Long-term lichen trends in a rust belt region

Abstract

Abstract Deindustrialization and national air pollution standards greatly reduced air pollution in the USA since the mid-20th century, particularly in the ‘rust belt’ industrial cities of the Great Lakes and Northeastern regions. Still, sprawling urbanization, vehicular traffic and coal-fired power plants may maintain regional heat islands and NOx and SO2 pollution. Lichens are one of the first, and longest used, bioindicators of urban heat island effects and atmospheric pollution, but there are few long-term studies of lichen bioindications. We examined herbaria records for lichens collected between 1869 and 2016 in the Western New York (WNY) region (USA). We hypothesized a long-term trend of increasing pollution-sensitive lichens in the region as well as increased desiccation-tolerant species from urban heat island effects. We also evaluated local (urban and tree land use cover) and regional (ecological zones) influences on pollution-sensitive and desiccation-tolerant lichens. We found that the WNY lichen communities appear to be shaped by urbanization with desiccation- and pollution-tolerant species dominating areas adjacent to the urbanized/industrialized core, and direct local effects of the urban heat island and vehicle traffic within the urban core. These results suggest that despite deindustrialization and tighter air quality standards, an industrial imprint remains on the lichen communities of WNY. However, despite urban filtering toward desiccation- and pollution-tolerant lichen species, the urban landscape contributed unique lichen species to the region, increasing WNY’s overall lichen biodiversity as much as the relatively pristine Allegheny Plateau. Hence, the urbanized areas of WNY contribute unique species to the regional lichen flora.