Lichens as ecological indicators for the effects of environmental changes in urban context: ongoing research and major challenges
(1) cE3c - Center for Ecology, Evolution and Environmental Changes & CHANGE - Global Change and Sustainability Institute, Faculdade de Ciências, Universidade de Lisboa. (2) CEG – Centro de Estudos Geográficos, IGOT – Instituto de Geografia e Ordenamento de Território.
Although cities are places for human fulfilment, urbanization causes environmental problems, such as atmospheric pollution and the urban heat-island effect. These can be quantified by sensors, but measuring its effects on urban ecosystems biodiversity and provision of ecosystem services remains a challenge. To overcome this, the aim of this work is to present ongoing research, challenges, and application on the use of lichens as ecological indicators in cities. This includes both the use of lichens to measure the effect of environmental drivers and to measure the provision of ecosystem services by urban ecosystems. Overall, the selection of the more appropriate lichen-based metrics was based on the intensity of the environmental driver: taxonomic-based or trait-based metrics and/or physical-chemical analysis of lichen thallus to understand pollutants deposition and origin in ecosystems. Analysis of lichen metrics over space enhanced the interpretation and application of lichens as indicators for factors working at different spatial scales. Still multi-city studies, across continental gradients, remain challenging, as disentangling the local effects from the large trends observed in a continental scale is still ongoing. Urban ecosystems are impacted by environmental changes, but also contribute to ameliorating its effects, by providing ecosystem services. We used lichens to quantify how green and blue infrastructure characteristics affect the provision of ecosystem services, e.g. how green areas characteristics (e.g. tree-density or habitat fragmentation) influence the amount of microclimate or air quality regulation. Still, measuring ecosystem services provision under the effects of multiple drivers remains a challenge. Addressing such challenges could allow us to improve even further the use of lichens as ecological indicators, contributing to the planning and management of cities green infrastructure and to adapt cities to future environmental changes.
Keywords: urban areas; air pollution; urban heat island; ecosystem services;
