What natural environment do we want?

The Industrial Revolution that took place in the UK during the 18th and 19th centuries involved the introduction of steam power mainly driven by coal. The increased coal burning, released sulphur which was carried by wind to Sweden and precipitated as acid rain. However, the acidification process was at first slow and the environmental acidification low, says Jens Fölster, active in SLU’s environmental monitoring of the acidification of Swedish waters.

‘After WWII the acidification accelerated and became substantial with the large-scale production of energy by the industry. Apart from our own emissions, Sweden received a large amount of sulphur emissions from coal and oil fired power plants in the UK and the Ruhr region in Germany,’ says Jens Fölster.

Acidification process discovered by SLU researcher
Svante Odén, at the time active as soil researcher of SLU, is known for his discovery of acid rain and the acidification process. His article “The acidification of precipitation” ("Nederbördens försurning") was published October 24, 1967 by the newspaper Dagens Nyheter.  In his article he showed that the pH value had dropped dramatically since the 1950s and argued it was a result of sulphur emissions from the European industry. While the article was taken seriously by Swedish Government, it proved to be considerably more difficult to convince remaining European governments to take action.

Forest death in the 1980s
In the late 1970s and early 1980s, trees with a thin crown and yellow needles were seen across Europe. In some regions trees died. The damages were regarded as a consequence of acid deposition.

‘These ideas gained support by models predicting imminent forest death. Researchers of SLU questioned these models. They wanted to give a more balanced picture of the situation, for instance, of the soil’s buffer capacity through weathering, and trees’ sensitivity to soil acidification,’ says Jens Fölster.

The fears of massive forest death came to nought. Dry summers and extreme temperature variation in some regions turned out to be the cause of the sudden death of trees.

Countermeasure liming
Liming of water and forest land is a much debated measure to combat the effects of acid deposition on primarily the aquatic, for example fish death. Liming started on the Swedish west coast at the end of the 1970s and became widely used during the 1980s.

‘During the 1990s a much debated expansion of the liming of lakes and watercourses in Norrland, northern Sweden, started. Again researchers of SLU contributed to a better basis of knowledge for the discussions. They showed that many lakes are naturally acidic as a result of humic substances. It’s often difficult to know if liming is a sensible measure in such waters,’ says Jens Fölster.

Ongoing recovery, but towards what?
Since the end of the 1990s much of the environmental monitoring is about following the natural environment’s recovery from the human-induced acidification.

‘In the beginning of the 1990s political upheavals in Eastern Europe led to markedly reduced industrial emissions in these countries and we observed a sharp recovery of the water quality of Swedish lakes, and to some extent the aquatic,’ says Jens Fölster.

SLU’s environmental monitoring today, concerning acidification, includes water chemistry, benthic fauna and fish, phytoplankton in lakes and algae fouling on stones in streams.

Jens Fölster points out four important questions for the future: How much does an intensified forestry contribute to increasing the environmental acidification? What effects have a warmer climate on the acidification process? What waters can we stop liming? The natural environment is recovering, but towards what?

The answer to the last question may not be as straightforward as it may seem when looked upon from a longer historical perspective. Following the Ice Age, soils and waters became naturally acidified when easily weathered materials were consumed and the humus content increased. Through extensive clearing of forest land for pasture and cultivation, man turned the acidifying trend and the pH value was raised.

‘The reference condition of a lake or a stream has been set to the estimated acidity in 1860. In those days, the Swedish landscape contained much more arable and pasture land and a smaller area of forest. The question is whether this reference condition is possible or even desirable to achieve. Sediment analyses suggest that the water in many lakes in southern Sweden was browner back then, something we perhaps wouldn’t appreciate whether it be drinking water catchments or lakes for swimming,’ says Jens Fölster.