Defining ecosystem restoration potential using a multiple reference condition approach: Upper Mississippi River System, USA

[摘要] Large scale ecosystem restoration is an important societal issue because significant risks, costs, and benefits can accrue on large landscapes. It is important to understand baseline ecosystem conditions, existing condition, and to the extent possible estimate ecosystem response to alternative management scenarios. Incorporating ecosystem process and function into restoration planning and implementation will make ecosystem restoration projects sustainable. The Upper Mississippi River System is an excellent case study for such issues because it is an important, multiple-use ecosystem with significant ongoing investment in ecosystem, agri-system, and navigation system management.Large-scale geomorphology, hydrology, and land cover information was compared among presettlement, contemporary, and potential future reference conditions to examine ecosystem state and evaluate mechanisms responsible for ecosystem condition. The UMRS was scaled by physiographically similar characteristics into large floodplain reaches several hundred river miles in length, geomorphic reaches 50 to several hundred miles, and a mile-by-mile segmentation of the river floodplain extent. Ecologically relevant geomorphic classes were devised from existing data and evaluated by river reach to characterize presettlement geomorphology, and dams and levees were superimposed to reflect the altered hydrogeomorphology of the contemporary ecosystem. A pre- and post-impact Indicators of Hydrologic Alteration river stage analysis evaluated dam impacts, and pre-dam and post-dam aquatic habitat class distribution was compared. A floodplain inundation simulation analysis provided new information on the potential spatial distribution of frequent floods. Land cover data available for presettlement and modern reference periods were compared at several spatial scales. Multivariate analyses evaluated land cover characteristics among geomorphic reaches, as well as to assess the influence of hydrogeomorphic drivers on land cover for presettlement and contemporary reference periods.The objective of this research was to clearly delineate the divergence of environmental conditions among reference periods to evaluate which drivers need to be, and can be, altered to change ecosystem state. Hydrogeomorphic response to development indicates several restoration objectives that are appropriate system-wide and others that are best suited to specific river reaches. Similar data sources are available for much of the rest of the United States through the Public Land Survey and engineering surveys of any significant civil works projects.

[发布机构] University of Iowa