A misreading of Islam led to Niger’s explosive birth rate, hampering the country’s fight to adapt to the climate crisis and preserve its shrinking resources, the country’s president has said.

This nexus of issues is likely to have an increasingly direct impact on European politics, said Mahamadou Issoufou, who warned warned that migration may exceed the levels it reached during the second world war.

“Everything is connected in a global village. As they say, a butterfly flaps its wings in Brazil and there can be a tornado in Houston,” said Issoufou, who has been feted by Emmanuel Macron and Angela Merkel as one of Africa’s most articulate leaders.

Issoufou claims he has been slowly driving down his country’s birth rate of more than seven children per woman, the highest birth rate in the world for the past decade.

He told the Guardian: “Before Islam came, women used to be married at the age of 18 but, due to a misreading of Islam, young women were having babies at the age of 12 or 13. But what does the Qur’an say? If an educated person reads the Qur’an, it talks about responsible parenthood. Islam says you should only have children if you can take good care of them and properly educate them.

“Schools need to educate young girls because we do not want them having children at 12 or 13. Ideally, we want to keep them in school as long as possible, until age 18. This is something new to us.”

He insists that, in a country that is 98% Muslim, his views do not conflict with imams or religious leaders. Although Issoufou has faced resistance from some muslim leaders for advocating family planning, he insists: “Religious leaders are with us in raising awareness among the people, and that is why we are seeing … a decrease [in birth rates]”.

With the spread of contraception and family planning schools for men, the birth rate has slowly declined to about six children per woman, but more needs to be done, the president said. The last official figures from the World Bank, from 2016, put the rate at 7.2 children per woman.

Niger’s population stood at 8 million in 1990 and reached 22.4 million in 2018. “We have a 4% annual increase in population,” said Issoufou. “The population will double in the next 17 years. By 2050 we may have the second biggest population in Africa apart from Nigeria.”

It is a continent-wide phenomenon, he said. “In Africa there are 1.3 billion people today … [there will be] 2.4 billion by 2050. That means 30 million young people per year entering the labour market. If we do nothing to keep people in Africa by creating jobs domestically, there will be a huge wave of migration as people look for jobs elsewhere.”

He knows the scale of migration from Niger – one of the poorest countries in the world – depends on how the climate crisis progresses, but Issoufou warned that the Sahel will be one of the main contributors to the predicted 230m migrants by 2050, a figure he points out will be far larger than the mass migration caused by the second world war.

“In Niger we are already living with the practical results of climate change. Floods alternating with droughts [are] already having huge consequences on agricultural production. There is a degradation of soil, forests are getting lost, there is less land, and an advance of the desert. Lake Chad has lost as much as 90% of its water, and there are more problems with domestic rivers. Niger loses 100,000 hectares (250,000 acres) of agricultural land every year,” he said.

“The people of Niger may not fully understand the causes of this, but they are experiencing it in their daily lives. They do know there is a link between degradation of soil and their poverty. The world worries about a rise of two degrees, but we have already experienced that increase since the 60s.”

He added: “There is a growing risk of anger across Africa as the people come to realise the root cause of this evil. As people come to understand the causes of climate change, it could lead to the finding of solutions, but equally it may lead to anger and social turmoil.”

“Those least responsible for the climate change suffer its worst consequences. The situation is not helped when industrialised nations do not always deliver on their promises.”

Earlier this year, Issoufou was involved in the launch of a $400bn (£311bn) climate investment plan for the Sahel region.

The precise extent to which climate change and demography in Africa could lead to migration into Europe is disputed, with most saying it will lead mainly to internal migration within Africa. A World Bank report last year claimed that if no action is taken, sub-Saharan Africa may have as many as 86 million internal climate migrants by 2050.

Issoufou argues that much depends on Africa’s ability to find jobs for this new labour force, which in turn hangs on the continent’s ability to grow in the model of Asian economies, and to integrate economically.

As chair of the Economic Community of West African States, Issoufou has been involved in plans to build a pan-African free trade zone of 1.2 billion people, now supported by 54 African states. He said the aim is to end what he describes as “the Balkanisation of the continent by colonialists”.

The free trade zone came into force this summer, and Issoufou now talks of “marching boldly” towards a single currency for Africa, a plan that may meet widespread resistance.

Unlike Asia, he argued, “Africa had remained chained in the colonial pact, that is to say supplier of raw materials and consumer of finished products manufactured elsewhere. She remains a victim of unequal exchange.”

His critics claim Issoufou has become a victim of an unequal exchange himself. In 2015, Niger – at the EU’s request – became the first country to criminalise people-smuggling, a move that has badly disrupted the hidden economy of the north.

The EU gave Niger €610m (£526m) to police what has effectively become Africa’s new border with Europe in the wake of the collapse of Libya.

The aim was to slow the flow of migrants into Libya, which led to mass migration across the Mediterranean into Italy, peaking in 2017, and prompted the rise of the populist right. One issue with the approach is whether those who have been forced out of smuggling have received the EU aid designed to give them a different way of life.

Issoufou made no apology for being the gendarmerie of illegal migration. “I am not prepared to see Africans die in transit in the heat of the Sahara or exploited by smuggling rings,” he said.

European lectures on the consequences of the Libyan intervention do not impress him. He first heard about the fateful Franco-British intervention of Libya in 2011 on the radio. “It has left us in a state close to chaos ever since.”