Moving beyond habitat analogs: Optimizing green roofs for a balance of ecosystem services

Abstract

Green roofs are increasingly popular as a result of their ability to provide local ecosystem services in the urban landscape. The number and intensity of the services provided is a function of the abiotic and biotic design elements chosen for a given green roof design. We manipulated experimental semi-intensive green roof plots in order to uncover which combinations of design choices created the system most capable of providing ecosystem services with the lowest number of trade-offs. We monitored performance of planted vegetation, weeds, soil carbon, and stormwater runoff in a complete factorial experiment involving three different green roof system types (conventional green roof, blue-green roof, and quasi-traditional green roof), two plant community types (restoration and horticulture), and two arbuscular mycorrhizal fungal treatments (inoculated or non-inoculated). We hypothesized that more natural designs (i.e., less engineered systems) had the potential to provide a greater amount of ecosystem services with fewer trade-offs. However, our results showed that natural design elements did not consistently perform better than engineered design choices, which does not support the idea that habitat templates should guide green roof design. We found system type to be most impactful on ecosystem services. In particular, the blue-green roof provided the most services with the lowest number of trade-offs and may represent the ideal intermediate worthy of further investigation.