Climate Change and Managed Ecosystems - Chapter 18 pdf

355 18 Knowledge Gaps and Challenges in Wetlands under Climate Change in Canada B.G. Warner and T. Asada CONTENTS 18.1 Introduction 355 18.2 Common Misconceptions 356 18.3 Wetland Classification and Inventory 356 18.4 Hydrological Landscape Modifications and Water Budget Fluctuations 360 18.5 Sedimentation and Water Quality Changes 362 18.6 Carbon Cycling and Climate 363 18.7 Invasive Species 363 18.8 Wetland Archival Records 366 18.9 Wetland Ecotechnology: The Way of the Future 367 18.10 Summary and Conclusions 367 References 368 18.1 INTRODUCTION Wetlands are a characteristic element of the Canadian landscape. They occur any- where supplies of water on the land surface sustain waterlogged conditions and anywhere specialized biotic communities are adapted to extreme variations in soil oxygen between periods of wetness and dryness. The geomorphologic setting of the land and the buildup of sediments in the wetland itself, especially in the case of peat landforms, are important factors controlling water conditions in wetlands. Climate determines the amount of water that enters via precipitation and leaves via evapo- transpiration and, more indirectly, influences the supply of water that may enter via surface runoff and groundwater seepage. Human activities can affect the supplies of water entering wetlands by physically modifying the natural shape and size of the wetland and its surrounding watershed, by drawing water directly from the wetland and the sources supplying it, and by altering the vegetation cover, which, © 2006 by Taylor & Francis Group, LLC 356 Climate Change and Managed Ecosystems in turn, affects the inputs from and losses to the atmosphere. To understand wetland and climate relationships is to understand relationships between climate and water, but these relationships upset the natural balance when human activities interfere and threaten wetlands and their supplies of water. Several reviews demonstrate Canada’s considerable progress toward understand- ing and managing its wetland resources. 1–5 There is a national classification system, a fundamental first step for defining and recognizing wetlands. Regional inventories have been performed based on concepts and terms in the classification system. Much has been learned about differences in the character and dynamics of wetlands through scientific research and information gathering, which, in turn, wetland managers have used to develop policies governing wetland protection and wise use. These are not small accomplishments considering the extent and great diversity of wetlands in Canada, estimated to be about 18% of the world’s freshwater wetlands. 6 Yet there is a rudimentary appreciation for the delicate linkages among climate, water, and wetlands. Wetlands still have not attained the attention they require in assessments of human impacts on the natural environment. This is exemplified by the number of threats to drinking water supplies, water pollution problems, major floods, droughts, fire, and other environmental disasters in recent years in Canada that revolve around climate, water, wetlands, human health, and economy. Wetlands are, or should be, considered central to these issues. This chapter highlights some topical issues, gaps in our understanding of the role of wetlands in natural and human-dominated landscapes, vulnerability of wet- lands and the environment when climate compounds the problems, and what we need to know to better deal with the wetland and water issues in the future. It is by no means complete but is intended to give a sense of the nature of some problems and the gaps in knowledge. Wetland ecotechnology presents the opportunity to direct natural self-organization processes in wetlands to solve problems for the benefit of both the natural environment and society. 18.2 COMMON MISCONCEPTIONS Wetland specialists have met at intervals to review progress and prioritize future directions and information needs. Several workshops have addressed knowledge gaps and challenges in the science of wetlands for measuring, predicting, mitigating, and adapting to demands of society including consideration of future changes to climate. 7–10 The needs and issues with respect to wetlands identified at these national forums, some more than 10 years ago, still hold to the present. This may, in part, be due to the needs being so diverse and complex that the wetland community is challenged to meet all of them and, in part, from a lack of will owing to a number of common misconceptions about wetlands in Canada (Table 18.1). 18.3 WETLAND CLASSIFICATION AND INVENTORY Classification is a fundamental prerequisite for all work on wetlands, because it provides a system for defining and recognizing wetlands in the landscape. Two © 2006 by Taylor & Francis Group, LLC Knowledge Gaps and Challenges in Wetlands 357 editions of the Canadian wetland classification have been published, the last of which is the culmination of nearly 20 years of work. 11 The classification system captures the range of both peatland and mineral wetland types, including those that are on land and along freshwater and marine coasts. It also includes those influenced by permafrost processes. Classification systems provide the framework for naming and mapping wetlands in national and regional inventories. It provides the standard “taxonomy” used to TABLE 18.1 Some Common Misconceptions about Wetlands in Canada Perception Reality Wetlands are abundant in Canada and are not threatened. Wetlands are most abundant in the Boreal Ecozone. They are threatened in southern Canada, especially in the most heavily populated and agricultural areas and elsewhere due to dam construction and hydroelectric reservoir development. Wetlands quality is high and they are not degraded. True for the most pristine and remote regions, but wetlands closest to inhabited regions are in various degrees of deterioration because of incompatible land uses in and around wetlands, long-term degradation from the historical past, urbanization, agriculture, discharge of chemical and biological contaminants, influx of invasive species. Wetlands are wastelands and obstacles to development; human society and wetlands cannot live together. Great progress has been made toward effective management and conservation of wetlands; however, there remains poor appreciation for the value of wetlands, some perceive wetlands as frightening and dangerous places, legislation works against wetlands in some jurisdictions, and there has been a relaxation by groups and organizations to respect the benefits and virtues of wetlands. Restored and created wetlands are undesirable and unachievable. Wrong! Many successful restored and created wetlands exist in Canada, some of which are recognized as internationally important. Wetlands are not linked to climate and are unwanted, because they contribute greenhouse gases that warm the climate. There is a complex linkage between carbon cycling processes in wetlands and climate. Wetlands not only contribute but also remove greenhouse gases from the atmosphere in ways that vary greatly among different wetland types, among similar wetland types, and within the same wetland basin. The knowledge base about wetlands is complete and there is no need for further work and research on wetlands. Wrong! The global scientific community is moving fast to discover new and important attributes about wetlands that need to be explored in Canada. For example, we know almost nothing about aspects of wetland biogeochemistry, hydrology, microbial ecology, and biodiversity in Canada, much less the services and values that wetland might contribute to human society. The peat moss industry is the only economic value of wetlands. Wrong! Canada’s wetland industry as a whole, of which the peat moss industry is a part, probably contributes as much to the economic well-being of Canadians as most of the other natural resource sectors, yet is largely ignored. © 2006 by Taylor & Francis Group, LLC 358 Climate Change and Managed Ecosystems name representative wetland types and organize them into groups and subgroups. Unfortunately, the classification system has not been universally adopted across all sectors of the federal government even though the Federal Cabinet accepted the national classification system as the standard to follow when it adopted the Federal Wetlands Policy in 1992. 12 The 1997 classification system is incomplete and needs refinement. Our concepts of swamp and bog remain confusing as indicated by some discordance between definitions of the classification system and the maps produced by Tarnocai et al., 6,13 largely due to incomplete understanding of the hydrology of wetlands throughout Boreal Canada. Consideration should be given to explicitly recognizing the condition or state of the wetland at probably the form or type level in the classification (Table 18.2). This would recognize restored and created wetlands, which are not included. Degraded wetlands are problematic because they have characteristics that do not readily fall into the current classification, which is based largely on pristine wetlands. Further work is required in areas such as the following: the classification needs to be reevaluated and field-tested for redundancies, generalities, and incompleteness, and should be brought up to date with current scientific concepts of bog, swamp, fen, marsh, and shallow open water; restored and created wetlands were largely overlooked in the 1997 classification and need to be included in the classification system; in view of the occurrence of corals in Canada’s offshore areas, consideration of whether the Canadian definition of wetlands needs to be expanded to be brought in line with the international definition of the Ramsar Convention, which recognizes coral reefs as components of wetlands; the classification should be used as the basis for more regional classification systems as recognized by the federal government; some consideration needs to be given to developing classifications that are based on both scientific and regulatory needs, such as hydrogeomorphic functional classifi- cations widely used in the U.S.; 14 and the Canadian classification should be broad- ened and modified into a classification system for North American wetlands (i.e., with the U.S., Mexico), and perhaps toward a global classification for the Northern Hemisphere. 15 Inventories are only as good as the classification system used as the standard reference for naming and differentiating the wetland units. The most comprehensive national inventories are those of Tarnocai et al. 6,13 Most wetland inventories in Canada exclude large areas of marine, brackish, and freshwater coastal wetlands (both marsh and shallow open water), and overlook many restored and created wetlands. The National Wetland Inventory that has been recently launched holds much promise to improve our knowledge of the extent and distribution of wetlands, primarily because it utilizes satellite imagery with modern digital imagery processing techniques. 16 This new initiative must build on the Canadian Wetland Classification system, and perhaps can help to resolve outstanding problems, such as accurate differentiation of Picea swamp vs. Picea forest in the Boreal Ecozone, and open water wetland vs. lake and ocean in coastal zones. Such challenges can only be confirmed by accurate and supporting field surveys. Inventory work such as that of Snell 17,18 for southern Ontario needs to be updated and expanded to other regions of the country, where a significant extent of wetland has been converted to alternative land uses since European settlement. Such inventories © 2006 by Taylor & Francis Group, LLC Knowledge Gaps and Challenges in Wetlands 359 serve to identify priority regions and sites where wetlands are especially vulnerable and where conservation efforts and protection should take precedence (Figure 18.1). Regions where wetlands may not be especially widespread anymore but existed in the TABLE 18.2 Classification Considering State of Wetland Condition Wetland Type Wetland Condition Degree of Human Intervention Degree of Direction by Humans to Organize Wetland Ecosystem Natural Pristine Degraded (a) Minor Degradation: partly influenced by humans retaining same wetland form and type as before human contact (b) Moderate Degradation: a viable wetland is retained but some parts and forms of the wetland have changed and the wetland is in a state of transformation from one wetland type to another (c) Major Degradation: the wetland form and type have been severely influenced by humans and there is a general trend of species impoverishment or replacement of dominant species by others Restored Passively restored Returned to some preexisting state by one-time human action and remaining in the new state Actively restored Returned to some preexisting state by ongoing human action Created Human-initiated Bringing wetland into existence by intentional or unintentional action where none existed previously; able to persist thereafter Artificial Bringing wetland into existence by deliberate action where none existed previously; without ongoing human actions it would revert to its original condition Small Great Greatly directed Not directed on purpose Slightly directed © 2006 by Taylor & Francis Group, LLC 360 Climate Change and Managed Ecosystems historical past reflect areas of high probability of success and should be targeted for restoration. The problem is compounded, because regions where wetlands are most vulnerable due to historical reasons are also regions where climate-warming scenarios predict extreme warming and drought. 19 18.4 HYDROLOGICAL LANDSCAPE MODIFICATIONS AND WATER BUDGET FLUCTUATIONS Our unwise use and poor management of water resources has created problems for wetlands that, if they continue, will only pose more serious threats to wetlands under climate change scenarios. Humans have disrupted the magnitude and timing of natural river flows through land clearance, dam and reservoir construction, diversion and transfer of water across watersheds, exploitation of groundwater aquifers, channeliza- tion of streams, and reconfiguration of coastlines in Canada. These activities allow control of water resources to generate electricity, supply water for agriculture and industry, mitigate flooding, navigate rivers and lakes, and use the land and near shore for purposes incompatible with natural conditions. 20,21 Canada ranks third next to the FIGURE 18.1 Map of Canada showing regions where wetlands are most threatened. (Mod- ified after Rubec. 76 ) 0 500 1000 kilometers N High Moderate Low to None © 2006 by Taylor & Francis Group, LLC Knowledge Gaps and Challenges in Wetlands 361 U.S. and Russia in having the greatest number of major dams. 21 Innumerable wetlands and aquatic habitats have been lost and altered as a result of these landscape changes. Land clearance by early settlers changed the land from being forest, wetland, and water-dominated to one that is open, drier, and largely devoid of wetlands. Smaller water bodies and streams were obliterated and larger ones became larger, so large that rivers overflowed and changed their channels and water levels rose in the receiving water bodies. Land-use history necessitated the creation of the Conservation Authorities system in the 1940s in Ontario to monitor floods. 22 The loss of wetlands and water bodies on the Prairies prompted the formation of Ducks Unlimited Canada in 1938 to reverse the historical trends and restore wetlands. 22 Large to small dam construction has increased fivefold since the 1950s. This has resulted in major changes in the volume of water flowing in rivers by water being impounded in upper reaches and significant decreases in volumes reaching lower reaches and the river mouth. Extent of dam construction on a single water- shed can be substantial. For example, the Columbia River Basin in Canada and the U.S. has 19 dams on its 2000-km length; only 70 km of the river remains free flowing and natural. 21 What has this kind of control of natural water flow done to wetlands in the watershed? Another serious problem is the change to natural seasonal patterns of river discharge. This has led to an increase in the age of waters reaching the river mouth because it may take water more than a year to reach the mouth compared to days and weeks under natural conditions. The hydroperiods of wetlands in riparian zones have changed, the influx and/or efflux of nutrients have increased, and water and/or nutrients in downstream areas are diminished. The reservoirs themselves have altered natural habitats. Source and sink strength for greenhouse gases have been affected by the reservoirs that can emit large quantities of greenhouse gases. 24 Hydroelectric reservoirs are particularly a prob- lem because not only are they sources of greenhouse gases, but also of methyl- mercury, which accumulates and biomagnifies in the aquatic food chain. 25,26 Hydro- electric development is the primary threat to wetlands in central parts of Manitoba, Ontario, and Quebec (Figure 18.1). Wetlands must be a central concern in understanding the impact of hydrological alterations. The obvious impacts are complete displacement and destruction of wet- lands, but less known are the less obvious subtle changes to wetland water budgets and the responses by wetland biota. Detailed information needs include the follow- ing: undertake detailed evaluation of the state of existing knowledge base and prioritize information needs on impact to wetlands of hydrological alterations; assess impacts of seasonal changes to river runoff cycles on water budgets and hydroperiods of associated wetlands, especially wetlands in riparian and floodplain zones; identify linkages between large-scale hydrological alterations, regional water cycles, wet- lands, and climate; determine changes to hydrological conditions, nutrient cycles, and biota in wetlands in upstream vs. downstream reaches; undertake historical comparisons between pre-disturbance and present-day landscapes, wetland ecosys- tems, and climate, which can be readily done using paleoecological techniques, and long-term monitoring sites need to be established to assess future impacts; and consider conversion to wetland for reservoirs and impoundments when they are © 2006 by Taylor & Francis Group, LLC 362 Climate Change and Managed Ecosystems decommissioned and taken off-line. Gorham et al. 27 have reviewed the merits of the longer time frames and spatial scales offered by paleoecological approaches in dealing with environmental problems that directly and indirectly affect peatlands. There needs to be much greater use and recognition of the archival record in peatlands as an important management tool for climate change. 18.5 SEDIMENTATION AND WATER QUALITY CHANGES Overloading of sediments and nutrients due to poor land-use practices is a major threat to wetlands. The gaps and needs in this area with respect to wetlands are complex and have been addressed by the workshops referred to earlier. They are also closely related to issues surrounding hydrological alterations discussed previ- ously. This area has received little attention in the context of wetlands, but likely is a large problem in the vicinity of the mouths of many streams and rivers and along the associated lake shores and ocean coasts of Canada just as it is in other parts of the world. It has likely escaped the attention of Canadians because the problems have not yet reached catastrophic proportions although there may well be accidents waiting to happen. There have been intermittent reports in the Canadian popular press in recent years that report fish kills in our water bodies that are usually attributed to natural cyclic phenomena. There needs to be discussions of nutrients and overall water quality when such fish kills do occur to ensure that poor land-use practices are not contributing to “natural phenomena.” Lessons learned from the Mississippi basin issue can help in Canada. The Gulf of Mexico hypoxia problem in the U.S. serves as a good example for Canadians to illustrate the magnitude of problems of poor land-use management and the catastrophic environmental and economic consequences exacerbated by warm climate. Nutrient loading and sedimentation throughout the Mississippi River basin has been shown to increase significantly in recent decades. A zone of low oxygen levels less than 2 mg l –1 has been noted on the continental shelf of the northern part of the Gulf of Mexico. 28–30 Transport of excess nutrients by the Mis- sissippi River has contributed to increased primary production along with warm summers and regional water circulation processes has been found to be responsible. Nitrate concentrations from the Mississippi River show major increases in the 1950s after nitrogen fertilizer came into widespread use and after expansion in other activities such as artificial drainage and hydrological alterations in the basin, such as increased runoff, wastewater discharge from urban settlements, and intensification of agriculture contributed to the problem. 29 Hypoxia is exacerbated by warm climate. Restoration of wetlands is viewed as ways by which nutrients and sediments can be controlled from entering the river and transported downstream to the river mouth. 28 Sedimentation and a decline in water quality in the Great Lakes have been attributed to agriculture and urbanization in adjacent watersheds and efforts are under way to restore wetlands to correct the problem. 31 © 2006 by Taylor & Francis Group, LLC Knowledge Gaps and Challenges in Wetlands 363 18.6 CARBON CYCLING AND CLIMATE Wetlands contain the largest quantities of carbon in both their living biomass and in their deep peat and sediments in the terrestrial biosphere. Canada contains around one third of the global peatland carbon although uncertainties exist on extent of peatland and carbon in the world. 32 Wetlands in Ontario are estimated to contain about 19% of Canada’s wetland carbon and about 6.6% of the wetland carbon in the world. 33 The recent review of McLaughlin 32 presents a good summary of the current state of knowledge of wetland carbon cycling that, despite a focus on Ontario, applies to much of Boreal Canada. Large-scale assessments of general climate change effects on carbon cycling processes are reasonably clear. 33–39 Specific topics that have received considerable attention include the following: net primary produc- tion and litter decomposition, 40–42 peat carbon accumulation, 39,43–46 and methane and carbon dioxide production and emission. 47,48 Different models are being developed to scale up peatland carbon to landscape, regional, and global scales. 19,49,50 There are several important areas that require further research to refine our understanding of carbon pools, fluxes, and cycling processes at different temporal and spatial scales. 32,51 Considerable effort has been directed at quantifying the various carbon pools but gaps still exist. For example, belowground carbon in litter and roots is thought to be large in peatlands covered by vascular plants, yet real estimates are poor at best. There remains incomplete understanding of variability in the nature of temporal and spatial variability of carbon sink and source strength at microtopo- graphic scales. Plant community composition differs markedly and climate is expected to exhibit enough influence to cause vegetation composition to shift both peatland structure and community type. For example, fens are expected to shift into bogs and swamps. Such vegetation changes will vary the nature of carbon being added to the litter and long-term storage. Little is known about how climate will interact with the new litter quality, oxidation–reduction processes, and microbial communities. Recent studies show that smaller-scale intrinsic factors such as water tables, vegetation composition, and litter governed by peatland microtopography and peat formation may be stronger forces in carbon cycling processes than larger scales and longer-term responses to changes in climate. 52,53 Climate is expected to enhance effects of ultraviolet-B (UV-B) radiation on production and decay rates. 54 How will radiation affect carbon cycling and sequestration processes in peatlands? Much of the attention on wetland carbon cycling and climate has focused on peatlands. Mineral wetlands contain significant quantities of carbon, albeit much less than in peatlands, but in quantities that should not be ignored. 33,55 18.7 INVASIVE SPECIES Wetlands seem to be particularly favorable habitats for invasive species and warmer climate may be compounding the problem by allowing more species to survive the winter period than would otherwise under more severe conditions. Invasive species are both non-native species and native species that become harmful to the ecosystem and, in turn, likely cause harm to the economy and humans. The list includes animals (insects, mollusks, fishes, birds, herpitiles, mammals), plants (algae, bryophytes, © 2006 by Taylor & Francis Group, LLC 364 Climate Change and Managed Ecosystems vascular plants), fungi, and microbes. Unfortunately, there is no complete list of what these species are in Canadian wetlands and aquatic habitats. To compare, a total of 334 non-native aquatic species have been introduced into wetlands in the U.S. 56 The Global Invasive Species Database (http:// www.issg.org) lists 18 taxa (Table 18.3) in Canadian wetlands, but this is only a small fraction of invasive species actually known to affect fresh, brackish, and marine wetlands. This list does not include well-known examples such as Dreissena polymorpha (zebra mussel), Tinca tinca (tench fish), or Cabomba caroliniana (fanwort macrophyte), which are having major impacts on freshwater wetlands. 57 There are at least 150 non-native invasive species in the Great Lakes basin that have been introduced in the 1900s. 57 The vast majority of these live in or close to wetlands. A comparable number of invasive species are associated with marine and estuarine wetlands of the Strait of Georgia in southwest British Columbia. Included are such species as Sargassum muticum (brown seaweed), Zostera japonica (dwarf eelgrass), Venerupis philippinarum (Manila clam), and Branta canadensis (Canada goose). 57 The status of many alien invasives is poorly understood. A good example is Phragmites australis, a common wetland plant widely distributed across Canada. It has become a nuisance in the eastern U.S., and is expanding its dominance throughout TABLE 18.3 Invasive Species Reported in Wetlands in Canada from the Global Invasive Species Database (http://www.issg.org/database) Scientific Name Common Name Alien or Native Status Plants Cirsium arvense Canada thistle (herb) Alien and/or uncertain Elaeagnus angustifolia Russian olive (tall shrub) Alien Fallopia japonica Donkey rhubarb (herb) Alien Hedera helix English ivy (woody vine) Alien Lespedeza cuneata Chinese bush-clover (herb) Alien Lythrum salicaria Purple loosestrife (herb) Alien Myriophyllum spicatum Eurasian water- milfoil (herb) Alien Phalaris arundinacea Reed canary grass (herb) Uncertain Phragmites australis Common reed (herb) Alien and/or native Potamogeton crispus Curly pondweed (herb) Alien Animals Cyprinus carpio Carp (fish) Alien and/or uncertain Gambusia affinis Mosquitofish (fish) Alien Micropterus salmoides American black bass (fish) Alien, uncertain, and/or native Mustela erminea Short-tailed ermine (mammal) Uncertain and/or native Orconectes virilus Northern crayfish (crustacean) Native Passer domesticus English sparrow (bird) Alien Rattus norvegicus Norway rat (mammal) Alien Microbes Flavivirus spp. West Nile virus Uncertain © 2006 by Taylor & Francis Group, LLC [...]... testing and parameterizing into standardized designs; and data are needed to assist regulators and managers with decisions on these nontraditional wetland technologies 18. 10 SUMMARY AND CONCLUSIONS Wetlands are sensitive to climate changes, especially since they lie between terrestrial ecosystems and open water bodies A small change in the quantity of water in the system can cause the wetland to become... Lilley, J., Mortsch, L., and Rubec, C., Canadian inland wetlands and climate change, in The Canada Country Study: Climate Impacts and Adaptation, Vol 7, Environment Canada, Ottawa, 1998, 190– 218 10 Rubec, C.D.A., Ed., Wetland Stewardship in Canada, North American Wetlands Conservation Council (Canada), Report 0 3-3 , 2003, 145 pp 11 Warner, B.G and Rubec, C.D.A., Eds., The Canadian Wetland Classification System,... wetland industry is especially vulnerable because it is diffuse and includes many small, family-run operations in rural and economically disadvantaged parts of the country Wetlands are commonly confused with terrestrial and aquatic ecosystems in the landscape Human activities can dramatically alter the supplies of water entering wetlands So too can climate affect water exchanges between wetlands and. .. lost and enhance existing wetlands Wetlands affect climate and climate affects wetlands Do we need to be reminded of the “Dirty 30s” in the southern Prairies when drought conditions dried up all surface water bodies and wetlands? Would this period have been as “dirty” and as dry if decades before extensive surface water bodies, wetlands, and natural vegetation had not been converted into cultivated land?... Group, LLC 372 Climate Change and Managed Ecosystems 66 Warner, B.G and Bunting, M.J., Indicators of rapid environmental change in northern peatlands, in Geoindicators: Assessing Rapid Environmental Changes in Earth Systems, Berger, A.R and Iams, W.J., Eds., A.A Balkema, Rotterdam, 1996, 235–246 67 Chambers, F.M and Charman, D.J., Holocene environmental change: Contributions from the peatland archive,... present or future climate be affecting these wetlands? Canada contains abundant peatlands and as such offers the potential for reconstructing widespread longer-term climatic © 2006 by Taylor & Francis Group, LLC Knowledge Gaps and Challenges in Wetlands 367 and environmental changes for most parts of the country Compared to lakes, wetlands have not received the attention they deserve 18. 9 WETLAND ECOTECHNOLOGY:... Vegetatio, 118, 3, 1995 16 Leahy, S., Wetlands from space: the national wetland inventory, Conservator, 24, 13, 2003 17 Snell, E.A., Wetland distribution and conversion in southern Ontario, Working Paper 48, Inland Waters and Land Directorate, Environment Canada, Ottawa, 1987 18 Snell, E.A., Recent wetland loss trends in southern Ontario, in Wetlands: Inertia or Momentum? Bardecki, M.J and Patterson,... issues threatening wetlands, which are further exacerbated by climate changes Unfortunately, Canadians are ill prepared to recognize and deal with the threats to wetlands Canada is well positioned to utilize more widely wetland ecotechnology and nature-sensitive practices to correct historical wrongs and to work in harmony with nature for the benefit of both wetlands and society so that climate will not pose... Wetlands Conservation Council, Report 0 3-0 2, 2003, 81–92 75 Rubec, C.D.A., Lynch-Stewart, P., Wickware, G.M., and Kessel-Taylor, I., Wetland utilization in Canada, in Wetlands of Canada, National Wetland Working Group, Polyscience Publishers, Montreal, 1988, 381–412 76 Rubec, C.D.A., Policy for conservation of the functions and values of forested wetlands, in Northern Forested Wetlands: Ecology and. .. Taylor & Francis Group, LLC 370 Climate Change and Managed Ecosystems 27 Gorham, E., Brush, G.S., Graumlich, L.J., Rosenzweig, M.L., and Johnson, A.H., The value of paleoecology as an aid to monitoring ecosystems and landscapes, chiefly with reference to North America, Environ Rev., 9, 99, 2001 28 Mitsch, W.J., Day, J.W., Gilliam, J.W., Groffman, P.M., Hey, D.L., Randall, G.W., and Wang, N., Reducing nitrogen . Classification and Inventory 356 18. 4 Hydrological Landscape Modifications and Water Budget Fluctuations 360 18. 5 Sedimentation and Water Quality Changes 362 18. 6 Carbon Cycling and Climate 363 18. 7 Invasive. Innumerable wetlands and aquatic habitats have been lost and altered as a result of these landscape changes. Land clearance by early settlers changed the land from being forest, wetland, and water-dominated. issues. This chapter highlights some topical issues, gaps in our understanding of the role of wetlands in natural and human-dominated landscapes, vulnerability of wet- lands and the environment when climate