Yesterday's Earth Day was unlike any in the past 50 years.
Worldwide, millions of people who were hunkered down in their homes marvelled at the blue skies outside and near-empty roads.
Air pollution has plunged in big cities and industrial belts, rivers are running cleaner and birdsong can be heard more clearly, no longer drowned out by relentless traffic.
Greenhouse gas emissions have also dropped markedly and oil demand has fallen off a cliff.
The global economy and people's lives have been tipped upside down, giving the planet a breather and showing what things could be like if humanity really valued the environment and ended its reliance on polluting fossil fuels.
In a perverse way, the pandemic has opened that window. But many of the environmental benefits are unlikely to last once the lockdowns across the globe are lifted.
The question is: Will everything go back to the way it was, or will there be lasting change?
That is hard to answer.
But there have been loud calls by the European Union and others for the massive stimulus packages offered by many countries to include spending on clean energy and more sustainable projects.
The sight of blue skies and satellite imagery showing a marked drop in deadly air pollution have opened many eyes.
The pandemic is expected to drive carbon dioxide (CO2) emissions down 6 per cent this year, the World Meteorological Organisation said yesterday, but this will not be enough to stop climate change.
Dr Ralph Keeling, a geochemist from the Scripps Institution of Oceanography in the US, said on Twitter that fossil fuel use would have to fall by about 10 per cent around the world and be sustained for a year to show up clearly in levels of CO2, the heat-trapping gas causing global warming.
With accelerating threats from climate change and escalating damage to the environment, the pandemic and the recovery phase represent a huge opportunity to rethink and reset the way we live and how our economies work.
Last year, a global assessment of life on earth found nature to be declining at an unprecedented rate and the pace of extinction of plants and animals accelerating, putting economies and people's well-being at risk. Up to a million species are threatened with extinction, said the report from the United Nations' Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services.
That matters, because mankind cannot exist without nature.
"Every breath of air we take, every mouthful of food we eat, depends upon a healthy natural world," says British natural historian David Attenborough in a video for Earth Day.
A series of landmark reports by the UN's Intergovernmental Panel on Climate Change (IPCC) in 2018 and last year underscored the urgent need to overhaul the way we grow food so as to ensure less waste and end the wholesale destruction of forests, wetlands and grasslands - ecosystems which can help fight climate change.
Of the 7.8 billion ha of arable land on the planet, 2 billion ha are already degraded, the UN Development Programme says.
Climate change, land degradation, water shortages and worse droughts are expected to drive up the number of refugees and trigger conflicts.
The IPCC says humanity has to make deep cuts in greenhouse gas emissions this decade to have a reasonable chance of limiting global warming to 1.5 deg C above pre-industrial levels.
The good news is, action is being taken, and there are solutions. But the action needs to speed up.
Globally, renewable energy investment is growing. Last year, almost three-quarters of new electricity generation capacity built used renewable energy, an all-time record, according to data from the International Renewable Energy Agency.
The data shows solar, wind and other green technologies now provide more than one-third of the world's power, also a record.
Elsewhere, the transition away from coal is gathering pace, with 21 financial institutions this year announcing policies to end or limit financing for new coal projects.
Globally, financial institutions are progressively restricting or ending financing to fossil fuel investments or clients with CO2-polluting assets, while hundreds of cities have committed to achieving net-zero emissions by 2050.
Youth climate groups and environmental shareholder advocacy organisations are also pushing for environmentally friendly policies and practices inside boardrooms.
For now, most people are just focused on surviving the pandemic. But some have already decided that they want the blue skies to remain.
According to The Guardian, Milan plans to introduce one of Europe's most ambitious schemes, reallocating street space from cars to bicycles and pedestrians, in response to the coronavirus crisis.
The Italian city announced on Tuesday that 35km of streets will be transformed during summer, with a rapid experimental citywide expansion of cycling and walking space to protect residents.