Given their wide adoption in places like Melbourne, Australia, biofilters have a potential to provide significant ecosystem services and ecological values (together referred to as co-benefits) by retaining and treating stormwater runoff, providing esthetic and amenity value, and increasing urban biodiversity. With the exception of stormwater runoff treatment and retention, these co-benefits are not well documented in stormwater biofilters but their value is increasingly recognized. Provision of these co-benefits may be strongly related to plant functional diversity (i.e., the diversity of functional traits among the ecosystem) as is commonly the case in natural and other ecologically engineered ecosystems. A functionally diverse plant community incorporates a variety of plant types (e.g., graminoids, forbs, shrubs, trees), growth types (e.g., clustering, spreading, rhizomatous, etc.), and varying degrees of morphological characteristics (e.g., leaf area, root area, root length, root diameter, etc.). Some of these traits are good indicators of stormwater treatment, but traits associated with other co-benefits and combinations of these traits have not been investigated. Here, we review the literature and describe how incorporating functional traits into plant selection processes may improve biofilter function.
