Lichens point to cleaner air quality

Posted on July 26, 2011


Saint John’s air is getting cleaner, according to the crusty, green vegetation that dots tree trunks around the city.

Stephen Clayden, the head of botany and mycology (the study of fungus) at the New Brunswick Museum, has been researching how tree lichens can tip off changes in air quality. He’s found evidence that there is less sulphur dioxide floating around Saint John. Sulphur dioxide – not to be confused with the gas that gives natural hot springs their signature rotten egg smell – is toxic. It emits a sharp, acrid smell, Clayden said, like burnt matches.

Breathe in too much of it, and a person could experience breathing problems, respiratory illness, or worsening of cardiovascular disease. Someone with asthma would be particularly sensitive.

High concentrations of sulphur dioxide also cause acid rain, which deteriorates buildings and poisons crops and lakes. It can also burn away lichens on trees.

“It’s a nasty pollutant,” Clayden said. Most of the area’s lichens appear to share the sentiment.

Lichens are picky. Different species can grow in some of the most extreme climates in the world, from Antarctica to the Sahara, but each kind is very sensitive to the environment that suits it. This makes lichens the canaries of the coal mine when it comes to the environment.

For instance, most of the lichens native to the Saint John area tend to die off when there is too much sulphur dioxide in the air.

In the mid-1970s, Saint John only had about a half a dozen species of tree lichens, Clayden said. Now there are more than 40 species just in King’s Square. More diversity usually means a healthier environment, he said.

While the general variety of lichens is going up, the population of one particular species is simultaneously declining. But this species was introduced from Europe and thrives in high-sulphur conditions.

Clayden’s study results haven’t been published yet, but from what he’s seen so far, the Saint John’s air quality in the core area is significantly improving.

“It’s a great success story,” said David Coon, executive director of the Conservation Council of New Brunswick.

A report on New Brunswick air quality, released Tuesday by the provincial Department of Environment, is similarly positive. It reported that the 2009 levels of sulphate in precipitation – a measure of acid rain – were the lowest on record since New Brunswick began acid rain monitoring in 1986.

In the same year, Saint John had the fewest instances when emissions exceeded air quality standards for sulphur dioxide.

Clayden said he thinks the shift might be because industries are trying to cut their sulphur emissions and are using cleaner fuel, in response to government capping.

Still, Statistics Canada recently reported that sulphur dioxide accounted for almost 40 per cent of substances released in the air across Canada.

Coon said while the government’s efforts to lower sulphur dioxide levels has been impressive, there is still lots of work to be done to target greenhouse gases.

Previously published July 14, 2011; Telegraph-Journal

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