The following paper was written by request in 1999 by staff at the Wisconsin Department of Natural Resources.  Although it was written by DNR staff this should not be considered official policy of the Department.

Environmental Issues Related to Cranberry Production in Wisconsin

Cranberry cultivation is an important and growing industry in Wisconsin. As with any agricultural practice, environmental impacts can occur. Cranberry cultivation has the potential to impact surface water quality, alter water levels in lakes and streams, and cause the loss of wetlands. With the industry’s intensive use of water and the application of fertilizers and pesticides in a wet environment, impacts to streams and lakes can be more direct than for other agricultural operations. There are also increasing water quantity conflicts between cranberry growers and other water users. The cranberry industry is working on best management practices and other methods to better protect surface waters and wetlands.

Authority for the Wisconsin Department of Natural Resources to regulate cranberry operations is limited by exemptions in state laws. Because of a law adopted in 1867, commonly referred to as the "Cranberry Law," cranberry growers are exempt from having to obtain state permits for many of the activities that result in physical alterations to lakes and streams, including diverting irrigation water, ditching, and the construction of dams.

Studies of several northern lakes located downstream from cranberry operations have shown increased levels of nutrients and phosphorus. The increased nutrients may cause excessive weed and algae growth and reduce dissolved oxygen in downstream surface waters into which these waters discharge.

Increased sediment loads to adjacent waters may occur during construction, ditch maintenance activities, and from eroding dikes, resulting in turbidity and sedimentation. Discharges of sediments to sensitive wetlands and coldwater resources, like trout streams, are of particular concern.

There is a potential for pesticides applied to cranberry beds to be discharged to downstream surface waters or wetlands. Several studies have found pesticides in waters receiving cranberry bed discharges. Although these studies were conducted downstream of existing cranberry operations, no direct causal link has been established between the pesticides and the industry.

In response to the concerns about pesticide impacts, the cranberry industry has reduced the amount and frequency of their pesticide use through a program called Integrated Pest Management, reducing applications of pesticides by 25% in the last three years. 55 % of Wisconsin growers employ IPM programs. The industry is also researching the use of natural control agents as a means to address pest problems on crops.

Another water quality issue associated with cranberry cultivation is the potential for increased water temperature in waters downstream from an operation. Studies have found stream temperatures several degrees warmer downstream from cranberry reservoirs than upstream of the reservoir. The increased temperatures, especially if added to other factors degrading habitat, can adversely affect trout streams. To address this issue the cranberry industry is working cooperatively with the WDNR to evaluate how the use of bottom-draw dams may help mitigate these adverse temperature impacts.

Surface waters are the primary water sources for the considerable amounts of water used for irrigation, frost protection, winter flooding and harvest. In spring when water levels are generally high, cranberry operations discharge excess water into receiving waters. In summer drought and in the fall, cranberry beds are irrigated or flooded, reducing the amount of available water to nearby waterways and lakes. The timing of diversions from and discharges to waterways may increase water level fluctuations in some waterways and lakes beyond what would naturally be expected. Diversion of water from a stream may temporarily reduce downstream flows, possibly increasing temperatures and reducing suitable habitat for existing aquatic life. Increased use and storage of water in cranberry operations located upstream of managed wildlife areas may decrease water supplies to associated waterfowl impoundments.

As the demands for a limited water supply increase for multiple users, conflicts have begun to arise. Cranberry growers have worked to improve water use efficiency through management and technological advances, especially with sprinkler systems. Some growers also recycle and reuse water.

The public and other industries have expressed concerns over reservoir management flooding adjacent properties. Since water diversion laws are not applicable to cranberry operations, dams are not regulated by the WDNR and cranberry growers work directly with neighbors to address these concerns.

Creation of reservoirs often necessitates the construction of dams on natural streams. These dams may impede fish migration to spawning areas, thus reducing reproductive success of certain species of fish.

Historically, wetlands were lost when cranberry beds, ditches, dikes and roads replaced natural sedge meadows, bogs and shrub and forested swamps. Cranberry beds currently occupy approximately 15,000 acres of former wetlands in Wisconsin. In addition, the industry has about 23,000 acres of reservoirs statewide, and much of this acreage is former wetland. The wetland loss associated with the industry is a small percentage of the total historic loss of about 5.3 million acres of the state’s wetlands from all causes, including other forms of agriculture.

Cranberry cultivation accounts for a substantial portion of permitted wetland losses in recent decades. In a study of wetland losses and impacts authorized by US Army Corps of Engineers individual wetland fill permits between the years of 1982 and 1989, 97 individual permits were issued for cranberry operations, authorizing a total of 4,986 acres of wetland impact. During that same time period the total wetland loss authorized by all other individual permits was 9,247 acres. In 1991, Wisconsin established wetland rules that allow for better protection of wetlands and have resulted in a reduction of wetland losses from cranberry expansion and from other industries. Although the cranberry industry has continued to expand into wetlands, cranberry growers are increasingly avoiding wetland impacts and much of the recent expansion has been into upland areas. Since the rules were established, approximately 284 acres of wetland loss have been authorized for cranberry activities.

In addition to direct losses of wetlands, wetlands may be indirectly lost or degraded through hydrologic changes when cranberry growers ditch, dike and divert surface waters through wetlands. For example, much of the area flooded by reservoirs was wetland before it was flooded. Sedge meadow, floodplain forest, conifer swamp and conifer bog complexes have been converted to open water marsh. Flooding of natural communities eliminates the habitat for the species inhabiting them and eliminates or displaces those species. Since permits are not always required for reservoir construction, these indirect losses and impacts have not been quantified.

Although reservoirs may flood out important wetland community types, they may also create or enhance wetland and surface water habitat. Many reservoirs provide important habitat for fish and wildlife such as largemouth and smallmouth bass, northern pike, ducks, geese, herons, sandhill cranes, ospreys and bald eagles. Many cranberry growers encourage wildlife use of property by erecting wood duck nesting boxes and eagle, goose and cormorant nest platforms, installing fish aerators, planting food plots and harvesting timber to enhance wildlife habitat. However, because the primary purpose of the reservoir is to provide water for cranberry cultivation, water level fluctuations may occur which may be harmful to aquatic and wildlife species.

Cranberry beds are intensively managed to support a single wetland plant species, which essentially eliminates the natural biodiversity of wetlands. No structural diversity and little cover is available for wildlife habitat. Wildlife species are discouraged from using cranberry beds. Studies of cranberry operations have generally shown little wildlife habitat remains in the intensively used beds, ditches, dikes and road areas. However, a substantial portion of "support lands" owned by cranberry operations is left relatively undisturbed, and continues to serve as important wildlife habitat.

Cranberry cultivation has the potential to result in loss and degradation of wetlands, lakes and streams and their associated wildlife, fish and other aquatic life. While wetland habitat loss has occurred, some cranberry reservoirs have had beneficial impacts upon wildlife habitat. Also, more cranberry growers have reduced the amount of pesticides they apply through Integrated Pest Management programs. The WDNR has been working with the industry to encourage the use of practices that protect wetlands, water quality and water quantity.