Exotic species are constant threats and already are causing major disruptions to the balance of the ecosystem of land and water within the park, Michigan, Lake Michigan and the Great Lakes. What a mess! Niagara Falls was a wonderful natural barrier to foreign elements preventing their entry into the upper Great Lakes. The Welland Ship Canal was constructed for ship passage around the falls. The sea lamprey came in too and devastated the native lake trout. Rainbow smelt came to Lake Michigan as an accidental release in Crystal Lake near the park and are competing with the native lake herring and whitefish. Then came the alewife, also from the Atlantic and with lack of adequate predators, soon increased to more than 50% of the fish biomass of Lake Michigan. There followed large die-offs of alewife that covered Lake Michigan beaches in the 1960s and which still occur at varying levels today.
Perhaps nothing is as catastrophic as the exotics now gaining access to the Great Lakes in the water ballast of freight ships loading in European harbors and dumping in the Great Lakes. Some troubling new arrivals are zebra mussels whose waste adds nutrients in such quantity as to stimulate alga growth to polluting levels. Spiney water fleas also came to our shores in the ballast tanks of foreign freighters and impact the zooplankton on which native fish depend. Just at the door to Lake Michigan is the Asian big head carp and it will take concentrated efforts and cooperation to keep this fish from the lake and further harming the ecosystem balance.
The situation on shore is as bad. Mute swans, intentionally introduced from Europe, displace native waterfowl. Gypsy moths have been a threat to the forests for many years. Dutch elm disease has destroyed almost every American elm. The chestnut blight has killed all but a few American chestnuts. Now at the edge of the park we have oak wilt and beech bark disease.
Spotted knapweed is filling in our meadows, replacing native grasses and forbs. Baby’s breath is invading the dunes and crowding out Pitcher’s thistle and other beach vegetation. Purple loosestrife is threatening our wetlands.
