WHAT DO THE STOPLIGHT INDICATORS SHOW?
The eleven indicators are like “canaries in a coal mine” They are data based conclusions concerning the biological health and/or population trends of groups of key everglades species. The indicators are chosen not necessarily for their high media profile, but for the degree to which they have been determined by past research to represent or be particularly sensitive to a broad range of processes within the ecosystem such as changes in water levels, drying, food supply for species higher in the food web, nutrient loading and concentrations of various toxic compounds. The eleven indicator species/groups are:
• Fish and Macroinvertebrates such as crayfish and snails
• Wading Birds (Wood Stork and White Ibis)
• Wading Birds (Roseate Spoonbill)
• Florida Bay Submerged Aquatic Vegetation
• Florida Bay Algal Blooms
• Crocodilians (Alligators and Crocodiles)
• Periphyton-Epiphyton (communities of microscopic algae and bacteria which are the basis of most everglades food chains)
• Juvenile Pink Shrimp
• Lake Okeechobee Littoral Zone
• Invasive Exotic Plants
The eleven indicators above are known as “stoplight indicators” because each one is coded red, yellow or green depending on the severity of biological challenges represented by that species group. Each indicator is coded on three time scales: the status prior to 2007; the current level in 2008; and the level projected two years into the future.
Below are the six broad conclusions about trends in the ecosystem identified by these stoplight indicators overall in the 2008 executive summary. The conclusions are in the process of being updated as of 2010:
1. Water Management and Water Structures Matter. As shown by the indicators Roseate Spoonbills, Alligators, and Periphyton, the regions of the Everglades that are most removed from the actions or impacts of water management and water management structures appear to be relatively more stable biologically, biogeochemically and hydrologically. Important to note, however, are that 1) these areas still show negative impacts for some of the indicator species, particularly white ibis and wood stork; 2) even though more removed from impacts of water management these areas are still negatively impacted by water management, just more slowly or less frequently; and 3) relying only on small, less impacted portions of the remnant natural areas to support populations that research suggests may be at the edge of sustainability does not represent restoration.
2. Excess Phosphorus has negatively impacted the Everglades. As shown by the indicators Periphyton, and Lake Okeechobee Littoral Zone Submerged Aquatic Vegetation (SAV) excess phosphorus has impacted the Everglades most heavily in the northern areas and least in the southern areas of the Everglades, and areas more impacted by phosphorus are those closest to water management structures.
Periphyton also indicates that, so far—apparently a result of its southerly location—Taylor Slough is still pristine in relation to phosphorous in spite of being dramatically impacted by water management and contiguous to many water control structures. This indicates that future water management activities intended to increase flows to Taylor Slough must carefully take into account the need to ensure that only water with very low (~ 10 ppb) phosphorus content is allowed to enter Taylor Slough.
3. Littoral Zone Vegetation of Lake Okeechobee and the Northern Estuaries have been Seriously Affected by Restricted Outflow from the Lake. As shown by the indicators Lake Okeechobee Littoral Zone SAV, Fish and Macroinvertebrates, Wood Stork and White Ibis, Oysters, and Periphyton restricted outflow from the lake due to the Herbert Hoover Dike, and water management operations, including both water storage and water releases, have a serious negative impact on the littoral zone vegetation of the lake and the areas of the Everglades directly connected to lake management. Prolonged excessively high or low lake stages, usually exacerbated by extreme natural events such as heavy regionwide rainfall or serious droughts, can cause a significant loss of littoral zone vegetation and aquatic fauna. Water storage and water releases in Lake Okeechobee also are documented to have serious negative effects on oyster populations in the Caloosahatchee Estuaries and similar effects have been seen in the St. Lucie- Indian River estuaries.
4. Natural Events on Top of Human Impacts Cause Serious Negative Consequences. As shown by the Lake Okeechobee Littoral Zone SAV, Oysters, and Florida Bay Algal Blooms, natural events such as hurricanes or other large storms superimposed with human-caused perturbations (such as nutrient addition, road construction, water movement, etc.) can cause serious negative consequences. For example, the re-suspension of large amounts of nutrients (typically phosphorus) from urban and agricultural runoff has caused algal blooms that resulted in significant light attenuation. This results in the subsequent loss of submerged aquatic plants and aquatic animals.
5. There Is Too Little Water in Both the Wet and Dry Seasons Over Most of the Everglades. As shown by the indicators Alligators, Crocodiles, White Ibis, Wood Stork, Roseate Spoonbill, Pink Shrimp, Fish and Macroinvertebrates, Oysters, and Periphyton, and emblematic of the current hydrological system, most of the Everglades are negatively impacted by too little water in both the wet and dry seasons. These indicators also tell us (usually as a result of heavy rainfall events, or rapid drainage events in either the dry or wet seasons) that flood control operations can cause rapid and prolonged increases or decreases of water levels that negatively impact these species. Flood releases and drainage can cause water levels to be too high or too low, depending on how and where the water is moved.
a. Oysters, Alligators, Crocodiles, White Ibis, Wood Stork, and Roseate Spoonbill, in particular, reflect the seriousness of this second problem related to water operations which results in periods of too much or too little water during extreme events. These operations alter both the timing and duration of hydrological conditions, causing negative ecological impacts in regions that are affected by these actions.
b. Alligators, Roseate Spoonbills, and Periphyton again confirm that the areas more distant from water management impacts, such as central areas of Water Conservation Area 1, and Southwestern parts of Florida Bay, are more biologically and hydrologically stable. Most of the indicators in these areas show either improvements or are relatively stable. However, even though populations of some of these indicators may be stable, they are still below overall restoration targets for the species and indicate that small portions of the remaining natural areas are insufficient to support population levels that would be able to meet system-wide targets that represent biological restoration.
c. Oysters also indicate the same pattern for the northern estuaries as too much freshwater is released into the northern estuaries in the wet season and too little during the dry season. The timing and duration of these regulatory release patterns are not natural and negatively affect the oyster populations.
6. The Southern Estuaries Receive Insufficient Flows of Fresh Water During Both the Wet and Dry Seasons. As shown by the indicators Pink Shrimp, Florida Bay Submerged Aquatic Vegetation (SAV), Roseate Spoonbill, White Ibis, Wood Stork, Alligators, Crocodiles, Fish and Macroinvertebrates and Florida Bay Algal Blooms all of the southern estuaries receive insufficient flows of fresh water (including surface and groundwater flows) during both the wet and dry seasons. The shortage is particularly acute during the dry season. We see an unambiguous convergence of data related to shrimp, fish and macroinvertebrates and crocodilian populations, Florida Bay SAV, and locations of nesting wading bird colonies, indicating an extreme shortage of fresh water inflows.
a. Roseate Spoonbill and Crocodiles indicate that the southeastern estuaries of Florida Bay, at the southern terminus of Taylor Slough, are impacted by insufficient flows of water during the wet season and most especially during the dry season.
b. Florida Bay Algal Blooms indicate that the southern estuaries are still oligotrophic (very low in nutrients) and extremely sensitive to small increases in nutrient loading (phosphorous). This is likely related to insufficient flows to this region, keeping nutrient loads low. Care must be taken to ensure that any increased freshwater flows delivered to the southern estuaries do not increase anthropogenic (human generated) sources of nutrients to these areas (see also item 2 above).