Habitat loss in the Great Lakes is attributed to invasive species, pollution, shoreline development, passage of ships, disappearance of native species and water withdrawals from the Great Lakes basins. A small portion of habitat loss in the Great Lakes comes from natural phenomena, including natural disasters such as floods and droughts. However, most of the changes to this fragile ecosystem comes from human activity.
In the Great Lakes, along with other ecosystems, the introduction of nonnative species poses a significant threat. Invasive species are organisms such as plants, bacteria and animals that are transported into habitats from other locations. Upon introduction, these species may out-compete native organisms for scarce resources such as food, water and shelter. Invasive species may also kill native species by direct predation or, in the case of bacteria and viruses, through disease and illness.
Pollution is another factor in the loss of biodiversity in the Great Lakes region. Pollution comes in two primary forms: point source and nonpoint source. Nonpoint source pollution occurs when water from snowmelt and rain transports pollutants into waterways and groundwater supplies. Point source pollution comes from direct sources such as factories and coal-burning fuel plants. Lastly, the frequent passage of ships and motorized vessels across the Great Lakes contributes significant amounts of toxic chemicals and pollutants to the surrounding waters and air.