PORTLAND PRESS HERALD • September 18, 2025
“Every invasive species we track comes with its own set of problems, and the list is only getting longer,” said Chad Hammer, invasive plant biologist with Maine’s Natural Areas Program. “Maine has all the ingredients invasives need: wetlands, forests, disturbed soil, and a changing climate. Once something gets introduced, the conditions are right for it to spread.” Climate change, in other words, amplifies the pressures brought with nonnative species by further destabilizing ecosystems, tipping the balance in favor of invasives. Japanese knotweed crowds riverbanks with bamboo-like walls that choke out nearly all native plants. Glossy buckthorn ahas infiltrated wetlands and forests with the help of birds that carry its seeds far from yards. Purple loosestrife has transformed wetlands across the state into monocultures: areas where the invasive establishes itself exclusive to other plants. It isn’t just plants crowding out their neighbors. Insects and diseases like the emerald ash borer and hemlock woolly adelgid contribute to the elimination of tree species as forests change composition over time.