This week I attended a meeting of the UK and Ireland Lakes Network in Abergavenny. The keynote address “Remote Lakes: pristine or polluted” was given by Prof. Richard Battarbee FRS (University College London). He described Llyn Llagi and the Afon Gwy as star performers in terms of acid rain recovery in the UK. The blog republished below provides additional background to the acidification story in Wales and the evidence of recovery in Llyn Llagi.
This article was first published on The Welsh View the decommissioned blog of the Countryside Council for Wales. The text is republished here with permission from Natural Resources Wales. I am grateful to Ewan Shilland for permission to use the photographs.
I still remember the exciting feeling of walking in the doors of the young Countryside Council for Wales (CCW) in April 1992. The post of ‘Freshwater and Peatland Ecologist’ came with a remit to explore the diversity of wetland environments in Wales – bliss! However all was not well…
An insidious agent
Alarmingly, ‘Acid Rain’, caused by the burning of fossil fuels and the production of atmospheric sulphur and nitrogen acids, was affecting large areas of North America and Europe – including the mountains of Wales.
In CCW Carrie Rimes was putting the finishing touches to her landmark report on the freshwater acidification of Sites of Special Scientific Interest (SSSI) in Great Britain. She showed that on 141 SSSIs (covering > 433000ha), the freshwater habitats were probably damaged by acid rain. In fact, North Wales was the most severely affected area with over 55% of the total SSSI area potentially damaged.
Wales is particularly sensitive to the acid rain because its geology and soils had little buffering capability. In addition the impact was being made worse by local land use, especially by conifer plantations, which increased acid and toxic metal run-off.
Over half of Wales’ stream length (approx. 12,000km) was acidified to some extent with corresponding changes in the resident plant and animals. The species of spectacularly beautiful microscopic algae called diatoms were changing dramatically.
At the other end of the food chain, it was thought that our classic mountain stream birds, the Dippers, were going hungry and moving to less acid streams to find enough of their favourite invertebrate prey. Deaths of fish stocked into acid lakes were being reported, and natural salmon and trout populations were struggling to reproduce.
Welsh fishermen had good cause for concern and fishing businesses were paying a high price.
The fight back begins
I arrived in CCW knowing that the international scientific and political debate about the causes of acid rain had been brewing since the late 1970’s. It started with Scandinavia implicating polluted air blown from highly industrial areas in Europe, including Britain, as the cause for fish loss in Sweden.
Llyn Llagi in Snowdonia is one of the lakes monitored by the UK Acid Water Monitoring Network © Ewan Shilland
Indeed, at one stage the UK was being depicted in cartoons as “The dirty man of Europe”, and Norway was threatening not to send the UK its traditional gift of a Christmas tree for Trafalgar Square. Eventually an international investigative research project between the UK and Scandinavia was agreed, and in 1987 the Thatcher Government agreed to reduce sulphur emissions.
The scientific work evolved into the creation of a long-term monitoring programme called the UK Acid Water Monitoring Network (UK AWMN) to track any ecological responses to emission reductions. This network includes 2 lakes (Llyn Llagi; Llyn Cwm Mynach) and 2 streams (Afon Gwy, Afon Hafren) in Wales. The UK became a signatory to the ‘Convention on Long-Range Transboundary Air Pollution’ which required the production of ‘critical load maps’ showing the extent and relative degree of potential damage from acid rain and the potential for recovery if emissions were reduced.
In CCW at this stage my colleague Simon Bareham, Pollution Officer, was working with the other country conservation agencies to develop critical loads maps for assessing the effects of air pollution on habitats. Simon reminded me recently that map production was a very labour intensive job before GIS!
Recovery and reflection
By the start of this century, sulphur dioxide emissions had declined to 15% of the 1970’s peak, with discernible responses in water chemistry and biology. It has been a fascinating experience to witness this environmental recovery through access to the data generated by the Acid Waters Monitoring Network – Welsh fresh waters are making a comeback.
The water in our upland rivers and lakes is now less acid but browner. There has also been a decrease in the frequency of acid events and the release of toxic metal compounds. The recent increase in dissolved organic carbon (and browner water) is being interpreted as a return to pre-acidified natural conditions.
Some of the most convincing evidence of biological recovery in the UK has been found in Llyn Llagi, Snowdonia. When monitoring began acid tolerant species dominated the lake’s flora, especially quillwort (Isoetes lacustris), shoreweed (Littorella uniflora) and Water Lobelia (Lobelia dortmanna). Then in 1993, the sensitive Awlwort (Subularia aquatica) appeared, to be followed by the Water-Starwort (Callitriche hamulata) in 1999, and even more species in 2009.
Some of the most convincing evidence of biological recovery in the UK has been found in Llyn Llagi, Snowdonia © Ewan Shilland
CCW has played its part in this story through its support for the funding and work of the monitoring network. We have also facilitated experiments with the use of lime as a treatment for acidified waters but it has not proved to be the hoped for panacea. We have carried out supplementary investigations of individual upland lakes which were thought to be vulnerable to acidification.
In a recent review of CCW lake survey data for the UK National Ecosystem Assessment, we found that out of a total of 63 lakes examined, evidence of significant acidification was found in 25 lakes. In general through our support for research and monitoring in Wales, we have made a significant contribution to the UK and international picture.
New century, new pressures
The lessons learned from the acid rain story are still relevant to the environmental pressures which Welsh fresh waters will face over the next twenty years and longer, especially in the context of climate change. Wales is not immune to large scale environmental pressures and must play its part in the international responses needed to tackle these issues.
There is hope and evidence that an emission regulation response can work effectively and deliver environmental recovery. We have also learned that freshwater ecosystems can take a long time to recover or even reverse a negative trend, and we mess with them at our peril.
I will continue to follow the latest monitoring data because of its ability to inform land use policy, especially in relation to the development of forestry. It also gives CCW the capacity to comment on the state of the Welsh environment.
As sulphur has been cleaned up the role of nitrogen was revealed and its ability to act as another acidifier and polluting fertiliser is a current cause for concern. Also CCW is supporting the adaptation of the monitoring network to track evidence of climate change. As an organisation we consider it is critically important to continue to support the collection of key long term monitoring data.
In the context of the Natural Environment Framework, the story of acid rain illustrates how an environmental pressure can alter ecosystem structure and function, and the delivery of ecosystem services. It is also a powerful example of how environmental monitoring can be employed to assess ecosystem scale changes and health. Finally it shows it is possible to link chemical trends with biological change.
Some scientists are now saying that our rivers and lakes will not make a simple recovery to pre-acidified conditions because of the persistence and development of new pressures, like nitrogen and climate change. This make me question whether I’ve really witnessed an environmental recovery in Wales? It is certain that the acid rain story is not over yet and I wonder what the next twenty years will mean for the fresh waters of Wales?
After all, people are now starting to worry about the acidification of the world’s oceans…our work continues.
The Upland Waters Monitoring Network
In 2013 the UK Upland Waters Monitoring Network (UKUWMN) replaced the UK Acid Waters Monitoring Network (UK AWMN).
Funded by a consortium led by the Department for Environment, Food and Rural Affairs, the UK AWMN was established in 1988 to monitor the chemical and ecological impact of acid deposition in areas of the UK believed to be sensitive to acidification. Over twenty years on, its data-base provides an extremely valuable long-term record of water chemistry and biology which is unique for upland freshwater systems in the UK.