Finally, something not caused by global warming | Science Matters | David Suzuki Foundation

By David Suzuki with Faisal Moola

Global warming is becoming the Paris Hilton of environmental stories. Every time you pick up a paper or turn on the television, if there's a story remotely related to the environment, global warming will somehow be implicated.

This shouldn't be surprising. As much as we humans try to separate ourselves from the natural world, we can't get away from it. Earth's air, water and soils are all connected. So, if you change the composition of the atmosphere — in this case by increasing carbon dioxide levels by 30 per cent in the last 200 years — you're likely to see changes across the board. And that ultimately affects us too. Really, it's about time global warming was covered thoroughly in the media.

But not every environmental issue can be attributed to global warming. In spite of all the doom and gloom, there's some positive news out there too. You just have to look for it.

Case in point — dissolved organic carbon. Essentially, that's just a fancy name for any sort of plant or animal matter that's been broken down into such fine bits that it can be dissolved in water. In recent years, some researchers have become concerned about widespread increases in dissolved organic carbon flowing off surface waters in parts of Europe and North America.

In southern Sweden, Norway and Finland, as well as in the UK, the northeastern U.S., and parts of Ontario and Quebec, dissolved organic carbon levels in rivers and streams have increased considerably and consistently over the past couple of decades. This has led some researchers to conclude that there must be something amiss. Indeed, some evidence suggests that this increase in dissolved organic matter in the water is a result of rising temperatures or increased carbon dioxide levels in the air, which in turn has increased the decomposition of peat bogs.

Peat bogs hold vast amounts of carbon, some 20-30 per cent of the entire planet's stock of soil-based carbon. Evidence that global-warming trends are causing peat bogs to break down and release carbon into the rivers that drain them would be bad news. We really need that carbon to stay put.

However, according to a recent article published in the journal Nature, all that extra dissolved organic carbon may have an entirely different cause. And it's not global warming. Researchers looked at data from 522 remote lakes and streams in northern Europe and North America that had shown changes in dissolved organic carbon levels. After examining several different potential mechanisms that could account for the increases, they concluded that the cause was most likely reduced pollution.

That's right. Strange as it may seem, less pollution — specifically sulfur pollution — deposited from the atmosphere appears to be the reason for the increasing dissolved organic carbon. Commonly known as "acid rain," this type of pollution, largely from coal-fired power plants and heavy industry, peaked in the late 1970s. After that, the international community joined together and signed protocols designed to reduce it.

These agreements worked, and levels of acid rain have been decreasing since the 1990s. As this acidification has decreased, soils have started releasing dissolved organic carbon at pre-industrial levels, a process which researchers describe as "integral to recovery from acidification." Rather than being an alarming trend, this is a case of nature bouncing back. Of course, what this increase in dissolved carbon will mean for the carbon cycle is still unknown.

While we should in no way downplay the environmental challenges we face today, we should also make sure that we recognize good news. In this case, clean air laws helped reduce pollution and acid rain, creating a situation that looked like more bad news at first, but turned out to be a small flame of hope. It's a reminder that our actions do make a difference and we can still fix things when we try.

November 30, 2007
http://www.davidsuzuki.org/blogs/science-matters/2007/11/finally-something-not-caused-by-global-warming/