Activity: Decision Making and Issue Analysis

The Salvinia Problem Across Southern Louisiana

The educator reads the following excerpt from a Times Picayune article dated September 24, 1991, Section A, p.1, column 2) regarding the Salvinia problem across Southern Louisiana: illustration of Salvinia

Salvinia minima sparkles in the morning dew as it drifts quietly on the bayou waters of Jean Lafitte National Park.

The fine hairs of its tiny leaves hold dew in beads, catching the sun's rainbow like so many jewels, and for a short while it seemed like one of nature's fortunate accidents.

But the beauty has proved deceptive. The diminutive fern threatens to grow into a bayou-choking, oxygen-killing presence if not brought into check.

The plant resembles native duck weed, which, as its name implies, ducks eat. But Salvinia, like many exotic plants that somehow escaped into the Louisiana environment, doesn't seem to be food for much of anything.

It does provide a fine habitat for mosquito larvae, and it is a troublesome and costly obstacle to boaters, said Glen Montz, chief of the Corps of Engineers aquatic growth control unit in New Orleans.

The plants, which form a carpet on the surface of the water, have invaded every waterway in the park and the shallow freshwater swamps. It has massed in layers 3 to 4 inches thick in some places, making canoeing somewhat like paddling through malted milk.

Salvinia may be from either Africa or South America, although nobody knows how it got here. It has lived in Florida for several years and recently spread rapidly across South Louisiana.

"It causes navigation problems for small boats..." said Richard Bassette, state Department of Wildlife and Fisheries aquatic plants section coordinator.

It has the potential for causing more serious problems, too, he said. It can imitate water hyacinth in blocking sunlight from the water depths. That reduces or stops growth of minute plants that are the basis of the aquatic food chain.

It also can reduce the amount of oxygen getting into the water, which can kill fish, Montz said. Even though no fish kills have been reported as a result of Salvinia, wading birds such as egrets may not be able to find food because of the fern.

It sounds potentially disastrous, joined with the knowledge that Salvinia has gone from covering one acre of water surface in 1980 to nearly 6,000 acres now, Montz said...

...Efforts to control it include herbicides and mechanical harvesters. The Corps of Engineers and the U.S. Department of Agriculture also are studying possible natural controls, such as insects, Montz said...

The educator guides the students through the decision-making process, allowing them to: (a) brainstorm and research solutions, and b) make decisions.
Scenario/Issue Analysis
Situation Salvinia are clogging navigable waterways all across southern Louisiana, especially in the LaBranche and Bayou Sauvage wetlands in the Lake Pontchartrain Basin.
Problem Uncontrolled reproduction of exotic species and lack of any natural controls allow Salvinia to expand unchecked.
Values Conflict To remove unwanted Salvinia without using high concentrations of chemical pesticides which may or may not further damage fragile wetlands.
Possible Solutions


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