By way of emphasizing the fact that having observed one good or positive event does not mean all is well, the Greek philosopher Aristotle once said, “One swallow does not make a summer.”

Applied more broadly, this adage means an isolated event should not be taken as indication of a trend.

And especially in recent years, those who are concerned about environmental issues such as climate change have gotten plenty of practice reminding people of this principle.

Every time a major wintry weather event occurs and is seized upon by skeptics of climate science, proponents of the theory are quick to remind the public that weather and climate are different things and that a single weather event whose occurrence seems unlikely in a warming world does not constitute a reversal of the long-term worldwide warming trend.

It is strange, then, that environmental activists who oppose offshore drilling have been so quick to exploit the recent BP oil spill in the Gulf of Mexico by making the case that this spill proves the danger of extracting oil from beneath the sea floor.

As Aristotle might have told them, just as an April blizzard does not prove the existence of a climate change conspiracy, so a single oil spill does not make drilling an environmental hazard.

In fact, although the spill might yet become the largest in U.S. history, it will nevertheless contribute to a surprisingly small chunk of all oil leakage into oceans.

Oil spills coming from offshore wells or tanker ships might be the best-known sources of oil leakage, but they are actually among the least significant.

A NASA study found that most oil that ends up in oceans comes in the form of runoff from cities and industrial areas, which accounts for some 363 million gallons per year.

The second most significant source was ship maintenance (137 million gallons per year), and natural seepage from oil deposits beneath the ocean floor accounted for about 62 million gallons per year.

For all the hype they generate, spills from offshore drilling accounted for just 15 million gallons per year, according to the study.

This means that, given the dramatically higher rate of leakage resulting from natural factors, those who want to rid the seven seas of the scourge of oil should be clamoring for drilling in order to deplete the deposits that leak so much every year. This, of course, seems unlikely to happen.

But what a welcome change it would be if environmental activists reevaluated their consistently anti-oil rhetoric for once and considered whether they would even be doing the world’s oceans a service by eradicating offshore drilling.