By Lauren Krauss, and Megan Rippy.
This Plain Language Summary is published ahead of the article discussed; check back soon for a link to the full paper.
Urban infrastructure that is designed to manage flows of water and pollutants from paved surfaces increasingly incorporates elements that are inspired by nature, and relies on natural processes to generate services that benefit society. Plant communities play an integral role in the design and performance of this nature-based urban water infrastructure. To guide the selection of appropriate vegetation, plant lists have been developed for different climates that contain a variety of natural (native) as well as exotic species. The intent of such lists is laudable; to streamline plant selection, limit the use of invasive species that may spread and cause health, ecological, or economic harm, and improve infrastructure performance, but the lists may also have downsides, as it is not clear how selecting plants to perform specific functions will impact ecosystem health and resilience in the long-term.
This study focuses on whether current plant lists for nature-based urban infrastructure lead to novel plant communities that have fewer strategies for responding to stress (physiological damage) and disturbance (physical damage) than native plant communities. Our results suggest that current plant lists do significantly bias plant communities, and that these biases vary with climate. In hot, dry climates, plants recommended for nature-based infrastructure are more adapted to survive nutrient and water stress than native species; in wet, humid climates, plants recommended for nature-based infrastructure are more adapted to be fast growing and outcompete other plants than native species; and across all climate zones, plants recommended for nature-based infrastructure are less likely to tolerate disturbance than native species.
Formal evaluation of plant selection rules from infrastructure design manuals suggests that these biases are correlated with human concerns related to water availability, water conservation, and climate. They do not appear to reflect natural climate limits (i.e., limits independent of people’s plant preferences and infrastructure design choices), because comparable biases are not present in native plant communities. This suggests it may be possible to expand the range of plants presently considered for use in nature-based infrastructure, relaxing some of the biases we observe. This could be beneficial for the long-term performance of such systems, particularly their resilience to disturbance, which we expect is limited relative to native landscapes where disturbance-adapted species are more prevalent.