Cleaner air, but not for all


Germany's air-quality gauging stations indicate that the country's air and rain have become cleaner, but the data conceal the whole story, as some small and inconspicuous organisms show.

BioMedNet, News, 23. März 2003


BMN230303 - "Air and rain between the North Sea and the Alps is much cleaner than decades ago," announced Germanys Federal Enviroment Agency (FEA), presenting its annual report of Germanys nationwide air pollution monitoring network. The FEA body responsible for the data, the Umweltbundesamt (UBA) consists of 23 stations that are situated in rural areas across the country. The concentration of a range of air pollutants, including sulphur dioxide (SO2), nitrogen oxides (NOX) and fine particulate matter (PM10), and the pH-value of rain, are measured at each station. "

The 2001 data confirm the last two decades decline," notes the report. Annual concentrations of SO2 were at their lowest in 2000 and 2001 since measurements began in the early 1970s. "The strong decline over the last two decades is mainly a result of emission reduction in Germany," continues the report, released last month.

SO2-concentrations have declined by more than 90% between the 1980s and 2001. PM10-concentrations have decreased by 50% in the same period. "SO2 peak concentrations decreased drastically at some very polluted sites in eastern Germany," the report adds. As a result, rain in Germany is less acid than in the 80s. The pH increased from 4.2-4.3 in 1982 to 4.7-5.0 in 2001.

But, says Jan-Peter Frahm at the University of Bonn, the monitoring network does not tell the whole story. Air has become cleaner in Germany, but there is a problem that the gauging stations ignore. Frahm is an expert in lychens and mosses, and he uses these inconspicuous organisms as bioindicators. Frahm and colleagues Norbert Stapper and Isabelle Franzen have conducted a study on epiphytic lichens and mosses for the Ministry of Environment of the federal state of North Rhine-Westphalia (NRW), Germany's fourth largest state, covering about 34,000 square kilometers.

Epiphytic lychens and mosses live on the bark of trees and react very sensitively to pollutants in the air and acid rain. "As a consequence, most had became rare in a lot of regions in Germany in the 70s and 80s," said Frahm. But this has changed. "The results show that the number of lychens and mosses has arisen," he said. This is mainly due to the dramatic decline of SO2. Franzen and Stapper found 130 different species on about 2000 carefully selected trees in NRW. "We even found some endangered species listed in the red databook," added Norbert Stappen, who presented the results at a conference of the British Lichen Society in Taunton, Somerset, earlier this month.

But a closer look at the species list reveals a change in species composition. In "acid rain times" the only lychens that survived were acidophytic organisms. "Today we find these species only in the Highlands and near traffic rich streets of NRW," said Frahm. Lychens and mosses that favor nitrogen now grow in most other regions; they survive so well that they supersede other species. The nitrophytic lychens reveal a problem nobody was aware until now, revealing a lack in Germanys monitor network.

The growth of these lichens is triggered by something everybody can smell on a drive through the countryside. "What the people know as 'good country air' is ammonia, NH3," Frahm explained. "This is pure food for a lot of plants," Stapper added. Ammonia is an agricultural by-product; farmers fertilize their fields by spraying liquid manure over them, but the gauging stations of Germanys air monitoring network cannot measure this nitrogenous compound. Stapper and his colleagues have discovered a striking correlation between the distribution of nitrophytic lichens and the map of livestock distribution.

The researchers found that in these regions, the critical load of nitrogen uptake capacity of forest ecosystems is exceeded by 25 kilograms of nitrogen per hectare per year. Together with NOX from long-distance-traffic that means a lot of 'food,' says Stapper. "And it means bad news for ecosystems that prefer nutrient-deficiency, like dry grasslands," he adds. Ecosystems with high species diversity like these are rare in Germany.

The nitrogenous waste produced by agricultural and traffic endangers species diversity, say the researchers. Jan-Peter Frahm adds: "The irony," says Frahm, is that "SO2 neutralizes Ammonia." Thus, conclude the researchers, a replacement mechanism for monitoring pollution is called for - one that incorporates both gauging station measurements and a system of monitoring the diversity of pollution-sensitive organisms.

BioMedNet, News, 23. März 2003

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