Thursday, 04 November 2021
Rivers in South America, southern Africa and Australia are most at risk of extreme ecological changes from global warming according to a world-first study by a specialist team of geographers and hydrologists.
The researchers from the University of Nottingham, UCL and the UK Centre for Ecology and Hydrology have uniquely combined a range of global climate models and hydrological models with an environmental flow approach. The results, published in Earth’s Future, show significant variation in the risk of change to the ecology of the 321 river basins that cover around 50% of the Earth’s land surface.
Aquatic ecosystems underpin numerous ecosystem services that are vital to humans, such as food production, water supply and water purification. The team’s findings could help target hotspots for ecosystem conservation, through better understanding of the ecological risks from climate change-induced modifications to river flow.
The ecologies of the world's rivers are strongly controlled by the amount, variability and timing of water flowing within them. Changes in river flows impact on river depth and velocity, water chemistry and habitats, with implications for aquatic life and the ecosystem services provided by rivers to humans.
Using results from nine global hydrological models forced by five climate models, the researchers compared simulated river flows under a range of global warming scenarios with historical flows. They were able to project which basins were more likely to experience significant ecosystem change due to altered river flow.
Rivers projected to be at most risk include the Amazon and Parana in South America, the Limpopo and Orange rivers in southern Africa and Australia’s Darling River.
Across the globe, the larger the temperature increase, the greater the risk of change, particularly for low flows at the highest level of warming.
Professor Simon Gosling, Department of Geography, University of Nottingham
Professor Simon Gosling from the University of Nottingham’s School of Geography, led the climate change scenario analysis. He said: “Our research is very timely considering the COP discussions taking place in Glasgow this week. We are currently on course for 2.7°C warming compared to pre-industrial times. The Paris Agreement has a goal of 1.5°C, so the world is currently way off target. Our modelling and analysis show the risks to the ecological functioning of rivers is much larger if the 1.5°C goal is missed and we head towards 3°C. Our study’s results highlight the importance of having ambitious reductions in global greenhouse gas emissions if we are to avoid ecological degradation of some of the world’s largest rivers.”
Professor Julian Thompson, Department of Geography, UCL
Professor Julian Thompson from UCL’s Department of Geography said: “Climate change is expected to lead to an intensification of the hydrological cycle. Yet the climate change signal and its consequences vary throughout the world as revealed by our analysis. In some parts of the world there is large uncertainty.”
“If a river’s regime changes, the associated ecosystem service will change. Natural aquatic ecosystems have processes that can improve water quality – reduced river flow impacts their ability to dilute pollutants. Higher flows might be more associated with changes in sediment loads, which could put water purification under stress. The life cycles of aquatic animals, in particular many fish species, are synchronised with seasonal variations in river flow so that changes in discharge could increase pressure on fisheries, many of which are already stressed.”
The team have begun to expand their global analysis to include the impacts of human activities such as dams and water diversions. This will enable an attribution of future risks of ecological change between human interventions and climate change. The research also highlights the need for mitigating action such as changes to infrastructure – for example, the repurposing of dams to recreate more natural river regimes such as using artificial flood releases to mimic natural flows and maintain downstream environments that rely on rivers for their survival.
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For more information, please contact Professor Simon Gosling, School of Geography, University of Nottingham via email simon.gosling@nottingham.ac.uk or Emma Rayner, Media Relations Manager on 07738 291242 or emma.rayner@nottingham.ac.uk
Notes to editors:
About the University of Nottingham
Ranked 32 in Europe and 16th in the UK by the QS World University Rankings: Europe 2024, the University of Nottingham is a founding member of the Russell Group of research-intensive universities. Studying at the University of Nottingham is a life-changing experience, and we pride ourselves on unlocking the potential of our students. We have a pioneering spirit, expressed in the vision of our founder Sir Jesse Boot, which has seen us lead the way in establishing campuses in China and Malaysia - part of a globally connected network of education, research and industrial engagement.
Nottingham was crowned Sports University of the Year by The Times and Sunday Times Good University Guide 2024 – the third time it has been given the honour since 2018 – and by the Daily Mail University Guide 2024.
The university is among the best universities in the UK for the strength of our research, positioned seventh for research power in the UK according to REF 2021. The birthplace of discoveries such as MRI and ibuprofen, our innovations transform lives and tackle global problems such as sustainable food supplies, ending modern slavery, developing greener transport, and reducing reliance on fossil fuels.
The university is a major employer and industry partner - locally and globally - and our graduates are the second most targeted by the UK's top employers, according to The Graduate Market in 2022 report by High Fliers Research.
We lead the Universities for Nottingham initiative, in partnership with Nottingham Trent University, a pioneering collaboration between the city’s two world-class institutions to improve levels of prosperity, opportunity, sustainability, health and wellbeing for residents in the city and region we are proud to call home.
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