India’s rice export ban is boosting prices around the world, increasing the risk of political instability in Asia and Africa, according to the head of a United Nations agency.

Prices for the crop, a staple for half the world, surged to the highest in almost 15 years after the top shipper began curbing exports. India accounted for nearly 40% of the global rice trade in the past three years. Soaring prices are fueling concerns about food insecurity for billions of people in Asia and Africa who depend on the grain.

“Rice, especially in Africa, can certainly bring potential conflict or social unrest, which at this moment in time would be quite dangerous,” Alvaro Lario, who leads the International Fund for Agricultural Development, said in a Thursday interview in New York.

The export ban is bringing back memories of 2008, when a global rice crisis put 100 million people at risk, many in sub-Saharan Africa. Back then, both Vietnam and India restricted exports. Food shortages have also contributed to unrest in the past, with surging wheat prices helping spark the Arab Spring that toppled governments just over a decade ago.

Read More: India Further Tightens Rice Shipments in Threat to Global Supply

The impacts of bans “go beyond the borders of the countries” implementing such measures, Lario said. Rice is the “main concern” for food security — even more so than wheat, he said.

“Export bans have a lot of impact, especially on the most vulnerable, by raising prices and having a shock on prices,” he said. “Generally they are not positive, neither for the local populations in the medium term, nor for the other countries.”

Some regions in Africa that are more reliant on rice imports are already seeing impacts from higher prices, Lario said.

“We have to understand that many of these people who consume this type of crop are sometimes on the brink of poverty,” he said.