‘City life, or how to deal with urban heat, habitat fragmentation and light pollution’ | Thomas Merckx (VUB)
Biodiversity-wise, urbanisation involves a ‘cocktail’ of stressors, such as habitat fragmentation, the urban-heat-island effect (UHI) and light pollution. Here, I first assess how this ‘cocktail’ is driving homogenisation in butterflies and moths by comparing communities along urbanization gradients. With increasing urbanization, abundance and diversity severely decline, with communities shifting towards generalist, thermophilous, and mobile species, and with some species shifting towards larger, more mobile individuals. Next, I assess the scope for urban evolution, with a focus on seasonal life-history plasticity, which mainly relies on photoperiod as a cue to predict future seasonal change. Settings where anthropogenic changes alter either the cue or the environment can create mismatches; previously adaptive plasticity can become maladaptive unless evolution corrects for the mismatch. In the case of urbanization, these mismatches can arise because the UHI raises temperatures (i.e. alters the environment) or because light pollution alters photoperiod (i.e. the cue) in urban settings. Using common-garden experiments with two species, I show that the photoperiodic reaction norm for diapause induction has evolved in the direction predicted by the UHI. I will also briefly report on an experiment showing that even dim light pollution (skyglow) heavily impacts seasonal life-cycle regulation in a widespread moth species across Europe. I conclude that despite some local adaptations, urbanization is heavily impacting Lepidoptera communities across the globe, but also that these impacts could be mitigated via multi‐scale creation and improvements of urban green infrastructure and via implementing mitigation measures for outdoor lighting.
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Thomas Merckx is a Professor of global change biology. After having obtained a Master degree in Leuven and a PhD degree in Antwerp (2005), he moved to Oxford, Lisbon, Louvain-la-Neuve and Oulu for postdoctoral research. Since December 2021 Thomas is tenure-track professor at the Department of Biology, VUB. His research so far has mainly focused on ecology, evolution and landscape-scale conservation of butterflies and moths, in contexts as varied as forest loss, agri-environmental scheme design, farmland abandonment and rewilding, and urbanization.