Landscape Level Assessment
Relatively new methods of Landscape Level Assessment (or Level 1 Assessment) are currently emerging to support broader evaluation of wetland functions on a watershed or landscape scale, typically based on remotely sensed or GIS data. This level of wetland assessment is typically used to support watershed planning, zoning decisions, definition of wetland restoration/protection priorities, and similar purposes at the local or regional level. In addition, landscape level assessment can assist in setting priorities for more detailed monitoring of wetland condition and function, and will play a role in the statewide and regional evaluation of wetland status and trends from pre-settlement thru current times.
The department's wetlands program is using cutting edge geographic information technology to improve the evaluation of wetlands on a watershed scale in a cooperative effort supported by multiple agencies and organizations. Although wetland evaluation presents a complex challenge given the scope and diversity of these resources, wetlands play a critical role in maintenance of water quality and quantity, and wetland protection and restoration should be an integral component of watershed planning.
One of our current approaches uses a computer model to integrate wetland maps, updated with current aerial photography, with hydrologic data, site topography, and other ecological information to evaluate the wetland functions provided by each mapped wetland area. The resulting analysis can be used to provide a generalized map of current wetland functions within a watershed, the loss of wetland function associated with past land use changes, and potential wetland restoration areas.
Status and Trends
EGLE recently analyzed wetland inventories from three time periods, 1978 to 1981, 1997 to 1999, and 2000 to 2005, to analyze wetland trends over the last 30 years in Michigan. Based on the analysis of these inventories, Michigan currently has approximately 6,465,109 million acres of wetlands. Michigan originally contained approximately 10.7 million acres of wetland prior to European settlement, but by 1978, that number had dropped to approximately 6,506,044 million acres. Since the passage of Michigan’s wetland protection law in 1979, the rate of wetland loss has declined dramatically. The total decline of wetland since 1978 is estimated at 41,000 acres, with the rate of decline slowing between the periods 1978-1998 (loss of approximately 1,642 acres per year) and 1998-2005 (loss of approximately 1, 157 acres per year). This analysis shows that our wetland resources continue to be depleted at a rate that, while slowing, is still faster than efforts to restore or create wetlands. Furthermore, areas with historic loss of wetlands are still struggling with the consequences of that loss (e.g., water quality issues, flooding and flashy streams, and loss of wildlife). Michigan’s wetlands also continue to face increasing threats, including historic threats such as agriculture and development, as well as new threats like invasive species and climate change.