Post-industrial sites are often considered to have no conservation value but frequently host considerable biodiversity, including rare and unique species. We hypothesize that spontaneous communities on brownfield sites in many cases constitute novel ecosystems. We explore this idea in the Calumet region on Chicago’s southeast side, a landscape heavily impacted by the steel industry. A ubiquitous legacy of this industry, especially in former wetland areas, is slag, steel making waste that forms a hard gravel or pavement-like substrate. We set out to assess spontaneous communities on slag in several ways. For a regional view, we compiled iNaturalist observations on slag throughout the Calumet. In 2020 we established monitoring plots along a 600m transect in Big Marsh Park entirely on slag. We analyzed soil from these plots once and surveyed plant species present in two consecutive summers. Our goals were (1) to assess existing biodiversity and other ecosystem services in a self-assembled plant community and (2) to formulate specific restoration goals and strategies that encompass this existing novel ecosystem.
At slag sites across the region, iNaturalist contributors observed 854 species of animals, plants, and fungi, including several species considered uncommon or conservative in the region. Slag soils are rocky with low organic matter, higher pH (avg 9.3), and higher heavy metals than other natural areas in the region. We found a positive correlation between plant cover and soil organic matter along the Big Marsh transect. We observed a characteristic suite of species found at Big Marsh and other slag sites that does not resemble plant communities found in other ecosystems in the region.
We conclude that historical baselines are inappropriate in shaping specific restoration plans for these sites due to extensive habitat modification by the steel industry. Further, existing biodiversity suggests that current communities are novel ecosystems worthy of conservation. Restoration strategies should seek to build on this existing value. In pursuit of such strategies, future work will compare plant community composition at slag-dominated sites to habitat analogs like dolomite or gravel hill prairies.