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Across Belle Isle State Park, a tall grass is quickly invading. Phragmites australis, or the common reed, is a perennial grass found all around the world. The grass grows an impressive 6-13 feet tall with upright stems and long, flat, smooth leaves. Its preferred habitat is wetlands, ditches, swales, streams and pond banks.

Phragmites on Belle Isle and in the Great Lakes region is a concern because it is an invasive species. According to the National Invasive Species Management Plan, an invasive species is not native to the original ecosystem and its introduction causes or is likely to cause harm to the economy, environment or human health. In Michigan, a non-native species is one that was not present in Michigan prior to European settlement. Only about 5 percent of introduced species become invasive, however the effects can be devastating to an ecosystem.

Phragmites establishes quickly when introduced to an area, especially if the area has been disturbed recently by development or construction. It spreads mainly by an aggressive system of horizontal and vertical rhizomes (roots). Dense strands of the common reed take up most of the nitrogen and phosphorus from the soil, making these nutrients unavailable for other wetland plants. The resulting decrease of native wetland species means that wetlands and coastal marshes may not be able to serve as habitat for aquatic wildlife and migratory birds.

When phragmites die and decay, the plant debris covers the ground and significantly reduces the ground temperature. The cooler temperature can prevent amphibians, fish and insects from completing their life cycles. It is uncertain how this invasive strain was introduced to North America and the continental United States; it may have been introduced by the shipping industry when ship ballast was emptied.

On Belle Isle, several methods are currently being used to control and prevent phragmites. The management techniques include a combination of chemicals, controlled burning and disking (breaking up the soil). These methods have proven to be effective, but it is important to recognize that it is impossible to completely eliminate phragmites.