Ecological Impacts
Wetlands are unique habitats because they provide critical habitat for wildlife, reduce flood severity, and improve water quality. These functions are facilitated through complex interactions between the numerous plant and animal species found in healthy wetland ecosystems.
Purple loosestrife threatens the integrity of wetland habitats by out-competing native vegetation. On exposed substrates, purple loosestrife seeds germinate at such a high density that they out-compete the native seedlings. Loosestrife can also invade deeper waters and form dense stands that displace other emergents and floating vegetation, eventually closing open water spaces. The herbivores and pathogens that keep loosestrife from dominating European wetlands are absent in North America. This lack of natural enemies combined with prolific seed production (over 2 million seeds/mature plant) gives purple loosestrife a substantial advantage over the native vegetation. Diverse wetland plant communities can quickly be displaced by monotypic stands of purple loosestrife. Reductions in plant diversity translate into a loss of food and shelter for the numerous insect, amphibian, mammal, and bird species that depend on healthy wetlands for their survival.