Controlling Invasive Species

January 31, 2012, Department, by Richard J. Dolesh

Cuban Tree Frog photoThe control of invasive species is becoming an increasingly important management consideration—and a challenge—for many park and recreation agencies.  Depending on the type of species (plant, animal, or insect), the presence of invasive species in parks can impact recreation opportunities for the public, destroy native wildflowers and wildlife, result in significant economic damage, and generally provide a huge headache for land managers and the public. 

While some invasive species are capturing national headlines, such as the more than 100,000 Burmese pythons now estimated to be thriving in South Florida, other species are often far under the radar of the media and the public.  Whether they are in the public eye or not, invasive species are estimated to be causing nearly $140 billion in damage annually to the U.S. economy and their competition with native species is affecting the survival of more than 40 percent of all federally listed threatened and endangered species.

Is the control of invasive species an important conservation priority for public park and recreation agencies?  Some managers say yes, definitely, that it is absolutely critical to take measures to prevent and control the damage from invasive species.  Others, however, say no; it’s just too much for park and recreation agencies to take on. After all, controlling well-established invasive species is mostly a lost cause anyway, not to mention that funds for control of invasives often must come from existing operating budgets.  And in support of those who say that many of our native ecosystems have been altered beyond repair, some scientific evidence is emerging that the removal of certain invasive fruiting plant species could have a negative effect on native birds.  Clearly, there are opposing points of view on the amount of time, effort, and funds that should be expended on the control of invasive species in parks. As the largest landowners and managers of open space in most jurisdictions, park and recreation agencies are the most visible of all the public sector land managers when it comes to dealing with the impacts of invasive species, even if primary responsibility for control measures might lie with state or local departments of agriculture, natural resources, or environmental resources. 

Just because a species is non-native, it is not necessarily classified as “invasive.”  To be considered invasive, such non-native species must also be proven to cause environmental or economic damage or otherwise be harmful to humans.  Certain species of non-native plants and animals can be attractive and even beneficial in certain regions, such as small amounts of purple loosestrife in freshwater wetlands or multi-flora rose in certain wildlife habitats. But when they occur in other bio-geographical regions, they can expand explosively, becoming habitat-destroying invaders that wipe out native species and diminish public recreation value.

Park and recreation agencies today must deal with a host of invasive terrestrial and aquatic species including buckthorn, English ivy, garlic mustard, Japanese honeysuckle, multi-flora rose, mile-a-minute weed, common reed (Phragmites), Eurasian water milfoil, hydrilla, zebra mussels, emerald ash-borers, gypsy moths, house sparrows, starlings, Asian carp, snakeheads, and many more.   Virtually every park manager or natural resources professional in the U.S. can point to one or more invasive species that is damaging local ecosystems or negatively affecting the public’s enjoyment of parks and public lands.

The National Invasive Species Management Plan, prepared by a council of experts from 13 federal agencies, calls for the national response to invasive species to be: “Prepare, Prevent, and Protect.”   At the local, regional, and state level, many park systems have been working on controlling invasive species for years, but some have only recently started to engage in prevention, management, and restoration activities. 

Techniques for controlling invasives range all the way from simple human-powered pulling, digging, and chopping to multiple-pronged strategies involving mechanical, chemical, and biological controls, sometimes employed simultaneously.  Many agencies have instituted Integrated Pest Management (IPM) programs to reduce the use of herbicides and insecticides as well as reducing costs of control. Controlling large-scale invasive plant infestations may also involve controlled burns, conducted with state forestry agencies and local fire departments. 

Most park agencies that are working to control invasive species use volunteers in some fashion, and in fact, the utilization of volunteers is an essential component of public education strategies.  Dave Moilanen, director of Huron-Clinton Metroparks in Michigan, says, “We use a combination of paid staff and volunteers to do invasive species control in the Huron-Clinton Metroparks. Full-time and part-time staff have developed master plans for most of the Metroparks with regard to habitat management. We’ve prioritized areas for stewardship activities, identifying habitats that are high floristic quality and then have developed management plans for each of these. We then use primarily part-time staff, but also some of our full-time interpretive staff, to organize, promote, and conduct volunteer stewardship work days. We have had pretty good success at obtaining volunteers for these work days.”  In addition, many agencies have made invasive species control a key component of youth stewardship activities.

Some agencies with large-scale invasive plant outbreaks also use outside contractors—firms specializing in ecological restoration or landscape contractors with knowledge and experience in controlling invasives.  Herbicides such as Round-Up or glyphosphate may be permitted to be used in parks or in ponds and wetlands.  Contracts are written on a performance basis, specifying the percentage of eradication within a given area.  In certain cases, prescribed burning is the preferred alternative, with its added advantages of being chemical free and restorative to native plant regimes.  Where prescribed burning is employed, park and recreation departments have developed productive new partnerships with fire departments, universities, and state agencies that enhance long-term control strategies.

Zhanna Yerkamov, natural areas manager for the Chicago Park District, says, “The reason that we control invasive species is that we are striving for natural areas that are more resilient and healthy.  We know that natural areas that are more diverse are more resilient, more aesthetically pleasing, and attract a greater diversity of wildlife, such as butterflies and migratory birds.”  Yerkamov also notes, “We do not perform invasive species management on its own.  Successful ecological restoration requires a multi-prong approach, coupled with native plant seeding and planting.  In other words, as we control invasive species, we plant and seed native plants that can take advantage of the opportunity to grow and thrive.  It is not just about controlling invasives, but it is also about promoting native diversity.”

Whether a large-scale program of invasive species control is initiated by park systems depends on the scale of impacts, the amount of land or recreational opportunity affected, and the mission of the agency.  Carrie Morrow, assistant resource manager for Columbus and Franklin County Metroparks in Ohio, is emphatic about the need for control.  “We see invasive species as a true threat to our natural resources, and we are committed to controlling them.

“As to the question of why bother, yes, it can be frustrating, and sometimes the job will be overwhelming.  We focus on high quality areas and where we can make a difference. We don’t waste time on areas that we know are long lost,” Morrow continues. “But you will be paying for inaction in the long run.  You can invest a small amount now or pay a very large amount in the future.”

Moilanen agrees, “While the efforts to remove invasive plants is daunting and the task seems overwhelming, we feel it is important and worthwhile not only for improving the health of the natural environments within the Metroparks, but also for the development of community support for the parks and development of a stewardship ethic in general. It’s exciting to see families come out with children to help on these work days. It’s a great way to develop the next generation of stewards.”

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Richard J. Dolesh is NRPA Vice President for Conservation and Parks.