How climate change and unplanned urban sprawl bring more landslides
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Over the past 50 years, disasters caused by landslides have become ten times more frequent3. And landslide risk is set to escalate, owing to two increasing trends — climate change and urbanization. Now, researchers need to assess where and to what extent such risks will rise.
More than 80% of fatal landslides occur in the tropics1. They are triggered mainly by heavy rain, often during cyclones and monsoons. Climate projections show that, on average, the intensities of tropical deluges could double by the end of the century4. But it’s hard to say what will happen in any given place.
The rapid pace of urbanization, especially in low- and lower-middle-income nations in tropical regions, will put more people in the path of landslides. For example, the population of Freetown in Sierra Leone has nearly doubled, to more than 1.2 million, since 2000
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Landslides occur when gravity overcomes the resisting forces of soil or rock on an incline, causing a mass to slide, fall or flow downhill. Heavy rainfall is the main trigger — as water infiltrates the ground, it increases the pressure in pores, weakening the soil. In general, the steeper the hillslope and the weaker the material it’s made from, the more unstable it will be. Other factors, such as plant roots, might provide some reinforcement.
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Decision makers should aim to use disaster risk reduction funding and policies to develop ‘pro-poor’ approaches to landslide resilience, by listening to and helping vulnerable people in their region. Reorienting city planning away from top-down approaches, towards joint government–community working groups is key. Good examples can be seen in Quito as well as in Medellín in Colombia and Kathmandu in Nepal
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