Cumulative effects on wetland landscapes: Links to wetland restoration in the United States and southern Canada

Abstract

The cumulative effects of human actions on wetland ecosystems motivate current efforts at wetland restoration. They also have created in part the context within which restorations are undertaken. Using modern hydrogeological understanding of wetland-landscape linkages, I argue that restorations should begin with a cumulative impact analysis for the entire region in which the restoration is proposed. The analysis, however, should not focus merely on number of hectares of wetlands lost or degraded. It should be based on the concept of templates for wetland development. These templates are the diversity of settings created in specific landscapes by the complex interactions of hydrogeologic factors and climate. They control key hydrologic variables and hydrologically influenced chemical variables that cause specific wetland types to form and to be maintained through time. They also determine in large part the biogeochemical cycling characteristics specific to different types of wetlands. They thus account for both the biological and functional diversity of wetlands. A cumulative impact assessment for restoration purposes should identify the kinds, numbers, relative abundances, and spatial distribution of wetland templates in a region--both past and present. These past and present profiles of the wetland landscape can be used to make decisions regarding the type and location of restorations. Matching type and location to the appropriate hydrogeologic setting will maximize the probability of success for individual projects. Regional wetland diversity can be restored if individual restoration decisions about wetland type and location are made in light of the diversity of templates in past and present regional profiles.

Groundwater-induced redox-gradients control soil properties and phosphorus availability across four headwater wetlands, New York, USA

“…Fens that have not been impacted by humans often host a diversity of plant species, many of which are locally or globally rare (Amon et al 2002;Johnson and Leopold 1994). Our previous work relating nutrient limitation to wetland plant diversity (Bedford 1999;Drexler and Bedford 2002;Drexler et al 1999) suggested that groundwater might influence plant diversity, in particular, through effects on soil phosphorus (P) availability.…”

Where is the avoidance in the implementation of wetland law and policy?

“…Matthews and Endress (2008) suggested that the use of benchmarks could help agencies with permit approvals, selection of mitigation site locations, calculation of compensation ratios, development of performance criteria, and implementation of postconstruction monitoring protocols. Bedford (1999) argued that wetland restoration will be more successful if individual wetland restoration decisions are made in light of past and present regional profiles, and Olsen and Christie (2000) highlighted the importance of locally and socially relevant indicators to build local ownership of coastal (wetland) management, especially for direct users/abutters of wetlands. Watershed planning can also provide rich opportunities for more place-based and prescriptive restoration goals (Stanturf et al 2001;Olsen and Christie 2000), thereby addressing some of the competing goals (individual to structural) that limit overall restoration effectiveness.…”

Wetlands as natural assets

“…Thus, as a wetland landscape varies in scale, due perhaps to conversion, draining or other human-induced disturbances, the impact on the provision of and synergies between wetland services can be substantial. Such a landscape approach is being used increasingly for assessing the cumulative effects of wetland loss and degradation, characterizing wetland boundaries and identifying restoration or mitigation opportunities (NRC 1995, Bedford 1996, 1999, Gwin et al 1999, Mitsch and Gosselink 2000, Simenstad et al 2006. It follows that the various goods and services provided by a wetland will also be tied to, and thus defined by, its landscape extent; i.e.…”

“…Increasingly, a hydrologybased landscape approach is being used to assess the cumulative effects of wetland loss and degradation, characterizing wetland boundaries and identifying restoration or mitigation opportunities (Bedford 1996, 1999, Gwin et al 1999, Mitsch and Gosselink 2000, NRC 1995, Simenstad et al 2006. As emphasized in this paper, such an approach is consistent with the view of wetlands as natural assets that generate multiple ecosystem services.…”