Satellite data analysed by scientists at the US space agency shows that Russia’s occupation of eastern and southern Ukraine gives it control of land that produces 28% of the country’s winter crops, mainly wheat, canola, barley, and rye, and 18% of summer crops, mostly corn and sunflower.

The war’s disruption of harvesting and planting – including farmers fleeing the war, the lack of labour and fields pockmarked by shelling – could have a heavy impact on global food supplies, Nasa scientists said.

“The world’s breadbasket is at war,” said Inbal Becker-Reshef, director of Nasa’s Harvest programme, which uses US and European satellite data to study global food production.

According to US data, before the war Ukraine supplied 46% of the sunflower oil traded on global markets, 9% of the wheat, 17% of the barley, and 12% of maize.

Russia’s invasion has blocked exports of food from Odessa, the main port on the Black Sea, and destroyed storage and transport infrastructure in some areas.

That means farmers in the entire country, but especially in occupied areas, have less options for getting their output into storage and to markets.

And it also threatens the planting of winter crops in the fall.

“We’re in the beginning stages of a rolling food crisis that will likely affect every country and person on Earth in some way,” said Becker-Reshef.