A study from the University of Cardiff in Wales reveals that the after-effects of acid rain in the 1970s and 1980s can still be felt today. Many streams in Scotland’s Galloway, the Scottish
Highlands and Wales are still highly acidified, and biological recovery of the ecosystem has been particularly poor.

The project, carried out by the School of Biosciences, at Cardiff University the Centre for Ecology and Hydrology and the National Museum Wales, found that although there was a decrease in
acidity in Welsh headwaters, it was slower than expected. Two out of three streams sampled still displayed acidity to the point of causing biological damage during high flow.

As a result, sensitive stream insects tend to die after only a few days in the most acidic streams. Furthermore, conservation areas such as the Welsh River Wye, as well as salmon fisheries, are

‘Pollution reductions are slowly improving in upland waters, but there is a long way to go,’ says Professor Steve Ormerod of the School of Biosciences at Cardiff University. ‘The large
biological effects of acid episodes shown by this work mean that it is vital to continue monitoring these ecosystems if we are to protect them in the future.’

Despite action taken across Europe over the past 20 years, Wales’ natural habitat might need at least 50 years to recover, Professor Ormerod warns. The findings are inconsistent with other
recent studies which showed some encouraging early signs, he adds.

Acid rain occurs when sulphur dioxide and nitrogen oxides are emitted into the atmosphere, for instance by burning fossil fuels in energy generation and industry. They are absorbed by water
droplets in clouds. When the droplets, which display an unusually low potential of hydrogen (pH), fall to earth, this increases acidity of the soil and affects the chemical balance of lakes and

In the 1970s and 1980s, acid rain was one of the world’s worst pollution problems, affecting large areas of upland Britain, as well as the rest of Europe and North America. In Wales, more than
12,000 kilometres of streams and rivers have been acidified. The acidification has harmed fish, insects and river birds.

For further information, please visit: