Explanation of Indicator
Many ecosystems, particularly those in tropical and subtropical regions, are vulnerable to disturbance and invasion by introduced non-indigenous plant species. Such invasions have social, economic, and environmental impacts and focus attention on the thr
eats these plants place on unique and irreplaceable ecosystems. Because of its warm climate and abundance of aquatic habitats, Florida is particularly susceptible to infestations of exotic aquatic and wetland plants. Florida is also home to a large exot
ic aquarium plant and ornamental foliage industry that imports millions of non-native species each year. Many of these imported plants have escaped. Control efforts on exotic aquatic plants have cost Florida taxpayers more than $104 million to control s
ince 1980.
Hydrilla, an exotic aquatic plant species, was brought into the United States from Sri Lanka by aquarium plant horticulturists in the early 1950s. Hydrilla provided the aquarium industry with a plant that could grow under the low light conditions typical ly found in aquariums. Because of its ability to grow in low light conditions, its rapid growth rate, and a high capacity for survival, hydrilla has become a serious aquatic weed in Florida. It has the ability to quickly fill waterways, limiting recreat ional and commercial boating, wildlife use, and flood control. It is difficult to control because of its rapid rate of growth and resistance to management techniques. This growth rate allows hydrilla to out-compete native submerged aquatic plant communi ties, thereby reducing plant diversity. Dense infestations of hydrilla can reduce dissolved oxygen levels, increasing the potential for fish kills. Hydrilla accelerates eutrophication by causing increased sedimentation. Hydrilla is present in fresh wat ers of Asia, Europe, Africa, Australia, and the United States.
Waterhyacinth, a native to South America, was imported into and is a major weed species in 53 countries. This floating pest was introduced into Florida in the 1880s, and by the early 1960s it covered more than 125,000 acres of public lakes and navigable rivers. Since then the U.S. Army Corps of Engineers has reduced waterhyacinth to approximately 2,000 acres. The growth rate of waterhyacinth is among the highest of any plant. In Florida, waterhyacinth populations can double in as little as twelve days by sending off short runner stems which develop new plants. It also reproduces by seed. Waterhyacinth blocks waterways and limits boat traffic, recreation, flood control and wildlife use. By shading and crowding out native aquatic plants, this exotic species reduces biological diversity in aquatic ecosystems.
Data Characteristics
SOURCE
This information can be obtained from Don Schmitz, Wetland and Upland Alien Plant Coordinator for the Bureau of Aquatic Plant Management, Florida Department of Environmental Protection, Innovation Park, Collins Building, 2051 East Dirac Drive, Tallahassee
, Florida 32310, or at (904) 488-5631.
ACQUISITION
The data can be obtained in hard copy format at no cost.
COLLECTION
These estimates are collected on an annual basis, statewide.
Data Limitations
The biggest limitation to these data is that information is collected for the entire state and not by county. The figures presented here are for exotic aquatic plants throughout the state rather than just in coastal counties.
Data Analysis
Management efforts have been able to reduce the acreage of infested waters. In 1982, the estimated acreage infested with waterhyacinth was about 6,252 acres. The following year experienced an increase of 201 percent when this plant infested an estimated
18,804 acres. Since 1983, however, there has been a general downward trend; from 1983 to 1991, there was a decrease of 88 percent, with only 2,199 acres of waters infested with waterhyacinth by 1991.
Infestation by hydrilla, on the other hand, has increased substantially. In 1982, 13,146 acres were infested by this exotic aquatic plant. The following year experienced an increase of 204 percent when 39,907 acres of Florida’s waters were infested. Si nce 1983, there has been a general upward trend with decreases in 1986 and 1989. In 1991, over 40 percent of Florida’s public lakes and rivers were infested with hydrilla, which covered an estimated 66,618 acres, making it the most abundant fresh water p lant in Florida public waters. There was an overall increase of 407 percent from 1982 to 1991.
Year Water-hyacinth Hydrilla 1982 6,252 13,146 1983 18,804 39,907 1984 8,253 41,587 1985 4,473 48,778 1986 6,919 35,755 1987 5,832 36,200 1988 2,965 52,657 1989 2,175 41,612 1990 1,087 57,055 1991 2,199 66,618
Recommendations
The Florida Department of Environmental Protection’s Bureau of Aquatic Plant Management should collect acreage totals annually for each county in Florida.