p>Nearly a half-century ago, a young American army officer named John Kerry returned from his tour of duty in Vietnam to testify before the Senate Committee on Foreign Relations. After detailing the atrocities, the injustice and the pointlessness of the war, he said: "We are asking Americans to think about that, because how do you ask a man to be the last man to die in Vietnam? How do you ask a man to be the last man to die for a mistake?"

It's a question that can be asked around the world — many of us have engaged in civil disobedience trying to ask it in connection with Canada's tar sands and America's coalfields. Pacific Islanders have used traditional canoes to blockade Australia's coalfields, which are the largest in the world.

But in Europe, where large-scale exploitation of fossil fuels got their start centuries ago, it's the brave tree-sitters of Hambach who are asking this question in its most poignant form.

Their adversary, RWE, a utility company, is the continent's largest carbon emitter. North Rhine-Westphalia, where the forest sits, spews more greenhouse gases than any other part of Germany. It is, for Germans, the heart of the fossil fuel beast.

Seeing the future

And 2018 is very near the end of this particular war — or, at least, we're at the point where its hideousness is clearly visible.

The carbon stuck in the ground beneath that swath of forest will just add to the toll of carnage, making it that much harder for those who come after us.

Taking down this patch of trees won't just mean that no lilies of the valley will carpet the forest floor ever again; it will increase the strain on every forest on earth, because that carbon means more heat, which means more pests, more droughts, more giant fires.

It's always difficult to shut down a way of doing business, even when we've begun to realize the stakes. You get used to doing something and you don't want to stop, because this is the way you know.

RWE has machinery in the neighborhood — they've already mined beneath most of this 12,000-year-old forest. To them it must seem as if all they want is one more small chunk — how much harm could it do?

Monuments to our folly

John Kerry — who, it should be noted, would one day rise to become US secretary of state and help to negotiate the Paris climate accords — ended his Vietnam speech with these words by excoriating the leaders who couldn't bring themselves to put an end to the war: "These men have left all the casualties and retreated behind a pious shield of public rectitude. They've left the real stuff of their reputations bleaching behind them in the sun."

That sun has grown hotter in the last decades, thanks to all the coal and gas and oil we've burned. It's not too much to ask that the carnage stop here and now — to understand that the small strip of Hambach Forest still standing should be left as a monument to our folly — but also to our ability to shift course and do the right thing.

In this most important war for the planet's future, it's clearly sacred ground.

Bill McKibben is Schumann Distinguished Scholar in environmental studies at Middlebury College in Vermont, co-founder of the global climate campaign 350.org, and author of the forthcoming book Falter: Has the Human Game Begun to Play Itself Out?