Last week, the U.S. rejoined the Paris Climate Agreement. But even if its targets are met — and most countries are far from hitting them — the world will still likely be headed for a 3°C global temperature rise. In the coming decades many of our beloved coastal cities may be wiped off the map. The United Nations High Commissioner for Refugees warned earlier this year that the world must get ready for the displacement of millions of people. At this late hour, those preparations must include helping people move before disaster strikes.

A growing number of scientists are calling for planned relocation (also known as “managed retreat”) as part of the U.S. government’s strategy to tackle climate disruption. It’s an idea that has gained traction in recent years: In 2016, the Department of Housing and Urban Development awarded a $48 million grant to the Biloxi-Chitimacha-Choctaw tribe on Isle de Jean Charles, a sinking Louisiana island, to facilitate resettlement. Last year, the Federal Emergency Management Agency introduced the Building Resilient Infrastructure and Communities (BRIC) grant program, worth half a billion dollars, to help underwrite “larger-scale migration or relocation.”

Until now, the government has resorted to post-disaster recovery: buying and demolishing a handful of houses here and there. (Homeowners receive the pre-disaster value of their property so they can move to safer ground.) But this strategy is changing as more and more policy makers recognize the need to move ever larger numbers of people out of flood- and fire-prone areas to avoid loss of life and the waste of taxpayer dollars used for rebuilding efforts.

Large-scale relocation could cost hundreds of billions or even several trillion dollars. But the current default — rebuilding in disaster-stricken areas — could eventually prove more costly than relocation.

This article is part of our Climate Justice collection. Learn more about climate justice, or read the full article about relocating communities to avoid climate disaster  by Shanelle Loren at Grist.