About 450 projects of Integrated Weed Management were identified to control these exotics. Exotic weeds are a form of biological pollution. They can replace the entire native flora of an ecosystem, cause a staggering loss of biological diversity, and severely reduce the number of already endangered plants. For example, a single melaleuca tree can replace dozens of native plant species, and collectively such trees can overtop and destroy natural wet meadows in the Florida Everglades. Similarly, leafy spurge, which has become common in some northern states, can crowd out all native grasses and forbs.
Soil erosion increases drastically when exotic weeds replace native grasses.
The harm from exotic plants is not confined to native flora but extends to native fauna. Muskrats and nesting waterfowl abandon wetlands taken over by purple loosestrife. Risks of Herbicides Herbicides chemicals that kill weeds are important in the control of weeds but pose risks to humans and the environment. Human Health and Safety. Exposure to some herbicides can cause nausea, headache, skin rashes, and other symptoms.