Leaders across the continent need to tackle a “taboo” against birth control and ensure their youth have prospects, he said as he launched his foundation’s annual index showing the state of governance across 54 African countries.

“We see the risks – we can see the rise in armed groups (like) Boko Haram and al Shabaab,” he said, referring to Islamist militants in northern Nigeria and Somalia.

“It isn’t a coincidence, it’s linked to dissatisfaction arising from a number of factors, most importantly lack of hope when young people can’t see a future,” he told the Thomson Reuters Foundation in London.

The index report found governance is slowly improving on average across Africa.

However, it warned the economic growth of the last decade was “mainly jobless”, while many children and young people were missing out on quality education even as the continent’s population increased sharply.

“Population growth is outstripping our economic growth. It is like running on a treadmill and we are not moving forward,” said Ibrahim.

Africa is expected to account for more than half the world’s population growth between 2015 and 2050, according to U.N. data. Its population is projected to double by 2050, and could double again by 2100.

Ibrahim said a lack of prospects was pushing some youth toward militant groups and also helping to drive the migrant crisis that has seen tens of thousands enter Europe each year.

“I’m really afraid that unless we deal with the issue of rising population and the large number of unemployed youth then we are in for trouble,” he said.

Mauritius, the Seychelles and Cape Verde were the top performers in terms of governance overall, while Libya, South Sudan and Somalia ranked worst.

Zimbabwe, where longtime leader Robert Mugabe was ousted last year, was among the most improved countries, while war-torn Libya was named as having the worst deterioration.

Civil rights and freedom of expression have on average eroded over the last five years, the report said, amid what Ibrahim described as a “global phenomenon” for political “strongmen” who have often stripped back freedoms.

The report cites surveys from the last three years by research network Afrobarometer which found over a quarter of Africa’s citizens are not free to say what they think and almost three quarters are careful about what they say when discussing politics.

Countries are also increasingly diverging in their performance, the report warned, with the best showing swift improvements as others decline.

“We see countries that get it right are able to go on and build on that, and we see countries that are going into this downward spiral of lack of governance,” said Ibrahim.