4

Ecosystem Trajectories
Affected by Water Quality and Quantity

Previous National Research Council (NRC) reports on Everglades restoration noted that progress had not yet occurred (NRC, 2007) or that it was slow (NRC, 2008, 2010) and emphasized that tangible restoration progress is needed to prevent irreversible ecosystem declines. Such declines result from disruptions in hydrologic and water quality conditions that have been so altered from their natural states that the ecological conditions in the remnant Everglades have departed ever further from the target conditions envisioned in the restoration plan. As noted in Chapter 3, restoration initiatives have focused mainly on the perimeter of the Everglades with little benefit to the remnant Everglades. The latest (August 2011) Integrated Delivery Schedule (IDS; see Figure 3-1) gives little cause for optimism, because the bulk of the Water Conservation Area (WCA)-3 Decompartmentalization and Sheet Flow Enhancement (Decomp) project has been delayed beyond 2020. Recent state budget cuts threaten to slow restoration progress even further. In light of the ongoing declines and the slow pace of restoration progress, NRC (2010) recommended “a rigorous scientific analysis of the short- and long-term tradeoffs between water quality and quantity for the Everglades ecosystem.”

In this chapter, the committee explores recent trends, possible future trajectories, and timescales for recovery of 10 ecosystem attributes of the remnant Everglades to better understand the implications of the current slow pace of progress and the potential consequences of focusing on water quality at the expense of water quantity, or vice versa. The chapter is organized in four main sections. First, the committee examines the context for water quality and quantity issues and discusses instances when water quality concerns have delayed restoration progress or have the potential to impact the future pace of implementation. Second, the committee synthesizes its analysis of current conditions and trajectories for 10 ecosystem attributes under three generic restoration scenarios to provide insights on how ecosystem attributes might respond differentially to management efforts. Furthermore, the committee explains the tradeoffs involved



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4 Ecosystem Trajectories Affected by Water Quality and Quantity Previous National Research Council (NRC) reports on Everglades restora- tion noted that progress had not yet occurred (NRC, 2007) or that it was slow (NRC, 2008, 2010) and emphasized that tangible restoration progress is needed to prevent irreversible ecosystem declines. Such declines result from disruptions in hydrologic and water quality conditions that have been so altered from their natural states that the ecological conditions in the remnant Everglades have departed ever further from the target conditions envisioned in the restoration plan. As noted in Chapter 3, restoration initiatives have focused mainly on the perimeter of the Everglades with little benefit to the remnant Everglades. The latest (August 2011) Integrated Delivery Schedule (IDS; see Figure 3-1) gives little cause for optimism, because the bulk of the Water Conservation Area (WCA)-3 Decompartmentalization and Sheet Flow Enhancement (Decomp) project has been delayed beyond 2020. Recent state budget cuts threaten to slow restora- tion progress even further. In light of the ongoing declines and the slow pace of restoration progress, NRC (2010) recommended “a rigorous scientific analysis of the short- and long-term tradeoffs between water quality and quantity for the Everglades ecosystem.” In this chapter, the committee explores recent trends, possible future tra- jectories, and timescales for recovery of 10 ecosystem attributes of the remnant Everglades to better understand the implications of the current slow pace of progress and the potential consequences of focusing on water quality at the expense of water quantity, or vice versa. The chapter is organized in four main sections. First, the committee examines the context for water quality and quantity issues and discusses instances when water quality concerns have delayed resto- ration progress or have the potential to impact the future pace of implementa- tion. Second, the committee synthesizes its analysis of current conditions and trajectories for 10 ecosystem attributes under three generic restoration scenarios to provide insights on how ecosystem attributes might respond differentially to management efforts. Furthermore, the committee explains the tradeoffs involved 95

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96 Progress Toward Restoring the Everglades when restoration efforts focus on only water quality or water quantity. Third, the committee discusses each of the 10 attributes considered in the condition and trajectory analysis, including supporting evidence for the synthesis section. Finally, the committee identifies key conclusions. CONTEXT FOR WATER QUALITY AND QUANTITY ISSUES The problems in the central Everglades result from hydrological conditions that make some areas often too dry, while other areas are often too wet. The sheet flow that characterized the original ecosystem occurs only in some areas when sufficient water is available. Moreover, compartmentalization has limited areas that can sustain flow velocities necessary to support the historic landscape fea- tures, such as the ridge and slough. As a result, topography and inter­ onnected c biological communities have changed. Issues with water quality present additional challenges to future restoration progress. Additional stormwater treatment areas (STAs) and/or source controls (e.g., best management practices) are needed to address elevated concentrations and loads of nutrients, most notably phosphorus, in current sources of inflow to the central Everglades (EPA, 2010). Thus, hydrologic restoration involving additional flow volumes or even redistribution of existing flows cannot proceed as planned without introducing levels of contaminants that would substantially affect the ecosystem and likely lead to potential violations of the 1992 Consent Decree. This difficulty was discussed in detail in the committee’s previous report (NRC, 2010). Restoration challenges are exacerbated because the original Com- prehensive Everglades Restoration Plan (CERP) assumed that water quality would be largely addressed outside of the CERP by the state’s Everglades Construction Project. Additionally, the natural system was likely sustained by large pulses of wet season flows, but STA performance depends upon dampening such flows (e.g., through the construction of flow equalization basins) to maximize phos- phorus removal. Thus, new planning is essential to determine how to support substantive flow restoration while simultaneously protecting the ecosystem from adverse water quality impacts. Attempts to restore flows in WCA-3 provide a clear example of the chal- lenges stemming from the interplay between water quality and quantity. The hydropattern restoration project component in WCA-3 has been delayed by water quality concerns, and there are additional concerns about the ability to operate Decomp Part 1 under anticipated water quality conditions. The hydropattern restoration component, designed to spread treated water from the STAs along the northern boundary of WCA-3A to better replicate pre-drainage flows, was originally part of the Everglades Construction Project, begun in the 1990s (FDEP, 1999). However, concerns about distributing water with high phos-

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Ecosystem Trajectories Affected by Water Quality and Quantity 97 phorus concentrations into unimpacted areas have delayed this effort, which has now been moved into Decomp Part 1 (Baisden et al., 2010). The project implementation report for Decomp Part 1, which includes plugging or filling the Miami Canal and hydropattern restoration in northern WCA-3A, has been delayed, largely because of concerns that the project (currently scheduled in the IDS to be completed by 2020) would not be operational because of water quality issues (USACE, 2012b). One of the key features of Decomp is sheet flow through WCA-3. The Modified Water Deliveries to Everglades National Park (Mod Waters) project included preliminary steps toward that goal via plans for conveyance features in the L-67 levees that would enable water to flow from WCA-3A into WCA-3B and into Northeast Shark River Slough. The Florida Department of Environ- mental Protection (FDEP) has raised concerns that this restoration component could compromise water quality in WCA-3B, which is currently a rainfall-driven system (E. Marks, FDEP, personal communication, 2012). Additionally, during wet ­ eriods, stage constraints in WCA-3B and in the L-29 canal limit the flow p of water through WCA-3B and into Northeast Shark River Slough. Instead, water will continue to flow from WCA-3A into the L-67 and L-29 canals, bypassing WCA-3B, and then under the new 1-mile bridge into Northeast Shark River Slough. This flow pattern, which likely will remain the only option until water quality and stage issues are resolved, is hardly the vision of restoration. Even the small adjustments in flow of existing water from WCA-3A to the south repre- sented by the switch from the Interim Operational Plan (IOP) to the Everglades Restoration Transition Plan (ERTP; see Chapter 3) has raised concerns about a decrease in the quality of the water delivered to Everglades National Park (­ urratt, 2010). With anticipated new water to increase flows, these concerns S about where and when water can flow will be further magnified. SYNTHESIS OF THE CURRENT STATUS AND TRAJECTORIES OF ECOSYSTEM ATTRIBUTES UNDER VARIOUS SCENARIOS The following sections discuss the current state, trajectories, and timeframes of recovering ecosystem declines for 10 ecosystem attributes of the remnant E ­ verglades. These ecosystem attributes include total phosphorus (TP) loads, inte- rior TP concentrations, soil phosphorus, cattail (Typha domingensis), periphyton, fish mercury concentrations, peat depth, ridge-and-slough topography, tree islands, and snail kites. These attributes are thought to be good measures of changes in structure and functioning that have occurred because of disruptions in the quantity, distribution, and quality of water inflows. The committee also selected these attributes because they reflect important and valued system char- acteristics and because there is considerable information on their status from past

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98 Progress Toward Restoring the Everglades monitoring and research. The spread of nonnative species, most notably Burmese pythons, reflects a significant change in the Everglades ecosystem (Dorcas et al., 2012), but abundance, effects, and potential for control of these species are not obviously related to water quality or flow, and so they are not included in this analysis. The attributes selected for this committee’s evaluation are both similar to and different from those selected for other assessment reports. For example, except for periphyton these attributes do not overlap with the stoplight indicators of the South Florida Ecosystem Restoration Task Force (SFERTF, 2010b), which largely focus on organism response. In contrast, there is considerable overlap with the System Status Report (RECOVER, 2010) and CERP performance mea- sures (RECOVER, 2007). Table 4-1 summarizes the committee’s assessment of status, current trends, and trajectories of all 10 ecosystem attributes under three generic restoration sce- narios involving water quality and hydrology. More detailed discussions of each attribute that support the committee’s assessment appear later in the chapter. By necessity, the table simplifies the complex ecosystem responses to management actions (much like a doctor’s health checkup), but the chapter sections attempt to capture some sense of the underlying dynamics and complex interactions among the various ecosystem attributes. This analysis provides a realistic qualitative assessment that underscores the increasingly degraded condition of the remnant Everglades and illuminates the consequences of various restoration scenarios. The current conditions of the 10 ecosystem attributes in varying states of decline are highlighted in Table 4-1. These conditions are driven by decades of diminished flow volumes and velocities, compartmentalization with associ- ated distortions of water depths, altered hydroperiods,1 and poor water quality. The committee summarizes the condition of each attribute by providing “grades” of the current state relative to the pre-drainage system: “A” no significant degra- dation, “B” evidence of degradation, “C” degraded, “D” seriously degraded, and “F” near irreversible2 degradation. For most attributes, these grades range from B to C (evidence of degradation to degraded; e.g., interior TP concentrations, TP load, soil P, cattails, periphyton) to D (seriously degraded; e.g., peat, tree islands, ridge and slough, fish mercury). For the snail kite, whose population has declined to near extirpation, the conditions are dire (grade of F or near irrevers- ible damage). The overall grade (or condition) for the 10 attributes is seriously degraded. Clearly the Everglades is in need of an aggressive and sustained res- toration effort, beyond what is currently under construction (see Chapter 3), if 1 “Hydroperiod describes the depth, duration and timing of inundation,” (Sklar and van der Valk, 2002). The term is sometimes also defined as the length of time (usually within a year) that a feature or an area is flooded (Bedford et al., 2012). 2 The committee considers irreversible degradation to represent ecosystem loss that cannot be restored over many centuries. Extinction is one example of irreversible degradation.

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Ecosystem Trajectories Affected by Water Quality and Quantity 99 its structure and functioning are to improve. The grades are not intended to be used to prioritize restoration of a single attribute to the detriment of others, but to highlight the urgency for ecosystem restoration actions that could benefit a wide range of attributes, as well as the cost of inaction. Table 4-1 also summarizes the current trajectories of the attributes (improv- ing, stabilizing, or degrading), which are discussed in more detail in the follow­ ing sections. The current trajectories in Table 4-1 can be characterized as those largely driven by hydrology (i.e., peat, tree islands, ridge and slough, snail kite); those largely affected by phosphorus concentrations (i.e., interior TP concen- trations, periphyton) or load (i.e., TP load, soil phosphorus, cattail); and those largely responding to other mechanisms, although with linkages to hydrology (i.e., fish mercury). As shown in Table 4-1, the attributes most affected by hydrology, in general, are described as degrading, while those affected by phos- phorus concentrations show a range of responses. Phosphorus-related stressors are stabilizing or stable to improving, because of the construction of STAs and implementation of source controls since the mid-1990s. Ecosystem conditions affected by phosphorus concentration are stable (periphyton), and those affected by loads are degrading but at slowing rates in some areas (cattails). Using available science, monitoring, and modeling, the committee also con- sidered how the current trajectories of the 10 attributes might change in response to three hypothetical scenarios of management actions: 1) improved water quality (with no increase in flow), 2) improved hydrology (with no additional water quality treatment), and 3) the combination of improved water quality and hydrology (see Box 4-1 for details on each scenario). Scenario 3 is the preferred scenario because it reflects the original CERP objective, but when it is achieved depends on the implementation schedule of restoration projects addressing water quality and quantity. These scenarios are simplifications of management alternatives. In Table 4-1, the effects of the three restoration scenarios on each ecosystem attribute are evaluated relative to the attribute’s current trend. Thus, a 0 rating for an attribute that is currently degrading means it will continue to degrade under that scenario. Estimates of the timescales for recovery are also described. These timescales reflect the committee’s qualitative estimates of the time required after substantial degradation has occurred to recover the losses in that ecosystem attribute (i.e., snail kites, tree islands, ridge-and-slough topography, periphyton, peat, cattail) or to attain established restoration criteria (i.e., phosphorus concentrations and loads in the water and soil, fish mercury concentrations). The importance of providing estimates of the timescales for recovery is to emphasize that some attributes will take longer to recover than others. The outcome of this analysis is an understanding that near-term progress that addresses only water quality or water quantity leads to continued system declines of many components. The

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100 Progress Toward Restoring the Everglades TABLE 4-1  Summary of Trajectories of Different Ecosystem Attributes in the Current System and under Three Restoration Scenarios Effects of Restoration Scenarios on Current Trends (1) (3) Effect of Current Effect of (2) Improvements “Grade” of Current Improved Effect of in BOTH Water System System Water Improved Quality and Timescales of Attribute (A to F) Trend Quality1 Hydrology1,2 Hydrology1 Recovery3 Stressors TP load C Stable to ++ –– + Years Improving Interior TP B to C4 Stable to ++ – + Decades conc. Improving Soil P C Stabilizing + –– + Decades to centuries Ecosystem condition Cattail C Degrading, + –– + Decades to centuries but (years if actively degradation managed) slowing in some areas Periphyton C Stable ++ –– + Years. Recovered communities may not be the same as prior to disturbance Peat D Degrading 0 ++ ++ Centuries in dry areas Tree islands D Degrading 0 +5 +5 Decades to centuries; may require active restoration Ridge and D Degrading 0 + ++ Centuries; could slough involve adaptive management Snail kite F Degrading 0 + + Years to irreversible Fish mercury D Stable – + + Years to decades continued analysis also helps to prioritize the focus: stabilizing and ultimately reversing declines of attributes that would take a long time to recover merit higher priority than attributes that would recover more quickly, all other things being equal, especially if other aspects of the restoration depend on them. Observations The committee’s qualitative analysis (explained in more detail in the a ­ ttribute-specific sections later in the chapter) led to several overarching observa- tions. If only system hydrology were to be addressed in restoration projects over

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Ecosystem Trajectories Affected by Water Quality and Quantity 101 TABLE 4-1  Continued 1 The three scenarios considered are detailed in Box 4-1. 2 Hydrologic improvements are assumed to address flow volumes, flow velocity and direction, flow vari- ability and frequency, and water depths and their spatial distribution, timing, and duration. 3 Timescales of recovery reflect the committee’s qualitative estimates of the time required after sub- stantial degradation has occurred to recover the losses in that ecosystem attribute (i.e., snail kites, tree islands, ridge-and-slough topography, periphyton, peat, and cattail) or to attain established restoration criteria (i.e., phosphorus concentrations and loads in the water and soil, fish mercury concentrations). 4 The grade of B applies to Everglades National Park and WCA-2, while a grade of C applies to WCA-3 and LNWR. 5 The “+” for scenario 2 for tree islands reflects minor improvement given the potential negative impacts of increased phosphorus on low elevation islands, whereas “+” for scenario 3 reflects moderate improve- ment (see the tree island section later in this chapter for more detail). NOTES: The following reflect responses to the three scenarios relative to the current system trend: ++ Major improvement in trend + Minor to moderate improvement in trend 0 No change - Minor to moderate decline in trend - - Major degradation in decline in trend “Grades” are based on an assessment of the current level of impairment of that ecosystem attribute relative to a pre-drainage state: A No significant degradation B Evidence of degradation C Degraded D Seriously degraded F Near irreversible degradation The trajectories presented in this table do not consider climate change and sea level rise effects, because the analysis was intended to highlight implications of decision-making alternatives over the next 1-2 decades. Climate change and sea level rise could certainly impact long-term trajectories of recovery and timescales of recovery, but these effects were not analyzed for this report. the next decade, then minor to moderate improvements could be expected for the trajectories of ridge and slough, tree islands, fish mercury, and snail kites, and major improvements for peat. However, these improvements would be accom- panied by major expansion of cattails and continued accumulation of soil phos- phorus. Soil phosphorus and dense cattail stands, if not actively managed, may persist for decades to centuries because soil phosphorus will continue to impact vegetation—even as phosphorus concentrations in inflow waters improve—until the soils are buried by less contaminated organic matter. However, the timescale for recovery for periphyton is anticipated to be relatively short. In contrast, if restoration priorities in the central Everglades focus only on

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102 Progress Toward Restoring the Everglades BOX 4-1 Three Scenarios of Management Action Used in the Committee’s Analysis of Ecosystem Attribute Trajectories The committee developed the following three scenarios for its analysis of likely changes to current ecosystem trajectories under different management actions: 1. Improved water quality (with no increase in flow). For this scenario the committee assumed a decrease in TP concentrations supplied to the Everglades Protection Areas from the STAs to meet the 18 parts per billion (ppb) TP annual flow-weighted mean, which was identified in the Amended Determination as one of two parts of an enforceable framework necessary to meet the 10 ppb geo- metric mean water quality criterion in the Everglades Protection Area. The second part was a require- ment that STA discharge concentrations not exceed 10 ppb as an annual geometric mean (equal to approximately 12 ppb TP as a flow-weighted mean) in more than two consecutive years (EPA, 2010). An STA discharge of 18 ppb TP represents a 28 percent decrease in current flow-weighted mean TP concentrations and loads without any change in flow (compared to the flow-weighted mean of 25 ppb TP across all STAs; Pietro et al., 2010). Meeting both parts of the Amended Determination framework would require lower long-term TP averages than the short-term 18 ppb annual limit considered in this scenario. 2. Improved hydrology (with no additional water quality features). The committee considered improved hydrology to address flow volumes, flow velocity and direction, flow variability and frequency, and water depths and their spatial distribution, timing, and duration. For this scenario, the committee assumed an increase in flow volumes into the northern end of the Everglades Protection Area from the current annual average of 1.4 million acre-feet (MAF) to the CERP-proposed discharge of 1.7 MAF. Nevertheless, based on recent science suggesting a wetter pre-drainage system (~2.1 MAF; Wilcox, 2012), higher total flow volumes could be considered, as was done in the River of Grass planning process. An average annual discharge of 1.7 MAF represents a 21 percent increase in flow. Given that the current extent of STAs do not have capacity to accommodate this additional flow, such a scenario would involve 0.3 MAF of untreated water from Lake Okeechobee (at an assumed concentration of 100 ppb, see Figure 4-2) reflecting an additional 37 metric tons (mt) TP/year load. This represents an approximate 30 to 50 percent increase in the total TP load to WCAs -1, -2, and -3 (considering the five-year moving averages for 2009-2011; see Figure 4-3). The actual load increase could be even greater if the Lake Okeechobee water were distributed to only a single WCA. Additionally, the scenario assumes restoration features, including decompartmentalization, to address the currently altered water distribution and depths in the central Everglades, and releases that generate a flow velocity in the ridge and slough of at least 2.5 cm/s for a few weeks per year. 3. Improvements in both hydrology and water quality. The third scenario assumes the same hydrologic improvements of scenario 2, but it also assumes additional water quality features to reach the water quality objectives outlined in scenario 1. The combination of a 28 percent decrease in phos- phorus concentration and a 21 percent increase in flow results in an assumed 13 percent decrease in phosphorus load to the Everglades Protection Area. As noted previously, these are hypothetical scenarios with postulated endpoints, primarily to illuminate the different trajectories that ecosystem attributes could take under different scenarios. The committee has not analyzed what (or whether) specific project features could create these results.

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Ecosystem Trajectories Affected by Water Quality and Quantity 103 the water quality of existing flows, then the ecosystem should see some recovery in periphyton and slow improvement in soil phosphorus and cattails. However, peat loss would continue in over-drained areas (e.g., northern WCA-3), and t ­rajectories of deteriorating condition would continue for characteristic land- scape features such as tree islands and ridge and slough. Most of these losses would require decades to centuries to recover under ideal conditions. The reality is that these optimal conditions might never occur, and opportunities for restora- tion could be lost. Meanwhile, the Everglade snail kite faces a serious threat of extirpation. Attributes most directly influenced by hydrology are continuing to decline and are the most difficult to recover (e.g., peat, tree islands, ridge and slough), making addressing them a high priority. The areas of the Everglades where these hydrology-driven attributes are relatively intact and functioning therefore merit priority for protection and management. The benefits of restoration are not as simple and clear-cut as a tradeoff between water quantity and water quality. In many ways, improvements in water quality are linked with improvements in water quantity, and vice versa. For example, increases in water depth and duration will decrease the decomposition rates of peat and the associated release and transport of phosphorus, sulfur, and other nutrients associated with soil organic matter and therefore improve water quality. Likewise decreases in TP loads will likely encourage the development of native vegetation and the peat, landforms, and hydrology associated with that vegetation. Thus, benefits associated with management actions that improve water quality and water quantity are interconnected. Therefore, this qualitative analysis should be viewed only as a first step toward an integrated analysis of water quantity and water quality management actions. It points to the need for a more critical and comprehensive quantitative analysis using models to evaluate management issues in an integrated manner (see Chapter 5). Nevertheless, based on this qualitative assessment of the central Everglades system components’ status and trajectories, the committee concludes that near- term progress is needed in the central Everglades to address both water quality and quantity to prevent continued degradation that will take decades or longer to recover under optimal conditions. The committee is encouraged by the C ­ entral Everglades Planning Project, which intends to expedite the planning of the next increment of projects focused on the “core” rather than the periphery of the Everglades. This effort represents a significant step forward, although many details remain unresolved. The committee has not reviewed specific project plans, because the planning process was only in the early stages when this report was being finalized. But the Central Everglades Planning Project conceptually offers an opportunity to make significant steps toward reversing the declines in the remnant Everglades.

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104 Progress Toward Restoring the Everglades ANALYSIS OF ECOSYSTEM ATTRIBUTE TRAJECTORIES The following sections summarize the current state of the science of key ecosystem attributes of the remnant Everglades and provide the basis for the committee’s analysis of current status and trajectories under various restoration scenarios, as summarized in Table 4-1. These ecosystem attributes include: phos- phorus loads and concentrations, soil phosphorus, cattails (Typha), periphyton, fish mercury concentrations, peat, tree islands, ridge-and-slough topography, and snail kites. Phosphorus The wetlands of the historical Everglades were primarily low‑nutrient, p ­ hosphorus-limited systems. These biotic communities, including microbes, algae, and aquatic plants, are efficient in utilizing and conserving nutrients through reallocation and uptake of nutrients at very low concentrations. How- ever, phosphorus loading from agricultural and urban lands has converted some of these areas from low-nutrient to high‑nutrient systems, particularly near the source areas and along canals. The phosphorus inputs have led to substantial alterations to the indigenous system, including large incursions of cattail and disappearance of periphyton (discussed later in the chapter; McCormick et al., 2002; Noe et al., 2001, 2002; Richardson, 2008; Scheidt and Kalla, 2007). Phosphorus Concentrations and Loads This section describes trends in phosphorus loads and concentrations in Lake Okeechobee and in the Everglades Protection Area. Because a substantial quan- tity of “new water” for the CERP will be delivered from Lake Okeechobee, water quality trends in the lake have important implications for Everglades restoration plans. Five-year trailing moving averages (5YrTMA) of total phosphorus (TP) loads to Lake Okeechobee increased from 1994 until about 2006 to a maximum of about 700 metric tons (mt) per year, peaking after two consecutive years of heavy hurricane activity, and since 2006 the trend has been downward after several dry years (Figure 4-1). Even at the level of 500 mt in 2010, the average TP load is still far above the annual target of 140 mt. Phosphorus concentrations in the lake have seemingly returned to pre-hurricane levels following the sharp increases starting in 2005, although the current values (~100 parts per billion [ppb]) remain far above the target concentration of 40 ppb TP (Figure 4-2). It is too early to discern from the data whether the long-term increasing trends in loads and concentrations are, in fact, beginning to level off. Nevertheless, if increased amounts of Lake Okeechobee water are to be conveyed in the near term to the

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Ecosystem Trajectories Affected by Water Quality and Quantity 105 FIGURE 4-1  Annual total phosphorus loads and five-year trailing moving average loads to Lake Okeechobee. Reported loads include atmospheric deposition. SOURCE: Data from Zhang and Sharfstein (2012). 250 Annual 5-Yr Moving Average 200 Target TP Concentration, ppb 150 100 50 0 5 7 9 1 3 5 7 9 1 3 5 7 9 1 8 8 8 9 9 9 9 9 0 0 0 0 0 1 19 19 19 19 19 19 19 19 20 20 20 20 20 20 FIGURE 4-2  Annual average concentrations of phosphorus in Lake Okeechobee. SOURCE: Adapted from Zhang and Sharfstein (2012), Figure 8-12.

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138 Progress Toward Restoring the Everglades The length of time required to restore areas of ridge and slough that are p ­ resently disappearing is unclear although losses are likely to occur more quickly than restoration. Researchers do not completely agree on how long restoration of ridge and slough might require, but computer simulation models that account for some of the system drivers suggest that many centuries would be needed (Harvey et al., 2012). Other researchers, however, including some at the public session where Harvey et al. (2012) presented their results, have indicated that more rapid restoration may be possible. In some instances where dense wet prairie vegetation now clogs the sloughs in extremely degraded areas, additional efforts, such as vegetation removal, could be required to facilitate restoration. Tree Islands Tree islands are “small, slightly elevated forested wetlands within a ridge- slough matrix” (Sklar et al., in review). Two major types of tree islands occur in the Everglades. Pop-up tree islands (also known as floating or barrier tree islands) originate when a large portion of peat detaches from the substrate and are colonized with shrubs and trees; these occupy Loxahatchee National Wildlife Refuge and WCA-2A. Fixed teardrop-shaped tree islands are associated with topographical variations in the mineral substrate and extend from WCA-3 to Shark River Slough in Everglades National Park (van der Valk and Sklar, 2002). Tree islands play a crucial ecological role in the Everglades, providing habitat for a range of fauna, sequestering and cycling nutrients, and contributing to the spatial heterogeneity and landscape complexity of the ecosystem (Sklar et al., 2011; van der Valk and Sklar, 2002; Wetzel et al., 2005, 2011). Tree islands also have long-established and deep-rooted cultural heritage and societal impor- tance. Hence, maintenance and restoration of tree islands are key components of Everglades restoration. Drainage, compartmentalization, and subsequent changes in hydrology resulted in a loss of 67 percent of tree island area from 1940 to 1995 (Figure 4-22; Sklar et al., 2005). Further declines of 6 percent in total acreage of tree islands continued between 1995 and 2004 (Figure 4-23) (Sklar et al., 2011). Although some tree islands have experienced gains in acreage, many more have declined (Figure 4-23). The conditions causing tree island degradation and decline have not abated and therefore continued declines can be expected. The greatest ongo- ing threats to tree islands are altered hydrological regime and altered fire regime. Four components of hydrology—depth, hydroperiod, flow, and quality—can impact tree islands if extreme conditions outside the normal historic range are experienced for extended periods (van der Valk and Sklar, 2002). Because tree islands are nutrient hotspots and serve as nutrient sinks, water quality is regarded as the least important stressor among these components. However, water quality

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Ecosystem Trajectories Affected by Water Quality and Quantity 139 FIGURE 4-23  Tree island trends between 1940 and 2004 in WCA-3. The apparent increase in acreage and number of islands between 1940 and the mid-1950s is likely a combination of differences in mapping techniques and increases in areas covered by trees and shrubs (e.g., colonization of ridges) after extensive drydowns and shortened hydroperiods. Figure 4-22 SOURCE: F. Sklar, SFWMD, personal R02233 (Everglades 4)2012. communication, 2010, raster iamge is an important factor in the accumulation and distribution of phosphorus on tree islands (Wetzel et al., 2005, 2011). High water depths and long periods of inundation or flooding cause plant stress, failure of seed germination, and diminished wading bird nest habitat (Sklar and van der Valk, 2002). Simulations with the Everglades Landscape Vegetation Model (ELVM; a simulation model that links fire, nutrient dynamics, hydrologi- cal regimes, and vegetation succession on tree islands to analyze management alternatives) suggested that in WCA-2A tree island water depths of 30 cm for longer than 150 days result in loss of tree island species, and these results align well with historical records (Wu et al., 2002). Nevertheless, for Shark River Slough tree islands, water levels deep enough to protect the thin peat covering from both microbial oxidation and fires were critical to the elevated areas’ ability to support woody species. Shallow water depths and reduced hydroperiods result in peat oxidation and muck fires, which lower the elevations of peat-based tree islands. The overall effect and legacy of the 1915 to 1950s period of uncontrolled Everglades drain- age was a flattening of the landscape: lowering the tree islands and the ridges

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140 Progress Toward Restoring the Everglades relative to the sloughs and moving the elevations of tree islands closer to those of ridges (McVoy et al., 2011). Subsided tree islands with reduced peat become more vulnerable to flooding even under normal water depths and particularly under restored conditions. Peat oxidation and loss of up to 1 cm per year can occur under extended periods of shallow water depth (F. Sklar, SFWMD, per- sonal communication, 2011), with greater rates in a muck fire. The May 1981 muck fires in the northern portion of WCA-3A resulted in 9 to 28 cm of peat loss (Wetzel, 2002). In Shark River Slough 55 percent of islands and 58 percent of tree island hectares have been lost because of peat oxidation caused by fires and lack of water (Sklar, 2012). Fire frequency in the Everglades is estimated to be approximately 10-14 years (Gunderson and Snyder, 1994), but drier conditions increase the frequency, size, and intensity of fires. Under wetter conditions fire is a natural part of the disturbance regime and does not have the devastating effects evident with the large, frequent, and high-intensity fires under drier conditions. WCA-3A currently experiences hydrologic extremes to differing degrees. In general, the northern part of WCA-3A has become drier, whereas tree islands in the southern areas experience higher water depths, ponding, and longer hydro­ eriods. p Wetzel (2002) reported that tree island peat depths are generally shallower in northern WCA-3A (0.62-1.08 m) compared to southern WCA-3A (1.08- 1.22m) as a result of peat oxidization. The northern tree islands in WCA-3A have also become more vulnerable to fires than their southern counterparts. If water depths are substantially reduced for extended periods of time, then peat will oxidize, lowering the elevation of the island. The island then becomes more susceptible to inundation and drowns, reducing the diversity of floral species on the islands to those that are flood tolerant (Wetzel, 2002). However, even woody species that are flood tolerant can perish under sustained extreme flooding events, resulting in “ghost islands” that are lacking in floral diversity; it is estimated that the drowning process can take 20 years (Sklar, SFWMD, personal communication, 2011). Eventually, if tree islands subside to the extent that they lose their elevation above the surrounding ridges, then they can no longer sup- port woody vegetation, and the vegetation is replaced by sawgrass and cattails. If existing conditions are maintained, then the decline of tree islands will continue. Unless decompartmentalization occurs, tree islands in the southern portions of WCA-3A will continue to experience inundation and ponding and to lose species diversity (shifting to more flood-tolerant species). Hydrologic restoration (e.g., increased flow volumes, more natural hydroperiods and water depths) offers opportunities for recovery of tree islands, particularly in the southern and central portions of WCA-3A, where the greatest number of higher elevation tree islands remains. Much of the tree island acreage in northern WCA-3A has already been lost because of peat subsidence, and some remaining subsided islands may experience greater inundation, reduction in floral diversity,

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Ecosystem Trajectories Affected by Water Quality and Quantity 141 and ultimate loss with hydrologic restoration. Nevertheless, there is substantial variability in the current elevations of tree islands, which will result in differ- ent responses to restored water depths. With hydrologic restoration, many tree islands that are currently on a trajectory of drowning can recover, particularly if their elevation differences remain, although active restoration in the form of tree planting may be needed in some cases (van der Valk and Sklar, 2002). Natural recolonization of degraded islands can occur through seed dispersal if there are nearby islands with sufficient diversity and abundance of species (van der Valk and Sklar, 2002; Wetzel et al., 2005; Wu et al., 2002). Nevertheless, with long-term flooding and associated declines in plant diversity, opportunities for natural recovery through natural seed dispersal and recolonization will be lost over time. It may be possible to restore severely subsided tree islands by raising the elevation of their heads, although such efforts would be expensive and labor intensive (van der Valk and Sklar, 2002). The restoration of hydrologic flow, water depths, and duration will benefit many tree islands, but high phosphorous levels may promote cattail and willow encroachment on islands with elevations that are low relative to the surround- ing marshes. However, as phosphorus increases, vegetation and peat increase on tree islands that sequester and redistribute phosphorus (Wetzel et al., 2011). Hence, the detrimental effects of altered water depths and duration are expected to exceed the effects of water quality on tree islands. Improved hydrology and water quality offer the best opportunity for tree island restoration across the landscape (Bedford et al., 2012), although some subsided islands may become inundated and lose floral diversity because of variations in tree island elevation across the landscape. When considering restoration alternatives, the choice does not appear to be one of causing harm versus not, but instead one of causing the least overall harm while promoting the most improvement. ELVM simulations suggest that restoration of 60 percent of tree islands known to be lost could occur within 50 years (Wu et al., 2002). However, there are reasons to believe that the time to recover tree islands in WCA-3A is substantially underestimated. The predictions were based on flows that had been increased to pre-drainage levels and not the lower flows proposed under the CERP. Furthermore, the model was designed for, and calibrated well with, tree island dynamics in WCA-2A, but it did not calibrate well with islands in WCA-3, in part because WCA-3 has experienced substantial fire-induced peat losses that were not explicitly modeled. Snail Kite Snail kites in the Everglades are part of a subspecies (Rostrhamus sociabilis plumbeus) that includes other populations in Cuba and northwestern ­ onduras H

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142 Progress Toward Restoring the Everglades (Sykes et al., 1995). The two other subspecies of snail kite extend through Mexico, Central America, and all of South America. The Everglade kites are the only snail kites in the United States, and the population has been designated as endangered because of its limited distribution and declining numbers. The decline of the snail kite in South Florida reflects the degradation of the ecosystem on which it depends. The committee’s previous report (NRC, 2010) discussed the decline of the snail kite over the past decade, which has reduced the population to an extremely low level (Figure 4-24). Kite populations have fluctuated historically in response to drought cycles, with prior low points in the 1960s (Takekawa and Beissinger, 1989) and late 1980s (Beissinger, 1995), but the current decline differs in being driven by degradation of habitat in previ- ously productive areas (e.g., Lake Okeechobee, WCA-3A) as well as by climate (Reichert et al., 2011). Kites are highly mobile, and they move throughout the system to find conditions favorable for foraging and breeding (Bennetts and Kitchens, 1997; Takekawa and Beissinger, 1989). However, in recent years con- FIGURE 4-24  Population size and associated 95 percent confidence intervals of snail kites, 1997-2010. SOURCE: Reichert et al. (2011). Figure 4-24 R02233 (Everglades 4) raster iamge

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Ecosystem Trajectories Affected by Water Quality and Quantity 143 ditions have generally been unfavorable everywhere, and the kite population in the Everglades has declined precipitously. One can argue that the current trajectory of the kite population, which has brought it to the brink of extirpation, mirrors the current trajectory of the ecosystem and reflects the fact that every part of the Everglades has been altered, such that the kites have increasing difficulty finding suitable conditions anywhere (Kitchens et al., 2002). The most recent decline of the snail kite has been specifically linked to unfavorable conditions in southwestern WCA-3A, their primary nesting area during the past decade (see Endangered Species Issues in Chapter 3). Prolonged high water levels in southern WCA-3A have well-documented, adverse effects on kites (NRC, 2010). However, the problem is more complicated than wet season water levels that are too high and last too long. These conditions and the accompanying loss of tree islands that serve as nesting sites might explain the lack of kite nesting in some former nesting areas, such as eastern WCA-3A (Figure 4-25). However, kites also suffer from dry season lows that are too low and rates of recession that are too fast (FWS, 2010). Kites are highly specialized feeders, relying on apple snails (Pomacea paludosa) to feed themselves and their young. Not coincidentally, these snails are also adversely impacted by these same hydrological problems, that is, prolonged wet season high water, prolonged dry downs in the dry season, and rates of recession that are too fast (FWS, 2010). It is actually rapid rates of recession and low water levels in the dry sea- son, not prolonged high water during the wet season that explain poor nesting success in southwestern WCA-3A over the past decade (NRC, 2010). It is the minimum stage, not the wet season high water maximum, that is most highly (and positively) correlated with kite nesting success (Cattau et al., 2008; FWS, 2010). Historically kite numbers have decreased during droughts and increased during wet periods (Takekawa and Beissinger, 1989). This explains the seemingly paradoxical pattern that kite nesting, which is adversely affected by prolonged high water, is concentrated in southern WCA-3A, where water levels are the highest, rather than in central or northern WCA-3A. When the kites shifted away from the ponded areas in eastern WCA-3A in the 1980s, they initially moved to central WCA-3A (Figure 4-25). However, these areas now dry out too much and too fast to support kite nesting. Thus the kites have shifted to the seemingly unsuitable southwestern portion of WCA-3A, not because conditions there are ideal, but because conditions everywhere else in WCA-3A are even worse. In some places prolonged high water has converted the wet prairies and emergent marshes that the kites use for foraging to other habitat types (Holling et al., 1994; Sklar et al., 2001; Zweig and Kitchens, 2008). These habitat types still occur in abundance; however, the more pervasive problem is that the historical wet season/dry season water cycles that support kite nesting and large apple snail populations (SEI, 2007) no longer reliably occur in these habitats.

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144 Progress Toward Restoring the Everglades FIGURE 4-25  Shifts in the distribution of nesting snail kites in WCA-3A, 1968-2006. SOURCE: FWS (2010). Figure 4-25 Looking beyond WCA-3A, (Everglades much the same. The kites formerly R02233 the picture is 4) nested in large numbers inraster iamge Chain of Lakes, Lake Okeechobee the Kissimmee (Cattau et al., 2009), and WCA-3B and WCA-2 (Bennetts et al., 1994; Sykes, 1983). Thus, the dependence of kite reproduction on WCA-3A is a relatively recent phenomenon (Figure 4-26), and the dependence on the southwestern portion of WCA-3A is even more recent (Figure 4-25). In most of these former nesting areas, hydrology or habitat (or both) are altered in ways that make it unlikely that kites will return in significant numbers without restoration. Lake Okeechobee continues to be unproductive under current water management, although there were a few nests there in 2010 following three years with no nests (Figure 4-26). WCA-2 has experienced extensive loss of the tree islands (Sklar et al., 2009), which kites use as nesting sites, and no nesting has occurred there

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Ecosystem Trajectories Affected by Water Quality and Quantity 145 FIGURE 4-26  Number of young fledged from kite nests in the Water Conservation Areas (WCA), Kissimmee Chain of Lakes (KCOL), and Lake Okeechobee (Okeechobee), 1992-2009. SOURCE: Cattau et al. (2009). Figure 4-26 R02233 (Everglades 4) raster iamge in recent years. The ridge-and-slough landscape of WCA-3B is highly degraded (SCT, 2003), and there have been a few nests there in some years and none in others. Some nesting has occurred in Everglades National Park, but the dry season water levels there tend to be too low. Interestingly, kites have resumed nesting in the Kissimmee Chain of Lakes, coincident with their increasing abil- ity to forage on an invasive apple snail species (Pomacea insularum) found in abundance there (see below). This area has been the primary nesting area during the past few years because productivity in WCA-3A has declined to near zero (Figure 4-26). The kites are not as directly impacted by deterioration of water quality as are many other fauna and flora of the Everglades, although they can be indirectly impacted by changes in habitat mediated by water quality, such as cattail inva- sion. Instead, the problems that have plagued the kites in various areas of the central Everglades result from altered flow regimes; that is, they are problems of water quantity and distribution, especially seasonal cycles, rather than water

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146 Progress Toward Restoring the Everglades quality. Restoration of historical seasonal cycles of water levels and recession is necessary not only to create suitable nesting conditions for kites, but also to support the life cycle of their apple snail prey. Snail kites are very successful in other areas with extensive, shallow wetlands (e.g., the Llanos of Venezuela and the Pantanal of Brazil), and although little is known about where snail kites were most successful in the pre-drainage Everglades and to what extent their distribution changed during wet and dry cycles, the committee judges that conditions for the kite should improve in the Everglades with system-wide hydrologic restoration. Two independent panels of ornithologists and wetland experts have reached the same conclusion (SEI, 2003, 2007). The strength of the kites’ response will be complicated by the fact that restoration might reduce the amount of preferred wet prairie habitat while increasing the quality (due to restored hydrological cycling) of remaining habitat. Conservation increasingly focuses on those few areas that remain potentially suitable for the snail kite. Recent changes in water management in WCA-3A focus on improving conditions for kites and apple snails in the area on which kites have become most dependent, that is, southwestern WCA-3A (see Chapter 3). This likely will improve the kites’ nesting success in the target area (southern WCA-3A) but at the expense of making conditions even worse for them (and other system components) in other areas (central and northern WCA-3A). Until more substantial progress is made with all that the CERP is designed to accomplish in the central Everglades—increased inputs of water, a shift in the distribution of water from west to east, restoration of sheet flow and historic seasonal cycles of water levels and recession—kite conservation likely will remain in crisis as the system continues to degrade. Local actions, such as in WCA-3A, may ward off extirpation, but having a viable population is likely contingent on system- wide restoration. Not until then will the kites’ mobility and resiliency become the assets they once were. The kites’ adaptability may enable them to persist despite continuing system degradation. Specifically the kites appear to be increasingly able to sustain them- selves on exotic apple snails: recent increases in nesting in the Kissimmee Chain of Lakes (Cattau et al., 2009) and in the STAs (see Chapter 3) involve use of this prey. The kites may be adapting to these large snails by foraging for juveniles (Cattau et al., 2009) and by adults feeding snails to nestlings (Williams, 2011), and even by behavioral changes in prey handling that enable the kites to extract the large exotic snails more efficiently (H. Tipton, FWS, personal communication, 2011). CONCLUSIONS An assessment of the status and trajectories of 10 ecosystem attributes reveals that conditions for tree islands, ridge-and-slough landscape, snail

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Ecosystem Trajectories Affected by Water Quality and Quantity 147 kites, and peat continue to degrade and that cattail coverage continues to expand 12 years after the initiation of the CERP. These declines can be attributed to altered hydrology and/or the elevated supply of phosphorus in the remnant Everglades. Despite its ability to search throughout the Everglades ecosystem for suitable conditions, the Everglade snail kite has experienced a precipitous decline in numbers over the past 15 years and is in danger of extirpation. The state’s extensive phosphorus control efforts over the past two decades appear to be stabilizing or improving the current trends for several ecosystem components driven by phosphorus (e.g., periphyton, soil P). Cattail expansion, however, is continuing but at a decreasing rate in some areas (e.g., WCA-2). Implementation of STAs and best management practices has markedly decreased phosphorus loads to the WCAs, and interior phosphorus concentrations have decreased in WCA-2 and -3 in response to decreases in the concentrations of inflowing waters. Despite this progress, impacted areas of the WCAs consistently fail the four-part test for compliance with Florida’s water quality standards. Thus, it is widely recognized that additional water quality improvements are needed to prevent further degradation and reverse ongoing adverse impacts to the eco- system caused by elevated phosphorus. In contrast, the restoration of flows in the central Everglades has been limited, and the ecosystem attributes most directly influenced by hydrologic factors continue to decline. In many cases these ongoing losses can only be recovered over long time scales. The velocity, depth, and duration of water in the Everglades are important controlling factors for the distinctive terrain of the Everglades: tree islands, ridge-and-slough topography, and peat accumulations. These landscape components have been severely degraded by flow alterations during past decades. Recovering additional losses will require decades if not centuries. Of the many projects under construction, only Mod Waters (a non- CERP project) and the C-111 Spreader Canal (a CERP project) offer promise of direct, significant effects in the central Everglades. Substantial near-term progress to address both water quality and hydrol- ogy in the central Everglades is needed to prevent further declines. Near-term progress that addresses only water quality or water quantity leads to continued system declines of many components. Additionally, many improvements in water quality are linked with improvements in water quantity. Thus, decisions on restoration project design and scheduling should not be viewed as simple tradeoffs between water quantity and water quality. Instead, this qualitative analysis points to the need for a more critical and comprehensive quantitative analysis using models and field data to evaluate management alternatives in an integrated manner (see Chapter 5). Also, it highlights the importance of stabiliz-

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148 Progress Toward Restoring the Everglades ing and ultimately reversing declines of attributes that would take a long time to recover, particularly if other aspects of the restoration depend on them. Because of its focus on the remnant Everglades and accelerated planning, the Central Everglades Planning Project conceptually provides promise for rehabilitating the remnant Everglades.