The name “Nairobi” comes from the Maasai phrase Enkare Nyirobi, which means “place of cool waters,” an interesting and fitting identity for Nairobi, both in the city’s origin as a landscape of wetlands, streams and the prolific Nairobi River, and now its current glaring feature: floods.
This year alone, flooding killed over 40 people in Nairobi in March, washing away vehicles, submerging homes, and displacing people. But that figure sits within a pattern that is getting harder to ignore. In 2024, flooding killed 294 people across Kenya, with Nairobi County recording the highest number of those affected. In 2025, floods triggered a cholera outbreak and landslides that killed dozens more. Three years running. Each time, the same city. Each time, the same root causes are left unaddressed.
And the worst might still yet come. The heavy rains that typically drench Nairobi through June and July are still ahead.
This is the consequence of what scientists predicted a long time ago – climate change. And nature has been warning us about it for years.
A city built on, and destroying, its own flood defences
Nairobi was built on wetlands. Before the city grew, a living web of papyrus swamps, riparian forests, and seasonal floodplains covered this landscape. These were our living environment working as infrastructure: absorbing rainfall, slowing water, filtering it, and releasing it steadily into rivers and underground systems. They were, in every practical sense, Nairobi’s flood defence.
The Nairobi River, once surrounded by papyrus and fig trees, now runs through concrete channels choked with waste. Wetlands have been drained, built on, and forgotten. Where water once had space to spread and slow, it now has nowhere to go but through people’s homes. The communities paying the heaviest price are those in informal settlements built in floodplains. They are, unfortunately, the people who had the least say in how this city was designed, but suffer most when the designs fail.
The Earth is sending us signals
This World Environment Day, on 5 June, the United Nations Environment Programme is asking all of us to listen. The theme is Climate Action, and the message is clear: the Earth is sending us signals. Rising seas. Raging wildfires. Heatwaves. Melting glaciers. Flooding cities.
Earlier this month, in May, scientists and international agencies warned that 2026 could be one of the most extreme years of weather events on record globally, driven by rising global temperatures and the emerging return of El Niño. Nairobi’s floods are part of a global picture that also includes forest fires in Chile, snowstorms in Japan, a cyclone in Sri Lanka, and heatwaves across Europe. These are not isolated disasters. They share the same cause of climate change.
The question this World Environment Day asks is what signals we are sending back.
Bring back nature, starting with what Nairobi has already lost
But there is hope, and we know exactly what to do. It starts with bringing nature back.
Rewilding – the large-scale restoration of ecosystems and the return of wildlife to degraded habitats – is a solution to combat climate change being implemented across the world. For Nairobi, rewilding is a practical flood management strategy. Cities from Rotterdam to Singapore to Kampala are already restoring urban wetlands as core climate infrastructure. Kenya’s own government launched the Nairobi Rivers Commission in 2023, with a mandate to restore the rivers and green corridors that run through the city. The science and the political framework exist. What we need now is action at scale.
The most powerful indicator of a recovering Nairobi wetland is one many people might not recognize: papyrus. This tall, feathery grass once covered vast areas of the East African wetland landscape. A single hectare of papyrus swamp can absorb and store millions of litres of water during heavy rain and acts as a natural sponge. It also filters pollutants, absorbs carbon, and provides habitat for dozens of other wild species. When papyrus returns to the banks of the Nairobi River and its tributaries, we will know that recovery has truly begun.
But look also for the grey crowned crane. Kenya’s iconic national bird, and one of the most visible signs that wetlands are coming back to life. These birds nest in papyrus, feed in shallow water, and disappear when wetlands degrade. Their return to Nairobi’s urban green corridors would mean that the ecosystem is healing and functioning.
And then there is the African clawless otter: shy, playful, and deeply sensitive to water quality. Spotted by camera traps in Karura Forest’s rivers and in the Ruaka River as recently as 2025, these animals are one of nature’s most reliable signals that a river is clean enough to support life again. But they are more than a sign of recovery. They are active participants in keeping rivers healthy. As apex predators in freshwater ecosystems, otters regulate fish populations, which in turn keeps aquatic vegetation from choking drainage channels. Overgrown, clogged waterways slow the movement of floodwater and make flooding worse. Healthy otter populations help keep rivers open and flowing. Where otters thrive, rivers flow. Where rivers flow, cities flood less.
They are engineers and guardians of the living systems that protect us.
Karura is proof that urban rewilding works — and it is under threat
Nairobi already has a living example of what restored urban nature looks like. Karura Forest, a 1,000-hectare green lung in the north of the city, is home to indigenous trees, clean-running rivers, the grey crowned crane, and those otters. It is one of the largest urban gazetted forests in the world. It is proof that a degraded landscape can be transformed when communities and government work together to protect it.
It is also, right now, under serious threat.
In 2025, land clearance, tree cutting, and heavy machinery were documented inside the forest. The community organisation that has protected and restored Karura for over two decades, Friends of Karura Forest, had its management arrangements abruptly disrupted. A court order was needed to halt the construction works. This echoes the fight that Wangari Maathai and the Green Belt Movement had to wage in this same forest in 1998, when developers began clearing sections for private construction.
The government cannot simultaneously claim to be responding to Nairobi’s flood crisis while authorising construction inside the urban forests and wetlands that reduce flooding and mitigate climate.
What needs to happen
Kenya has the tools. The National Biodiversity Strategy and Action Plan. The Nairobi Rivers Commission. Commitments under the Global Biodiversity Framework to protect 30% of land by 2030. What is needed now is for county and national governments to enforce protections on remaining riparian corridors, restore wetlands at scale, protect the wild animals that maintain and rely on these ecosystems, and treat nature as infrastructure in every urban planning decision made from here on.
It also means keeping Karura whole, and keeping community-led conservation at the heart of how we manage what remains of Nairobi’s green spaces.
What signals are we sending back?
When we protect wetlands and restore green corridors through our cities, we reduce flood risk. When we allow wildlife back into restored habitats, we strengthen biodiversity and make ecosystems more resilient to the shocks of a warming world. When we invest in nature-based solutions, we protect the most vulnerable communities, who always bear the heaviest cost when floods and climate disasters strike.
This World Environment Day is a moment to listen to the signals the Earth is sending, and for all of us – government, civil society, and citizens – to respond by committing to rebuilding the city’s relationship with the nature around it.
