Up to 5.5 billion people worldwide could be exposed to polluted water by 2100, a modelling study has found.
Researchers mapped surface water quality under three different visions of future climate and socio-economic development.
In every case, sub-Saharan Africa was shown to be among the worst-affected areas.
The predictions, published in Nature Water on 17 July1, offer “a temporal and spatial analysis of what has been, until now, anecdotal evidence regarding water quality in sub-Saharan Africa”, says Tafadzwa Mabhaudhi, who studies climate change and food security at the University of KwaZulu-Natal in Durban, South Africa.
Without adequate investment in water infrastructure or treatment, “we are definitely sitting on a time bomb”, adds Joshua Edokpayi, a researcher in water-quality management at the University of Venda in Thohoyandou, South Africa.
According to United Nations estimates, two billion people worldwide already struggle to access safe drinking water. In the past few decades, East Asia and the Pacific region have had the most surface water pollution, owing to booms in industrialization and population that have led to increasing demand for water in areas that do not have the infrastructure to support it.
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To investigate the future effects of similar trends, researchers modelled water quality in 20-year chunks from 2005 to 2100, using existing models of global water quality.
They considered three future climate scenarios used by the Intergovernmental Panel on Climate Change, known as SSP1-RCP2.6, SSP5-RCP8.5 and SSP3-RCP7.0. SSP stands for ‘shared socio-economic pathways’, and considers various societal factors, whereas RCP describes ‘representative concentration pathways’, referring to trajectories of greenhouse-gas concentrations. For example, SSP5-RCP8.5 denotes a ‘business-as-usual’ trajectory defined by continued strong technological progress with limited concern for global warming. SSP1-RCP2.6 defines an optimistic ‘green’ future where sustainability becomes globally prioritized.
The water crisis is worsening. Researchers must tackle it together
The team found that under all of the scenarios, water quality got worse in countries in South America and sub-Saharan Africa with emerging economies. By contrast, in many wealthy countries, levels of organic pollutants and substances that can cause disease tended to decrease, owing to improved water treatment.
The SSP3-RCP7.0 projection, which describes an upcoming ‘bumpy road’ of increasing national rivalries coupled with slow economic and environmental progress, stood out as the worst-case scenario (see ‘Pollution predictions’). In this model, organic water pollution in sub-Saharan Africa more than quadruples by 2100, leaving 1.5 billion people exposed to unsafe water. Deterioration in water quality in South Asia, the Middle East and North Africa also leads to increased pollution exposure in those regions.
This came as a surprise, says study co-author Edward Jones, a geoscientist at Utrecht University in the Netherlands. He adds that although a ‘business-as-usual’ scenario would involve unsustainable dependence on fossil fuels, it could also lead to improved water infrastructure and thus water quality, as has already been seen in some countries. The SSP3-RCP7.0 scenario is characterized by poor economic growth, severe climate change and population expansion, which leads to much worse water-quality management.
Both Edokpayi and Mabhaudhi say that the research highlights the need for better implementation of regional water-quality policies. Under the UN’s Sustainable Development Goals, everyone worldwide should have access to safe drinking water by 2030. However, Mabhaudhi says there is a disconnect between global policies and the reality on a smaller scale, and that the world needs joined-up approaches that “place people and planet outcomes at the core”.
Pollution defies national boundaries, says Edokpayi, and cross-boundary collaborations will be crucial to keep the worst predictions from coming true.