The little sign at the head of the long driveway is dark green with a narrow red stripe down each side. A small symbolic tree-of-life decorates the top centre. In strong white letters below the tree are the words, "Go green or die".

Perhaps the words were hastily written; perhaps they weren't. Regardless, they appear with the precision of a meticulously crafted haiku or a fastidiously edited manuscript. They invite our serious consideration.

Although Canada is in the middle of a federal election, the little sign is not overtly political. "Go" is used instead of "Vote". And "green" is not capitalized so it doesn't refer to the Green Party. The "or" identifies a choice, a crossroads, a juncture of some unspecified significance. But the "die" is unequivocal, a three-letter word that is unsettling and powerful, shocking and threatening. The little sign seems like an ultimatum. And it is.

Elections are times for ultimatums. Electors demand candidness and truth from their candidates, trying to exact promises and integrity, honesty and loyal service. In return, each political party presents its platform and warns of dire consequences if the voters don't follow their prescriptions for a safe and prosperous future. And amid the flurry of claims and pronouncements, theatrics and posturing, nuances and dramatics, the one election issue that dwarfs all others is easily forgotten.

The little sign is a reminder that the issue is "green", together with all the complex implications that the word has come to imply over the last few decades. Basically, it means that if we don't find some way of learning to live sustainably on our planet then we die. Indeed, the little sign's ultimatum is stark, blunt and unequivocal. But, does it exaggerate the seriousness of our environmental situation?

Well, every individual dies as a natural consequence of being alive. And species also die – paleobiologists tell us that 99.9999 percent of all the species that have lived during the Earth's history are now extinct. Given probabilities, we are unlikely to be an exemption. But are we hastening our own demise as a species?

Life is tenacious, and extinction isn't easy to accomplish. And centuries or even millennia are practically instantaneous in the great tides of biological history. But we could cause grievous injury to ourselves and to the ecologies that sustain us if we collectively make serious errors of strategy, especially given the environmental influence we have accrued through powerful technologies and the impact of our huge population. The human species would probably survive any ecological catastrophe we could cause but the misadventure would be horrific.

Scientists, philosophers and serious thinkers of almost every ilk are warning with near unanimity that we are not responding with appropriate urgency to the environmental dangers that are looming ever larger on the horizon of our near future. Consequently, we are rapidly losing our opportunity for a controllable and comfortable adjustment that will avoid the worst of an impending ecological and humanitarian disaster.

Jeffrey Sachs, one of the world's most celebrated economists and humanists, has a message for politicians and voters as both Canadians and Americans move toward their elections. We are entering a "new period" of history, he suggests in a Globe & Mail interview (Sept. 13/08), that is far more complex than any previous governments and their leaders have ever had to confront. "We are up against so many incredible stresses that are leading towards mass displacement", he warns with euphemistic understatement. These stresses are now almost too numerous to list but the greatest is global warming. And, in the midst of this evolving crisis, we are suffering from a profound "communication" problem that, Sachs confesses, "I think about most hours of the day. Given how divided we are in every way – culturally, linguistically, educationally, by class – how do we have a serious conversation about this?" His concern is palpable. "But we are at a critical crossroads and we are not discussing the real issues honestly or, worse, knowledgeably."

Sachs has some answers. Among others, he suggests we give special status to such groups as the Intergovernmental Panel on Climate Change, a worldwide collection of scientific experts that has been able "to convey a scientific consensus to the world in an area that is incredibly complicated..." Despite "facing deliberately misleading efforts... it is having some effect." This panel has inadvertently become a model for effective communication, credibility and motivation.

Our obligation as citizens and voters is to listen and learn from such knowledgeable and trustworthy sources, then to direct our politicians to lead us in the direction of sustainability for our ecologies and for ourselves. As usual, our politicians are hesitant because we are hesitant.

This malaise of mutual hesitation is driven by doubt, uncertainty and even denial. But a brave and searching examination of the growing number of political, economic and social challenges we now face reveals that most are directly or indirectly caused by environmental stresses – we misinterpret the symptoms as the causes, Sachs says. If we are unaware that fracturing and collapsing ecosystems are the root cause of much of the tension in the world these days, then distractions at election time will leave us without the guidance to mend the fundamental structural problem endangering us.

Jeffrey Sachs would agree that the moment is becoming more urgent and our future more precarious. He and many others would undoubtedly concur that our choice is rapidly narrowing to "Go green or die".