Climate change has caused a rapid warming of Scottish lochs and reservoirs, according to new research reported by the BBC, the Independent and Scottish Government.

A report by Scotland’s Centre of Expertise for Waters (Crew) found that 97% had seen an increase in temperature between 2015 and 2019. The researchers have warned that the changes create a greater risk of harmful algal blooms developing. The Scottish government said it was “vital” that more action was taken to tackle and adapt to global warming.

The report says that most lochs and reservoirs in Scotland warmed by between 0.25C and 1C per year over the four-year period. However, the temperatures in 9% of them increased by 1C to 1.3C per year.

Researchers said this, combined with changes in rainfall patterns, could mean a greater risk of algal blooms. This could restrict their use for recreation and water supply, and as a safe habitat for wildlife. They predicted that waters in the south and east of Scotland will warm the most at first, but that the impact will have reached all parts of Scotland by 2040.

The report also warns about long-term effects such as “lake heatwaves” – short periods of extremely high water temperatures. It says these are “likely to push aquatic ecosystems beyond the limits of their resilience, posing a threat to their biodiversity and related benefits they provide to society”.

Some of the key report findings include:

  • Climate change is affecting the water quality of Scottish standing waters, specifically in relation to algal blooms, at multiple scales; mostly through increases in air temperatures and changes in rainfall patterns.
  • Climate change will increase the risk of algal blooms developing in Scottish lochs and reservoirs – especially potentially harmful cyanobacteria.
  • Increases in algal blooms are often associated with a higher risk of potentially harmful toxins from cyanobacteria being released into the water; the likelihood of this occurring will increase with warmer temperatures and lower flushing rates.
  • An integrated catchment-based approach needs to be taken for setting water quality targets and planning interventions.

The news release can be read here and also here. The main report found here.

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