I had a text from my brother a week or two ago telling me to go outside and look up. And there in the night sky was a stunning pairing of the crescent moon and Venus, that brightest of planets, blazing 25 million miles (more than 40 million kilometres) away.

Even from a city drowned in street lights, it was a spectacular sight, a quiet moment of wonder in these unsettling times.

I thought of that quote from the famous late American astronomer Carl Sagan. He was writing about a photograph taken by Voyager 1 in 1990 as it headed for the outer fringes of the solar system. There, barely discernible in the vast reaches of space, was a pale blue dot, a lonely speck. It was Planet Earth.

"Look again at that dot. That's here. That's home. That's us," Sagan wrote. "On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives."

Sagan's words are a short and powerful treatise on our one chance on this one planet. With the dead from COVID-19 being buried in their thousands, it is no time to lecture on how we should live. But there will be an opportunity soon enough to act on the lessons learned from this crisis.

"The Earth is the only world known so far to harbour life," Sagan wrote. "There is nowhere else ... to which our species could migrate ... like it or not, for the moment the Earth is where we make our stand."

And right now, that stand is against a virus of our own making, a crisis that has all but stopped the human world turning on its axis. It is a frightening and scarcely credible time in which to be living.

It is thought that COVID-19 originated in a live animal market in China. Such establishments are a fetid mixing bowl for disease, supplied as they are by the illegal wildlife trade. In an interview with the Guardian, the United Nations' environment chief Inger Andersen said: "Never before have so many opportunities existed for pathogens to pass from wild and domestic animals to people."

China has now banned live animal markets. But it is critical that the ban is maintained and also extended across the world.

Opportunities from tragedy

This could be a turning point on many levels.

Right now, an unintentional but illuminating, large-scale experiment is under way on global emissions. The pandemic has shut down industrial activity and airline flights, minimised car exhaust fumes and slashed air pollution in our cities. It is this pollution which has created a scourge of respiratory illnesses over time and which has now made millions more susceptible to the worst effects of the coronavirus.



Stanford University research But suddenly the air we breathe is cleaner than it has been in decades. In China, the drop in airborne pollutants over two months is estimated to have saved the lives of 4,000 children below five and 73,000 adults above 70, according to

CO2 emissions have plunged - China's industrial output alone dropped by 13.5 percent in January-February from the same period a year earlier. That is the weakest reading since January 1990, when Reuters news agency records started.

But as soon as the pandemic is over, economies will need to rebuild. Typically, after a downturn, like the financial crash of 2008, there is a surge in emissions as nations crank up their economies. This will almost certainly happen this time, too.

But the outbreak has shown that governments can take radical and urgent action to tackle a clear and present danger. The problem is, the dangers presented by the climate crisis seem too distant to matter to most, especially politicians. But if we think COVID-19 is bad, we ain't seen nothing yet: the effects of the climate emergency will be far worse down the line.

Amid tragedy, we have had a sniff of a cleaner, safer future. Once this pandemic is over, never will there be a better moment to put our shoulder to the renewable energy wheel and take on the technological challenge of big-scale energy storage for when the wind doesn't blow and the sun doesn't shine. Or we will sleepwalk into another global crisis more malevolent by far than the coronavirus.



Your environment round-up

1. The biggest conference in 10 years on biodiversity may have been postponed because of COVID-19. But that has not stopped the UN biodiversity chief calling for a ban on wildlife markets.

2. Earth online. Young people are now mobilising online under the hashtags #ClimateStrikeOnline and #DigitalStrike, posting pictures of their climate strikes while on lockdown. Fridays for Future have also launched Talks For Future, weekly webinars with scientists, journalists and activists.

3. A story from the archives - one of the most spectacular locations - the remote Lofoten Islands in Norway and the annual cod migration threatened by a changing climate.

4. And a jolly tale of taming the robin.

The final word