Dennis Cook / AP

Former Canadian Prime Minister Brian Mulroney will deliver one of the four eulogies for President George H. W. Bush at his state funeral Wednesday.

This is fitting, and not only because the two men were close friends. Mulroney and Bush were joint architects of one of the most important environmental achievements of the past three decades: the great reduction of acid rain.

In the late 1980s, lakes and waterways across the northeastern United States and Canada were doused in rain laden with sulfuric acid. Acidic water killed trees, threatened wildlife.

The New York Times reported in 1988:

Over a quarter of the lakes and ponds in the Adirondack Mountains are so acidic that the vast majority of them can no longer support fish, a three-year study by New York’s state environmental agency has found. An additional one-fifth of the lakes in the region are so acidic they are considered “endangered,” according to the study.

Addressing a joint session of Congress earlier that year, Mulroney tallied the damage to Canadian waterways:

You are aware of Canada’s grave concerns on acid rain. In Canada, acid rain has already killed nearly 15,000 lakes, another 150,000 are being damaged and a further 150,000 are threatened. Many salmon-bearing rivers in Nova Scotia no longer support the species. Prime agricultural land and important sections of our majestic forests are receiving excessive amounts of acid rain.

The culprit: sulfur-rich coal. Coal-fired electricity generators in both the United States and Canada emitted vast quantities of sulfur dioxide. The gas rose into the atmosphere, reacting with oxygen, water vapor, and other pollutants—especially nitrogen oxides—to seed the clouds over North America with sulfuric and nitrous acids. When those clouds released their rain, the water carried the acid back to the rivers and lakes on the surface of the Earth.

This explanation is generally accepted now, but it was fiercely resisted in the 1980s. The coal industry sought to argue that acid rain was not man-made. An elegantly produced documentary from the time cast doubt on environmental concerns. “The serious question, though, is: How much has nature been producing on her own over many, many years before man really began to influence the pollutant burden in the atmosphere? And that question, that division, between what man has contributed and what nature is contributing has never really been quantified satisfactorily, to say, ‘If I reduce man’s activities by 10 percent, 20 percent, is that really going to make a material change in the chemistry of precipitation?’”

There was nothing serious to worry about, argued the most aggressive industry-funded groups. If anything, the rise of acidity represented a kind of environmental progress, as one analyst at the Competitive Enterprise Institute argued in 1996:

Slash-and-burn logging at the turn of the century removed a lot of vegetation—a major source of acid in the soil and water—making the soil less acidic. During that time the lakes supported aquatic life. When logging ended, they reverted to their natural state. Some minor man-made acidification has caused fish deaths in lakes only marginally habitable to begin with.

The Reagan administration resisted any rapid response to the problem. Congress had funded a 10-year study back in 1980—why rush to costly action until the study was complete? Taking action meant tangling with Robert Byrd, the West Virginia Democrat who assumed leadership of the Senate majority after the election of 1986. West Virginia coal was especially packed with sulfur; new standards might put West Virginia miners out of work.

And there the matter stood when George H. W. Bush assumed the presidency in 1989. Bush cared intensely about the Canadian relationship. Bush’s first presidential trip outside the United States took him to Ottawa, in February 1989. On that visit, the 41st president committed to address the acid-rain problem.

Bush’s task was eased by Senate Democrats, who elbowed Byrd out of the majority-leader job that same year. The new Senate leader, George Mitchell, represented Maine, a state that suffered especially badly from acid rain.

The result was an important amendment to the Clean Air Act in 1990, and a new U.S.-Canada air-quality agreement in 1991. Over the next two decades, U.S. emissions of sulfur dioxide would tumble by 67 percent.

True to Bush’s conservative principles, the reduction was not achieved by government command-and-control, but by a market-friendly system: cap-and-trade. The government would set a steadily decreasing maximum permissible limit on total emissions. Underneath that cap, individual firms could buy and sell pollution rights. Those firms that could most easily and efficiently reduce their emissions would set the pace, incentivized by profits from selling their pollution rights to less innovative competitors.

North American lakes are still recovering from the damage done by pre-1990 acid rain. And, of course, acid rain has not been eliminated, only very substantially reduced. But still, that reduction is a success story. And it’s a success story that showed the way to other environmental possibilities, including the ultimate challenge: a reduction in greenhouse-gas emissions.

But what George H. W. Bush proved 28 years ago was that progress can be achieved—and that a market-oriented Republican can head that progress, in a way consistent with market principles. He debunked the “It’s not harmful” and “If it is harmful, it’s not man-made” excuses from self-interested groups and their hired mouthpieces.

Along the way, he demonstrated a commitment to mutually beneficial partnership with America’s neighbors and friends.

All these things were done before. They can be done again. George H. W. Bush showed us how. Let that be remembered when he is lowered into the earth he did so much to protect and restore.

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