Showing papers in "Ecological Applications in 1996"

The Report of the Ecological Society of America Committee on the Scientific Basis for Ecosystem Management

Abstract: Ecosystem management is management driven by explicit goals, executed by policies, protocols, and practices, and made adaptable by monitoring and research based on our best understanding of the ecological interactions and processes necessary to sustain ecosystem composition, structure, and function. In recent years, sustainability has become an explicitly stated, even legislatively mandated, goal of natural resource management agencies. In practice, however, management approaches have often focused on maximizing short-term yield and economic gain rather than long-term sustainability. Several obstacles contribute to this disparity, including: (1) inadequate information on the biological diversity of environments; (2) widespread ignorance of the function and dynamics of ecosystems; (3) the openness and interconnectedness of ecosystems on scales that transcend management boundaries; (4) a prevailing public perception that the immediate economic and social value of supposedly renewable resources outweighs the risk of future ecosystem damage or the benefits of alternative management approaches. The goal of ecosystem management is to overcome these obstacles. Ecosystem management includes the following elements: (1) Sustainability. Ecosystem management does not focus primarily on deliverables" but rather regards intergenerational sustainability as a precondition. (2) Goals. Ecosystem management establishes measurable goals that specify future processes and outcomes necessary for sustainability. (3) Sound ecological models and understanding. Ecosystem management relies on research performed at all levels of ecological organization. (4) Complexity and connectedness. Ecosystem management recognizes that biological diversity and structural complexity strengthen ecosystems against disturbance and supply the genetic resources necessary to adapt to long-term change. (5) The dynamic character of ecosystems. Recognizing that change and evolution are inherent in ecosystem sustainability, ecosystem management avoids attempts to freeze" ecosystems in a particular state or configuration. (6) Context and scale. Ecosystem processes operate over a wide range of spatial and temporal scales, and their behavior at any given location is greatly affected by surrounding systems. Thus, there is no single appropriate scale or time frame for management. (7) Humans as ecosystem components. Ecosystem management values the active role of humans in achieving sustainable management goals. (8) Adaptability and accountability. Ecosystem management acknowledges that current knowledge and paradigms of ecosystem function are provisional, incomplete, and subject to change. Management approaches must be viewed as hypotheses to be tested by research and monitoring programs. The following are fundamental scientific precepts for ecosystem management. (1) Spatial and temporal scale are critical. Ecosystem function includes inputs, outputs, cycling of materials and energy, and the interactions of organisms. Boundaries defined for the study or management of one process are often inappropriate for the study of others; thus, ecosystem management requires a broad view. (2) Ecosystem function depends on its structure, diversity, and integrity. Ecosystem management seeks to maintain biological diversity as a critical component in strengthening ecosystems against disturbance. Thus, management of biological diversity requires a broad perspective and recognition that the complexity and function of any particular location is influenced heavily by the surrounding system. (3) Ecosystems are dynamic in space and time. Ecosystem management is challenging in part because ecosystems are constantly changing. Over time scales of decades or centuries, many landscapes are altered by natural disturbances that lead to mosaics of successional patches of different ages. Such patch dynamics are critical to ecosystem structure and function. (4) Uncertainty, surprise, and limits to knowledge. Ecosystem management acknowledges that, given sufficient time and space, unlikely events are certain to occur. Adaptive management addresses this uncertainty by combining democratic principles, scientific analysis, education, and institutional learning to increase our understanding of ecosystem processes and the consequences of management interventions, and to improve the quality of data upon which decisions must be made. Ecosystem management requires application of ecological science to natural resource actions. Moving from concepts to practice is a daunting challenge and will require the following steps and actions. (1) Defining sustainable goals and objectives. Sustainable strategies for the provision of ecosystem goods and services cannot take as their starting points statements of need or want such as mandated timber supply, water demand, or arbitrarily set harvests of shrimp or fish. Rather, sustainability must be the primary objective, and levels of commodity and amenity provision must be adjusted to meet that goal. (2) Reconciling spatial scales. Implementation of ecosystem management would be greatly simplified if management jurisdictions were spatially congruent with the behavior of ecosystem processes. Given the variation in spatial domain among processes, one perfect fit for all processes is virtually impossible; rather, ecosystem management must seek consensus among the various stakeholders within each ecosystem. (3) Reconciling temporal scales. Whereas management agencies are often forced to make decisions on a fiscal-year basis, ecosystem management must deal with time scales that transcend human lifetimes. Ecosystem management requires long-term planning and commitment. (4) Making the system adaptable and accountable. Successful ecosystem management requires institutions that are adaptable to changes in ecosystem characteristics and in our knowledge base. Adaptive management by definition requires the scientist's ongoing interaction with managers and the public. Communication must flow in both directions, and scientists must be willing to prioritize their research with regard to critical management needs. Scientists have much to offer in the development of monitoring programs, particularly in creating sampling approaches, statistical analyses, and scientific models. As our knowledge base evolves, scientists must develop new mechanisms to communicate research and management results. More professionals with an understanding of scientific, management, and social issues, and the ability to communicate with scientists, managers, and the public are needed. Ecosystem management is not a rejection of an anthropocentric for a totally biocentric worldview. Rather it is management that acknowledges the importance of human needs while at the same time confronting the reality that the capacity of our world to meet those needs in perpetuity has limits and depends on the functioning of ecosystems.

Land Use and Avian Species Diversity Along an Urban Gradient

Abstract: I examined the distribution and abundance of bird species across an urban gradient, and concomitant changes in community structure, by censusing summer resident bird populations at six sites in Santa Clara County, California (all former oak woodlands). These sites represented a gradient of urban land use that ranged from relatively undisturbed to highly developed, and included a biological preserve, recreational area, golf course, residential neighborhood, office park, and business district. The composition of the bird community shifted from predominantly native species in the undisturbed area to invasive and exotic species in the business district. Species richness, Shannon diversity, and bird biomass peaked at moderately disturbed sites. One or more species reached maximal densities in each of the sites, and some species were restricted to a given site. The predevelopment bird species (assumed to be those found at the most undisturbed site) dropped out gradually as the sites became more urban. These patterns were significantly related to shifts in habitat structure that occurred along the gradient, as determined by canonical correspondence analysis (CCA) using the environmental variables of percent land covered by pavement, buildings, lawn, grasslands, and trees or shrubs. I compared each formal site to four additional sites with similar levels of development within a two-county area to verify that the bird communities at the formal study sites were rep- resentative of their land use category.

Environmental Sustainability: Universal and Non-Negotiable

Abstract: After deploring the mystification of the term sustainability and tendencies to conflate it with society's desiderata, we desegregate three types of sustainability: social, economic, and environmental. After clarifying these three linked and overlapping concepts, and construing them with sustainable development, we distinguish quantitative throughput growth from qualitative development, and mention intergenerational equity and scarcity of natural capital that together lead to the definition of environmental sustainability by the output/input rule, i.e., keep wastes within assimilative capacities; harvest within regenerative capacities of renewable resources; deplete non-renewables at the rate at which renewable substitutes are developed. After distinguishing development from sustainability and from growth, the paper describes the concept of natural capital and uses the concept to present four alternative definitions of environmental sustainability. Next, the paper presents criteria for analyzing environmental sustainability and uses the Ehrlich-Holdren framework in which Population," Pffluence, and Technology are examined separately. The paper then nuances the I = PAT identity and starts to disaggregate the components of sustainability into more dynamic formulations. The final section describes how one large development agency, the World Bank, is endeavoring to incorporate these new principles into its operations.

Economic Growth, Carrying Capacity, and the Environment

Abstract: Nat iona l and international economic policy has usually ignored the environment. In areas where the environment is beginning to impinge on policy, as in the General Agreement on Tariffs and Trade (GATT) and the North American Free Trade Agreement (NAFTA), it remains a tangential concern, and the presumption is often made that economic growth and economic liberalization (including the liberalization of intemational trade) are, in some sense, good for the environment. This notion has meant that economy-wide policy reforms designed to promote growth and liberalization have been encouraged with little regard to their environmental consequences, presumably on the assumption that these consequences would either take care of themselves or could be dealt with separately. In this article we discuss the relation between economic growth and environmental quality, and the link between economic activity and the carrying capacity and resilience of the environment (1).

Designing a Cost‐Effective Invertebrate Survey: A Test of Methods for Rapid Assessment of Biodiversity

Abstract: We investigated three procedures that may lead to rapid and accurate assessment of epigaeic arthropod biodiversity. They are: (1) the identification of taxa whose diversity is correlated with that of others: (2) the identification of times and methods of sampling that produce estimates of diversity representative of more intensive sampling; and (3) the use of morphospecies inventories generated by non-specialists. Ants, beetles, and spiders were sampled from four forest types, in three seasons, using two collecting methods: pitfall trapping and extraction from litter. Specimens were sorted by a non-specialist to morphospecies and by specialist taxonomists to species. Richness (α-diversity) and turnover (β-diversity) were compared for different sampling regimes using morphospecies and species inventories. We found no significant positive correlations between ant, beetle, and spider species richness but there was a strong negative correlation between ant and beetle richness. For beetles alone, richness within the families Carabidae, Scarabaeidae, and Pselaphidae (i.e, avoiding taxonomically problematic families) was significantly correlated with richness within all other families. Assessment of turnover revealed that: (1) the four forest types contained significantly different assemblages of ants and beetles but not spiders and 92) the four forests were less clearly discriminated using species from the three beetle families Carabidae, Scarabaeidae, and Pselaphidae when compared to species from all beetle families pooled. Analyses of single sampling periods and methods revealed that summer and spring pitfall samples were most representative of more intensive sampling. That is: (1) the richness of ants and beetles in these samples was significantly positively correlated with the richness of all other samples and 92) turnover of beetles and ants among the four forests revealed by summer pitfall samples was similar to turnover using all samples. The three beetle surrogate families recorded by pitfall samples in spring, and to a lesser extent summer, showed significant correlations in richness with all other beetle species recorded in the same samples. However, the assessment of turnover was less accurate when only surrogate families were used. The most accurate and cost-effective assessment of turnover was generated by a summer pitfall sample in which data for ants, carabid, and scarab beetles were combined and analyzed as a single data set. Results were largely consistent regardless of whether species or morphospecies were used, which suggests that monitoring and assessment of terrestrial invertebrate biodiversity may be achieved by the careful use of morphospecies. Our results also suggest those invertebrate taxa, sampling methods, and sampling periods that yield the most consistent and reliable assessment of epigaeic invertebrate biodiversity in Australian temperate hardwood forests. However, empirical studies that follow the protocols discussed in this paper are urgently required in different environments. These studies may point the way to more representative monitoring and assessment of terrestrial biodiversity.

Effects of Groundwater Decline on Riparian Vegetation of Semiarid Regions: The San Pedro, Arizona

Abstract: Groundwater depletion threatens many riparian ecosystems in arid and semi- arid regions of the world. The aquifer that sustains Arizona's San Pedro River riparian ecosystem, for example, is threatened by regional groundwater declines and localized pump- ing from the alluvial aquifer. This paper demonstrates the important role of shallow ground- water in structuring the San Pedro River plant community, portions of which function as reference areas that indicate site potential for a globally rare forest type (Sonoran riparian Populus-Salix forests). Several ecological indicators varied with depth to groundwater, including a weighted average wetland indicator score calculated for herbaceous and woody plant species, cover of plants within wetland indicator groups, and frequency of indicator plant species. These relationships can be used in a space-for-time substitution to predict consequences of groundwater decline. For example, the wetland indicator score changed sharply as depth to groundwater ranged from 0 to 4 m, and abundance of obligate wetland herbs (the group most sensitive to groundwater changes) declined sharply at groundwater depths below -0.25 m. Such sequential "desertification" of the riparian flora (i.e., loss or reduction in cover of species based on their probability of occurrence in wetlands) is one predicted response to groundwater decline. Other predicted impacts of groundwater decline include reduced establishment of Populus fremontii-Salix gooddingii forests, and reduced cover of herbaceous species associated with the fine-textured soils and shady conditions of floodplain terraces stabilized by these early seral tree species. High floodplain terraces (depth to groundwater of 5-8 m) had wetland indicator scores below those of upland sites and were vegetated by species (e.g., Prosopis velutina and Sporobolus wrightii) with low sensitivity to groundwater changes.

Improving the Success of Wetland Creation and Restoration with Know-How, Time, and Self-Design

Abstract: The creation and restoration of new wetlands for mitigation of lost wetland habitat is a newly developing science/technology that is still seeking to define and achieve success of these wetlands. Fundamental requirements for achieving success of wetland creation and restoration projects are: understanding wetland function; giving the system time; and allowing for the self-designing capacity of nature. Mitigation projects involving freshwater marshes should require enough time, closer to 15-20 yr than 5 yr, to judge the success or lack thereof. Restoration and creation of forested wetlands, coastal wetlands, or peatlands may require even more time. Ecosystem-level research and ecosystem modelling development may provide guidance on when created and restored wetlands can be expected to comply with criteria that measure their success. Full-scale experimentation is now be- ginning to increase our understanding of wetland function at the larger spatial scales and longer time scales than those of most ecological experiments. Predictive ecological mod- elling may enable ecologists to estimate how long it will take the mitigation wetland to achieve steady state.

An Introduction to Bayesian Inference for Ecological Research and Environmental Decision‐Making

Abstract: In our statistical practice, we ecologists work comfortably within the hypothetico-deductive epistemology of Popper and the frequentist statistical methodology of Fisher. Consequently, our null hypotheses do not often take into account pre-existing data and do not require parameterization, our experiments demand large sample sizes, and we rarely use results from one experiment to predict the outcomes of future experiments. Comparative statistical statements such as we reject the null hypothesis at the 0.05 level, which reflect the likelihood of our data given our hypothesis, are of little use in communicating our results to nonspecialists or in describing the degree of certitude we have in our conclusions. In contrast, Bayesian statistical inference requires the explicit assignment of prior probabilities, based on existing information, to the outcomes of experiments. Such an assignment forces the parameterization of null and alternative hypotheses. The results of these experiments, regardless of sample size, then can be used to compute posterior probabilities of our hypotheses given the available data. Inferential conclusions in a Bayesian mode also are more meaningful in environmental policy discussions: e.g., our experiments indicate that there is a 95% probability that acid deposition will affect northeastern conifer forests. Based on comparisons with current statistical practice in ecology, I argue that a Bayesian ecology would (a) make better use of pre-existing data; (b) allow stronger conclusions to be drawn from large-scale experiments with few replicates; and (c) be more relevant to environmental decision-making.

Spatial and Temporal Patterns in Terrestrial Carbon Storage Due to Deposition of Fossil Fuel Nitrogen

Abstract: Fertilization of the biosphere by nitrogen deposition represents an important connection between atmospheric chemistry and the global carbon cycle. We describe a modeled estimate of terrestrial carbon storage arising from deposition of nitrogen derived from fossil fuels that accounts for spatial distributions in deposition and vegetation types, turnover of plant and soil carbon pools, and the cumulative effects of deposition. Vegetation type has a pronounced effect on C uptake; the combination of high C: N ratios and long lifetimes in wood may create a significant sink in forests, but much of the nitrogen falls on cultivated areas and grasslands, where there is limited capacity for long-term carbon storage. We estimate 1990 net carbon uptake due to deposition of fossil-fuel N to be between 0.3 and 1.3 Pg C/yr (1 Pg = 1015 g), depending on the fraction of C allocated to wood, with a best estimate of 0.44-0.74 Pg/yr. Cumulative C storage since 1845 is estimated to be about 25% of the proposed terrestrial sink for anthropogenic CO2. Continued exposure to high N deposition, however, will decrease the extent of N limitation in terrestrial eco- systems, thereby limiting the persistence of any N-derived carbon sink.

Biological Diversity, Ecosystems, and the Human Scale

Abstract: This paper considers the significance of biological diversity in relation to large-scale processes in complex and dynamic ecological-economic systems. It focuses on functional diversity, and its relation to production and maintenance of ecological services that underpin human societies. Within functional groups of organisms two important cat- egories of species are identified: keystone process species and those essential for ecosystem resilience. The latter group represents "natural insurance capital." In addition to basic research on the interplay among biological diversity, functional performance, and resilience in complex self-organizing systems, we suggest that a functional approach has two main implications for a strategy for biodiversity conservation: (1) Biodiversity conservation to assure the resilience of ecosystems is required for all systems, no matter how heavily impacted they are. It should not be limited to protected areas. (2) The social, cultural, and economic driving forces in society that cause biodiversity loss need to be addressed directly. Specifically, (a) differences between the value of biological diversity to the private indi- vidual and its fundamental value to society as a whole need to be removed; (b) social and economic policies that encourage biodiversity loss should be reformed, especially where there is a risk of irreversible damage to ecosystems and diversity; and (c) institutions that are adaptive and work in synergy with ecosystem processes and functions are critical and should be created at all levels.

The Role of Reference Wetlands in Functional Assessment and Mitigation

Abstract: Compensatory mitigation for damages to wetlands in the United States occurs largely without explicit analysis and replacement of wetland functions. We offer an approach to standardize such analyses and strengthen the connection between ecological principles and policies for wetland resources. By establishing standards from reference wetlands chosen for their high level of sustainable functioning, gains and losses of functions can be quantified for wetlands used in compensatory mitigation. Advantages of a reference wetland approach include (1) making explicit the goals of compensatory mitigation through iden- tification of reference standards from data that typify sustainable conditions in a region, (2) providing templates to which restored and created wetlands can be designed, and (3) establishing a framework whereby a decline in functions resulting from adverse impacts or a recovery of functions following restoration can be estimated both for a single project and over a larger area accumulated over time. To establish reference standards, conditions inherent to highly functioning sites must be identified for classes of wetlands that share similar geomorphic settings. Ecological functions are then identified, and variables used to model the functions are employed in developing reference standards. Variables range from the highest levels of sustainable functioning to the complete absence of functions when a wetland ecosystem is displaced. An example given for wet pine flats in the North Carolina coastal plain illustrates how to determine the loss of a given function for an impacted wetland, how to calculate recovery (gains) in function through compensatory mitigation, and how to use the relationships between the two (loss vs. gain in function) to set minimum replacement ratios of restored to impacted area. In all cases, data from reference wetlands provide the benchmarks for making these estimates and for directing restoration or creation of wetlands toward the standards established for the wetland class. Programs to implement the use of reference wetlands require regional efforts that build upon the knowledge base of existing wetlands and their functioning.

Principles for the conservation of wild living resources

Abstract: We describe broadly applicable principles for the conservation of wild living resources and mechanisms for their implementation. These principles were engendered from three starting points. First, a set of principles for the conservation of wild living resources (Holt and Talbot 1978) required reexamination and updating. Second, those principles lacked mechanisms for implementation and consequently were not as effective as they might have been. Third, all conservation problems have scientific, economic, and social aspects, and although the mix may vary from problem to problem, all three aspects must be included in problem solving. We illustrate the derivation of, and amplify the meaning of, the principles, and discuss mechanisms for their implementation. The principles are: Principle I. Maintenance of healthy populations of wild living resources in perpetuity is inconsistent with unlimited growth of human consumption of and demand for those resources. Principle II. The goal of conservation should be to secure present and future options by maintaining biological diversity at genetic, species, population, and ecosystem levels; as a general rule neither the resource nor other components of the ecosystem should be perturbed beyond natural boundaries of variation. Principle III. Assessment of the possible ecological and sociological effects of resource use should precede both proposed use and proposed restriction or expansion of ongoing use of a resource. Principle IV. Regulation of the use of living resources must be based on understanding the structure and dynamics of the ecosystem of which the resource is a part and must take into account the ecological and sociological influences that directly and indirectly affect resource use. Principle V. The full range of knowledge and skills from the natural and social sciences must be brought to bear on conservation problems. Principle VI. Effective conservation requires understanding and taking account of the motives, interests, and values of all users and stakeholders, but not by simply averaging their positions. Principle VII. Effective conservation requires communication that is interactive, reciprocal, and continuous. Mechanisms for implementation of the principles are discussed.

Land Ownership and Land‐Cover Change in the Southern Appalachian Highlands and the Olympic Peninsula

Abstract: Social and economic considerations are among the most important drivers of landscape change, yet few studies have addressed economic and environmental influences on landscape structure, and how land ownership may affect landscape dynamics. Watersheds in the Olympic Peninsula, Washington, and the southern Appalachian highlands of western North Carolina were studied to address two questions: (1) Does landscape pattern vary among federal, state, and private lands? (2) Do land-cover changes differ among owners, and if so, what variables explain the propensity of land to undergo change on federal, state, and private lands? Landscape changes were studied between 1975 and 1991 by using spatial databases and a time series of remotely sensed imagery. Differences in landscape pattern were observed between the two study regions and between different categories of land ownership. The proportion of the landscape in forest cover was greatest in the southern Appalachians for both U.S. National Forest and private lands, compared to any land- ownership category on the Olympic Peninsula. Greater variability in landscape structure through time and between ownership categories was observed on the Olympic Peninsula. On the Olympic Peninsula, landscape patterns did not differ substantially between com- mercial forest and state Department of Natural Resources lands, both of which are managed for timber, but differed between U.S. National Forest and noncommercial private land ownerships. In both regions, private lands contained less forest cover but a greater number of small forest patches than did public lands. Analyses of land-cover change based on multinomial logit models revealed differences in land-cover transitions through time, between ownerships, and between the two study regions. Differences in land-cover transitions between time intervals suggested that addi- tional factors (e.g., changes in wood products or agricultural prices, or changes in laws or policies) cause individuals or institutions to change land management. The importance of independent variables (slope, elevation, distance to roads and markets, and population density) in explaining land-cover change varied between ownerships. This methodology for analyzing land-cover dynamics across land units that encompass multiple owner types should be widely applicable to other landscapes.

Marine Reserves: Rates and Patterns of Recovery and Decline of Large Predatory Fish

Abstract: A major objective of the use of marine reserves in management of coral reef fisheries is protection of a critical spawning stock biomass to ensure recruitment supply to fished areas via larval dispersal. However, very little empirical evidence exists on the rates and patterns of increase of density and biomass of target species following the closure of a coral reef or part of a reef, nor on how quickly any gains potentially useful to fisheries can be lost if reserves are subsequently opened to fishing. This paper presents empirical evidence derived from the visual monitoring of density and biomass of large predatory coral reef fish (Serranidae (Epinephelinae), Lutjanidae, Lethrinidae and Carangidae as a group) in two small marine reserves and at two control sites in the Philippines from 1983 to 1993. At one reserve (Sumilon) a complex history of management allowed seven mea- surements of density and biomass at durations of reserve protection ranging from -2 (i.e., fished for 2 yr) to 9 yr. At the second reserve (Apo), seven measurements were taken at durations of reserve protection ranging from 1 to 11 yr. Density of large predators provided an excellent indicator of the effects of marine reserve protection and fishing. Density decreased significantly twice when the Sumilon reserve was opened to fishing (1985, 1993), and increased significantly three times following durations of marine reserve protection of 5 yr (Sumilon reserve and nonreserve sites, 1987-1991) and >6 yr (Apo reserve beyond 1988). Density of large predators at the Apo nonreserve site (open to fishing) did not change significantly, remaining low throughout the study. Significant positive linear correlations of mean density of large predators with years of reserve protection were observed at both reserves. The rates of increase were 1.15 and 0.72 fish-1000 m-2.yr-' at Sumilon and Apo reserves, respectively, with mean density ranges of -4-17 fish/1000 m2 (-2 to 9 yr of protection) at Sumilon and 0.5-9.5 fish/1000 m2 (1-11 yr of protection) at Apo. The pattern of increase of mean biomass with years of reserve protection was more curvilinear than that of mean density, particularly at Sumilon, where a slow increase was observed in the first 3-5 yr (reflecting delayed recruitment and a natural delay to the period of maximum individual mass growth), followed by an increasing rate over the next 4 yr. Mean biomass ranges were -1.5-18 kg/1000 m2 (-2 to 9 yr of protection) at Sumilon and 1-10.5 kg/ 1000 m2 (1-11 yr of protection) at Apo. At Sumilon reserve, 2 and 1.5 yr of unregulated fishing, respectively, eliminated density and biomass gains accumulated over 5 and 9 yr of marine reserve protection.

Relative Abundance of Plant Functional Types in Grasslands and Shrublands of North America

Abstract: We analyzed the geographic distribution and climatic controls of the distri- bution of plant functional types (PFT) in temperate grasslands and shrublands of North America. It has been widely accepted that temperature is the principal control on the distribution of C3 and C4 species. Our results show that precipitation and its seasonal distribution are also important. C4 grass distribution was positively related to three climatic variables: mean annual precipitation, mean annual temperature, and the proportion of the precipitation falling in summer. These variables accounted for 66% of the total variability of this functional type. C3 grass abundance decreased with mean annual temperature and increased with the proportion of the precipitation falling during winter (r2 = 0.37). Sixty- two percent of the variability in the relative abundance of shrubs was explained by mean annual precipitation and the proportion of winter precipitation. Latitude and longitude explained a substantial portion of the variability of the distri- bution of the relative abundance of shrubs, C3 grasses, and C4 grasses (53, 46, and 61%, respectively). Along a given longitude, C3 grasses increased with latitude. As one moves westward, C4 grasses are replaced by shrubs. The relative abundance of C4 grasses reached a maximum at southern latitudes and eastern longitudes. Succulents showed a marginal decreasing trend with latitude. No relationship with geographic variables was detected for forbs.

Phosphorus Loads to Surface Waters: A Simple Model to Account for Spatial Pattern of Land Use

Abstract: Modeling nonpoint-source phosphorus (P) loading from land to surface wa- ters can be both complex and data intensive. Our goal was to develop a simple model that would account for spatial pattern in topography and land use using geographic information system (GIS) databases. We estimated areas of the watershed that strongly contributed to P loading by approximating overland flow, and modeled annual P loading by fitting three parameters to data obtained by stream monitoring. We calibrated the model using P loading data from two years of contrasting annual precipitation for Lake Mendota, a Wisconsin eutrophic lake in a watershed dominated by agriculture and urban lands. Land-use scenarios were developed to estimate annual P loading from pre-settlement and future land uses. As much as half of the Lake Mendota watershed did not contribute significantly to annual P loading. The greatest contribution to loading came from a heterogeneous riparian corridor that varied in width from 0.1 km to :6 km depending on topography and runoff conditions. We estimate that loading from pre-settlement land use was one-sixth of the loading from present land use. A future scenario, representing an 80% increase in existing urban land (from 9 to 16% of total watershed area, which would be reached in 30 yr with current land- use trends), showed only modest increases in annual P loading but possible significant effects on water quality. If the watershed were to become entirely urbanized, P loading to the lake would double and potential effects on water quality would be severe. Changes in P loading were strongest with conversions of undisturbed vegetated lands, especially ri- parian areas, to either urban or agricultural uses. Variability in total annual rainfall leads to variability in the riparian area that affects P loading, with implications for policies intended to control nonpoint nutrient inputs.

Effect of Landscape Structure on Parasitoid Diversity and Parasitism in Agroecosystems

Abstract: The armyworm (Pseudaletia unipuncta) was used as a model host insect to explore the influence of agricultural landscape structure at two spatial scales on larval parasitoid species richness and rates of larval parasitism in southern Michigan First, within fields, we compared parasitoid communities in maize fields near, and distant from, a hedge- row edge Second, we replicated these studies within a complex landscape (agricultural fields of small size embedded in a landscape with abundant hedgerows and woodlots) vs a simple landscape (agricultural fields of large size embedded in a landscape with few hedgerows and woodlots) The structural differences between the simple and complex agricultural landscapes were characterized by analysis of aerial photographs and digital land-use data After landscape analysis, three maize fields from each area were selected for the experimental studies The complex landscape contained fields that were 75% smaller, had 63% more perimeter of wooded field edge per hectare of field area, and had 81% more field edge in wide hedgerow than fields in the simple landscape Fields in the simple landscape had 74% and 53% more field edge in herbaceous roadside and crop-to-crop interfaces, respectively, than did fields in the complex landscape In the six selected maize fields, third and fifth instar P unipuncta were released indi- vidually onto maize plants 5 m and 90 m from a hedgerow edge Larvae were recovered after 4-5 d and reared in the laboratory to record parasitoid emergence Parasitoid species diversity was similar in both landscape types (simple landscape: four species; complex landscape: five species) Mean percentage parasitism was significantly higher in the complex landscape than in the simple landscape (13 1% vs 24%) but was not affected by the location within fields (near hedgerows vs distant from hedgerows) in either landscape type

The Vegetation of Restored and Natural Prairie Wetlands

Abstract: Thousands of wetland restorations have been done in the glaciated mid-continent of the United States. Wetlands in this region revegetate by natural recolonization after hydrology is restored. The floristic composition of the vegetation and seed banks of 10 restored wetlands in northern Iowa were compared to those of 10 adjacent natural wetlands to test the hypothesis that communities rapidly develop through natural recolonization. Restoration programs in the prairie pothole region assume that the efficient-community hypothesis is true: all plant species that can become established and survive under the environmental conditions found at a site will eventually be found growing there and/or will be found in its seed bank. Three years after restoration, natural wetlands had a mean of 46 species compared to 27 species for restored wetlands. Some guilds of species have significantly fewer (e.g., sedge meadow) or more (e.g., submersed aquatics) species in restored than natural wetlands. The distribution and abundance of most species at different elevations were significantly different in natural and restored wetlands. The seed banks of restored wetlands contained fewer species and fewer seeds than those of natural wetlands. There were, however, some similarities between the vegetation of restored and natural wetlands. Emergent species richness in restored wetlands was generally similar to that in natural wetlands, although there were fewer shallow emergent species in restored wetlands. The seed banks of restored wetlands, however, were not similar to those of natural wetlands in composition, mean species richness, or mean total seed density. Submersed aquatic, wet prairie, and sedge meadow species were not present in the seed banks of restored wetlands. These patterns of recolonization seem related to dispersal ability, indicating the efficient-community hypothesis cannot be completely accepted as a basis for restorations in the prairie pothole region.

Biotic Indices and Stream Ecosystem Processes: Results from an Experimental Study

Abstract: We investigated the ability of the North Carolina Biotic Index (NCBI) and the Ephemeroptera + Plecoptera + Trichoptera (EPT) index to track an experimental ma- nipulation of the invertebrate community and resultant alteration of several ecosystem-level processes in a headwater stream at the Coweeta Hydrologic Laboratory in western North Carolina. Indices were calculated from quantitative monthly or bimonthly benthic samples of moss-covered rockface and mixed substrate habitats, as well as habitat-weighted values based on the proportion of each habitat in the two streams. One stream (C 55) served as a reference stream over the 6-yr period of late 1984 through 1990, whereas the other (C 54) received seasonal treatments with an insecticide for 3 yr (1986-1988). Throughout pretreatment, treatment, and recovery, both the NCBI and EPT indices tracked the distur- bance regime of the treatment stream. Indices for the reference stream varied little during the 6-yr period. Both the NCBI and EPT suggested strong changes in the treatment stream during treatment relative to both pretreatment and the reference stream. Following cessation of insecticide treatments, both indices reflected improved biotic conditions during first and second years of recovery in C 54. Compared with fauna of mixed substrates, rockface fauna had lower (better) NCBI values during pretreatment, and exhibited a greater proportional increase in tolerant taxa during treatment than mixed substrates, emphasizing the importance of including rockface communities in environmental monitoring programs. Changes in both the EPT and NCBI indices closely corresponded to changes in ecosystem- level processes observed in C 54 from pretreatment to treatment, and recovery periods. These processes include: leaf litter processing rates, organic matter storage, fine particulate organic matter generation and export, and secondary production. With the exception of organic matter storage, all of these processes declined during treatment of C 54, and subsequently increased during recovery. Our results demonstrate the potential of such indices to detect and monitor stream ecosystem changes during and following disturbance. The EPT index was by far the easiest to use from both the standpoint of time required for sample processing and ease of application. Compared with the labor-intensive sample processing, specimen identification and measurement, and data entry required for secondary production calculations, the EPT index was relatively simple and displayed a remarkable ability to track secondary production of invertebrates in the treatment stream. Our data strongly support the inclusion of the EPT and NCBI indices in these southern Appalachian headwater streams as indicators of both degradation and recovery of stream ecosystem processes from chemical-induced disturbance.

Epiphytic Lichen Biomass in Managed and Old-Growth Boreal Forests: Effect of Branch Quality

Abstract: To maintain biodiversity in managed forests we must understand the patterns and processes that regulate the occurrence and dynamics of species in undisturbed eco- systems. We compared biomass and species composition of canopy lichens on 180 lower branches of Norway spruce (Picea abies) in three pairs of old-growth and managed (se- lectively logged) stands in northern Sweden (30 branches per stand). The purpose was to evaluate the effect of substrate quality (branch characteristics) on patterns of lichen biomass for two different growth forms (foliose and fruticose). Old-growth stands had six times higher lichen mass per spruce branch, and two times higher expressed as percentage of branch mass, compared to mature stands of managed forest. Lichen mass was strongly related to mass, diameter, and age of branches. Fruticose, pendulous species (Alectoria sarmentosa and Bryoria spp.) were highly sensitive to forest practices. In contrast, type of forest had no significant effect on foliose species. Species number per stand was the same (15 species) in both types of forest, but there were marked differences in the relative abundance of different lichen groups. Results suggest that limited amount of substrate (i.e., small branches) available to lichens, and young branches, pro- viding only a short time for lichen colonization and growth, are important factors limiting epiphytic lichen abundance in managed forests. Conversion of old-growth forest into young, managed stands will lead to a significant reduction in epiphytic lichen mass. This in turn may probably affect nutrient cycling in forests and has negative consequences for animals that utilize canopy lichens as food, shelter, or nesting material.

Models to Evaluate Headstarting as a Management Tool for Long‐Lived Turtles

Abstract: Most turtle species suffer highly mortality in their first year, have a long juvenile period, and can live for decades once they reach adulthood. Conservationists have implemented a number of recovery plans for threatened turtle populations, including experimental headstart programs. Headstarting involves the captive rearing of hatchlings from eggs collected in the wild. The hatchlings are held for several months to help them avoid high mortality in their first year. It is hoped that these turtles survive and grow like wild turtles after release. The purpose of our study was to evaluate headstarting as a management tool for threatened turtle populations. We critically examined the population-level effects of headstarting with a series of deterministic matrix models for yellow mud turtles (Kinosternon flavescens), a non-threatened, well-studied species, endangered Kemp's ridley sea turtles (Lepidochelys kempi). We show that management efforts focused exclusively on improving survival in the first year of life are unlikely to be effective for long-lived species such as turtles. Population projections for both turtles predict that head-starting can augment increasing populations when adult survival is returned to or maintained at high levels, provided that headstarted juveniles are as vigorous as wild turtles. However, when subadult and adult survival is reduced, headstarting cannot compensate for losses in later stages. Proportional sensitivity (elasticity) analyses of stage-based matrix models indicated that annual survival rates for subadult and adult turtles are most critical; small decreases in the survival of older turtles can quickly overcome any potential benefits of headstarting. In general, the biological benefits of headstarting programs may be overestimated for turtles, and a careful examination of stage-specific mortality sources, demography, and life history can guide us toward more effective management strategies.

The Effects of Land Use on the Structure of Ground‐Foraging Ant Communities in the Argentine Chaco

Abstract: We examined the responses of a ground-foraging ant community to a gradient of land-use intensity in a grazing agroecosystem in the Chaco of northern Argentina. The gradient extended from a highly degraded condition characteristic of traditional grazing practices, through an area of less severe disturbance where grazing was less concentrated, to two areas in which grazing had been managed for 3 and 18 yr, respectively. Ground cover changed along this gradient from bare to litter-covered, ground-layer vegetation changed from sparse to a structurally complex mixture of grasses and forbs, and canopy cover increased in areas of intermediate grazing intensity and then decreased. Community diversity varied among the sites depending on both season and scale of analysis. Site-scale ant species richness was slightly higher in sites of intermediate disturbance in the summer- wet season but was much greater in the least disturbed site in the winter-dry season. The same dry-season pattern was evident in both species richness and diversity at the scale of transects within sites, whereas species richness at the scale of individual traps within transects was significantly lower at sites of intermediate disturbance than at either highly restored or highly degraded sites. Abundances of individual ant species and functional groups also changed along the land-use gradient. Litter-inhabiting cryptic species and spe- cialized predators responded positively to grazing management, whereas opportunists and the hot-climate specialist Forelius nigriventris were prevalent in highly disturbed areas. Other functional groups exhibited redundancy and species turnover along the gradient. Detrended correspondence analysis (DCA) revealed that the ant faunas at the extremes of the land-use gradient were more similar than expected. We hypothesize that the interaction of local-scale habitat features with historical and biogeographic influences may determine the responses of this ant community to land use, and that highly degraded areas may have conservation value because they are regional sources of arid-adapted ants.

Surprise for Science, Resilience for Ecosystems, and Incentives for People

Abstract: It is an open question whether ecosystem management will become a passing fad, an expansion of existing rigid bureaucratic procedures, or a sustaining foundation for learning to deal with the interactions between people, nature, and economic activities. The report of the Ecological Society of America Committee on the Scientific Basis for Ecosystem Management makes a major contribution to the very best of those possibilities. Here I will comment on three consequences that flow from their conclusions-consequences for the kind of science, theory, and practice needed.

Threats to Wilderness Ecosystems: Impacts and Research Needs

Abstract: One of the primary purposes of designated wilderness areas is protection of natural ecosystems. However, the ecological integrity of these most protected of public lands is threatened by direct and indirect effects of human activities both internal and external to wilderness. Accelerated research programs on threats to wilderness are needed to realize the purposes for which wilderness was established and to improve our understanding of natural ecosystems. This paper reviews current knowledge and critical research needs for some of the most significant threats to wilderness ecosystems: (1) recreational use and its management; (2) livestock grazing and its management; (3) fire management; (4) introduction of alien species; (5) diversion and impoundment of water; (6) emission of atmospheric pollutants; and (7) management of adjacent lands. Some of these threats cause highly disruptive localized impacts, whereas some have a more widespread effect. Other threats are highly significant because they threaten rare or irreplaceable ecological attributes. Ecological science needs to be applied to improve evaluations of wilderness conditions, improve efforts to protect wilderness ecosystems from further degradation, and improve efforts to restore the integrity of disturbed systems.

Impacts of Lakeshore Residential Development on Coarse Woody Debris in North Temperate Lakes

Abstract: Coarse woody debris (CWD) is a critical input from forested watersheds into aquatic ecosystems. Human activities often reduce the abundance of CWD in fluvial systems, but little is known about human impacts on CWD in lakes. We surveyed 16 north temperate lakes to assess relationships among CWD, riparian vegetation, and shoreline residential development. We found strong positive correlation between CWD density and riparian tree density (r2 = 0.78), and strong negative correlation between CWD density and shoreline cabin density (r2 = 0.71) at the whole-lake scale. At finer spatial scales (e.g., between sampling plots), correlations between CWD and riparian vegetation were weaker. The strength of relationships between CWD and riparian vegetation was also negatively influenced by the extent of cabin development. Overall, there was significantly more CWD in undeveloped lakes (mean of 555 logs/km of shoreline) than in developed lakes. Within developed lakes, CWD density differed between forested sites (mean of 379 logs/km of shoreline) and cabin-occupied sites (mean of 57 logs/km of shoreline). These losses of CWD will affect littoral communities in developed north temperate lakes for about two centuries. Because CWD is important littoral habitat for many aquatic organisms, zoning and lake management should aim to minimize further reductions of aquatic CWD and woody vegetation from lakeshore residences.

Water Use by Tamarix Ramosissima and Associated Phreatophytes in a Mojave Desert Floodplain

Abstract: Water use by the introduced shrub Tamarix ramosissima and three co-oc- curring, native phreatophytes was measured in the lower Virgin River floodplain (southern Nevada) using the stem-heat-balance method During the 1993 growing season, measure- ments were conducted on Tamarix in a closed, monospecific stand and in a mixed community with the native species Pluchea sericea, Prosopis pubescens, and Salix exigua Our objec- tives were (1) to determine whether leaf-area-based water use of Tamarix is higher than that of co-occurring native riparian taxa, (2) to assess the role of Tamarix stand leaf area index (LAI, leaf area per unit ground area) on Tamarix water loss, and (3) to verify whether Tamarix is capable of using large amounts of water under the extreme evaporative demands that characterize arid environments Leaf-area-based sap flow rates were comparable in the four species despite large differences in individual leaf area and total water loss Daily water use of Tamarix (in grams per day) weighted by the daily potential evapotranspirati-on (PET) increased linearly with the total leaf area per plant, suggesting that water uptake was sufficient to compensate for water loss at the leaf level, even during times of extreme atmospheric water demand Under high PET, maximum sap flow rates of Tamarix on a leaf- area basis were significantly higher at locations where Tamarix LAI was lower, indicating that highly transpiring Tamarix stands may reduce leaf-level evaporative demand However, daily estimates of transpiration of dense Tamarix stands (LAI up to 35 m2/m2) in our study site exceeded PET by a factor ranging from 16 to 20, which confirms that mature Tamarix stands can lose very high quantities of water due to the maintenance of high leaf area Results from this and other studies demonstrate that, at least under moderate to high water tables, key variables controlling water use by riparian stands include structural character- istics such as LAI and density Management practices aimed at conserving water should be geared towards avoiding the development of dense Tamarix thickets along arid water courses, particularly if it is confirmed that these tend to attain higher LAI than native riparian communities

Effects of Nutrients and Hydroperiod on Typha, Cladium, and Eleocharis: Implications for Everglades Restoration

Abstract: The recent expansion of Typha domingensis (Typha) into areas of the Ev- erglades previously dominated by Cladium jamaicense (Cladium) communities has led to competing hypotheses about the importance of nutrient concentration vs. hydroperiod in controlling the distribution of these species. In this study, experimental mixtures of Typha domingensis, Cladium jamaicense, and Eleocharis interstincta (Eleocharis), a member of the Cladium community, were subjected to two levels of nutrient concentration and three contrasting hydroperiods to determine how these variables might affect Typha's ability to displace the Cladium community. Mixtures of the three species were established in outdoor tanks containing soil from the northern Everglades region where the experiment was con- ducted. Nutrient treatments consisted of nutrient additions to adjust ambient water con- centrations to either 50 ,ug/L phosphorus (P) or 100 pug/L P plus nitrogen (N). The three hydroperiods were achieved by maintaining water depths within ranges observed in the northern Everglades. Maximum water depths of 15, 30, and 60 cm were established through- out the wet season (May-November) followed by lowering to 5 cm during the dry season. Over a 2-yr period, biomass was monitored nondestructively and aboveground material was harvested at the end of the experiment. Analysis of the biomass changes over time showed that differences between the species developed by the end of the first growing season. Typha and Eleocharis had initial growth rates substantially higher than those observed for Cladium. Typha's growth in mixtures responded positively to both elevated nutrients (by as much as 45%) as well as to increased water depth (by as much as 60%), while Cladium and Eleocharis did not increase in response to these variables. Tissue P concentrations were found to be higher for Typha and Eleocharis than for Cladium under nearly all conditions. Net accu- mulation of P in Typha shoots was 2-3 times greater than in the other species. The en- hancement of Typha by elevated nutrients and increased flooding is associated with a syndrome of life history characteristics that includes rapid growth rates, high tissue con- centrations of P, tall leaves, and a greater response to contrasting environmental conditions. Cladium, in contrast, showed a slow growth rate, low tissue concentrations of P, a greater capacity to resist invasion by Typha in shallow waters, and less of a growth response to contrasting environmental conditions, traits that would seem to be well suited to the nutrient- poor, hydrologically unstable conditions natural to the Everglades. Results from this study suggest that attempts to limit the spread of Typha should consider hydrologic restoration as well as reduction in surface water nutrients.

Functional Equivalency Trajectories of the Restored Gog‐Le‐Hi‐Te Estuarine Wetland

Abstract: Assessing performance of restored and created wetlands for compensatory mitigation and restoration poses a mismatch between long-term processes and the short- term expediency of management decisions. If they were predictable, patterns in the temporal development of important wetland processes could reduce long-term uncertainty of the outcome of restoration projects. To test our ability to predict long-term trends and patterns in the development of a restored wetland based on the first 7 yr of its development, we analyzed 16 ecosystem functional attributes of the Gog-Le-Hi-Te Wetland, in the Puyallup River estuary, Puget Sound, Washington, USA. This estuarine wetland system was restored to tidal inundation in 1986. Only a few of the 16 ecosystem attributes analyzed showed functional trajectories toward equivalency with natural wetlands, and many were incon- clusive or suggested disfunction relative to reference wetlands. Natural variability among reference sites also inhibited our ability to interpret an expected asymptote in developmental trajectories. The ability of wetland managers to assess compensatory-mitigation success over short- term (e.g., regulatory) timeframes depends upon the selection of wetland attributes that can predict long-term trends in the development of the restored/created system. However, we are hampered by a basic lack of long-term data sets describing the patterns, trends, and variability in natural wetland responses to disturbance, as well as natural variability in wetland attributes in presumably mature wetland communities. Ultimately, it may be nec- essary to supplant our descriptive means of assessing functional equivalency with simple, controlled manipulative experiments or assays, standardized across restoration/mitigation and reference sites.

Demographic Responses of Estuarine Polychaetes to Pollutants: Life Table Response Experiments

Abstract: Capitella sp. I and Streblospio benedicti are infaunal, deposit-feeding polychaetes that occur in estuaries and littoral wetlands throughout much of the United States. Life table response experiments (sensu Caswell 1989a) were carried out in the laboratory to compare the demographic responses of these species to three common sources of estuarine contamination or enrichment: sewage (Milorganite), blue-green algae (Spirulina sp.), and hydrocarbons (No. 2 fuel oil). Life table data were used to generate two population projection models (a fully age-classified model and a simple two-stage model) for each species in each treatment and in a salt marsh sediment control. These models were used to quantify the effects of treatments on survival, reproduction, and age at maturity, and hence on population growth rate. For both species, survival was high in all treatments except the blue-green algae treatment, where oxygen depletion (to <1 mL/L) occurred. Treatments had dramatic effects on age at maturity, fertility, and generation time, which differed between species and among contaminants. Population growth rates (X) were higher in Capitella sp. I than in S. benedicti for all treatments, primarily due to earlier maturation and a fertility advantage exhibited by Capitella during the first few weeks of reproduction. In Capitella sp. I, explosive increases in X were seen in the sewage (X = 5.31) and algae (X = 2.81) enrichments relative to the control (X = 1.86) and the hydrocarbon treatments (X = 1.67). Reduced maturation time and increases in age-specific fertility associated with rapid growth and large body size were responsible. Hydrocarbons reduced X primarily through delayed maturation and reduced age-specific fertility. Population growth rates of S. benedicti in the hydrocarbon treatment (X = 1.11) and algae treatment (X = 1.09) were reduced relative to the control (X = 1.46) and sewage treatments (X = 1.41). The hydrocarbon reduction resulted from delayed maturity and reduced fertility, whereas the algal effects were caused by reductions in both juvenile survival and fertility. Our analyses revealed that Capitella sp. I's population growth rate was less sensitive than that of S. benedicti to these three common forms of estuarine contamination, that different sources of organic enrichment (sewage and blue-green algae) introduced at the same C and N levels could have varying demographic effects, and that when two contaminants (hydrocarbons and blue-green algae) caused similar reductions in population growth rate in a species (Streblospio), the underlying mechanisms may have differed. For both species all demographically important effects of contaminants occurred early in life, suggesting a need to focus on juveniles and young adults in field and laboratory testing. The experiments performed here demonstrated the sensitivity of polychaete demo- graphic properties to the condition of estuarine sediments. This sensitivity may be exploited to evaluate organic enrichment and hydrocarbon contamination in field settings.

The Need to Define Hydrologic Equivalence at the Landscape Scale for Freshwater Wetland Mitigation

Abstract: Attempts to replace wetlands or define hydrologic equivalence for wetland mitigation must be based on an understanding of the complexity of wetland hydrology and of the relationship of individual wetlands to the landscape. Because mitigation has the potential to re-configure the kinds and spatial distribution of wetland ecosystems over large geographic areas, I advocate a landscape approach to defining hydrologic equivalence. This approach does not depend on specification of hydroperiod or other hydrologic variables for individual wetlands. It relies instead on knowledge of landscape properties that control wetland hydrology and water chemistry. In this paper I develop the conceptual framework for defining hydrologic equivalence for wetland mitigation viewed as a de facto landscape management policy with the potential to reduce the diversity of wetland types within regions. I review modern hydrogeological understanding of where wetlands form in the landscape and identify key hydrologic variables responsible for the formation of specific wetland types. I also review existing evaluations of mitigation projects in several states. On the basis of these reviews, I argue that, in setting regulatory criteria for judging hydrologic equivalence, the scale must be enlarged from the individual wetland project to include the broader landscape. Only this broader view can provide the context within which decision-makers can evaluate the potential cumulative effects of individual mitigation decisions on- broad-scale patterns of wetland diversity. The landscape approach to defining hydrologic equivalence that I advocate is based on the concept of templates for wetland development. These templates are the diversity of settings created in specific landscapes by the complex interactions of hydrogeologic factors and climate. These interactions, in turn, control key hydrologic variables and hydrologically influenced chemical variables that cause specific wetland types to form. Hydrologic equiv- alence then can be defined at the scale of landscapes in terms of the kinds, numbers, relative abundances, and spatial distribution of wetland templates. The approach can be implemented through the identification of landscape goals and profiles based on knowledge of these templates. The profiles would catalog and map the diversity of wetland templates and the diversity of existing wetland types within a given landscape, focusing the attention of decision-makers on broad-scale patterns of loss in wetland types and providing a context within which individual mitigation projects could be evaluated. Landscape goals for main- taining a diversity of wetland templates are suggested.