Available translations: English


Scientists have outlined the urgent actions needed to protect Scotland’s lochs from the impacts of climate change, estimating that harmful algal blooms cost the national economy at least £16.5 million a year.

The UK Centre for Ecology & Hydrology (UKCEH) and The James Hutton Institute have outlined a series of recommendations in a new report for CREW – Scotland’s Centre of Expertise for Waters. It follows their previous study for CREW which revealed the country’s lochs and reservoirs are already undergoing rapid and extensive warming, with water temperatures of most monitored lochs rising by between 0.25 and 1 degree Celsius per year between 2015 and 2019. That study also projected that between 2020 and 2080, loch and reservoir temperatures could further increase up to 3 degrees Celsius in total over that period.

Coupled with high concentrations of plant nutrients such as phosphorus, most of which enter water courses via agricultural runoff, this is fuelling outbreaks of algal blooms. These blooms negatively affect water quality and aquatic biodiversity, and produce toxins harmful to animals and people. 

The estimated annual cost of £16.5 million includes higher water treatment costs, financial losses for local business when water courses are shut to the public, and reductions in property values in the surrounding area.

The new report for CREW, which is based at the Hutton, warns that if there is no action to limit global warming or nutrient pollution, the concentration of phosphorus in our waters could more than double, due to changes in land use and rainfall patterns. This, together with warmer waters, will greatly increase the risk of harmful algal blooms. 

However, the researchers at UKCEH and the Hutton estimate that, under a best-case scenario where there is action to reduce greenhouse gas emissions and to follow sustainable land management practices, phosphorus pollution could fall by 20 per cent compared to now.

The report underscores that, until there is significant global action to tackle emissions and meet Paris Agreement targets on global warming, it is important that other measures are taken across Scotland to mitigate impacts.

Prevention rather than cure

The main recommendation emphasises the need to implement efficient land management policies and practices aimed at reducing the amount of phosphorus entering lochs and reservoirs. This crucial nutrient is present in fertilisers as well as animal and human waste. 

Across most of Scotland, runoff from land is the main source of phosphorus pollution and is likely to increase because of climate change Only 1 per cent of the 7,000 lochs studied receive effluent from wastewater treatment works. However, excess nutrient pollution from wastewater is known to be an issue at some lochs, so tackling this would increase ecosystems’ resilience to the impacts of climate change,

Freshwater ecologist Dr Linda May of UKCEH, lead author of the report, said: “Our climate is changing rapidly and harmful algal blooms are becoming more common. This is reducing the value of our water courses for recreation, water supply and wildlife habitat. To mitigate these effects, we need to reduce nutrient inputs to our lochs and reservoirs. 

“Our report shows that, by adopting more sustainable land use practices and lifestyles we can protect our lochs for future generations to enjoy.”
The authors of Mitigating Climate Change Impacts on the Water Quality of Scottish Standing Waters say small-scale interventions, such as installing more buffer strips on land near lochs, have much less impact in reducing phosphorus run-off.

Dr Miriam Glendell of The James Hutton Institute said: “Our modelling has shown than more efficient use of fertilisers informed by regular soil testing to match applications to crop demand could almost halve the amount of nutrients being lost from land to water.”

Regarding other possible solutions, the authors say more investigation is needed into the effectiveness, cost and environmental impact of chemical treatments and the removal of nutrient-rich sediment or water.

Better monitoring 

The Climate Change Committee has said that many climate-related risks in Scotland are largely unknown due to a lack of effective monitoring of our environmental systems, including our standing waters. The new report published by CREW reiterates this, adding that the risks of phosphorus pollution and of algal blooms should be monitored at individual sites in addition to regular soil testing on farms to encourage improved nutrient use efficiency.

The authors also call for a comprehensive assessment of the cost impacts of algal blooms, saying their calculation, is likely to be an underestimate. For example, it excludes veterinary and medical costs. The estimated cost of a single outbreak at Loch Leven, based on loss of income to the fishery, hotels, restaurants and other local businesses, is about £2 million per year.

Threat to water quality

Rachel Helliwell, CREW Director, said: “If action is not taken to mitigate the effects of climate change, it is likely that the frequency and magnitude of harmful outbreaks of algal blooms will increase, resulting in the failure of many waters to comply with international water quality standards and exceed the upper limits for safe use set by the World Health Organisation.”

Màiri McAllan, Cabinet Secretary for Wellbeing Economy, Net Zero and Energy in the Scottish Government, said: “Like the linked challenge of climate change, the loss of species and degradation of our natural environment is an emergency. That’s why the Scottish Government has committed to spending £65m on nature restoration during the course of this parliament via our Nature Restoration Fund – Scotland’s largest ever fund for nature. This includes providing support for targeted tree planting on banks to help cool our rivers which will protect species such as wild Atlantic salmon. 

“We’ve also committed £315m since 2015 through our Agri-Environment Climate Scheme (AECS) to support sustainable and regenerative farming practices, and this year’s AECS also includes support for irrigation lagoons which should assist in water resource management and help in mitigating the effects of climate change.” 

Mitigating Climate Change Impacts on the Water Quality of Scottish Standing Waters is available on the CREW website at crew.ac.uk/publication/mitigating-climate-change-phase-2

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Media enquiries

The embargoed report and images of cyanobacteria are available on request. For interviews and more information, please contact Simon Williams, Media Relations Officer at UKCEH, via simwil@ceh.ac.uk or +44 (0)7920 295384. 

Notes to editors

The project idea was developed by CREW in collaboration with NatureScot, Scottish Environment Protection Agency, Scottish Water and the Scottish Government. The report was produced by a team of researchers from the UK Centre for Ecology & Hydrology (UKCEH) and James Hutton Institute.
Aside from land management practices, the report assesses several mitigation measures for tackling algal blooms:

  • Removing nutrient-rich sediment can improve water quality but this is an expensive management option and large-scale disposal requires large areas of land, unless it can be re-cycled for use as a fertiliser.
  • Removing nutrient-rich water can improve ecosystem recovery processes and lower loch water temperatures, but a large amount of clean water is required for this to be effective.
  • Some chemical treatments can clump cyanobacteria together causing them to sink rapidly to the lake bed, but these have not been tested comprehensively on a large scale in lakes and reservoirs and there is a risk that they may harm other aquatic organisms.
  • Ultrasound targets a relatively small area, only, and can affect other planktonic organisms, such as the common water flea that can remove algal blooms
  • Active habitat management can include removing invasive plants and herbivorous fish, and replacing them with more beneficial species, or increasing seed dispersal to increase the amount of aquatic plants in waters.

Previous research led by UKCEH and published by CREW in 2022 showed that water temperature increased at 97% of monitored Scottish lochs and reservoirs between 2015 and 2019.

About harmful algal blooms

Harmful algal blooms include cyanobacteria, also known as blue-green algae, which affect aquatic biodiversity. They can produce toxins that are potentially harmful for pets and watersports enthusiasts who ingest infected water. These toxins can cause damage to the liver or nervous system and be potentially fatal for pets. 

In the UK, dog deaths caused by the pets drinking contaminated water are recorded every year. People who have swum through, or swallowed, algal scum can suffer from skin rashes, eye irritation, vomiting, diarrhoea, fever and muscle and joint pain.

You can report outbreaks of cyanobacteria in water courses via UKCEH’s Bloomin’ Algae app.

About the UK Centre for Ecology & Hydrology (UKCEH)

The UK Centre for Ecology & Hydrology is a centre for excellence in environmental science across water, land and air. 
We have a long history of investigating, monitoring and modelling environmental change, and our science makes a positive difference in the world. We seek to understand the complex interactions that affect the availability and quality of water resources now and into the future, from local to global scales.
The UK Centre for Ecology & Hydrology is a strategic delivery partner for the Natural Environment Research Council, part of UK Research and Innovation.

ceh.ac.uk / X: @UK_CEH / LinkedIn: UK Centre for Ecology & Hydrology

About CREW – Scotland’s Centre of Expertise for Waters

CREW aims to deliver research to protect and improve the water environment and engage with a wide range of information users and communities, to maximise the benefits of the research to society.

Funded by the Scottish Government, CREW is a partnership between The James Hutton Institute and Scottish higher education and research institutes. It is based at the Hutton’s campus in Aberdeen.

crew.ac.uk / X: @CREW_waters  @JamesHuttonInst / LinkedIn: CREW – Scotland's centre of expertise for waters

UKCEH report authors

Employment history

  • PhD student, Paisley College of Technology, 1976-1979
  • Royal Society funded post doctoral reseach associate, Intitute of Limnology, Austria, 1979-1980
  • Freshwater ecologist, CEH, 1980 to present

Editing, lecturing and memberships of scientific organising committees

  • 2023 - present: Principal scientific officer, UKCEH, Lancaster, UK
  • 2013 - 2023: Senior scientific officer, (UK)CEH, Lancaster, UK.
  • 2005 - 2013: Higher scientific officer, CEH, Lancaster, UK.
  • 2002 - 2005: Scientific officer, CEH, Lancaster, UK.
  • 1999 - 2002: Doctoral student jointly supervised at Lancaster University and CEH at Windermere
  • 1996 - 1999: Ecology degree student at Lancaster University, UK

2014-present: Centre for Ecology & Hydrology (Edinburgh research site)

2008-2014: Spatial Scientist, Land-use and Ecosystem Services group, Forest Research

2007-2008: GIS Operations Engineer, Farrer Consulting, Edinburgh

2006-2007: Information Assistant as part of the Go-Geo! metadata project, Edina, Edinburgh

Erica obtained a First Class Honours BSc in Ecological and Environmental Sciences with Management from the School of Geoscience, the University of Edinburgh, in 2022. Her studies included core modules such as Ecological Measurement, Field Ecology, Data Science and Geoscience Outreach, as well as Marketing, Accounting and Economics.