LAGOS: When his boat capsized during a storm last year, Nigerian fisherman Tanti Leon clung to its upturned hull with his children and wondered if he should give up trying to fish in the waters around Lagos's flood-prone shanty town of Makoko.

The heavy rainfall also caused water levels to surge, destroying Leon's home, which like most buildings in the sprawling slum was built on sticks in the coastal lagoon facing the mansions and office towers of Nigeria's commercial capital.

But with no other way of supporting his family, the father-of-six continues to fish and live in Makoko: just the kind of poor, informal settlement on low-lying ground that is particularly vulnerable to climate change-linked sea-level rises and weather extremes, according to the latest report from the United Nations climate science panel. 

"I was so sad I made up my mind not to fish again, but then this is all I know how to do," Leon, 42, said has he sat in his boat in the lagoon.

Africa has contributed very little to climate-warming greenhouse gas emissions, but the world's hottest continent hosts some of the people who are most vulnerable to current and future fallout from the planet's further warming, according to the report, released on Monday. 

LIVING WITH EXTREME WEATHER

In Lagos, poorly planned construction to accommodate the rapidly expanding population of around 20 million people is also driving up flood exposure, a 2021 study in the journal Environmental Hazards found.

More than 34% of Lagos's territory was vulnerable to flooding in 2019, up from just 1% at the start of this century, it said.

In Makoko, residents try to adapt to extreme weather, nailing metal sheets to the bottoms of the boats they use for fishing and navigating the narrow waterways between the houses, where children splash in the shallows.

"We cover the body of every boat we make now with zinc, coal tar, aluminium so that when the storm hits it, the boat will not break or spoil," carpenter Segun Jisoro said at the boatyard.

Not all such efforts pay off. In 2016 heavy rains destroyed a floating school that was built to adjust to the changing water levels and withstand the storms that lash the city.

On a continent likely to record the world's fastest population growth this century, Lagos is set to become the world's largest city by 2100.

Tanti Leon's fishing net, empty but for bits of debris, gives a bleak illustration of another assessment made by the U.N. - rising sea temperatures could bring fish harvests down just as the population swells.

If global warming results in temperatures of 1.7 degrees Celsius above pre-industrial levels, leaner fishing could leave 1.2–1.7 million people in Africa vulnerable to iron deficiencies and hundreds of millions lacking vitamins by mid-century, the report said.

Leon aims to adapt his life to the inevitable storms to come. "The plan is to be able to save and buy a speedboat engine," he said. "Its very hard when I have to manually paddle a boat in the face of a storm."