[2]Cumulative stress to the Laurentian Great Lakes is determined from 34 individual stressors [3], along with habitat and lake-specific weights derived from an extensive survey of Great Lakes researchers. A stressor [4] is defined in this project as a pressure, which exceeds its range of normal variation due to human activity, affecting species, biological communities, or ecosystems.
Great Lakes stressors [3] were divided into seven categories:
- Aquatic habitat alterations [5]: Changes to aquatic habitat from diverse causes, such as shoreline hardening and erosion control structures, port and marina development, and tributary dams
- Climate change [6]: Changes to seasonal, average, and extreme temperature, precipitation, and ice cover
- Coastal development [7]: Land-based human development near lake margins, such as residential and commercial development and industrial activities
- Fisheries management [8]: Changes to Great Lakes ecosystems resulting from fishing pressure, stocking activities, and aquaculture
- Invasive species [9]: Changes to Great Lakes ecosystems from invasive and nuisance species in abundances not previously seen
- Nonpoint source pollution [10]: Nutrients, sediments, and waterborne contaminants transported from watersheds to the Great Lakes by streams and rivers and atmospheric deposition
- Toxic chemical pollution [11]: Chemical pollutants from industrial and agricultural sources