltd, Chichester, 2002 a community that existed prior to human disturbance. For Restoration, Ecosystem the purposes of this article, we also include rehabilitation projects, where it is recognized that past conditions cannot John P McCarty1 and Joy B Zedler2 be recreated. Instead, establishing some alternative ecosys- 1Environmental Protection Agency, Washington, DC, USA tem is the target. We also consider reclamation projects 2University of Wisconsin, Madison, WI, USA that attempt to create an ecosystem that will provide spe- cific ecological services, such as constructing a wetland to treat runoff, without regard for the species composition or Ongoing changes to the earth’s climate, disruptions of nutri- overall ecological integrity. ent cycles, and changes in land use are expected to result The typical goal of is to restore a past in extensive disruptions to natural communities and ecosys- state. Yet the very nature of environmental changes at the tems. These disruptions will likely result in the extinction global scale, especially global climate change, means that of valued species of plants and animals and the loss of conditions in a given area are changing in such a way that important ecological services. At the same time, the poten- they will no longer be appropriate for the communities of tial strategies for minimizing the effects of these changes on recent history. Instead, restoration will provide tools and at the regional scale are extremely limited. experience to smooth ‘the recovery and management of Restoration of degraded ecosystems is one promising ecological integrity’. For a given area, the target ecosystem strategy for reducing the negative impacts of global change. will be one consistent with the new and changing climatic Ecological restoration attempts to promote recovery of conditions. Restoration may also be valuable in helping ecosystems damaged by human activities. Restoration is to preserve currently existing, distinct communities by increasingly attempted in freshwater, wetland, grassland, establishing them in new areas where climate has become and forest ecosystems. The results of these efforts have favorable. been mixed. Many restoration projects involve high inputs In this article, we first review how restoration ecology of time and money for each hectare restored and ongo- is being applied in different types of ecosystems. For each ing maintenance is frequently required. In many cases, ecosystem, we consider how global change is expected to the species that make up a community can be estab- affect species and communities and how restoration ecol- lished but healthy ecosystem functioning is more difficult ogy might address problems that emerge. We focus on to restore. climate change, rather than other aspects of global change, In the future, restoration ecology will likely play an because changes in climate are expected to affect virtu- important role in speeding the recovery of ecosystems dam- ally all ecosystems (Intergovernmental Panel on Climate aged by global change. While some of the difficulties facing Change, 1996), and because prevention measures that might ongoing restoration projects are likely to be overcome with reduce impacts of changing climate have not been widely time and effort, it is probable that future ecological restora- adopted. The lack of prevention strategies increases the tion will be unable to restore degraded natural communities importance of approaches such as restoration that focus on completely. minimizing or reversing negative impacts on ecosystems. Restoration has proven to be a useful tool for address- ing ecosystem degradation due to non-climate components Restoration and related land-management projects offer of global change such as acid or nutrient deposition and potential tools for mitigating some of the effects of global changes in land use. Next, we discuss how ongoing restora- change on ecosystems. According to the Society for Eco- tion efforts might be modified to prepare for future climate logical Restoration, “Ecological restoration is the process change. Finally, we discuss the limitations and advantages of assisting the recovery and management of ecological of restoration ecology as a strategy for helping ecosystems integrity. Ecological integrity includes a critical range of adapt to climate change. While restoration has many advan- variability in biodiversity, ecological processes and struc- tages over other possible strategies for mitigating the effects tures, regional and historical context, and sustainable cul- of climate change on ecosystems, it is clear that none of tural practices.” This approach presents an attractive basis the currently available tools will be sufficient to avoid the for addressing some of the effects anticipated from changes negative effects of climate change. in climate, nutrient cycles, and land use patterns. Around the globe, restoration efforts are underway to reverse the damages of historical land use to restore ecosys- ECOLOGICAL RESTORATION AND tem services and natural diversity. Most projects are very POTENTIAL APPLICATIONS TO CLIMATE small, but a few large regional programs are underway (e.g., CHANGE restoring the hydrology of the Everglades (Florida, US) and restoring parts of the San Francisco Bay Delta, US). The Traditionally, much of the focus of environmental sci- ultimate goal of many restoration projects is to reestablish ence has been on removing sources of stress from the 2 THE EARTH SYSTEM: BIOLOGICAL AND ECOLOGICAL DIMENSIONS OF GLOBAL ENVIRONMENTAL CHANGE environment, such as removing toxic chemicals or reducing be most relevant where climate change exacerbates exist- inputs of nutrients. Global climate change challenges this ing problems, such as increased nutrient loading due to traditional approach in part because elimination of warming increased precipitation or decreases in dissolved oxygen associated with global climate change presents formidable concentration due to higher water temperature. technological, social, and political obstacles. Because it is Acid deposition is one component of global environmen- not likely that we will be able to reverse climate change tal change, and the scale of the efforts devoted to treat- in time to prevent widespread disruptions of ecosystems, ing impacted areas suggests that substantial resources can it becomes necessary to find other means of reducing the be dedicated to regional restoration efforts. One approach negative impacts of climate change. One approach will to restoring lake ecosystems affected by acid deposition be to speed the natural processes responsible for ecosys- involves application of lime to neutralize acid (Schindler, tem recovery. We suggest that restoration, especially large 1997). In Sweden alone, 7500 lakes have been repeatedly regional projects, can help address these changes in the limed as part of efforts to restore acidified lakes (Appleberg, future. It is also possible for ongoing projects to incorpo- 1998). Regular application of lime can moderate acidity but rate actions that will help buffer ecosystems against the additional restoration, such as restocking of fish, is usu- negative impacts of climate change. ally needed to restore communities fully (Schindler, 1997; Ecosystems will differ in how they respond to climate Appleberg, 1998). change, which would have far-reaching effects on natural Changes in thermal characteristics of habitats will likely ecosystems (Intergovernmental Panel on Climate Change, exacerbate the already high rates of endangerment of 1996). In general, the effects of climate change will act on aquatic species (Dobson et al., 1997). Many endangered populations and species. The tolerances of each species for and threatened aquatic species have geographic ranges that changing climatic conditions will differ, but it is expected encompass a narrow range of thermal conditions and have that many species will no longer be able to persist in part limited abilities to disperse to new habitats. Rising water or all of their current geographic ranges (Intergovernmental temperatures will tend to exclude fish species from areas Panel on Climate Change, 1996). Even species that can where they now exist, while appropriate thermal habitats tolerate wide ranges of climatic conditions are likely to be will occur to the north of current ranges. Restoration ecol- impacted as their predators, competitors, and prey respond ogy could play a role in providing new habitats for those to climate change. In response, species might shift their species in thermally appropriate areas. The slow rate of geographic range to suitable areas, change their behavior dispersal to new habitats, especially for species in isolated so they are active at cooler times of year, or evolve to lakes, will severely limit the ability of fish to shift their geo- tolerate the new conditions. Species that fail to adjust to graphic range in response to climate change. Translocations new conditions rapidly enough will become locally extinct. could speed the adjustment of dispersal-limited species. Here we describe progress in ecological restoration in However, many of the existing problems in aquatic sys- freshwater, wetland, grassland, and forest ecosystems. For tems result from introductions of species by humans to each ecosystem type, we briefly outline special challenges new habitats. Introducing species to cooler waters would they will likely face from changes in climate and outline need to follow thorough research on the potential impacts how restoration might be applied to meet those challenges. to species already in place and acknowledgment of the eco- logical risks involved. Creation of new habitats in enclosed Freshwater Ecosystems basins (reservoirs) may be one approach to minimize the risks from such assisted range extensions. Under generally accepted climate change scenarios, aquatic Of particular importance to future efforts will be improv- ecosystems face possible changes in both temperature and ing techniques for dealing with invasions by nuisance the amount of water available (Intergovernmental Panel on species. Changes in water temperature will probably allow Climate Change, 1996). Freshwater systems are already further expansion of the ranges of aggressive exotic species, severely challenged and contain large numbers of threat- exacerbating existing problems. Experience with aggres- ened and endangered species (Dobson et al., 1997). Many sive invaders such as rusty crayfish Orconectes rusticus aquatic organisms are sensitive to water temperature and and zebra mussel Dreissena polymorpha as well as numer- will face increasing stress from changes in thermal regimes. ous aquatic plant and fish species shows the difficulties Efforts to rehabilitate degraded lake ecosystems date managers face in attempting to limit ecosystem damage back many decades. Most early efforts were responses caused by invaders. Introductions of predatory game fish to excessive nutrient inputs and resulting eutrophication. have disrupted many unique communities, but significant Noteworthy examples include Lake Washington in Seattle, restoration can be initiated if the fish can be eliminated US and Lake Erie in the US and Canada, where reduc- (McNaught et al., 1999). Unfortunately, attempts to control tions in nitrogen and phosphorus inputs produced dramatic the species composition of aquatic communities, especially improvements in water quality. Similar approaches will smaller, non-game fish, algae, and higher plants, have had RESTORATION, ECOSYSTEM 3 limited success (Welch and Cooke, 1987) (see Lakes and the latter process, levees can be breached to allow salt Rivers, Volume 2). marsh to reestablish in low lying areas (Packham and Willis, 1997; Gilbert and Anderson, 1998) or broad inland Wetland Ecosystems buffers can be set aside to allow salt marsh migration up slopes. Climate change threatens to stress wetland species through One of the most damaging effects of climate change on direct effects of temperature and carbon dioxide (CO2) con- coastal wetlands may be from increased storm frequencies centration and through changes in hydrology due to precip- and magnitudes. Extreme high tides can carry salts inland itation, evaporation and sea level changes (Michener et al., on to intolerant vegetation and soils. Salty soils will favor 1997). Temperature increases are likely to damage wetlands the inland migration of halophytes, which will be necessary that store carbon in the form of organic matter. Cana- to maintain salt marshes where sediment accretion cannot dian peatlands and the Arctic tundra could release major keep up with inundation (Michener et al., 1997). quantities of carbon to the atmosphere through increased Species will likely migrate into newly inundated areas decomposition rates as a result of warming or drying (Inter- at different rates and be affected by different substrates governmental Panel on Climate Change, 1996). Experi- and competitors inland, so some species may need to be ments with multiple factors and many types of wetlands translocated. The high-intertidal marsh of Southern Cali- are needed to make long-term predictions of community fornia, US, is a good example of an assemblage that may change, however. The hydrologic restoration of drained need to be translocated in anticipation of sea-level rise. peatlands in advance of climate change would help buffer Three high-marsh perennials are already rare and they rarely the globe against these impacts. reproduce from seed. Frankenia palmeri has only one nat- Small ponded wetlands and dry-end wetlands will be ural occurrence in the US, but in Mexico it occurs in both very sensitive to altered hydrology (Sorenson et al., 1998). salt marsh and upland areas. Salicornia subterminalis (D Because half of North America’s waterfowl are reared in Arthrocnemum subterminale)andMonanthochloe littoralis prairie potholes, and because duck production is directly are more widespread in Southern California but their popu- correlated with the number of small ponds, there would lations have been greatly reduced by trails, roads, and other be measurable impacts to waterfowl following changes in disturbances. These species show promise for experimental precipitation and evaporation (Sorenson et al., 1998). The planting in upland buffers. Plants should be grown from acceleration of current efforts to restore drained potholes seed to provide genetic diversity, so that selection could throughout the Midwest could mitigate some of the negative operate after tides begin to inundate the populations. The impacts in advance, but biodiversity would still likely benefits (enhanced genetic diversity) and risks (contamina- decline, as not all species return with renewed ponding tion of local gene pools) of bringing in seed from Mexico (Galatowitsch and van der Valk, 1996). would first need to be weighed. Many wetlands have lost their natural water regimes, Much of the motivation for restoring wetlands is to especially flood pulsing and the accompanying mechanical provide ecological services, such as nutrient removal and disturbances and nutrient influxes that invigorate floodplain retention. Restoring specific functions is usually more dif- wetlands (Middleton, 1999). In some cases, restoration may ficult than simply reestablishing plant cover (Mitsch and be accomplished simply by removing impediments to water Wilson, 1996; Simenstad and Thom, 1996; Zedler, 1996b), flow (Gilbert and Anderson, 1998). Where dams perma- and even state of the art techniques cannot yet restore a nently reduce flooding of wetlands, significant improve- heavily disturbed ecosystem to a specific, self sustaining ments can be achieved by periodic water releases that mimic state. seasonal floods (Vaselaar, 1997; Middleton, 1999). The most restorable sites are those with some remnant Hydrological changes may be greatest for coastal wet- of natural topography, hydrology, or species composition. lands, where sea levels in many areas may rise more The return of the channeled Kissimmee River to its histori- than 0.5 m by 2100 (Intergovernmental Panel on Climate cal riverbed rapidly restored native wetland plant cover and Change, 1996). Salt marshes will be lost where sea walls attracted populations of desirable invertebrates, fishes, and obstruct their migration inland and/or where sedimenta- birds in the pilot demonstration project (Toth, 1996). More tion cannot keep pace with inundation. Restoration efforts challenging is the plan to restore water flows to the Ever- would help mitigate future losses due to sea level rise. glades, as water supplies are finite and Southern Florida, Methods include reestablishing tidal flow through removal US, metropolitan areas permanently divert much of the of dikes, reintroducing species, and excavating new wet- water that used to form the ‘river of grass’. On the positive lands (Simenstad and Thom, 1996; Zedler, 1996a; Williams side, the US National Park System sustains a large area of and Watford, 1997). Inundation problems can be combated native vegetation, and providing more water should help it by encouraging sedimentation and marsh building (Smit persist. Least restorable is the San Francisco Bay Delta, a et al., 1997) or accommodated by ‘managed retreat’. In huge complex system of river channels (mostly leveed for 4 THE EARTH SYSTEM: BIOLOGICAL AND ECOLOGICAL DIMENSIONS OF GLOBAL ENVIRONMENTAL CHANGE

flood control), water diversion canals (designed to move restore native communities. Compared to many restoration water to Southern California), and islands (leveed, because activities, controlled burning or grazing can impact large farming has caused substantial subsidence). Although the areas of habitat, as will be needed to mitigate effects of main ecosystem restoration goal is to enhance native species global change. and reduce exotics (especially fishes), there is little natu- Prairie restoration has focused almost exclusively on the ral habitat left and water demands preclude full hydrologic establishment of plant communities, assuming that ani- restoration. Restoration to historical conditions is not pos- mals will find their way to suitable habitats (Kline and sible, but this is just the type of project that could include Howell, 1987). While many prairie specialist birds and large experiments to create climate-buffered ecosystems. small mammals do become established on restored prairies, Some portion of the project could be designated as an exper- many others will not do so without active intervention. imental climate change reserve (see Marshes, Anthro- For example, mound building ants play an important role pogenic Changes, Volume 3). in natural prairie ecosystems by cultivating the soil and providing open space where forbs can become established. Grassland Ecosystems Experience with the restored prairies at the University of Wisconsin Arboretum, US, found that even 50 years after Grasslands and prairies occur where conditions are wet plant communities were in place, ants were absent from enough for grasses but too dry for shrubs and trees (or much of the available habitat (Kline and Howell, 1987). too disturbed by fire or grazing). Because moisture and fire Because most restored prairies require continual mainte- are key factors, grassland will be especially sensitive to nance (time and money), opportunities for mitigating the changes in precipitation and in climate variability. effects of climate change exist primarily at small spatial Grasslands and prairies have undergone extensive restora- scales. These efforts could provide important source pop- tion over the last 65 years to recreate the aesthetic structure ulations for the eventual natural spread of prairie species. of prairies, to reintroduce fire to rehabilitate prairie rem- Even relatively small patches of habitat may prove valu- nants, and to create functioning ecosystems on abandoned able in this role. For example, the 24 ha Curtis Prairie farmland (Kline and Howell, 1987; Muller et al., 1998). at the University of Wisconsin Arboretum, US, has main- Restoring biodiversity requires continual planting and con- tained populations of about 170 native prairie plant species, tinual management of exotic invasions. Some species are even though it is surrounded by non-prairie habitats (Cot- notoriously difficult to maintain, while many invasive tam, 1987). Manipulation of disturbance will be possible at exotics are notoriously difficult to eradicate (Cottam, 1987; larger scales, provided grassland species are already present Kline and Howell, 1987). A good understanding of the (see Temperate Grasslands, Volume 2; Tropical Savan- ecology of the organisms involved and ongoing manage- nas, Volume 2). ment, are needed to maintain restored habitats (Cottam, 1987). Difficulties are compounded when the original soil Forest Ecosystems is badly degraded and a diverse seed bank absent. Suc- cess of restoration attempts of species-rich grasslands in Forest ecosystems experience ongoing degradation and France has been slowest and least predictable in areas where destruction through harvesting and clearing activities. Re- intensive agriculture or engineering processes have caused maining fragments are subject to multiple stresses such degradation of soil quality and loss of seed banks (Muller as air pollution, , and new pests and et al., 1998). pathogens. Changes in temperature and moisture will be In North America, prairie restoration tools include the a source of added stress, which will likely alter forest pro- use of herbicides, cultivation, and planting (Cottam, 1987; ductivity and ecosystem functioning, while the distributions Kline and Howell, 1987). Labor intensive seed gathering of most temperate zone trees will shift poleward, changing and planting has been successful on small-scale plots (Cot- species composition (Intergovernmental Panel on Climate tam, 1987; Packard and Mutel, 1997). Larger scale efforts Change, 1996). have adapted agricultural practices to the harvest and plant- From the long history of tree planting, we know that ing of native species. many species can thrive when planted far outside their Perhaps the most important lesson from work on grass- natural ranges (Ashby, 1987). Hence, some tree species land restoration is the usefulness of controlling fire and should be able to survive despite climatic changes, while other disturbances as a means of altering or maintain- others should be able to grow when planted in favorable ing community composition. Many grassland communities sites. While this is encouraging, forests also provide some depend on the periodic disturbance caused by fire to pre- of the clearest examples of the need to plant locally adapted vent woody species from invading (Packard and Mutel, populations or ecotypes (Ashby, 1987). The ease with 1997; Davison and Kindscher, 1999). The manipulation of which trees are established in artificial settings does not disturbance in the form of fire or grazing can be used to mean that planted populations will be self-sustaining or RESTORATION, ECOSYSTEM 5 that other forest species of plants and animals will establish is highly valuable for evaluating impacts and adaptation a functioning ecosystem (Ashby, 1987). One of the more to global change, as well as our ability to compensate difficult factors to account for in future restoration of through restoration (see Boreal Forest, Volume 2; Nitro- forests will be the tight symbiosis between many plants and gen Deposition on Forests, Volume 2; Temperate Conif- mycorrhizal fungi. Most plants depend on mycorrhizae for erous Forests, Volume 2; Temperate Deciduous Forests, efficient uptake of water and nutrients, but the abilities of Volume 2; Rainforest, Volume 2). soil organisms to adapt to climate change are unknown. The ability of restoration to promote the rapid reestablishment of forest functioning will depend in large part on our BUILDING A CLIMATE CHANGE BUFFER INTO ability to establish healthy populations of soil organisms RESTORATION PROJECTS (Haselwandter, 1997). Longleaf (Pinus palustris) forest ecosystems pro- Significant uncertainties about future climatic conditions vide a good case history for restoration of forest landscapes. exist. This is especially true at the relatively small scale Longleaf pine forests once covered 60% of the Southeastern of ecological processes and for precipitation and climatic US coastal plain, stretching from North Carolina to Texas. variability. In order for current restoration efforts to prepare Longleaf pine forests host a surprising diversity of plant for the negative impacts of climate change, we need to and animal species, including a large number of threat- understand the nature of climatic changes anticipated for a ened and endangered species. Critical to the maintenance given site, and how land-management projects can best be of these systems are periodic fires carried by understory planned to accommodate them. Significant advances in both plants that prevent invasion by deciduous oaks. Today, less climatic modeling and in understanding how ecosystems than 10% of the original forests remain intact (Johnson respond to changing climate will be needed before this is possible. and Gjerstad, 1998). This loss of a valuable ecosystem All sizes of restoration projects can build in some buffer has led to an increasing interest in restoring longleaf pine against the negative aspects of climate change, but the communities by reintroducing fire and establishing popula- greatest potential lies with the larger projects, such as tions of indigenous plants and animals. Some of the largest the longleaf pine forest, Kissimmee River, Everglades, restoration projects ever undertaken are now in progress. and San Francisco Bay Delta projects in the US. Large The US Department of Defense military bases alone man- size restoration projects, like large preserves, can sustain age approximately 400 000 ha of longleaf-type vegetation more species and more genotypes. They can also support (Johnson and Gjerstad, 1998). more effective exotic-species control programs, as they Wiregrass (Aristida spp.) forms the dominant ground- are more likely to have smaller perimeter/interior ratios, cover in most natural longleaf communities and provides thus reducing chances for reinvasion. Finally, they would fuel to carry fires (Means, 1997). Attempts to create a have the space needed to include well-planned translocation wiregrass understory in longleaf pine restorations provide experiments. an informative example of the limitations of restoration Until more specific information is available, recommen- efforts. While wiregrass populations are present in many dations for buffering restoration sites are general, and stands undergoing restoration, and plantings can be estab- they focus on increasing the resilience of communities lished with relative ease, these populations have typically in the face of environmental variability. These actions failed to spread (Means, 1997; Seamon, 1998). Thus, while include: the species is present in the community, it fails to expand to serve a necessary function in the ecosystem (e.g., promoting 1. Reintroduction of the full range of biodiversity (plants, the spread of beneficial fires). animals, microbes) that was thought to occur prior to Large-scale restoration of tropical forests has been initi- site degradation. ated in both Latin America, Asia, and Australia. In Costa 2. Maintenance of topographic heterogeneity; too many Rica, restoration efforts have focused on facilitating the nat- restoration sites have artificial landforms that are unnat- ural recovery of ecosystems by promoting regeneration of urally smooth, due to modification by bulldozers. forest trees and by attempting to control disturbance due 3. Reintroduction of diverse gene pools. Growing plants to fire (Janzen, 1988; Holl, 1998). An alternative approach from seed in preference to vegetative propagation. If is to increase the ecological integrity of the large areas of the latter is necessary, ramets should be from multiple tropical forest that have been converted to timber planta- clones. tions. These areas may be improved, though not restored 4. Eradication of exotic species and monitoring range to a pristine state, by promoting the use of native species, expansion by new invasive species. planting mixtures of species, and altering landscape patterns 5. Allowing native species to remain on site. Some excep- of forests to provide buffers (Lamb, 1998). The expe- tions might be highly aggressive natives that might rience gained through landscape-scale forest restorations lower overall biodiversity. 6 THE EARTH SYSTEM: BIOLOGICAL AND ECOLOGICAL DIMENSIONS OF GLOBAL ENVIRONMENTAL CHANGE

6. Carefully monitored, experimental translocations of to be added to highly degraded restoration sites (Hasel- declining native species at restoration sites outside wandter, 1997). While this is a common tool, we do not these species’ natural range. This recommendation know the abilities of mycorrhizae and other soil organ- is consistent with biodiversity conservation efforts isms to adapt to climate change. Further complications may involving gardens, zoos, and seed banks but must be involve other microbes. carefully planned to avoid adverse effects from intro- Research will need to be done before we can rely ducing non-native species. on restoration tools to ameliorate the effects of climate change at the large scale. Some encouragement comes These suggestions are not specific to any climate scenario from fire and water management, however, as both have but are meant to increase the resilience of natural commu- been used to restore large expanses of habitats. The nities faced with a variety of anthropogenic stresses. Thus, release of flood waters from Glen Canyon provides a pos- they could be applied before reliable site-specific informa- itive model (Vaselaar, 1997), although the magnitude of tion on climate change becomes available. planned flooding can never match historical extremes. We encourage replication of flooding experiments over time and THE STATUS OF THE SCIENCE OF large-scale experimentation in general. RESTORATION ECOLOGY Several scientific challenges will need to be met before CONCLUSIONS climate-buffered ecosystems can be designed. It is unlikely that restoration tools can be used to prevent 1. Foremost, we will need reliable predictions of when, negative impacts on ecosystems caused by climate change. where, and how environmental conditions will change. However, global change can and should be considered when 2. Next, we need to predict how species will respond to designing restoration projects. Detailed adaptation of ongo- these changes, especially which species are most likely ing ecological restorations is hampered by the uncertainties to go extinct as a result of climate change and which about the exact nature of future changes in climate and ecosystem functions will be impaired. about ecosystem responses at specific sites. Until we have 3. We need to be able to select appropriate tools to sustain reliable, site-specific predictions, it is premature to suggest biodiversity. translocations into natural habitats, as we know too little 4. We need to understand the relationship between ecosys- about how the receiving site might be affected. A possi- tem structure and functioning. More attention will need ble exception would be restoration sites designed to sustain to be directed towards the interactions among species rare plants and animals beyond their natural range (climate that govern processes such as nutrient and water cycles, change reserves). community stability, and the regulation of primary In general, restoration tools will be more useful after productivity. natural systems are noticeably degraded by climate change. 5. We need to document the current status of reference If ecosystem degradation due to changing climate cannot sites. A major constraint on restoring historical habi- be prevented, then ecological restoration may be one of tats is our lack of knowledge of their structure and the few strategies available to ameliorate the damage. functioning. But looking ahead 50 to 150 years, we Once again, restoration is unlikely to compensate fully will have no excuse for not making detailed records of for the loss of species and the reduction in ecosystem conditions such as species composition, productivity, functioning that will likely result from significant climate and nutrient dynamics. With new technology, such as change. remote sensing, we can plot the precise locations of rare We expect that most efforts to ameliorate climate change species populations and the geographical boundaries of will be of small spatial scale. Nevertheless, they will be species with various traits, for which we hypothesize important. Small patches of habitat provide refugia for likely expansions, compressions, range shifts, or no sedentary species and sources of propagules and colonists change. This will provide future biodiversity managers for future natural expansion. Preservation of genetic diver- a basis for assessing change and considering restoration sity will offer greater potential for natural selection in actions. the face of changing climate. The result, especially if the Climate change may affect critical components of the restoration site is large, should tend toward a climate- ecosystem that are yet unknown. The processes that go on buffered ecosystem. below ground, for example, are at the frontier of ecology. Progress in developing restoration tools provides both a The tight symbiosis between plants and mycorrhizal fungi reason for hope and sometimes a sobering lesson in the has not received the attention it deserves. Owing to their complex task that awaits us. Additional research advances poor dispersal and habitat specificity, mycorrhizae need will be needed to understand how ecosystems function and RESTORATION, ECOSYSTEM 7 how humans can intervene in disturbed communities to Johnson, R and Gjerstad, D (1998) Landscape-scale Restoration promote diverse and healthy ecosystems. of the Longleaf Pine Ecosystem, Restor. Manage. Notes, 16, 41–45. Kline, V M and Howell, E A (1987) Prairies, in Restoration ACKNOWLEDGMENTS Ecology: a Synthetic Approach to Ecological Research,eds W R Jordan, III, M E Gilpin, and J D Aber, Cambridge Uni- We thank the American Association for the Advancement versity Press, New York, 75–87. of Science (AAAS) and the US Environmental Protec- Lamb, D (1998) Large-scale Ecological Restoration of Degraded Tropical Forest Lands: the Potential Role of Timber Planta- tion Agency’s National Center for Environment Assess- tions, Restor. 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