Some of the most serious threats facing the human species are gradual, making them all the harder to respond to. Catastrophic outcomes might be many years away, hardly conducive to decisive action for a species built to react to immediate dangers.
And because the future contains so much uncertainty, the end result is far from black and white. Threats - while to the best of current knowledge real and even cataclysmic - could morph in as yet unknown ways. Humans might, somehow, find a way to muddle through. Technology breakthroughs could provide at least a partial fix.
Thus it is with climate change. Because potential consequences are so dire and because almost all evidence - for now at least - points in one direction, it behooves the world to act on the menace. That is the precaution to safeguard the future.
There are parallels with the use of antibiotics. The alarms are ringing about inappropriate use and growing bacterial resistance. Extrapolate the growth of ''superbugs'' and the increasing failure of antibiotics to do their job and a planet where infections run rampant looms. It is only since World War 2 that cancer and heart disease overtook infections as leading causes of death.
A worst case sees a world where operations become far more dangerous, where transplants are no longer viable, where pneumonia and tuberculosis become commonplace killers. Do people then wear masks, decline to shake hands and fly in the recirculated air of aeroplanes at their peril?
Some estimates put the numbers dying because antibiotics fail about 700,000 a year and rising steadily. If no action is taken the prediction is 10 million will die a year by 2050. Last September then United Nations Secretary-general Ban Ki-moon said antibiotic resistance posed a fundamental threat to global health and safety.
Perhaps pharmaceutical companies can make repeated breakthroughs. Perhaps the frightening predictions will be incorrect. But, based on current knowledge, the world needs to act - and that means individuals, doctors, governments and agriculture.
The Ministry of Health and Ministry for Primary Industries are writing a national action plan to help tackle the global threat of antibiotic resistance, at the same time as use by New Zealanders soars.
It is accepted widespread antibiotic use promotes resistance. Yet, doctors often prescribe them when patients have viruses and self-limiting infections such as colds and flu. Antibiotics work against bacteria and not viruses and their unnecessary use is, by degrees, accelerating resistance.
Patients, for their part, often expect to leave their GPs with a prescription, putting pressure on the doctors. We are all in this together, so patients must change their expectations and doctors their prescribing habits.
New Zealand is a relatively low user of antibiotics in agriculture, and they are not widely used to prevent stock disease as they are in the United States. They are used here through veterinarians to respond to sickness. Nevertheless, as part of the across-the-board efforts, agriculture use also must be examined.
Consumer New Zealand last year said fast-food chains needed to move away from serving meat from animals raised on antibiotics. That would be another good step in both raising the profile of efforts to slow down the growth of resistance as well as sending a strong message.
About 50% of New Zealanders receive antibiotics every year, a figure described as ''outrageous''. If each of us, and New Zealand as a whole, is to do our part use must fall.
Antibiotics have proved again and again their worth as life-savers. They and other antimicrobial therapies, it has been argued, are the pre-eminent achievement of modern medicine.
Their effectiveness must be fostered so they work when they are actually needed.
