Over the past decade, development organizations have been working on improving the productivity of African farms to deal with food insecurity as the continent’s population booms. By closing the gap between what farms actually produce and what they could produce, Africa would have enough food to both feed itself and become a new breadbasket for the world.

But according to a new study published in the Proceedings of the National Academy of Sciences, even closing that gap will not be enough to meet Africa’s food needs. The study, based on 10 countries that account for 58% of the continent’s arable land, found that closing that gap would only maintain the current level of self-sufficiency. It will also need to dramatically increase its agricultural efficiency. Right now, Africa imports 20% of its cereal needs, despite having a quarter of the world’s arable land.

“We were surprised, because the assumption is that … if Africa could close that gap, then it could feed itself and even be a bread basket for the rest of the world,” said Kindie Tesfaye, one of the authors of the report.

With a population expected to expand by another 1.3 billion people by 2050, Sub-saharan African countries will have to import half of all needed cereals in the next 30 years, if drastic changes to agricultural methods aren’t taken, the study concluded. In addition to closing the gap between actual and potential crop yields, farms will need to increase crop intensity, or the amount of crops grown on the same field within a year, and expand irrigation.

“If intensification is not successful and massive cropland land expansion is to be avoided, [sub-Saharan Africa] will depend much more on imports of cereals than it does today,” the authors concluded.

Sub-saharan Africa is the only region in the developing world where agricultural productivity on average is falling, a trend that some blame on governments’ lack of investment in an industry that employs more Africans than any other sector. In 2003, most African states signed the Maputo Declaration, which commits governments to allocating at least 10% of their budget to developing agriculture. Only four countries (p. 62), Burkina Faso, Malawi, Mozambique, and Zimbabwe, had met the quota in 2014.