When good elements go bad

SCIENCE MATTERS by David Suzuki with Faisal Moola

If you’ve been following news about the upcoming Beijing Olympic Games, you may have seen photos of thousands of workers trying to clean huge swaths of algae from the waters and beaches in co-host city Qingdao. The algae have proliferated over a third of the waters where sailing events will be held.

This is not an unusual occurrence, but it is a symptom of an underlying problem with potential repercussions far more serious than hampering Olympic events or adding to the negative publicity surrounding China’s games. The blooms – along with a host of other problems – are caused by excessive amounts of nitrogen from sources such as road and industrial run-off, untreated sewage and, most of all, fossil-fuel combustion and agricultural fertilizers.

Because it is a major component of proteins and the atmosphere, nitrogen is a vital element in the biosphere. In the soil, nitrogen stimulates growth in plants. Normally, bacteria in soil can take atmospheric nitrogen and combine it with hydrogen to create a molecule that plants can use. We can “fix” nitrogen from the air into fertilizer in a process that takes a lot of heat from fossil fuels.

Applied on farmers’ fields, this artificial fertilizer induces plant growth, but scientists believe that this has resulted in nitrogen entering the Earth’s soils at more than twice its natural rate. This ripples out from the land to affect freshwater and marine ecosystems. Besides giving Chinese Olympic organizers headaches, algal outbreaks have also contaminated drinking water supplies used by millions of people.

Excess nitrogen can also disrupt or change plant growth patterns (including contributing to the spread of invasive species), poison freshwater environments, deprive ocean ecosystems of the oxygen needed to support aquatic life and even contribute to global warming.

In one particularly troubling example of the impact of all this nitrogen, scientists predict that a massive “dead zone” in the Gulf of Mexico will grow to more than 26,000 square kilometres this summer, which is more than 50 percent greater than the yearly average since 1990. That’s an area about half the size of Nova Scotia! Dead zones are caused by nitrogen and phosphorous washing into the ocean and stimulating growth of excessive amounts of algae and other plants, which then starve the area of oxygen.

Ironically, the increase is fuelled in part by the rush to find alternatives to fossil fuels that contribute to global warming. Farmers along the Mississippi River have been planting more corn and using more fertilizer to meet the demand for corn-based biofuels. Corn’s shallow roots don’t hold and absorb all of the fertilizers so much of it washes into streams that flow into the Mississippi, which drains into the Gulf of Mexico.

In a process known as eutrophication, the nitrates and phosphorous from the fertilizers, along with carbon from the air, stimulate growth of algae and other nuisance plants in the water. When the plants grow, die and decay, they block the sun and use up oxygen, thus decreasing the supply of dissolved oxygen in the water. This process occurs in lakes and oceans. The decayed plants also fall to the bottom and create layers of slime on the lake or ocean floor. Scientists say these dead zones are growing in size and number, with as many as 200 now believed to have formed in the Earth’s oceans.

Nitrogen also contributes to global warming, through fossil-fuel emissions and other human activities such as agriculture, as well as by eutrophication. Nitrogen itself is harmless and makes up 80 percent of our atmosphere, but nitrous oxide, a by-product of nitrogen from fossil fuels and agricultural practices, is 300 times more potent as a greenhouse gas than carbon dioxide, although carbon dioxide is far more prevalent in the atmosphere.

Because we know where much of the excess nitrogen in the environment comes from, we know how to reduce the levels. First, we must cut back on fossil fuels. But we can also reduce our use of chemical fertilizers in agriculture, on golf courses and even in our own back yards. We may not be able to fix the problem in time for the 2008 Olympics, but we need to get on it now or we’ll have far bigger problems to contend with than where to hold Olympic sailing events.

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