Scientists warn of urgent need to tackle changes impacting river deltas
University of East Anglia
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Climatic and anthropogenic drivers of change in the world’s deltas. a, A three-dimensional view of the system. b, A conceptual cross-section from the sea to the mountains, featuring the surface and groundwater variability along the river.
view moreCredit: ©Deltares: artwork by Dirma Janse
New research identifies the key causes of changes affecting river deltas around the world and warns of an urgent need to tackle them through climate adaptation and policy.
Deltas are low-lying areas that form as rivers and empty their water and sediment into another body of water, such as an ocean, lake, or another river.
Some of the largest in the world, such as the Rhine, Mekong, Ganges-Brahmaputra-Meghna, and Nile, are threatened by climate change, facing rising sea levels and increasing frequency of extreme events.
With approximately 500 million people today living within or adjacent to delta systems, this is a major issue.
To address this, a team of international scientists has developed a new framework that identifies the 10 main drivers of change in deltas globally. These are: climate change, sea level rise, deforestation, intense agriculture, urbanisation, impoundments, land subsidence, ground water extraction, flood defences, and resources mining.
Most local, human-induced causes show measurable impacts within years and the framework provides a clear basis for prioritising timely, locally grounded action with a deeper understanding of the systems that shape these complex and dynamic environments.
Publishing their findings today in Nature Climate Change, the team includes scientists from the Universities of East Anglia (UEA), Southampton and Oxford in the UK, and Deltares, TU Delft, Wageningen University and Utrecht University in The Netherlands.
“Deltas are the most complex coastal systems in the world and recognising these multiple drivers and how they operate in each delta is fundamental to finding solutions,” said co-author Prof Robert Nicholls, from the Tyndall Centre for Climate Change Research at UEA and the University of Southampton.
Effective adaptation requires more than isolated measures, that often overlook an important step in deeper assessments of the system as a whole.
The diagnostic framework links these drivers of change with their direct and indirect impacts across scales in time and space (divided in centuries, decades or temporal scales). It is intended to support policymakers, technocrats, engineers, and stakeholders in developing locally grounded adaptation strategies that are both realistic and resilient.
It aims to help identify and understand the interconnectivities within the biophysical system, from source to sink, and how these link with local/regional/transboundary socio-economic structures.
While climate change threatens the world’s deltas, anthropogenic drivers - largely reflected in sediment starvation and resource extraction, profound land-use change and hydrological regime shifts - can outpace climate change in the short to medium term.
Nearly all local anthropogenic drivers result in measurable impacts within years or decades, emphasising the significance and relevance of local and regional causes for effective and timely climate adaptation and policy development.
“If we want to give deltas a real chance at long-term climate resilience, we need collective comprehension of the human footprint and the underlying drivers of change,” said Dr Sepehr Eslami, lead author and coastal expert at Deltares.
“By promoting system-level thinking, this framework encourages more critical and collaborative approaches to adaptation. It helps identify the solutions with the highest chance of being implemented successfully, especially when embedded in a longer-term vision.”
The diagnostic framework can also foster constructive dialogue among stakeholders and ensure that adaptation efforts are both science-based and socially relevant.
“Decision making in delta systems is extremely difficult due to all the complex interactions between different processes,” added Dr Amelie Paszkowski from the University of Oxford.
“But this framework helps to disentangle these dynamics and diagnose the challenges in a delta, which is a fundamental first step in defining adaptation solutions that tackle the root causes of the impacts felt.”
The research was inspired by the work of the Rise and Fall Project, a collaboration between Deltares and the Utrecht University, and also involved researchers from the University of Cologne and University of Padova.
Over a period of nearly three years, the team combined decades of knowledge on vulnerabilities in deltas and adaptation efforts to develop a framework that can facilitate diagnosing the key processes and interactions shaping a delta system. The goal: to offer a holistic foundation for planning effective, context-sensitive adaptation strategies.
‘A systems perspective for climate adaptation in deltas’ is published in Nature Climate Change on July 7.
Journal
Nature Climate Change
Article Title
A systems perspective for climate adaptation in deltas
Article Publication Date
7-Jul-2025
New Reichman University study introduces innovative index for assessing the condition of streams in Israel: A tool to support decision-making about stream rehabilitation and restoration
Reichman University
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Dr. Shiri Zemah-Shamir' Reichman University’s School of Sustainability
view moreCredit: Gabriel Baharlia
A new study conducted at Reichman University’s School of Sustainability presents an innovative tool to help decision-makers better understand the condition of streams and thereby advance their restoration and rehabilitation. The tool, called SESBI — the Stream Ecosystem Services and Biodiversity Index — is designed to measure what is called “stream health,” meaning the degree to which a stream functions ecologically and contributes to public welfare.
When determining whether or not a stream is “healthy,” it is not only the water itself that is taken into account, but also the diversity of animals and plants it supports, the quality of the water, the physical structure of the stream and its surroundings, and the stream’s capacity to handle floods, purify water, and provide recreational opportunities. What sets the SESBI apart from other indices is that it evaluates the stream’s ecological condition based on the services it provides to people — rather than the other way around. If people can swim in the stream, walk along its banks, and enjoy the scenery, and if the stream is able to purify itself and mitigate floods, these are strong indications that it is functioning well.
The idea behind the SESBI is to make the subject of stream restoration accessible even to those without ecological expertise. The index is based on available or easily obtainable data, and presents a relatively clear and simple assessment — using a scale of 1 to 10 — enabling decision-makers to quickly understand the stream’s condition, identify specific problem areas, and prioritize investments of effort and budget. Instead of relying on complex chemical or biological tests, the SESBI uses six indicators directly tied to the benefits streams provide: biodiversity, water purification, the quality of the vegetation around the stream, enjoyment derived from the landscape, recreational activities, and the stream’s ability to cope with floods.
In addition, the index was developed specifically for streams in Mediterranean and arid regions, such as Israel, where there are extreme seasonal changes between winter and summer, and streams may flow only during certain times of the year. Existing indices are generally designed for large rivers in Europe or North America, and are not suited to Israel’s completely different hydrological regime.
The study, led by doctoral student Geula Michael-Bitton under the supervision of Dr. Shiri Zemah-Shamir and Prof. Boris Portnov from the University of Haifa, tested the index on three streams in Israel: the Na’aman, Yarkon and Kishon. The health scores obtained were 6.38 for the Na’aman, 6.06 for the Yarkon, and 4.47 for the Kishon — with higher scores indicating healthier streams and a greater variety of services provided. The goal is to enable smarter planning and management of water and natural resources in Israel. The index also lays the groundwork for future development, where it will be possible to translate the contribution of each stream into economic terms — for example, illustrating the benefits that the public and authorities gain from investing in stream restoration. Looking ahead, the researchers hope to expand the index to include additional social, economic, and spatial dimensions.
According to Dr. Shiri Zemah-Shamir, “The new index allows us to view streams not only as natural infrastructure, but as sources of real benefits for humans — such as shade, cooling, opportunities for hiking and picnicking, and reduced flood damage. In an era of climate change and water scarcity, this is an essential tool to support wise decision-making that preserves both nature and our quality of life.”
Journal
Journal of Environmental Management
Method of Research
Experimental study
Article Title
Managing stream restoration: Framing and assessing the stream ecosystem services and biodiversity index (SESBI)
