Malngaye Adam grimaces as he squats on a mat in a hot, dusty compound in Tagal, a village of one-storey mud and wooden houses on the shore of Lake Chad. “Life has become very difficult,” he says, flanked by his wife and 10 children.

In the country’s southwestern Lac region, flooding, raids by radical Islamic Boko Haram militants — and government-forced displacement in response — have squeezed the amount of land he has to cultivate. Drought has reduced his crop of maize to a fraction of previous levels. A recent influx of refugees from neighbouring Nigeria — and the accompanying aid workers — has pushed up food prices.

He glances round at his nine boys and single girl, unable to recall their precise ages, and says he cannot afford to pay the fees to send any of them to school. “It’s a matter of pride to have a big family,” he says. “Lots of children help you. It was not my choice. God gave them to me.”

He married his wife, Kattouma, when she was 15 and he was 22. He is now 52. “If she had given me only two children, I would have taken a second wife — if I’d had the money,” he says with a smirk. But, as she breastfeeds her nine-month-old youngest, Kattouma says firmly that she has had enough children and would have used contraception had she known about it earlier.

Their situation is typical in Chad — one of the world’s poorest countries with the fourth highest fertility rate. With an average of nearly seven children per mother — and rising — the country defies the typical global pattern of so-called “demographic transition”. Normally, improved health and development reduces early deaths and a fall in birth rates follows, resulting in a balanced population for each age group.

This is an insular population living precariously, in ignorance, with no education or health infrastructure

The population of Chad, however, is around 13m and growing at 3.5 per cent a year, with two-thirds of its people aged under 25. Without greater efforts to limit this expansion, experts warn that Chad risks missing out on the “demographic dividend” — a surge of people entering the workforce to boost economic growth.

Instead, rising overall numbers of young dependants in Chad are exacerbating health and nutrition problems, triggering conflicts and forcing communities to spread any gains very thinly at the expense of improved services.

The culture remains impenetrable. People think of girls as women as soon as they reach reproductive age

“I tell heads of state that the best asset they have is their people,” says Babatunde Osotimehin, a former health minister of Nigeria and now executive director of the UN Population Fund, which is active across the region in promoting improved family planning. “Young people can transform societies, but if you have so many it’s not sustainable.”

In Tagal, a two-hour drive from the Lac region’s capital of Bol along rugged desert tracks more often used by camels and long-horned cattle than cars, traditional practices prevail. The local chief, Ali Koura, preaches the merits of “family limitation” and says that five or six children are sufficient, although he has 13 by five wives.

In a nearby walled compound of huts, Ashta Mohammed, now aged 22, says she was forced by her parents to marry at 14 and had the first of her four children within a year. “I suffered a lot,” she recalls of the birth, saying she would now like to pause for three years. But she sees herself eventually having a family of at least eight. “[Having] lots of kids will help me.”

© Kate Holt

In Africa’s fifth-largest country, which sits on significant oil reserves, some pronatalists argue there is no need for birth control, with plenty of land to go round. The different tribes and faiths vie for influence and are concerned about security, with hostile neighbours across the largely uninhabited northern and eastern sub-Saharan desert regions, including Libya and Sudan.

Most of Chad’s population is concentrated in pockets of the west and the more verdant south, where rising fertility rates are driving malnutrition and unnecessary deaths of mothers and infants as well as creating environmental pressures such as overfishing and farming and desertification of agricultural land. As resources are squeezed, periodic conflicts break out.

Fishermen at work on the lake by the village of Tagal, where resources are under increasing pressure © Kate Holt

“Things have become difficult,” says Mohammed Kale, one of Tagal’s many fishermen. “There is less water and too many people are fishing. Ten years ago there were plenty of fish. Now I catch a sixth as much and most of them are smaller. I’m only 40 years old, but I have grey hair from the stress of looking after my eight children.”

In Bol, Youssef Mbodou Mbami, Chad’s former ambassador to Niger and Nigeria who has returned to his roots as the traditional leader for the region, points to longstanding but intensifying feuds linked to nomadism and transhumance (the moving of cattle in search of pasture). “The number of people has increased but the space is the same. There are tensions between farmers and cattle herders. Everyone wants land,” he says.

Youssef Mbodou Mbami, the traditional chief of the Bol region © Kate Holt

His family has provided leaders in the region for six generations. He himself has 15 children, and he stresses underlying causes in the isolated, landlocked country that help account for unrest and high fertility. “This is an insular population living precariously, in ignorance and with no education or health infrastructure,” he says.

The neglect of the population’s social needs reflects both the legacy of 60 years of colonial rule by the French and half a century of instability and conflict since independence in 1960. Long before the displacements triggered by the rise of Boko Haram in the past three years, military and security activities dominated government.

Foreign powers, with an eye on containing Islamic extremism, have also focused on Chad’s strategic importance, ignoring the need for domestic reform. There is a large French military base near the airport in the capital N’Djamena and a new multistorey, fortress-like US embassy is being constructed on the outskirts.

856 maternal deaths per 100,000 live births

Health accounts for less than 7 per cent of the state budget and, with most people required to pay out of their own pocket even for nominally free public services, total spending on health was just 3.6 per cent of gross domestic product in 2014, according to the World Bank, compared with 17.1 per cent in the US and 8.8 per cent in South Africa.

This lack of investment helps explain both the high rates of infection and death and the scant use of family planning. Supply and demand for modern forms of contraceptives are among the lowest in the world, with surveys suggesting they are used by less than 5 per cent of women in Chad.

More indirect ways to lower fertility are also absent. Literacy for girls is at 20 per cent and just 12 per cent even start secondary school. Instead, nearly 68 per cent are married before the age of 18 and 29 per cent before they reach 15, according to Unicef. Girls begin giving birth while they are still physically immature, leading to complications such as obstetric fistula (internal tearing during childbirth that leads to incontinence). They then face a long reproductive cycle, often marked by inadequate spacing between births, and the inability to produce sufficient breast milk to feed their children.

139 deaths of children under five per 1,000 live births

“Here, the woman has no power,” says Bakary Sogoba, head of child protection for Unicef in Chad, drawing a contrast with neighbouring countries that have lower fertility rates. “In Mali, there is a long tradition of travel. Chad is less open to the exterior. The culture remains impenetrable. People think of girls as women as soon as they reach reproductive age — they are sometimes even promised to a boy at birth. And where there is polygamy, you can have competitive reproduction between multiple wives vying to have more children than their rivals.”

“There is progress, but it’s not enough,” says Moussa Khadam, Chad’s minister of public health, whose grandfather had 63 children but who has limited himself to two. “Chad has very high illiteracy and is already overpopulated in the centre and the south. We need better tools for family planning and greater awareness to tackle traditions that are centuries old.”

When public money is provided, however, it is not always used effectively. Behind Khadam’s ministry building in N’Djamena are more than 100 unused ambulances neatly parked among growing weeds; none of them even has a number plate. Even if they are eventually deployed as intended, and do not quickly break down on the country’s few passable roads, many see them as a wasted investment.

In rural areas, practically nothing is being done. We are going backwards

Rolland Kaya, country manager for the Médecins Sans Frontières humanitarian aid mission in Chad, argues that much more public funding should go into supporting basic prevention methods and local health clinics. “Often there are no supplies, no vaccines, no bed-nets against malaria, no hygiene training to stop infection, and workers are not paid,” he says.

The result is that people turn instead to traditional healers, whose interventions often make matters worse. He cites strange herbal concoctions, incisions made into the skin as supposed treatments and, in one case, a remedy for diarrhoea that involved burning the affected young child’s anus.

Such practices explain why Chad ranks among the world’s worst performing countries in terms of health. With maternal deaths of 856 per 100,000 live births in 2015, and infant deaths of 85 per 1,000 live births, life expectancy at birth is just 53.1 years. In part, the country has not experienced the demographic transition because many of the pre-determinants are not yet in place. Having more children remains a way to replace those who do not survive.

At a therapeutic feeding centre in N’Djamena, Nelkam Dadimra, who is barely 15, cuddles her malnourished 10-month-old daughter, Salut. She came to the capital three years ago to find work as a cleaner and gave birth at home, leading to complications and stomach pains from which she still suffers. Unable to breastfeed, she fed her child a millet porridge made with water which she is too young to digest. This has caused diarrhoea and fever. “God gives us children,” she says. “Maybe I will have 10.”

Girls use the waters of Lake Chad to do the washing © Kate Holt

With malnutrition affecting 40 per cent of Chad’s children, Dr Ibrahim Dicko, who runs the centre, says he sees such cases frequently. One reason is the extremely low use of exclusive breastfeeding by mothers, partly because of a belief that if either mother or child is ill, breast milk will be harmful. “They give herbs, ashes, buy powdered milk and mix it with water,” he says. “Gastroenteritis is very common.”

While most of the 100 children currently being treated at the feeding centre need at least seven days’ care, Dr Dicko says mothers sometimes take them home sooner while they are still ill, or even abandon them. “Husbands want their wives at home, and there is family pressure to look after the other children. They think they can always have more.”

At a family planning clinic in N’Djamena’s main market, where women can slip in discreetly while selling or shopping, Josephine Nangtan, a counsellor, gestures towards a box on her desk containing dozens of registration cards. “They ask me to keep them here, because if their husband sees them, it could be a reason for violence or divorce,” she says.

Nelkam Dadimra, 15, with her 10-month old daughter at a therapeutic feeding centre in N’Djamena © Kate Holt

Attitudes are beginning to change. Protestant Church leaders support contraception — not to limit family size but to stress the need for a “responsible” number of healthy children, starting later and spacing births. The Catholic Church takes a similar line, while stressing it only encourages natural methods. The same is true of Muslim leaders. Sheikh Abdaddayim Ousman, secretary-general of the Higher Council on Islamic Affairs, says: “The prophet told us to marry and have a family of quality, not quantity. Islam also distinguishes between marriage and the consummation of marriage.”

On paper, at least, legislation passed in 2002 guarantees access to reproductive health in Chad, overturning colonial-era laws that banned birth control and widespread practices that, until far more recently, required husbands or parents to authorise any family planning. An official plan has set four children per woman as an objective for the country by 2030.

More radically, last year President Idriss Déby Itno pushed through a law banning marriage before the age of 18 — a first in west Africa and a move possibly linked to his current international profile as the chair of the African Union. Khadam, the health minister, says some violations have already been prosecuted.

Yet for now, as Abbot Gabriel Dobade from the Catholic Church’s Episcopal Conference, puts it, there are few signs of broader public investment in Chad’s development. “In rural areas, practically nothing is being done,” he says. “We are going backwards in areas where we should be advancing. There is injustice and poor governance.”

After years of rising government revenues, the drop in the oil price in recent months has imposed fresh austerity. The conference centre where the African Union was supposed to hold its meeting in N’Djamena last year sits unfunded and unfinished. Public sector workers and students on grants have not been paid in weeks, triggering marches, strikes — including in health centres — and stone-throwing by young people.

Just as the state’s ability to invest in health, family planning and other public services has been reduced, the most recent swelling cohort of young people is moving towards adulthood and is beginning to make its frustration felt.