Research finds recovery from acid rain much slower than expected

Acid rain emerged as a concern in the 1960s with observations of dying lakes and forest damage in northern Europe, the United States, and Canada. It was one of the first environmental issues to demonstrate a large-scale regional scope. The chief pollutants — oxides of sulfur (SOx) and nitrogen (NOx) from combustion of fossil fuels — can be carried hundreds of kilometers by winds before being washed out of the atmosphere in rain, fog, and snow. Acid rain kills plant life, destroys agriculture and forests, pollutes rivers and streams, and erodes stonework.

Over the last 20 years, serious action has been taken across Europe to clean up acid pollutants from power generation and industry, which was widely expected to bring recovery. However, new research led by Cardiff University's School of Biosciences shows that the expected improvements in rivers are far short of expectations.

The dissappointing findings are important for the developing world, and in particularly for Asia, where acid rain still is a major problem. There, energy consumption has surged and reliance on coal and oil remains very high. By 2020, Asian SO2 emissions could reach 110 million metric tons if no action is taken beyond current levels of control (graph, click to enlarge). As a result, damage to natural ecosystems and crops is likely to increase dramatically, at an enormous social and economic cost.

An example from India illustrates the dramatic effects of acid rain on agricultural productivity: researchers there found that wheat growing near a coal-fired power plant where SO2 deposition was almost five times greater than the critical load (the amount the soil can safely absorb without harm) suffered a 49 percent reduction in yield compared with wheat growing 22 kilometers away.

Damage could be largely avoided if modern pollution control technologies, such as flue-scrubbers, are widely adopted and if low-sulfur fuels are used. In this context, bioenergy and biofuels offer a major alternative to coal and oil. Co-firing low-sulfur biomass in power plants combined with a transition to 100% biomass power plants and biofuels in transportation can drastically reduce both SOx and NOx emissions.

From the Cardiff University scientists we learn that these efforts are urgent, because ecosystem recovery from acid rain takes much longer than expected. Recent studies in Galloway, the Scottish Highlands and Wales reveal that many streams are still highly acidified, decades after the first pollution control measures came into effect. Biological recovery has been particularly poor.

Key findings from the projects, carried out by combined teams from Cardiff University, the Centre for Ecology & Hydrology and National Museum Wales, include:
energy :: sustainability :: biomass :: bioenergy :: biofuels :: coal :: oil :: sulfur :: acid rain ::

• Acidity in Welsh headwaters is declining, but only slowly
• More than two thirds of all streams sampled were acid enough during high flow to cause biological damage, with metals at toxic concentrations
• Sulphur pollution from man-made sources is still an important cause of acid episodes, particularly in Wales
• Sensitive insects survive conditions in the most acid streams for only a few days
• Headwater acidification is still a significant problem for important salmon fisheries, and Special Areas of Conservation such as the Welsh River Wye.

Professor Steve Ormerod of the School of Biosciences, a leading researcher into the biological effects of acid rain for more than 20 years, said: "Organisms and ecosystems are the best indicators of recovery from pollution, so these results will alarm anyone interested in the well-being of our rivers. We need to understand the factors responsible for such delayed recovery, particularly since climate change is likely to make the acidification problem even worse."

Dr Chris Evans, an acid-rain specialist from the Centre for Ecology & Hydrology in Bangor, added "pollution reductions are slowly improving in upland waters, but there is a long way to go. 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 future."

The research contrasts with other recent studies which showed some encouraging early signs and will come as disappointing news to those who thought the acid rain problem was solved.

Graph credit: World Resources Institute.

References:
Eurekalert: Recovery from acid rain 'much slower than expected' - September 28, 2007.

World Resources Institute: Acid Rain: Downpour in Asia.