As humanity’s demand on natural resources is increasingly exceeding Earth’s biological rate of regeneration, environmental deterioration such as greenhouse gas accumulation in the atmosphere, ocean acidification and groundwater depletion is accelerating. As a result, the capacity of ecosystems to renew biomass, herein referred to as ‘biocapacity’, is becoming the material bottleneck for the human economy.

Original Source

Urban water demand will increase by 80% by 2050, while climate change will alter the timing and distribution of water. Here we quantify the magnitude of these twin challenges to urban water security, combining a dataset of urban water sources of 482 of the world’s largest cities with estimates of future water demand, based on the Intergovernmental Panel on Climate Change (IPCC)’s Fifth Assessment scenarios, and predictions of future water availability, using the WaterGAP3 modelling framework. We project an urban surface-water deficit of 1,386–6,764 million m³.