EXPLAINER: How did Russia-Ukraine war trigger a food crisis?

LONDON (AP) — Russianhostilities in Ukraine are preventing grain from leaving the “breadbasket of the world" and making food more expensive across the globe, threatening to worsen shortages, hunger and political instability in developing countries.

Together, Russia and Ukraine export nearly a third of the world’s wheat and barley, more than 70% of its sunflower oil and are big suppliers of corn. Russia is the top global fertilizer producer.

World food prices were already climbing, and the war made things worse, preventing some 20 million tons of Ukrainian grain from getting to the Middle East, North Africa and parts of Asia.

Weeks of negotiations on safe corridors to get grain out of Ukraine's Black Sea ports have made little progress, with urgency rising as the summer harvest season arrives.

“This needs to happen in the next couple of months (or) it’s going to be horrific,’’ said Anna Nagurney, who studies crisis management at the University of Massachusetts Amherst and is on the board of the Kyiv School of Economics.

She says 400 million people worldwide rely on Ukrainian food supplies. The U.N. Food and Agriculture Organization projects up to 181 million people in 41 countries could face food crisis or worse levels of hunger this year.

Here’s a look at the global food crisis:

WHAT'S THE SITUATION?

Typically, 90% of wheat and other grain from Ukraine's fields are shipped to world markets by sea but have been held up by Russian blockades of the Black Sea coast.

Some grain is being rerouted through Europe by rail, road and river, but the amount is a drop in the bucket compared with sea routes. The shipments also are backed up because Ukraine’s rail gauges don't match those of its neighbors to the west.

Ukraine’s deputy agriculture minister, Markian Dmytrasevych,...