Two keystone catastrophes in the making



The next time you pass a stone archway, look for the stone at the top joining the two sides of the arch.  It’ll probably be shaped a little differently than the stones on either side. It will be the keystone — the one stone that locks all the others in place. Take it out, and the arch collapses.

In ecosystems, a similar kind of structure exists. There will be a keystone process, perhaps one that governs rainfall, or a keystone species, such as plankton in ocean waters. And if the process, or the species, is wiped out, the ecosystem will crash.

The recent news that the Amazon rain forest in Brazil is being destroyed twice as fast as had been thought, has raised fears that a keystone process might be overthrown before anyone realizes that it’s at risk.

How much clearing of land, for instance, can continue before heat reflected from the cleared land, and the loss of trees to return water vapour to the air, begin to change the climate? And how much will the climate have to change before the rain forest becomes unstable?

No one knows the answers. A new study by the Woods Hole Research Centre in Massachusetts and the Institute of Environmental Research in Belem, Brazil,  has discovered that the rate of rain forest destruction is more than double what had been estimated. Instead of 13 per cent, at least 16 per cent of the forest has been cleared.

We Canadians tend to be easily outraged over destruction of the rain forest, partly, I suppose, because it’s easy to be outraged over something half a world away, and partly because the rain forest influences climate patterns around the world.

But there are similar keystone issues right here at home, perhaps not as momentous as rain forest destruction, but serious enough to court disaster if ignored.

Pollination, which is a keystone process, is one such issue. If it fails, wild plants won’t reproduce, agricultural crops won’t mature, and everything that relies on them will falter.

As with the rain forest, our understanding of what’s happening is surprisingly sketchy. For instance, we have barely begun to survey the impact on pollinators of pesticides, deforestation, pollution, forest fragmentation, and the plowing under of hedgerows and wood lots.

« We know the impacts have been extensive, but we don’t know how serious it is because they haven’t been surveyed,’’ says Peter Kevan, professor of environmental biology at Guelph University.

Nevertheless, it has been serious enough to cause the United Nations, under its Convention on Biological Diversity, to become alarmed about consequences for agriculture. It has issued a world-wide call for countries to submit case studies, not only on impacts to pollinators, but also to soil microorganisms.

« We’re doing our best to bugger up both of them (pollinators and soil microorganisms),’’ says Kevan. « What we see is the tip of the iceberg. There are going to be major crashing events world wide, and in short order, unless we change our approach….

« In North America, the biggest problems are with pollinators,’’ he adds. « In Europe, it is with mycorrhizae (the root fungi that help plants absorb nutrients and moisture from the soil).’’

Kevan is the author of numerous scientific papers over the past 25 years on pollination. It was his work that confirmed bees that pollinated blueberries in New Brunswick were being killed by spraying for spruce bud worm during the 1970s. Because they weren’t being pollinated, an estimated 665 tonnes of commercial blueberries a year failed to mature. Farmers sued, and in 1976 the company doing the spraying paid a settlement to farmers for their losses.

More research obviously is required — and I hope governments, foundations, and the private sector are listening. Says Kevan: « We need  to find out what we have to do to put these systems back in working order. They’re not irreparable yet, but we’re getting very, very close to irreparability.’’

When he talks like this about a keystone process, it’s time to pay attention.

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