Creation of Habitat and Enhancement of Biodiversity

In addition to remediation services, wetlands can provide habitat and thus may increase biodiversity. Because bio diversity in wetlands is typically greater than on dryland, where wetlands have been constructed or have formed naturally on mine wastes, the biodiversity in these areas is also greater than on dryland remediation sites. Another reason to prefer the wetland option over the dryland option is that, while semideserts with low biodiversity have been expanding worldwide, wetland habitats have been diminishing. The creation of wetlands for remedia tion ofmining therefore contributes toward compensation for loss of wetland habitat.

The number of wetland plant species used so far for remediation purposes has been very low, perhaps due in part to the incorrect assumption that many species will not grow on wastes high in metals. In most instances only Phragmites australis and Typha species have been used. Creation of Phragmites/Typha dominated wetlands only, particularly in areas where they did not naturally occur before, does not enhance biodiversity significantly. While it is likely that many more species can be used for reme diation of mines sites, only native species should be used. As the example of the spread of purple loosestrife (Lythrum salicaria) in North America shows, invasive species can greatly reduce biodiversity and associated ecosystem services.

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