There’s been some discussion in the news lately about the Northern Everglades’ Arthur R Marshall Loxahatchee National Wildlife Refuge (NWR) and the Old World Climbing Fern, an invasive species. The exotic plant is causing damages to the NWR’s native plants and animals, but controlling it is proving to be an extremely costly matter. We’re going to discuss below some of the history of the plant, the environmental damage it is capable of, current control methods, and the circumstances which are leading to difficulty in managing the plant.

Copyright US Department of the Interior, USGS
Copyright US Department of the Interior, USGS

Old World Climbing Fern, known by the scientific name of Lygodium microphyllum, is a species native to Africa, Asia, and Australia. It grows in a vine, which easily climbs up other plants, including trees, to obtain sunlight for photosynthesis. The fern has a rapid growth rate in a warm tropical climate. Old World Climbing Fern was first documented in Florida in the late 1950’s at a plant nursery in Delray Beach, and started spreading extensively in the 1990’s. Arthur R Marshall Loxahatchee NWR has reported large amounts of the plant present at various areas of the refuge.

The plant is capable of growing at such rapid rates that it can form thick mats of vegetation which shade out any plants previously growing beneath the fern. The mats can be so thick that they have been documented to have entrapped animals, turtles and small rodents, which become ensnared in the vegetation and are unable to free themselves. The presence of these vegetative mats can lead to alterations in wildlife movement patterns to avoid the vegetation, which decreases the available habitat for the animals. The fern also displaces native plants by usurping natural resources including sunlight, soil nutrients, and space. The Florida Exotic Pest Plant Council has listed the plant as a Category I invasive on the 2015 List of Invasive Plant Species.

Copyright USDA Agricultural Research Service

Copyright USDA Agricultural Research Service

There are multiple methods that various agencies are currently using in an effort to control Old World Climbing Fern.

  • Herbicides, mainly glyphosate, in both ground and aerial treatment applications.
  • Heavy equipment or hand-pulling to dig up the underground shoots and remove the vegetative mats.
  • Prescribed fire to destroy the plant.

Biological control, including the selective release of various insects is being researched. The main insect showing promise so far is the Brown Lygodium Moth. Researchers are working to determine whether the moth eats any other species of plants and/or interacts poorly with other insect or animal species. Any negative interactions would make this an infeasible option.

All of these control methods have one thing in common – they cost money. Sometimes quite a lot of money. At the NWR, land managers have been spending between $200 and $1,200 per acre per year to manage the plant. The budget for invasive species control at the NWR for 2016 is $1.65 million.

Even with the expenditure of that amount of money, the fern is still spreading throughout the NWR. In fact, there has been a 600% increase in the amount of acreage affected by the fern between 1996 and 2016. The land managers state that they would need $5 million per year for at least 5 years in a row to bring the plant into full maintenance control throughout the refuge, with $3 million required annually after the 5 year period to maintain the limited growth and prevent spread of the plant.

Fighting invasive species sure isn’t cheap. However, neither is the repair of the environmental damages that they can cause. For a further discussion on the impacts of invasives, give us a call at 800-627-1806.