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Re-Engineering Water Storage in the Everglades: Risks and Opportunities 3 Cross-Cutting Issues The previous chapter described the major storage components individually and offered some general comparisons among them. This chapter discusses cross-cutting issues related to implementation of storage components, considering lessons of other large restoration projects and principles of restoration ecology (e.g., NRC, 1992, 2001b; Science Sub-Group, 1993). The general considerations used in the following evaluations included sequencing of projects and the factors that should influence sequencing, ecological uncertainties associated with the interventions and with natural ecological processes, contingency planning, adaptive management, and the effectiveness of natural versus engineered processes. These considerations, and their application to the Restoration Plan, are discussed below. SEQUENCING As described in Chapter 1, the Restoration Plan involves large-scale hydrologic re-engineering for much of the Greater Everglades Ecosystem, and it consists of many individual projects, which are described in Chapter 2. In addition, other crucial projects are related to the Restoration Plan, such as Modified Water Deliveries to Everglades National Park. With so many components and so many constraints on this ambitious project, the way that the components are ordered in space, and especially in time, can profoundly affect the outcomes of the project. The project’s overall plan imposes some constraints on sequencing of its components, as is true, of course, for any construction project. The committee judged two criteria to be most important in deciding how to sequence components of a major construction or engineering project (the Restoration Plan): 1) protect against habitat loss and 2) provide ecological benefits as early as possible. Protect Against Additional Habitat Loss The first criterion is that the sequencing should protect the project against any damaging changes in external or environmental conditions, especially of ecologically valuable habitat and habitat that is potentially of ecological value, which would adversely affect the project’s completion and that could not be reversed if they occurred. In the case of the Everglades Restoration Plan, the most striking such environmental change would be the loss or irreversible alteration of land-surface required to implement the plan. The population of south Florida’s lower East Coast is projected to swell from 4.8 million in 1998 to 6.6 million in 2020 (Kranzer, 2003). If present
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities patterns of development continue, development will consume 311,000 acres in the five southeastern counties between 1995 and 2020 (Burchell et al., 1999). The most urgent and overriding sequencing criterion should be to protect from irreversible development all land that is or potentially could be included in the Restoration Plan. This kind of protection can be achieved by acquisition of the land, by obtaining easements, by zoning restrictions, or other methods. In the Restoration Plan, the primary method to be used is acquisition. A large amount has been spent on acquisition (Table 3-1), which reflects a recognition of the importance of protecting land for use in the restoration. The acquisitions listed in Table 3-1 began in 1991. Before then, Florida had various land-acquisition programs that operated in the region, including the Central and South Florida Project, Environmentally Endangered Lands, Save Our Rivers, and Save Our Everglades. Pre-1991-acquisitions date as far back as 1948 (Water Conservation Areas 1, 2, and 3). The 1991 and subsequent acquisitions reflect the startup of the 10-year Preservation 2000 program ($300 million per year statewide) and its successor Florida Forever program (another 10 years). In addition to those projects, since 1996, Florida agencies have acquired lands using grants from $200 million provided by the Federal Agriculture Improvement Act of 1996 (the Farm Bill) and $151 million from the Land and Water Conservation Fund (GAO, 2000). For the past several years, the governor and the legislature have pledged to budget $100 million per year for Everglades restoration land purchases. The additional funds for land acquisition (in excess of $100 million) are significant; the average spent yearly from 1999 to 2004 is $128.9 million. As of June 30, 2004, the estimated amount of land needed for the proposed projects in the Everglades restoration is 405,322 acres, with 206,109 acres (51%) already in SFWMD, state, or local-government ownership (LATT 2004). The figures in Table 3-1 reflect the slightly lower estimates of land needed in the 1999 Yellow Book, with land acquired as of March 2004. Despite the large amount of money devoted to land acquisition each year, and the large amount of land already acquired, the land remaining to be acquired is so extensive that the plan for land acquisition extends over more than two decades, during which time irreversible development of some land not yet protected is likely and an increase in the price of land is almost certain. To the degree that the land-acquisition part of the Restoration Plan departs from immediate acquisition or protection of all the land in the plan, the outcome of the Restoration Plan risks being compromised. Indeed some land within the footprint of the Restoration Plan already has been lost to uses incompatible with the plan, and further losses are occurring. Land adjacent to or in the CERP footprint and that has a pending application for an environmental resource permit currently is high on the acquisition priority list. Environmental resource permits are required by the SFWMD for activities that could affect wetlands, alter surface flows, or contribute to water pollution. The owners of that land include religious institutions; small businesses; large corporations, including real-estate development; federal and state agencies, and individuals. Land use and application information for those permits is available at http://www.sfwmd.gov/org/reg/rim/cerp/sheet1_1.html. Provide Ecological Benefits as Early as Possible As the restoration of the Everglades begins, reductions in distributions of some native species and loss of habitats distinctive of the Everglades continue. There is high potential for these losses to be irreversible. In addition, invasive species continue to increase in number and
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities distribution in the Everglades, despite efforts to eliminate some of them. As the ridge-and-slough and tree-island landscapes continue to deteriorate, Everglades landscapes become increasingly homogeneous. Communities of marl prairies and periphyton mats continue to diminish in areal coverage, and nutrient loading continues to be above historic levels. These factors and the great uncertainty associated with implementation of the Restoration Plan and ecological restoration goals all argue for increased emphasis on achieving near-term ecological results in the process. One example of this would be providing more natural flows (in terms of seasonal timing, volume, and flow velocity) to Everglades National Park. Doing so might not require large-scale TABLE 3-1 South Florida Water Management District Land Acquisition* for CERP SFWMD Fiscal Year Acres Purchased for CERP Lands Dollars Spent for CERP Lands Average Price Per Acre for CERP Lands SFWMD FY04† - Projected 12,411 $123,280,005 $9,933 SFWMD FY03 11,116 $215,090,573 $19,350 SFWMD FY02 15,851 $147,303,278 $9,293 SFWMD FY01 13,922 $82,992,095 $5,961 SFWMD FY00 4,475 $48,379,665 $10,811 SFWMD FY99 57,145 $156,262,777 $2,734 SFWMD FY98 2,627 $5,762,600 $2,194 SFWMD FY97 5,086 $31,201,884 $6,135 SFWMD FY96 2,154 $19,766,055 $9,176 SFWMD FY95 29 $318,650 $10,988 SFWMD FY94 3,686 $5,740,026 $1,557 SFWMD FY93 1,429 $20,111,079 $14,074 SFWMD FY92 73 $1,315,800 $18,025 SFWMD FY91 1,420 $19,571,730 $13,783 SFWMD before 10/01/1991§ 23,639 $9,803,764 $415 Miami-Dade Biscayne Bay Coastal Wetlands 2,397 $2,253,265 $940 DEP - Southern Golden Gates Estates 50,807 $89,584,311 $1,763 TOTALS 208,267 $978,737,557 $4,699 Total CERP Project Boundary Acres 402,479 Source CERPMaster 31-Mar-04 Total Estimated Cost $2,304,097,501 Source CERPMaster 31-Mar-04 *Except for FY04, estimates as of 24-Feb-02, will change as individual project boundaries are modified during planning and implementation. †SFWMD fiscal year is 1-Oct to 31-Sep. §Includes lands acquired by or deeded to SFWMD starting in 1948, e.g. from the Central and South Florida Project. SOURCE: Data provided by South Florida Water Management District. These totals do not include other land-acquisition programs described in the text.
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities changes in sequencing; instead, incremental changes could add up to be significant. As noted in Chapter 2, novel storage techniques requiring long-term pilot studies make up approximately 80 percent of the new storage provided by the Restoration Plan. That degree of reliance on novel techniques places major constraints on the ability of the Restoration Plan to provide early ecological benefits. Interim measures, such as modified operating rules for flows into and out of Lake Okeechobee and the WCAs, or construction of additional conventional surface reservoirs, might be necessary in the near term to reduce or mitigate the loss of animal and plant populations and habitat. The recent plan to accelerate the pace for completing some of the Restoration Plan’s scheduled projects (called “Acceler8”) was made public too late for this committee’s evaluation, but it is intended to “provide immediate environmental, social, and economic benefits” (Florida DEP, 2004). SYSTEM UNCERTAINTIES All restoration efforts involving complex systems confront a diversity of ecological uncertainties, and the Everglades restoration is no exception. As a result of the quantity and quality of available science, and the extensive, thorough planning effort in support of the Restoration Plan, uncertainty from some sources is less than in most restoration efforts. These sources include observation uncertainty (i.e., inaccurate measurement of the state of the ecological system) and subjective uncertainty (i.e., uncertainty arising from the interpretation of incomplete data) (Regan et al., 2002; SEI, 2003). Process uncertainty (i.e., natural variation and inherent stochasticity of ecological systems) assuredly is a major concern in the Everglades. Indeed, it is the variability and unpredictability of magnitudes and patterns of rainfall that have caused water management to be such a critical issue in south Florida, ultimately resulting in the creation of the Restoration Plan. The process uncertainty within the Restoration Plan has been explored somewhat for the hydrologic processes that drive ecosystem change through use of simulation modeling based on a multi-decadal rainfall record that incorporates unusually wet and dry years. The Restoration Plan is designed to provide a consistent source of water to the natural and human systems despite process uncertainty. However, little has been published concerning process uncertainty for the ecological models. A fundamental reason for uncertain restoration outcomes is that the Restoration Plan does not intend to restore the full natural range of physical processes that created and maintained the Greater Everglades Ecosystem. In particular, extremes of naturally occurring wet and dry periods harmful to the coastal metropolis or adjacent agriculture will not be allowed in the engineered, restored system. It is an open question whether the lesser variation of physical processes will restore or maintain a reasonable facsimile of the original Everglades. Indeed, it is not even certain as to what the final restored hydrologic and ecological conditions will be, when they will be attained, or how variable they will be. For example, Trexler and his colleagues have shown that hydrologic variations alone are not sufficient to explain variations in fish populations in south Florida, at least in part because nonnative fishes now present in the ecosystem make fish communities respond differently than the original native communities did to changes in water levels and duration of high and low water (Trexler et al., 2002; Kobza et al., 2004; Gaff et al., 2004). More problematic where the ecological response to the Restoration Plan is concerned are model uncertainties (i.e., use of oversimplified or over-parameterized models to predict the response of managed systems to management actions) and model errors (i.e., fundamental misun-
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities derstanding of variables and the functional form of the model) (Regan et al., 2002; SEI, 2003). Ecological models exist, including system-wide models such as the Across Trophic Level System Simulation (ATLSS), and the Everglades Landscape Model (ELM), conceptual models of ecological communities, and detailed models of the biology of individual species of interest (e.g., DeAngelis et al., 1998; Sklar et al., 2001). However, because the appropriate spatial scale for the ecological models generally is not the 2 × 2 mile scale used in the major hydrologic models (i.e., Natural System Model and South Florida Water Management Model), simulating anticipated ecological conditions is problematic. This is a source of considerable model uncertainty in projections of the ecological response to the Restoration Plan, beyond the usual uncertainty that comes with attempting to capture the dynamics of a complex system in a model. Also, despite the availability of several good ecological models, some important conceptual linkages between hydrologic and ecological variables have not been fully explored. The linkages include those between planned alterations in hydroperiod and spread of invasive species, patterns of mercury accumulation in biota, and expansion of the current area of eutrophication. The lack of linkage results in additional uncertainty about some ecological responses of the system. Model error will certainly exist in conceptualizations of the relationship between hydrologic variables and plant community composition and structure, and of the relationships of animals to plant communities. In some cases, relationships between the plant community and hydrologic variables are well understood and provide solid evidence that restoration can be accomplished. For example, evidence exists that areas of marl prairie that have been converted from muhly grass to sawgrass can be restored by altering hydroperiod (Nott et al., 1998). In contrast, it is not entirely clear that tree islands and ridge-and-slough landscapes can be restored by restoring historic water levels and altering flow patterns (NRC, 2003c). Habitat degradation is not always reversible, because the path from degraded condition to restored condition is not identical to the path that produced the original condition. Even if hydrologic conditions identical to historic ones can be recreated, whether the same ecological communities will be recreated is uncertain. Two other sources of uncertainty are related to conceptual and mathematical models specific to the structure of the Restoration Plan. First, there is uncertainty with respect to the model used to identify hydrologic goals for the Restoration Plan, the Natural System Model. A review of the NSM version 4.3 by Bales et al. (1997) estimated total uncertainty (i.e., uncertainty related to parameters, algorithms, and data) in water levels of about plus or minus one foot. This estimate is consistent with the more exhaustive uncertainty analysis done for the modern equivalent of the NSM, the South Florida Water Management Model (Trimble, 1995). Trimble’s estimates for the half-width of the 95 percent confidence interval for total uncertainty ranged from about 0.6 to 0.9 ft, depending on the region. Relatively scant data on evapotranspiration, and to a lesser extent, on roughness coefficients and precipitation, are large contributors to the uncertainty (Trimble, 1995; Jayantha Obeysekera, SFWMD, personal communication February 28, 2000). Given that mean water depths in much of the system are of similar magnitude to the total uncertainty of the model estimates, use of the model may result in inappropriate hydrologic targets for particular locations (Bales et al., 1997; Ingebritsen et al., 1999). Second, model simulations have focused on a fully implemented Restoration Plan. Hence, regardless of the accuracy of these projections, there is uncertainty about what the hydrologic conditions and resulting ecological response will be during the transition from current conditions to a fully implemented Restoration Plan. It is possible that irreversible changes could oc-
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities cur during the transition that would preclude successful restoration when the Restoration Plan is fully implemented. Thus, the potential is high for several unanticipated outcomes to occur as a function of various types of ecological uncertainties. Because these outcomes include changes in the state of the Everglades system that could be irreversible in the time scale of the Restoration Plan, contingency plans must be developed in the near term to avert them insofar as possible. To that end, the following sections discuss specific uncertainties that, if not resolved and addressed, could undermine the fundamental goals of the restoration. Endangered Species The Endangered Species Act (ESA) has the potential to profoundly affect the implementation of the Restoration Plan by preventing or modifying implementation of water-management plans that are required for system restoration but that might have unanticipated detrimental effects on endangered species. The threat or actuality of litigation or enforcement related to the ESA influence all large-scale environmental management activities in the United States (e.g., NRC, 1995, 2004a, b), and the Everglades restoration is no exception. ESA decisions in general are characterized by law suits filed by diverse interest groups against each other and the agencies, sometimes even when other more cooperative avenues seem to be available (Ruhl, 2004). Recovery of endangered species is an explicit objective of the Restoration Plan (USACE and SFWMD, 1999), and much attention has been paid to the needs of endangered species in the Everglades. If the restoration is successful, the ecosystem will ultimately provide habitat for all the endangered species in it (e.g., SEI, 2003), and the U.S. Fish and Wildlife Service has legally supported this conclusion through the consultation process and development of recovery plans (USFWS, 1999). Yet despite the best planning, it is impossible to accurately predict how the ecosystem will move from the current state to a restored state, and in the transition endangered species may be adversely affected. An occurrence like this could mean that restoration of water to historic levels, timing, and distribution could fall victim to legal challenges. In recent years, management of the Everglades has been accompanied by constant litigation, much of it involving endangered species (see e.g., Rizzardi, 2001a). This pattern of litigation likely will continue, and attempts at restoration will not be immune from it: even temporary impacts on endangered species could provide fodder for those who wish to pose legal challenges to the restoration. In the Everglades, attention has focused mostly on endangered birds, and especially on one subspecies, the Cape Sable seaside sparrow (Ammodramus maritimus mirabilis). The desirability of a multi-species approach to endangered species management is recognized in the South Florida Multi-Species Recovery Plan for developed by the U.S. Fish and Wildlife Service (USFWS, 1999). While the Restoration Plan can be viewed as a revision of that multi-species plan, protection of single species under the ESA still can determine management. Indeed, after the numbers of Cape Sable seaside sparrows declined sharply in the mid-1990s, water deliveries to the southern Everglades have been designed to protect the sparrow, first in the form of modifications to the existing water-management plan, and later as a new interim management plan. Other endangered bird species in the Everglades are the wood stork (Mycteria americana), roseate spoonbill (Ajaia ajaja), and snail kite (Rostrhamus sociabilis). Because of their mobility and life histories, those species may be sufficiently resilient to persist through the
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities changes, anticipated and unanticipated, in the ecosystem caused by the Restoration Plan (SEI, 2003). But no clear evidence of similar resiliency exists for the Cape Sable seaside sparrow, which instead appears to be a highly sedentary bird with a short lifespan and limited capacity to colonize new habitat (Walters et al., 2000; Lockwood et al., 2001; SEI, 2003). Recent history indicates that increasing periods of high water in areas where sparrow populations currently reside can alter habitat and reduce nesting success and thereby significantly reduce or even eliminate those populations in only a few years (Curnutt et al., 1998; Nott et al., 1998; Jenkins et al., 2003). However, because of the sparrows’ limited capacity for dispersal, areas that currently are too wet for sparrows may not be readily occupied by the birds when the high-water period is shortened and habitat thereby improved (Walters et al., 2000; Lockwood et al., 2001). For this reason, a significant decline of Cape Sable seaside sparrows could occur at some point during the implementation of the Restoration Plan, and such declines could occur for other endangered birds. In addition, other endangered species than birds could similarly affect the Restoration Plan. Designing the Restoration Plan to totally avoid the possibility of conflict with the ESA is unrealistic. But it is possible to develop contingency plans for addressing such conflicts, and more could be done to anticipate them. Endangered species should figure prominently in contingency plans for addressing uncertainties in the relationship between ecology and hydrology. In addition, more analysis of the range of conditions anticipated during the transition from current conditions to a fully implemented Restoration Plan would be useful. Insufficiency of habitat for Cape Sable seaside sparrows and other endangered species is a much greater concern during the transition than when the Restoration Plan is fully implemented (SEI, 2003). Simulation modeling in support of the Restoration Plan has focused almost exclusively on the fully implemented system, and the transition period has received virtually no attention. Thus it is not clear whether, even without considering uncertainties, conflicts between the Restoration Plan and endangered species management are anticipated during the transition. We endorse recent efforts to conduct simulations of transitional scenarios, and to more closely examine potential conflicts between the Restoration Plan and ESA requirements (e.g., SEI, 2003), as a means to reduce the potential for endangered species to derail ecosystem restoration. Invasive and Irruptive Species The Restoration Plan could get the water right, but an irreversible change could occur as a result of invasive species dominating the system. Currently, a number of invasive species are problematic. The Everglades is a center of human activity that facilitates invasion of exotic species by creating disturbances in a region where the climatic conditions are favorable to a wide diversity of organisms from both the tropics and the sub-tropics. Construction and removal of earthworks during the restoration projects may create many new disturbance sites and remove barriers to establishment and dispersal of invasive species. An invasive species is defined as “a species that is 1) non-native (or alien) to the ecosystem under consideration and 2) whose introduction causes or is likely to cause economic or environmental harm or harm to human health (Executive Order 13112 of the National Invasive Species Council, 1999). Of the approximately 950 plant species (Avery and Loope 1983) in Everglades National Park, 221 are nonnative (Whiteaker and Doren, 1989). Of these species, three have been particularly troublesome: Australian bottle brush tree (Melaleuca quinquenervia), Brazilian pepper (Schinus terebinthifolius), and Australian pine (Casuarina equisetifolia). In
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities each case, the plant was introduced with a desirable goal in mind, but the outcome on the Everglades ecosystem has been severe and unanticipated. Another nonnative species, the Old World climbing fern (Lygodium microphyllum), has emerged more recently as an especially aggressive species in the Everglades system (Brandt et al., 2002; Langeland and Burks, 1998). Many wildlife species also have been introduced in the Everglades; often they were pets that the owner discarded. In particular, invasive species of fish from home aquaria, aquacultural activities, and other sources have been found in the Everglades. Examples include blue tilapia (Oreochromis aureus), spotted tilapia (Tilapia mariae), walking catfish (Clarias batrachus), and Asian swamp eel (Monopterus albus) (see examples of wildlife species introduced in the Everglades at http://www.flmnh.ufl.edu/fish/southflorida/everglades/Marshes/Exotic.html). Invasive species are not restricted to species from outside North America but can include North American species that are not native to the ecosystem of concern. In addition, species that are native to the ecosystem can irrupt, i.e., they can experience sudden increases in their numbers when ecological conditions change to favor them. In the Everglades ecosystem, the cattail (Typha domingensis) seems to be such an irruptive species that has been stimulated in the Everglades as a result of higher phosphorus concentrations, deeper water, and longer periods of high water in areas such as the WCAs and STAs that are created for storage (Davis, 1994). Under such conditions, cattail has replaced both sawgrass (Cladium jamaicense) and the diverse communities of green and blue-green algae, desmids, and diatoms that comprise periphyton mats, signature species of the Everglades (McCormick and Scinto, 1999). Indeed, the expansion of cattail has been so extensive in WCA 2A and along canals throughout the Everglades system that it has been a focus of law suits concerning water quality (John, 1994; Rizzardi, 2001a,b; Fumero and Rizzardi, 2001) and is one of the primary trends the Restoration Plan intends to reverse. Extensive research on cattail’s interactions with sawgrass, however, gives reason for concern that cattail will replace sawgrass over even greater areas before the Restoration is complete. While well adapted to periodic drought, fire, and the extremely low phosphorus levels of the native Everglades system, sawgrass performs less well than cattail under even mildly elevated phosphorus concentrations and longer periods of high water (Urban et al., 1993; Davis et al., 1994; Newman et al., 1996). Furthermore, cattail’s opportunistic pattern of phosphorus uptake, allocation, and growth allows it to take advantage of temporal variations in phosphorus inputs (Davis, 1994). Sawgrass is the superior competitor only under highly infertile conditions (Newman et al., 1996; Noe et al., 2001). Thus, cattail is likely to expand its distribution in the northern Everglades until phosphorus inputs and periods of high water are reduced. The number of invasive species already in the Everglades demonstrates the difficulty of controlling human activities that may intentionally or inadvertently lead to their introduction. The extent to which some of them have replaced native species and now dominate large areas of the system underscores the difficulty of predicting ecological outcomes. Research associated with invasive species in the Everglades should focus on the pathways of introduction for nonnative species and the prospect for an introduced species to become invasive in the Everglades. Limiting the spread of invasive species already established in the Everglades will reduce other costs and increase the probability of success of the restoration program.
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities Disappearance of Unique Everglades Communities Whether one considers the Everglades landscape from the level of the microscopic communities of periphyton mats or the entire assemblage of different plant and animal communities that constitute it, the term “unique” can be applied correctly. The Everglades is the only subtropical wetland within the United States. In fact, the particular combination of a warm and alternately wet-dry climate, relatively flat topography, and predominantly limestone geology that come together in south Florida has created a wetland that is unlike any other in the world – a subtropical, oligotrophic, calcareous, peat-based wetland. The organisms that inhabit this environment have evolved specific adaptations that allow them to survive frequent shallow inundation, low nutrient availability, periodic but extended drought, and episodic severe fire. Temporal and spatial variability in these factors over south Florida, as well as feedbacks between the biota and environment, produced a temporally dynamic landscape consisting of several distinctive vegetation types (Gunderson, 1994; Davis et al., 1994). Davis (1943) identified and mapped thirteen different vegetation types in the Everglades. At present, half of Everglades wetlands have been lost to agriculture and urban development, and diversity at both the community and landscape scales has been reduced in the remaining Everglades (Davis et al., 1994). Of the vegetation types mapped by Davis (1943), custard apple forest, peripheral wet prairie, and cypress forest have disappeared completely under human disturbance (Davis et al., 1994). Other types have been reduced substantially in area, notably the sawgrass plains and, to a lesser extent, southern marl-forming marshes. These two categories encompass five of Davis’s (1943) vegetation types, which Davis and others (1994) group into two pre-drainage landscapes–the sawgrass-dominated mosaic and the wet prairie-slough-sawgrass-tree island mosaic. In some of these latter areas, the former mosaic is losing its heterogeneity and becoming more uniform. Of particular concern is the loss of marl prairies (home to the endangered Cape Sable seaside sparrow, see above), tree islands, and open sloughs of submerged vegetation and periphyton mats. Many studies have attributed changes outside the areas where cattail now dominates to the past several decades of water and fire management in the water conservation areas, as well as to loss of flows throughout the system (Davis et al., 1994; SCT, 2003; NRC, 2003c). Numerous studies now are under way to reduce uncertainties in these attributions (Sklar et al., 2004). Insofar as the attributions have any validity, those involved in the restoration must recognize that the longer it takes to implement new water and fire management strategies, the more likely are further losses in the unique communities that are the Everglades. Loss of Tree Islands and Ridge-and-Slough Topography Tree islands, ridges, and sloughs hold a central place in people’s images of the Everglades system. “Ridge and slough” is one of nine major physiographic regions recognized within the Greater Everglades Ecosystem for modeling the restoration (USACE and SFWMD, 1999). “Landscape pattern” is one of only five functional groups into which all ecological performance measures have been aggregated for monitoring the restoration (AAT, 2001). Recovery of the acreage and number of tree islands is one of the specific restoration targets identified by the Task Force and RECOVER (Ogden and McLean, 1999). Tree islands have been the focus of an entire book (Sklar and van der Valk, 2003), and the role of water flow in maintaining tree is-
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities lands and ridge-and-slough topography has been the focus of reports by both the Science Coordination Team (SCT, 2003) and the National Research Council (2003c). Degradation of the landscape pattern of teardrop-shaped tree islands and sawgrass ridges (typically covered by shallow water) alternating with those of open-water sloughs seems apparent in aerial photographs and other imagery of the central Everglades (SCT, 2003). In a number of areas in the central Everglades, a strongly patterned landscape is being replaced by one in which topography and vegetation are more uniform. In the western part of Water Conservation Area 3, Sklar et al. (2003) found that differences in elevation between ridges and sloughs had decreased from between 30 and 90 cm to about 20 cm. The mechanisms by which the degradation is occurring, however, remain uncertain, as do the mechanisms by which the patterns initially formed. Several plausible mechanisms—e.g., underlying bedrock topography, differential rates of peat accumulation, transport of organic matter by flowing water, extreme hydrologic events, fire—have been proposed, but none has been examined in detail nor tested through process-based research (SCT, 2003; NRC, 2003c). A notable exception is the study by Conner et al. (2003) on the differential tolerance of tree species to changes in water depth. Furthermore, as noted by the SCT (2003), mechanisms that generated these features may differ from mechanisms that maintain them. Strong circumstantial evidence suggests that the direction and rate of water flow through the system play critical roles in maintaining the ridge and slough landscape (SCT, 2003). Of particular relevance is that the orientation of tree islands and the parallel ridges and sloughs align with inferred pre-disturbance patterns of water flow (Ingebritsen et al., 1999). Neither direction nor rate of water flow, however, enter explicitly into the Restoration Plan, which focuses instead on the timing and duration of water levels and water quality (NRC, 2003c). Water levels undoubtedly have effects on landscape patterns but they are not sufficient to explain how they are maintained (SCT, 2003; NRC, 2003c). Thus, the uncertainty surrounding the effects of the Restoration Plan on tree islands and ridge-and-slough topography is high. However, several specific approaches to reducing that uncertainty are available and have been identified by the Science Coordination Team (2003) and the National Research Council (2003c). Given that degradation already has occurred and is likely to continue under present conditions, placing a high priority on pursuing these approaches seems warranted. Expansion of Eutrophic Conditions One of the primary factors motivating restoration is the dramatic change in system state that has occurred in northern portions of the Everglades, where an oligotrophic ecosystem has been replaced by a eutrophic one (Davis, 1994). The most obvious manifestation of this state change is the advancing front of cattail that now dominates large areas once characterized by sawgrass, spike rushes (Eleocharis spp.), submerged and floating aquatic plants, and the species-rich assemblages of bacteria and algae associated with periphyton mats (Davis, 1994; Childers et al., 2003). At a more fundamental level, however, eutrophication means that the functioning, as well as the structure, of the entire system has changed as the result of nutrient inputs higher than those under which the Everglades system developed over the past 5,000 years (Gleason and Stone, 1994; Davis, 1994; Daoust and Childers, 1999; Miao and Debusk, 1999). Rates of nutrient uptake, biomass production, and decomposition have increased, as have many microbially mediated processes that circulate nutrients within the systems (Reddy et al., 1999). These
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities changes in system metabolism are reflected in higher concentrations of total and biologically available phosphorus in the detrital layer and shallow soils of phosphorus-enriched than of unenriched areas of the Everglades (Reddy et al., 1999; Childers et al., 2003). While the mechanisms by which cattail has replaced sawgrass and periphyton mats are well studied (Craft and Richardson, 1993; Newman et al., 1996; Newman et al., 1998; Miao and Debusk, 1999; McCormick and Scinto, 1999), and effects on overall system metabolism also have been much studied (Reddy et al., 1999), substantial uncertainty surrounds the question of whether or not the eutrophication process is reversible for the Everglades. In phosphorus-enriched areas of the Everglades, excess phosphorus has set up a positive feedback cycle in which increased microbial biomass results in higher rates of organic matter breakdown, greater release of inorganic forms of phosphorus and nitrogen from soils and litter layers, and consequently increased nutrient availability to plants (Reddy et al., 1999). With higher nutrient availability, the slow-growing, nutrient-conserving species of algae and vascular plants characteristic of the oligotrophic Everglades do less well than cattail, a fast-growing, nutrient-demanding species of eutrophic conditions (Newman et al., 1996). In turn, cattail produces more biomass, and its nutrient-rich litter supports higher microbial biomass, and decomposes more rapidly. This fuels an internal cycle of uptake and release of the inorganic forms of phosphorus that favors cattail growth. Shading by cattail then decreases the abundance of periphyton mats, which further drives eutrophication by reducing oxygen production and the removal and storage of phosphorus by periphyton (McCormick and Scinto, 1999). The development of oxygen limitation changes the composition of the microbial community and greatly increases the activity of anaerobes (Drake et al., 1996). Limiting periphyton growth also affects formation of calcareous soils, the basis of the marl prairies. The process of eutrophication is exacerbated by interactions with sulfate, which enters the Everglades from anthropogenic atmospheric sources and especially from agriculture (elemental sulfur is added to muck soils in the EAA as an acidifying agent to promote trace metal availability to crops, and the elemental sulfur is readily oxidized in the soil to sulfate). As limnologists have known for over fifty years, the release of phosphorus (as phosphate ion) from lake sediments can increase significantly when sulfate concentrations are increased (Hasler and Einsele, 1948). High sulfate concentrations in organic-rich, anoxic water and sediments promote the formation of sulfide. The anoxic conditions and high sulfide levels also promote the reduction of iron oxyhydroxides in sediments leading to the formation of ferrous sulfides. The net effect is to decrease the abundance of iron forms that can bind with phosphate in sediment (e.g., Wetzel, 1999). High sulfide concentrations also can be toxic to animals and plants and might explain changes in species composition associated with eutrophic regions in the Everglades. Consideration of the supply and spatial distribution of sulfate within the Everglades must therefore be part of any effort to understand and limit expansion of areas already converted to eutrophic states. Given that eutrophication effects a fundamental change in the system, and that once started it may become internally maintained, one must ask how long it might take to reverse the process after external phosphorus inputs are reduced. High phosphorus concentrations in sediments, plants, litter, and microbial biomass will continue to result in release of inorganic phosphorus to overlying waters–possibly for many decades–until fresh inputs of sediments with lower nutrient concentrations cover the nutrient-rich deposits or until the slow export of phosphorus in flowing water gradually depletes the system’s phosphorus stores. Given the number of processes involved and the complexity of their interactions, it is not clear when that might be.
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities Hence, preventing expansion of the areas where the system already has become eutrophic should be a high priority for the restoration. Mercury Deposition, Mobilization, and Bioaccumulation Processes occurring outside the system can change the Greater Everglades Ecosystem. One such process is atmospheric deposition of mercury (Hg). The factors controlling Hg deposition, transformation from unavailable to biologically available states, accumulation up the food chain (magnification), and implications to individual species are quite complicated. Impacts on higher trophic-level organisms could alter the way in which the Greater Everglades Ecosystem functions. The identification of high mercury concentrations in sediments (Drexel et al., 2000); water (Mauro et al., 2002); fish (Burger et al., 2004); birds (Frederick et al., 2002); alligators (Heaton Jones et al., 1997); and mammals (Facemire et al., 1995), including humans (Fleming et al., 1995) of the Everglades, is a reflection of the power of external forces to insert themselves unplanned into the restoration. While processes occurring within Everglades wetlands determine the rates at which mercury is converted from the unavailable to bioavailable form, and bioaccumulated within food webs, the sources of mercury lie largely outside these wetlands. Sulfate, which facilitates mercury methylation at low and moderate concentrations (Gilmour et al., 1998), also arrives from elsewhere. Insofar as the Greater Everglades Ecosystem is a precipitation-driven system, and methylation rates in part are a function of alternating wet and dry cycles, climate is a major external force that will affect achievement of restoration goals. Similarly, transport of mercury to and within the Everglades system is affected by climatic effects on wet and dry deposition. Restoration goals pertaining to animals, especially fish, higher trophic levels, and human health, and to providing recreational opportunities for human populations could be thwarted if insufficient attention is given to mitigating the mercury problem. As in most wetlands, the organic sediments in the Everglades accumulate inorganic mercury forms from a variety of atmospheric sources (Dvonch et al., 1998, 1999; Atkeson et al., 2003). However, under appropriate conditions, which occur in coastal and freshwater wetlands like the Everglades, these forms (primarily mercuric ion, Hg2+, in various complexes) are transformed to methylmercury. Methylmercury is a highly toxic form of mercury that is bioaccumulated within food webs. Effects on human health can be severe and include numerous forms of neurological damage to adults and neurodevelopmental deficits in children whose mothers are exposed to chronic low doses (NRC, 2000). Similar detrimental effects are observed in other higher trophic-level organisms–e.g., alligators, birds, and panthers. Cleckner et al. (1999) found that methylation of mercury occurs within the periphyton communities that occur throughout the Everglades. As defined by Cleckner et al., these communities consist of algae and bacteria growing in filamentous mats on top of the peat substrate, attached to macrophytes, or as free-floating mats. Rapid rates of methylation were found in periphyton communities where sulfur oxidation by photosynthetic bacteria was coupled with bacterial sulfate-reduction—specifically, a cycle in which bacterial sulfate-reduction is coupled to sulfide oxidation by photosynthetic sulfur bacteria. This finding is significant because periphytic communities serve as a direct food source to higher trophic levels (zooplankton and fish) and thus provide a tighter link between methylation and bioaccumulation of mercury by fish than is the case for the usually cited location of methylation–the bottom sediments.
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities Several kinds of bacteria can methylate mercury. In wetland sediments, sulfate-reducing bacteria such as Desulfovibrio spp. and Desulfobulbus proprionicus are responsible for the transformation (Choi et al., 1994; Benoit et al., 1999, 2001). The relationships among sulfate concentrations, activity of sulfate-reducing bacteria, geographic location within the Everglades, and other factors that affect the rate of methylation of mercury, including the concentration of methylmercury itself, are complex and are not fully understood (Benoit et al., 1999; Krabbenhoft et al., 2000). Whatever the precise relationships are, the concerns about mercury pollution in the Everglades make it critical to understand how sulfate affects the concentrations and species of mercury present in the Everglades. The State of Florida has taken some steps to control the Everglades mercury problem. Local atmospheric emissions of mercury in south Florida are estimated to have declined by over 90 percent from their peak levels in the late 1980s to early 1990s (Atkeson et al., 2003). Mercury concentrations in wet deposition in south Florida have declined by only about 25 percent since late 1993 (Atkeson et al., 2003), and the difference in the two numbers was attributed by Atkeson et al. at least in part to the fact that much of the decline in local emissions in south Florida occurred before wet deposition monitoring for mercury began in late 1993. The decline was found to be statistically significant and not related to changes in the amount of precipitation. Nonetheless, considerable uncertainty remains about the importance of long-range (continental and hemispheric) scales of transport as a contributor to mercury deposition in south Florida. According to Atkeson et al., various studies estimate that long-range sources contribute from 25 to more than 60 percent of the mercury to south Florida. Estimates for other parts of the country tend to be at the high end of this range (Engstrom and Swain, 1997; Fitzgerald et al., 1998). It is encouraging that declines in concentrations of mercury in largemouth bass and great egret chicks of about 80 percent have been observed at several locations in the Everglades over the past decade (Atkeson et al., 2003). These trends suggest that local emission controls have been successful in decreasing the magnitude of the mercury problem in south Florida. The trends might be explained by the nature of the mercury emission sources in south Florida, which were dominated by municipal and medical waste incineration (~86 percent of total emissions for Dade and Broward Counties in 1995-96). The mercury in these emission sources had a high fraction (~75 percent) of reactive gaseous mercury (thought to be mercuric ion, Hg2+), which is scavenged rapidly from the atmosphere by rainfall and settling particles and thus tends to be deposited locally. In contrast, most of the mercury in emissions from coal-fired power plants is thought to be elemental mercury, Hg0, which reacts very slowly in the atmosphere and has an atmospheric residence time of about one year, allowing it to be transported across the hemisphere many times before being deposited. Nonetheless, the above positive trends do not guarantee that the mercury problem in the Everglades is solved or will be solved simply by controlling local emission sources. Insufficient data are available to reliably define temporal trends in mercury levels in fish communities and other animals in the Everglades. Moreover, changes in the wet-dry cycle of the system, which are likely to result from the restoration process, might exacerbate the problem by stimulating more active methylation of mercury than under current conditions (see Chapter 2, section on EAA Reservoirs). Finally, methylmercury in water and its biota in the Everglades will be affected by seawater intrusion and other factors that alter water chemistry, including perhaps aquifer storage and recovery (ASR).
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities Regional Climate Change and Sea-Level Rise Climate change always has occurred and always will. The most important regional climatic factors subject to change are precipitation patterns (quantity, timing) and temperature. How those factors might change over the next several decades cannot be predicted with any accuracy, and thus there is an important source of uncertainty in modeling of the system. Though future climate is uncertain, the temperature is more likely to go up than down, and the variability in precipitation, including the frequency of extreme events, is more likely to increase than to decrease (IPCC, 2001). The frequency and severity of fires also could be affected by climate change (Davis and Ogden, 1994). For the Everglades, the most important global factor related to climate and subject to change is sea level. If significant global warming occurs, then for several reasons sea level is likely to rise. Current predictions are for a rise of approximately 0.6 to 1.5 m over the next century, but much uncertainty accompanies the predictions (IPCC, 1995). Because much of the Everglades, and much of south Florida, is so low-lying, a one-meter rise in sea level would have profound consequences for both natural and built environments there. According to Titus and Richman (2001), for example, 12,251 km2 of Florida’s 139,853 km2 of land (7.6 percent) is within 1.5 m of sea level. Much of that low land is in the south. CONTINGENCY PLANNING Because significant hydrologic and ecological uncertainties are to be expected as the Restoration Plan is implemented, we have recommended that a method of evaluating tradeoffs be developed (Chapter 5) so that options are not excluded. Consistent with this recommendation is the need for contingency planning, which is necessary to identify other options that should be available for consideration. Finally, as an assessment and management framework within which the need for implementation of contingency plans can be determined rapidly, active adaptive management should be considered. The need for both flexibility and adaptive management arises because initial actions will not always result in desired outcomes; surprises will occur and modifications to management actions will be necessary. In addition, as described in Chapter 2, approximately 80 percent of the new storage to be provided by the Restoration Plan involves novel technologies. Therefore, for an adaptive management strategy to be effective and flexible, contingency plans should be developed so that revised management actions can be efficiently implemented. For example, the Restoration Plan may not get the water right to achieve the desired ecological response. Active adaptive management is important to provide an early indicator of problems. Beyond that, flexibility in design and operations so that reasonable alternatives can be implemented is crucial. For contingency planning, assessment and modeling of perhaps less likely, but still possible, scenarios would be prudent. The scenarios for which contingency planning is needed should include both external forcing functions, such as climate change, increased water demand due to population growth, or greatly increased energy costs, as well as previously eliminated options, such as the EAA and Lake Okeechobee. Even if the water is made “right”, habitat modification that has already occurred is not always reversible. As noted above, populations of endangered species such as the Cape Sable seaside sparrow may not respond as predicted. What scenarios other than the predicted outcome might arise? What might happen during the transition period? Given the resources invested in the
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities Restoration Plan, and the consequences of unanticipated outcomes, it is important to think through questions of this nature and develop appropriate contingency plans. Clearly not all possible outcomes can be anticipated, which is underscored by using the word “surprise” to characterize some unanticipated outcomes. A strategy that includes contingency planning for alternative scenarios, flexibility to implement the contingency plans if needed, and active adaptive management to rapidly ascertain if the contingency plans are needed is strongly recommended. As a framework for contingency planning, long-range scenarios for development in the urban and agricultural parts of the Greater Everglades Ecosystem, making explicit the external forcing functions of the restored Everglades, will be essential. Such scenarios are essential tools to embed learning in the quest for sustainability (NRC, 1999). Long-range development scenarios sketch alternative long-range visions of how the system could change given what is known about trends, human desires, uncertainties and possible surprises, and pathways by which conditions might change. They make explicit the assumptions about values, lifestyles, and institutions, and they reveal the range of possible futures that should be contemplated. ADAPTIVE MANAGEMENT Adaptive management—implementing management policies as experiments (Holling, 1978; Walters, 1986)—has a large and rich scientific literature. Although it is not universally adopted as management practice—it can be difficult, time-consuming, and perhaps risky—there is much experience with its use and especially guidance on how to apply it (e.g., Carpenter, 1990; Walters and Holling, 1990; Gibbs et al., 1999; Gunderson and Holling, 2002; Meffe et al., 2002; Oglethorpe, 2002; Anderson et al., 2003). The Restoration Plan is committed to adaptive management, but it relies on passive, rather than active, adaptive management. The relative merits of the two approaches, and the consequences for the Restoration Plan of adopting a passive approach, were discussed in detail in an earlier NRC report (NRC, 2003b). We briefly summarize the critical points of that assessment here. Ideally, adaptive management allows resource managers to act despite acknowledged uncertainty, designing management actions to reduce uncertainty over time while permitting changes in response to surprising outcomes. Effective active adaptive management involves integration of model forecasts with post-implementation monitoring and large-scale management experiments; the combination of model forecasts and the new information (from monitoring and experimentation) should help to refine management actions and improve models over time. In contrast, passive adaptive management as proposed in the Restoration Plan does not include large-scale management experiments, but instead relies on an approach in which learning is based on each incremental step in the implementation plan. Adopting a passive-management approach represents a decision to limit power to obtain additional knowledge in order to avoid costs to the ecosystem (e.g., harm to endangered species) of obtaining knowledge. We recommend augmenting the passive approach with active adaptive management wherever possible to enhance conclusions about cause and effect and improve forecasting models. This is particularly important for assessing ecological responses to restoration actions. Examples of Restoration Plan components suited to active adaptive management include the pilot projects on ASR and other technologies, which should be tested in an experimental framework. Other possibilities might include experimental management to see whether (or to what degree and at what ecological cost) eutrophication is reversible; options for controlling in-
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities vasive species; the nutrient concentrations required to promote the growth of sawgrass instead of cattails; and so on. We are concerned that the Restoration Plan may not be sufficiently flexible, because anticipated outcomes are based on the fully implemented system, and the extent to which outcomes of individual projects can lead to changes in the design of later projects is unclear. It would be useful to assess the design and operational flexibility of the 68 proposed major projects that comprise the Restoration Plan in order to prioritize monitoring, experimental, and modeling activities, and to examine the relative ease with which projects could be modified in an adaptive-management process. To be effective, the process requires an explicit feedback mechanism for learning from management actions. This mechanism should begin with systematic, iterative monitoring followed by comparison of results with model predictions and project goals. Establishing formal linkages between scientists and decision-makers would ensure that scientific information is available and accessible to the decision-making process. Taken together, the monitoring by scientists and provision of conclusions to decision-makers would make possible the well-known engineering practice of feedback and control. Considering the 40-year time frame of the Restoration Plan and perhaps a century of system response, a regional information synthesis center (NRC, 1999) would enable the systematic provision of evolving, reliable knowledge in support of the policy process and the interested public who affect and are affected by the program. The center’s activities should include restoration activities that are not officially part of the Restoration Plan. A similar recommendation was made by a recent NRC committee reviewing the Critical Ecosystems Studies Initiative (NRC, 2003a). That committee recommended that south Florida restoration managers “should consider the benefits of a central and independent restoration science entity that strives to inform the greater restoration effort (including the [Restoration Plan], current non-[Restoration Plan] initiatives, and future restoration projects) with the best science available. Such a central science body could serve as a resource for scientific information, provide a mechanism for science coordination, and create a forum for visionary science synthesis.” We agree with the earlier committee that the entity should not influence or be responsible for restoration policy and decision making. Finally, while management objectives are an essential foundation for adaptive management, they themselves should be subject to change through the adaptive-management process. Much effort has been expended on defining restoration goals, objectives, and targets, and many general and specific ones have been identified. Yet it is still not clear exactly what a successful restoration will look like, and not all specific goals and targets are internally consistent. Adaptive management can be helpful here, since it need not be restricted to improving scientific knowledge and assessment. In fact, adaptive management is compatible with a dynamic decision process in which the knowledge gained through large-scale experiments may suggest that management objectives need to be re-examined and possibly reformulated. SUSTAINABILITY OF THE RESTORATION PLAN Large environmental restorations of ecosystems—especially aquatic ecosystems—usually face a tension between the need for human subsidies in the form of energy, time, and money, typically for the construction and maintenance of control structures, and the desirability of relying on natural processes to achieve the restoration program’s goals. Designing engineered systems and specifying their parameters often is easier than relying on natural systems. Engineered
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities systems allow for the provision of services unrelated to ecosystem functioning, such as drinking water, flood control, and recreation, and ecosystems can respond more quickly to changes in engineered systems than to many natural processes. In addition, many aquatic ecosystems to be restored already have many control structures in place, such as dams, levees, and pumps. However, experience with ecological restoration shows that goals are realized more often when natural processes are encouraged than when engineering solutions are substituted for natural processes (e.g., NRC, 1992; NRC, 1996a; NRC, 2001b). It is obvious even on superficial inspection that the Restoration Plan for the Everglades relies very heavily on engineered solutions. Aquifer storage and recovery (ASR) and the Lake Belt reservoirs are two components of the plan that will require large initial investments in engineered structures; ASR will require large continuing investments in its operation and maintenance as well. The Everglades shares with many other large aquatic ecosystems the presence of many control structures and many competing demands on its water supply. Therefore, opportunities to restore the system to one in which flows are controlled only by natural processes of rainfall, runoff, and storage in natural areas are severely constrained. This is the result of the restricted footprint (area) of the remaining natural areas in the Everglades, the proximity of urban and agricultural lands that cannot be subjected to flooding without significant loss of property values, and the current and future demands for urban and agricultural water supply. Many of the natural storage features of the system, which provided essential damping of seasonal and storm-driven flows, have been lost permanently as a result of agricultural and urban development. As described previously, simply routing excess water from Lake Okeechobee to the southern Everglades through pipes or other structures that bypass the agricultural area is also not an acceptable option. Although this would reduce the detrimental pulses of freshwater discharged to estuaries, it would generate unnaturally high flows and water levels in the terrestrial ecosystem. Although some of the natural storage and damping could be restored if agricultural land south of Lake Okeechobee were converted into a restored corridor connecting the lake to the southern Everglades, subsidence due to peat loss in the agricultural area south of Lake Okeechobee has altered the topography to the extent that the land surface is now lower than in areas to the south. Therefore, even if intensive agriculture were ended in the EAA (or large parts of it) and the area converted to wetlands, slow sheet flow to the south would not be restored in the area that was historically a sawgrass plain. Instead, water would need to be pumped out of the subsided region into areas of the Everglades to the south. A large wetland of this type would, of course, provide significant storage and damping of southward flows, and it would remove a substantial amount of nutrients from the water. However, depending on the water levels maintained in the former agricultural lands, this land conversion also could result in the inundation of established urban and industrial areas and agricultural lands surrounding the current perimeter of the lake, and it would increase the flooding hazard of other developed areas to the south and southeast. This potential restoration component, therefore, would require additional engineering measures for flood control. The inevitable conclusion is that some degree of engineering control will be necessary in any attempt to restore more natural water levels and flows in the southern Everglades. However, as is evident from the descriptions of storage components in Chapter 2, there is a considerable range in the degrees to which various proposed storage components involve complex design and construction measures, rely on active controls and frequent equipment maintenance, and require fossil fuels or other energy sources for operation. We therefore discuss the approaches for deal-
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities ing with this issue in some detail, and suggest considerations that enter into evaluating options on that basis. In discussing options for interventions to enhance the wild salmon runs of the Pacific Northwest, an earlier NRC committee (NRC, 1996) provided a framework that is largely applicable to the Everglades restoration as well. That committee considered four general approaches for dealing with the problem of declining salmon runs: allowing continued degradation, restoration, substitution, and rehabilitation. Other than the first, the approaches are not mutually exclusive. As was true for that committee, allowing continued degradation is outside this committee’s charge and is not considered further. We discuss the remaining three approaches below, based on the 1996 NRC report. Restoration. Restoration implies a return of the system to some former, specified condition (NRC, 1992). Restoration of the Everglades is no longer possible in many parts of the former ecosystem. Parts of the ecosystem have been so altered that it is impossible to know what the pristine condition was, and even intermediate historical conditions cannot be accurately defined. Other parts of the system have been irreversibly altered by human development. In addition, as the NRC’s 1996 report pointed out with respect to the Pacific Northwest, “the process by which the environment reached its current condition is not totally reversible. Genetic variability has been lost; evolution has occurred; exotic species have been introduced; human populations in the region have increased, and people have developed dependencies on a variety of modern technologies, cultures, and economic systems; and other natural and anthropogenic environmental changes have changed the range of biophysical and socioeconomic possibilities for future states of the system. In brief, the past provides opportunities for the future, but also constrains it.” Substitution. By substitution, the 1996 NRC committee meant “investing substantial energy, time, and money on a continuing basis to replace natural ecosystem processes that have been destroyed or degraded.” Examples of proposed Restoration Plan components that constitute substitution in the Everglades are obvious: they include ASR; Lake Belt Storage; the system of canals, levees, and pumps used to transport water; and treatment plants for reuse of wastewater for Miami. As in the case of salmon in the Pacific Northwest, substitution for natural processes to maintain hydrologic regimes in the Everglades is possible, at least in some respects. However, it is expensive—the current, probably low estimate for restoring the Everglades is $7.8 billion for construction and land-acquisition alone, with annual operating and maintenance costs of at least $150 million. The cost in human and financial resources is likely to increase rather than decrease or stabilize in the future. And as the earlier committee warned, “…as the ability of human actions to make up for natural processes lags behind expectations, the danger is that either more and more drastic interventions will be undertaken or the whole effort will be abandoned and the salmon will be lost” (NRC, 1996a). That danger seems to apply to the Everglades restoration as well. Rehabilitation. By rehabilitation, the earlier NRC committee meant “a process of human intervention to modify degraded ecosystems and habitats to make it possible for natural processes of reproduction and production to take place. Rehabilitation would protect what remains in an ecosystem context and regenerate natural processes where cost-
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities effective opportunities exist. It might be necessary to use the technologies and techniques suggested in the preceding paragraph to maintain the essential ecosystem components in the short term, but the ultimate goal is to modify (i.e., rehabilitate) the systems to the point where human input is substantially reduced or even stopped altogether. Substantial local opportunities for local ecosystem rehabilitation exist throughout the region and they should be taken advantage of. Although this framework implies reduced management costs over the long term, it requires a long-term commitment to achieve positive results.” Restoring the Everglades is not a perfect analogy with reversing the declines of Pacific salmon in the northwestern United States, but there are many parallels that are useful in this case. Before discussing those specifics, we briefly describe some examples of the use of a rehabilitation approach to environmental restoration elsewhere. In longleaf pine savannas, the historical habitat structure was characterized by open pine stands with little hardwood midstory and a rich groundcover. Managers can return this structure to degraded habitats by using the natural disturbance that maintained it formerly—growing-season fire—or through less-natural techniques such as removal of hardwood midstory vegetation mechanically or use of herbicides. All these techniques restore the desired open habitat structure, but use of fire resulted in higher diversity of virtually all kinds of organisms in the community (Litt et al., 2001; Provencher et al., 2001, 2002, 2003). More relevant to the Everglades are examples of restoration of rivers and riparian habitats. The Greater Everglades Ecosystem is like a river in many ways, albeit a very wide and shallow one, whose flow is dominated by the effects of a water-control infrastructure. The dams of this infrastructure are lower than similar structures on other systems, but they nonetheless control the timing, magnitude, duration, and rates of change of flow through the system just as dams on other rivers do. The restoration of aquatic and riparian habitats for the benefit of species and general ecosystem functioning is a process that begins with the physical components of the system. The flows of water, in turn, control the movement of sediment, nutrients, and contaminants through the river system, often with temporary internal storage. The inorganic parts of the ecosystem form the foundation step toward a restored ecosystem. Reconstruction of this foundation by controlling flows of water to mimic the natural hydrologic regime has proven much more effective than physical reconstruction of the inorganic parts of the ecosystem in the absence of restored flows. Thus the general objective in physical restoration is to combine artificially designed features with a modified set of natural processes to effect a naturalization of the existing engineered system (Rhoads and Herricks, 1996). The result is a set of forms and processes that are as close to natural as possible, but that also accommodate some human-derived components. The restored river system is often a scaled-down version of the pre-human one, because water diversions for purposes other than in-stream flows make it impossible to sustain an active channel and riparian system of the original size (Graf, 2001). The issue in the case of the Everglades is whether the Restoration Plan represents a system that is as close to natural as is achievable given existing constraints, especially with respect to storage. The effectiveness of natural process in restoration does not preclude an important role for management and engineering. Indeed, restoration of riparian habitat illustrates that considerable progress toward more natural ecosystem conditions is possible through the use of existing water-control infrastructures. Dams are sometimes thought of as major impediments to restoration, but because they represent control valves on flows in the watershed and its river, they also provide
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities an opportunity for modifications that could restore more natural flows and water levels in parts of the system. Glen Canyon Dam on the Colorado River, for example, caused substantial changes in water flows and sediment transport downstream of the dam in Grand Canyon (Carothers and Brown, 1991). Continuing adjustments and fine-tuning of the releases is a part of an adaptive-management effort to improve the hydrologic regime for ecological purposes (Collier et al., 1997). Controlled releases on other rivers have had similar restoration objectives, including on the Trinity River of California below Trinity and Lewiston dams (Pitlick, 1992), the Gunnison River in Colorado below Crystal Dam (Chase, 1992), and several rivers in the eastern United States, including small streams in New England and larger ones such as the Ocoee River of Tennessee. The many water-control structures in the Everglades could be operated to support similar restoration objectives. The ultimate technique for using natural process in restoration of riparian ecosystems is dam removal, and this is more and more frequently the option of choice when other human demands on the system do not preclude it (Heinz Center, 2002). More than 400 documented cases of dam removal throughout the United States in recent decades provide ample experience in considering this option (American Rivers et al., 1999; Heinz Center, 2002; Pohl, 2003). In most cases, the structures that have been removed have been obsolete, low-head dams similar to many of those in central and south Florida. Most of the structures stored small quantities of water and sediment, and their influence on the hydrologic regime was limited. Their presence in the channel system inhibited movement of organisms up- and down-stream, however, and the dams therefore affected an important component of the ecosystem. Removal of the structures resulted in an increase in populations for a variety of species ranging from micro-organisms to endangered fish species (Hart et al., 2002). A cautionary note based on experiences elsewhere is that decision-makers must take account of the fate of sediments stored upstream from structures to be removed, because such materials are likely to be re-mobilized along with any contaminants that might be attached to them. The movement of invasive species into habitats formerly free of them also is likely to be one result of removing dams or other water-control structures, such as those in the Everglades, or other impediments to water flow, such as roads. Application of Rehabilitation Approach to Evaluation of Everglades Restoration Options In considering options for restoring the Everglades hydrologic regime to a more natural condition, many factors need to be considered. As discussed elsewhere in this report, they include human demands for clean and stable water supplies, flood control, agriculture, and recreation, in addition to the ecological needs of the Everglades. Those demands must be balanced against considerations of construction costs, operation and maintenance costs over decades if not centuries, water quality, the susceptibility of the components to mechanical or power failure, and the changing human and natural environments that will characterize south Florida for the foreseeable future. Some components of the Restoration Plan or associated activities already appear to have been motivated by an approach similar to what we call the rehabilitation approach. For example, the Kissimmee River restoration project is of special interest to the Restoration Plan because it represents one of the relatively uncommon instances in which hydraulic structures and channels have been decommissioned in an effort to restore natural hydrologic and ecological functioning.
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities This is in contrast to the planned construction of wells, pumping stations, seepage barriers, and advanced wastewater treatment characteristic of many other aspects of the greater Everglades restoration effort. That effort is described in some detail at http://www.saj.usace.army.mil/dp/Kissimmee/Kissimmee2.html. The Kissimmee River restoration is only partial and represents a reversion of a “highly engineered” flood channel (C-38) to portions of its hydrologically simpler, historical, meandering self. Whether or not these efforts will provide the hoped-for hydrologic, ecological, and water-quality benefits remains to be determined; an extensive Kissimmee River Restoration Evaluation Program is designed to track initial and long-term responses to the reconstruction efforts. Similarly, efforts to “decompartmentalize” the Everglades ecosystem by removing various canals and flood-control structures and by altering parts of the Tamiami Trail (U.S. Route 41) where it crosses the Everglades so as to increase sheetflow also reflect a rehabilitation approach. Finally, the use of stormwater treatment areas (STAs), which are engineered wetlands but which rely to some degree on natural processes, represents some degree of the rehabilitation approach, especially as compared with the water-treatment facilities planned for the Miami wastewater reuse. On the other hand, ASR and Lake Belt Storage are firmly in the substitution category. The committee describes elsewhere in this report how pre-existing constraints; new demands on the system; the possibility that one or more of the proposed components of the Restoration Plan will be unable to function as proposed; the accumulating costs of building, operating, and maintaining the Restoration Plan; ecological uncertainties; and the specifications of the Restoration Plan far into the future make it virtually certain that the plan will have to be re-evaluated periodically. Options that had been previously ruled out or not considered at all might become the only options available to achieve even some of the Restoration Plan’s goals.
Representative terms from entire chapter: