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Removal of Invasive Plants in Cleveland Metroparks

Garlic Mustard, an invasive plant

They are far from home, but they're everywhere you look. They're pushing our biodiversity around like neighborhood bullies. And we're fighting back harder than ever against invasive plants in Cleveland Metroparks.

What Are Invasive Plants?

What is this green menace? Invasive plants are not the same as lawn or garden weeds, although they share many traits. The National Invasive Species Council defines an invasive plant as "[a] species which is non-native (or alien) to the ecosystem under consideration ... whose introduction causes or is likely to cause economic or environmental harm or harm to human health. Human actions are the primary means of invasive species introductions." Most plants introduced to North America from other parts of the world cause no trouble in our natural areas and parks, but a handful of non-native plants are first expanding into, then dominating our native ecosystems.

These are fast, tough plants, known for high growth rates, abundant fruit, vigorous vegetative spread, and efficient seed transport. Once established on a new continent, far away from their natural enemies, invasive plants outcompete the native flora. Some, like Asian bush honeysuckles, exploit the longer growing seasons in their new latitudes, getting and staying green much longer than their native neighbors. Others hybridize with native related species, producing strongly invasive offspring like the hybrid cattails.

Why Are Invasive Plants a Problem?

Invasive plants establish and spread quickly to from dense monocultures in native habitats. They can disrupt essential relationships between animals, plants and the environment, such as food supplies, breeding habitat, water availability and the physical structure and components of ecosystems. Invasive plants can arrive in waves, with multiple species moving in together, creating cascading negative effects on local biological diversity. In the worst cases, invasive plants are game-changers, actually altering or degrading natural functions of ecosystems, such as water quality, fire frequency or soil chemistry.

Invasive Plants in Cleveland Metroparks

Invasive Plant Infestations
Reservation Total Acreage Percent Infested
Bedford 2206 9%
Big Creek 781 26%
Bradley Woods 795 1%
Brecksville 3494 6%
Brookside 145 7%
Euclid Creek 345 7%
Garfield Park 213 5%
Hinckley 2682 1%
Huntington 103 5%
Mill Stream Run 3189 3%
North Chagrin 2140 1%
Ohio & Erie 312 64%
Rocky River 2572 12%
South Chagrin 1521 2%
Washington 59 8%
West Creek 278 4%
     

Cleveland Metroparks have their share of the worst invaders of northeastern Ohio, including woody species (shrubs and trees), wetland invaders, and upland grasses and forbs. The scope of the problem is impressive: Conservative estimates across the park system put the acreage of invasive plant populations at 1,000 to 1,400 acres. This translates to an average cover of 11% per reservation, with a range from 1% invaded area (North ChagrinBradley WoodsHinckley) to 64% (Ohio & Erie Canal). Each reservation has a distinctive combination of site conditions, invasive populations, and management history. Likewise, each has a distinctive set of management priorities and actions.

Park staff have been removing invasive plants for decades. Now the divisions of natural resources and park operations have joined forces for a multi-year, park-wide plan targeting the worst of the weeds. The action plan includes mapping and prioritization of sites and species, seasonal control teams for in-house control, supplemented by contract labor on some huge populations, and the development of volunteer early detection teams to survey, assess and map invasives at all the reservations.

Our strategy relies on common sense and realistic expectations. We want to keep small problems small, nip new problems in the bud, reduce medium and large problems to small ones, and focus on sites with the most serious problems first. This includes adopting good housekeeping practices to prevent or minimize the unintentional spread of invasives by human activities. This is a long-term project to manage the park's natural infrastructure with the same attention that is given to the park's physical infrastructure. Both the natural and the built systems require preventative maintenance and regular repair to ensure their integrity.

Each summer you might see evidence of the control teams at work, including all-terrain vehicles, brush removal crews, and selective spray teams. Watch for changes at some of your favorite parks, including "missing" shrub layers and patches of dead vegetation. Watch for our bright pink, "Invasive Plant Management Area" stake flags. Better yet, keep watching as the invasions abate and the natives recover.

—Jennifer Hillmer and John Mack