The Legacy of Past Pesticide Use:
As described in previous chapters, the ecological risks from pesticides remain high despite decades of environmental regulation and the banning of some of the most harmful pesticides. Despite the bans, however, many pesticides that pose substantial risks to wildlife and the environment in general remain on the market and are released into the environment in large quantities. Even where the US has banned or severely restricted a pesticide deemed to pose unreasonable adverse effects, however, environmental risks remain. As discussed in Chapter 13, a pesticide banned or severely restricted in the US may still be sold and used in other parts of the world. Equally disturbing, however, is the legacy of pesticide risk that remains in the US from pesticides banned decades ago. Despite EPA’s ban of most organochlorine pesticides in the 1970s and 1980s, the enormous historic use of these pesticides, coupled with their tendency to persist in the environment has resulted in continued environmental harm. Pesticides that were banned years ago can still be found on farms, in warehouses, and in garages throughout the US. Although these pesticides cannot be used legally, their continued existence creates the possibility that they will be illegally used, accidentally released, or improperly disposed of.
Another long-term concern with persistent organochlorine pesticides is that pesticides that are bound in soils may become biologically available when the soil is disturbed or where an area becomes intentionally or unintentionally flooded with water. This is of particular concern for large environmental restoration projects, such as those carried out under the federal Wetland Reserve Program (WRP), which typically involve restoring farmlands to historic wetland conditions. The most dramatic example of this occurred in 1998 when a massive bird die-off occurred on farmlands that had been rehydrated to their prior wetland state on lands adjacent to Lake Apopka in Florida.
Lake Apopka, Florida is located in central Florida near the city of Orlando. It is a large, approximately 31,000-acre lake, which served as a major sports fishing venue dating back to the 1800s.2 At one time, more than 20 fish camps were located on the shoreline, and sports fishermen traveled for long distances to take advantage of the excellent fishing and recreational opportunities on the lake.3 During the 1940s, the State of Florida gave away thousands of acres of wetlands along the north shore of the lake to encourage row crop, or “muck” farming operations on the nutrient-rich peat soils.4 To farm these wetlands, it was necessary to build a large levee between the wetlands to be farmed and the open-water area of the lake and then to pump water out of the farmlands into the lake proper.5 Consequently, approximately 20,000 acres of sawgrass marsh was isolated from the remainder of the lake by levees.6 The water pumped from the farms into the lake was laden with high levels of phosphorus.7 Water continued to be pumped on a regular basis from the farms into the lake from the 1940s until the 1990s.8 By the mid-1960s Lake Apopka was Florida’s most polluted large lake.9
After many years of efforts to control nutrient loadings into the lake through regulatory and non-regulatory mechanisms, the state of Florida decided that the only way to achieve the dramatic nutrient reductions that were necessary to restore the lake was for the state to purchase the lands surrounding the lake and take them out of agricultural production.10 The buy-outs involved 26 different property owners. The funding for the buy-outs came from both Florida’s Preservation 2000 land acquisition program and from the federal WRP.11 Because the Lake Apopka project was one of the first major WRP purchases, the WRP program did not yet have established rules or procedures. What turned out to be a major shortcoming in the WRP at that time was that it was assumed that individual Endangered Species Act (ESA) consultations for each restoration project would not be necessary because WRP staff believed that all of the projects would be covered by a programmatic consultation that had been conducted on the WRP as a whole.12
Prior to purchasing any of the farmlands, the St. Johns River Water Management District (SJRWMD), which is one of Florida’s five water management regulatory agencies and has jurisdiction over the Lake Apopka area, conducted environmental site assessments to determine if soils on the land previously used for farming were contaminated with pesticides.13 If significant contamination was discovered, SJRWMD required the seller to clean up the property prior to the purchase.14 In response to the site assessments, approximately 33,000 tons of soil contaminated with organochlorine pesticides were removed by the landowners, for a total remediation cost of more than $1.4 million.15 The environmental assessments revealed low levels of contamination over most of the farm fields tested, with higher concentrations in areas of the fields that had been used for the mixing and loading of pesticides. The federal partners in the WRP agreed to go forward with the purchases provided that SJRWMD conducted a risk assessment to determine what level of risk would be acceptable.16 SJRWMD conducted soil sampling on portions of the land to be flooded and used the data to conduct the risk assessment, and the WRP partners signed off on the risk assessment.17 In addition to the federal partners’ agreement with the risk assessment, the Florida Department of Environmental Protection also agreed to the conclusions of the risk assessment. The conclusion of the risk assessment was that the risk posed by organochlorine pesticides (OCPs) could be managed through wetland creation and natural attention.18 Although the scientists had concerns that the lower concentrations of pesticide residues in the field could pose a risk, based on best scientific judgment, founded in part on information from the scientific literature regarding how pesticides act in the environment and are metabolized by fish and wildlife, they concluded that the risks were not significant and the project could proceed.19
By August 1998, the SJRWMD, in partnership with the WRP of the USDA, had purchased most of the farms on the north shore of Lake Apopka.20 SJRWMD’s plan was to reflood the farmlands to mimic their pre-agricultural wetland state. Ultimately, SJRWMD planned to treat the fields with alum prior to reflooding to trap excess phosphorus before it entered the water column.21 The farmers in Unit 2, a 6,000-acre area on the northeast side of the lake, were asked to leave their fields shallowly flooded following their final crop harvest in the summer of 1998.22 Historically, during late summer and early fall, some farmers flooded their fields to minimize soil subsidence and erosion and to control nematodes.23 Short-term shallow flooding before pumping wastewater back into the lake was thus standard farming practice at the end of each year’s growing season.24 This pumping covered the area with approximately 18 inches of water for up to six weeks.25 The shallow-water habitats created by the flooding attracted large numbers of shorebirds, wading birds and other aquatic species.26 Even though the decades of farm flooding in late summer and early fall coincided with shorebird migration, and many birds had been visiting the flooded fields for decades, there had never been any reports of bird die-offs during previous flooding.27 In 1998, however, because the lands would no longer be farmed, the water was allowed to remain on the farms through the fall and into the winter.28 By eliminating the post-season pumping, the influx of phosphorous and pesticides to the lake would be reduced, and the growth of terrestrial vegetation on the farm fields would end.29
The fields were to be drained during the winter and treated to prevent phosphorus release.30 The late summer weather and farming conditions of 1998 were similar to previous years.31 However, as water levels began to rise with seepage and rainfall, and as fields remained flooded into late fall and early winter, more and more birds arrived.32
Lake Apopka is one of the most diverse areas for birds of any place in the southeast US. For example, the total species list for Lake Apopka is 336, as compared to the only slightly longer list of 343 species for the Florida Everglades.33 Because Lake Apopka is located in a migratory flyway, it is on the path of many thousands of migratory birds. In December of 1998, when the fields around the lake were flooded, the Audubon Christmas Bird Count (CBC) documented more than 46,000 birds, consisting of 174 species, present at the site, the highest recorded species diversity at an inland site in North America in the 100-year history of the CBC.34 More than 3,500 American white pelicans were seen on a single day in December 1998 in the former farming area—an unprecedented number.35