“We have lost everything,” my friend cried as we talked on the phone. I had last seen her the week before, after returning home after a year working as a doctor in Sierra Leone. She described water suddenly rushing through her house in the early hours of Monday. With her five children she managed to escape on to the roof, where she waited to be rescued. The flood took all of their possessions, apart from the clothes they wore. And she was one of the lucky ones.

Estimates of those who have perished in the mudslide and flash flooding that hit Freetown on Monday put the number at more than a thousand. As the enormous mudslide from Sugar Loaf mountain tore through Regent, the people sleeping had no chance: 400 corpses have already been retrieved by rescue teams; 109 of them were children. There are more than 600 people still missing. The Red Cross, which is working tirelessly at the scene of the disaster, estimates about 3,000 people are homeless.

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Sierra Leone, meaning literally “lion mountains”, was the name given to the country by a Portuguese explorer in the 1400s. As you move around Freetown you can see how it got its name – enormous hills fall away into the Atlantic. Initially built for a population of tens of thousands, the city now contains over a million people. Many live in “informal” (a euphemistic word for slum) settlements.

There are estimated to be 61 informal settlements in Freetown. I spent some time working in a children’s clinic in Kroo Bay, one of the city’s largest slums, wedged between the hills and the ocean. Whole families lived packed into tiny houses made from sheets of zinc, with no clean water or sanitation. The drains through which the rain falling on the city must flow out to the sea are blocked with rubbish, causing devastating floods. In the clinic in another part of town during rainy season we would see children with horrific injuries incurred when they were trapped under buildings that collapsed due to the rain, as well as illnesses caused by poor living conditions and unsafe water. Many people in Freetown live like this. Every rainy season the city floods, every year in Freetown people die. But this disaster was unprecedented. A combination of economic and environmental factors has culminated in massive loss of life.

Facebook Twitter Pinterest ‘Whole families have been destroyed in this disaster.’ People wait in a line to identify their relatives’ bodies at after the mudslides. Photograph: Anadolu Agency/Getty Images

People in the Regent area were living in a place known to be at high risk for flooding and mudslides. Poverty robs these people of the chance to live in safe housing and robs them of a voice too.

Failing to protect people living in dangerous areas has had devastating consequences, but there are also factors outside this country’s control which make the disaster so significant. Sierra Leone has received an unprecedented amount of rain this year. The US National Weather Service’s Climate Prediction Center reports that it is three times the usual seasonal rainfall. The effects of climate change are graphically evident – and nowhere more so than in Sierra Leone. It is the poor who suffer first and worst.

As Sierra Leone begins the second of seven days of national mourning, it is vital that we recognise that there are many more potential victims in the city, living in informal settlements, on unstable ground, in flood paths. The rainy season is not yet even halfway through. Further floods will happen. In the communities hit by the disaster there is a very real worry about cholera, which could lead to yet more preventable loss of life.

As this hideous disaster has unfolded, there has been barely a ripple across the international press. This landslide is a foreign tragedy in a foreign place. It is easy to look the other way. The Department for International Development and the Foreign Office have had remarkably little to say on the issue. But we cannot ignore it. Ignoring it shames us. It drives home the false message that if you are poor you don’t have a voice; your life counts for less; you do not matter.

Whole families have been destroyed in this disaster. Classes of schoolchildren are missing – young people who only last week were playing on the streets of Regent. There are a number of organisations on the ground doing an amazing job in the aftermath of the disaster. Street Child has been giving out emergency food and water to the displaced survivors.

But the British government should be doing even more to provide humanitarian support to these victims. They need to help assess what steps can be taken to prevent others from suffering in the same way in the future. In a globalised world the damage being done in one country to the climate is played out in a very real way in other places. Perhaps the bigger question is when will the world unite in understanding the seriousness of climate change? As the world gets warmer and weather more extreme, it is the poorest people – poor people without a choice – without safe places to live, who suffer.

• Hannah Mitchell is a doctor who has been working in Sierra Leone