Are urban areas better environmentally managed than countries ?

Government entities are crucial in implementing effective mitigation and adaptation strategies to cope with climate change. This article introduces an innovative quantitative composite index to assess environmental performance across the city and country levels: a Deterioration of Environmental Performance Index (DEPI). This new index provides valuable and objective insights into the sustainability of territorial development strategies. This article aims to understand how local and national governments address environmental challenges by leveraging these metrics. We compute the annual index evolution for ten countries from 2001 to 2020. Our findings reveal that, compared to baseline levels, environmentally harmful outcomes generally decrease more significantly (or increase less sharply) over time. In addition, countries tend to outperform their cities in managing five critical environmental impacts: air pollution, river flooding, coastal flooding, forest fires, and heatwaves.