Artificial barriers and estuarine squeeze: a novel assessment of estuarine vulnerability to climate change and sea level rise

Pietkiewicz, H, Mortimer, RJG, Hirst, AG, Lewis, JP, Clarke, L ORCID: https://orcid.org/0000-0002-8174-3839 and Little, S ORCID: https://orcid.org/0000-0001-5715-7429, 2025. Artificial barriers and estuarine squeeze: a novel assessment of estuarine vulnerability to climate change and sea level rise. Estuarine, Coastal and Shelf Science, 320: 109299. ISSN 0272-7714

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Abstract

Estuarine ecosystems are threatened globally by changes in climate and catchment land use, with upper estuarine tidal freshwater and low-salinity zones being particularly vulnerable, yet the most poorly understood. These zones play a pivotal role in estuarine structure and functioning but are overlooked in assessments of vulnerability to sea-level rise and climate change. Commonly the tidal limits or landward boundaries of these zones are defined by in-stream barriers, such as weirs and sluices. These barriers restrict the natural inland migration of estuaries, intensifying the risk of saline intrusion as sea levels rise and summer river flows decline – a phenomenon known as ‘estuarine squeeze’. This study provides the first estuarine squeeze vulnerability assessment for mainland England and Wales. Using an extensive dataset of salinity and electrical conductivity measurements, we delineate for the first time, tidal freshwater, oligohaline, brackish and marine zones across 85 estuaries. Of these, 59 (69 %) are constrained by in-stream barriers, and 45 (53 %) contain tidal freshwater and oligohaline zones. Nineteen of these 45 estuaries are bound by barriers at their tidal limits, making them susceptible to estuarine squeeze. These estuaries account for 64 % of all tidal fresh and oligohaline waters in mainland England and Wales. The Medway, Exe and Ouse estuaries in the south of England are identified as being most at risk. These zones are vital gateways, supplying and exchanging energy, matter, and organisms to the lower brackish estuary and upper non-tidal freshwater river. Their loss underscores the urgent need for their assessment, monitoring and management. However, it also presents an opportunity to compensate for their loss through for habitat creation, such as tidal freshwater marshes, offering ecosystem benefits and bolstering resilience against climate and other human-induced changes.

Item Type:	Journal article
Publication Title:	Estuarine, Coastal and Shelf Science
Creators:	Pietkiewicz, H., Mortimer, R.J.G., Hirst, A.G., Lewis, J.P., Clarke, L. and Little, S.
Publisher:	Elsevier BV
Date:	15 August 2025
Volume:	320
ISSN:	0272-7714
Identifiers:	Number Type 10.1016/j.ecss.2025.109299 DOI 2429269 Other
Rights:	© 2025. This manuscript version is made available under the CC-BY-NC-ND 4.0 license (https://creativecommons.org/licenses/by-nc-nd/4.0/)
Divisions:	Schools > School of Animal, Rural and Environmental Sciences
Record created by:	Laura Borcherds
Date Added:	23 Apr 2025 10:53
Last Modified:	23 Apr 2025 10:53
URI:	https://irep.ntu.ac.uk/id/eprint/53440

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