Sink or swim? What will human migration look like as climate change impacts take hold
What to do when the worst impacts of climate change are felt? In this extract from “Sink or swim: how the world must adapt to climate change” (Bloomsbury Sigma, 2025), author Susanna Fisherwho leads an international research program on climate adaptation at University College London, looks at the future of human migration. In it, she argues that as parts of the planet become uninhabitable, difficult choices will have to be made to manage the movement of people – whether organized resettlement or sudden displacement. But what will these choices look like in 45 years?
Imagine it’s 2070 and the world has battened down the hatches. People are moving away in large numbers from storms, droughts, floods and fires, usually within their own countries, into large camps for displaced people. The camps are located in the middle of nowhere in some cases, or in large urban areas in others, with few amenities or opportunities for assistance. People are struggling to rebuild their lives, but there’s not much left to return to.
Those who attempt to go further encounter internal or national borders heavily fortified by armed patrols. Humanitarian organizations are carrying out monthly distributions of food and clean water in the worst-affected areas, and the United Nations (UN) is teaching communities how to collect rainwater and cool their homes – but that is not enough.
Regional agreements allow people to move locally in times of disaster, but this does not help with the slow changes that have made life so difficult. There are now two global political alliances that transcend national borders: those living in the habitable zone and those living outside it.
The United States has erected a border around water-strapped southwest states to keep people out. States have turned against each other as they fight for the last flows of the Colorado River. Those who live in the “no-hab” zone increasingly care neither about the UN nor their own governments. Instead, they are strategizing together on how to use technologies like solar geoengineering to reinvigorate their regions.
Cities located in the habitable zone continue to lack population due to demographic changes, but the migration process to these cities is extensive and local communities do not accept “non-hab” applications.
Or another set of choices. A hurricane hits the coast of a small Caribbean country. The government had everything prepared: early warning systems sounded and people rushed to shelters before the storm ravaged the island. The day after the hurricane, the rapid attribution study is released and certified by the UN, showing that the hurricane’s winds were made much stronger due to climate change.
The government issues a set of climate passports and citizens can choose from a set of countries to host them. These countries include historical carbon emitters that accept responsibility for making the hurricane worse.
People can claim relocation grants from fossil fuel companies, which have been forced to pay after an unprecedented court case. The storm was scary and many people chose to go, taking the risk of a better life rather than the risk of another storm next month. This move may be temporary or longer term, but it gives people time to recover and continue their activities, education or training while rebuilding continues.
In Bangladesh, communities living in the delta are repeatedly hit by cyclones and floods. A young family decides they want more stability for their children’s education. They wanted to go to Dhaka but heard it was crowded and still flooded most monsoons. Instead, they approach the United Nations displacement center, where they hear about secondary cities that have room for new migrants. They evaluate the proximity to their family, the training and retraining opportunities offered and choose a small town with a dynamic cultural life. They enroll in a training program for a new life in the home of their choice. They have the opportunity to regularly return to their family in their old neighborhood and live between the two locations.
In the United Kingdom, a community of 400 families from a coastal area of Norfolk are settling into their new homes in the Peak District. The entire community, mostly close-knit, low-income families, was displaced from a place where they were under constant threat from floodwaters, storms and moisture seeping into their homes. Many didn’t want to go, but a wilderness company wanted to buy their land to run sightseeing and adventure tours.
They applied for the government’s resettlement program and developed a plan, setting out what was important to them and how they would like to spend the available money. The community negotiated with government agencies and eventually a plan was agreed upon for all residents. Some are happy with the move, others have returned near their former lands and take people by canoe past their former flooded homes.
In a small island developing state, the government has invested heavily in floating platforms and land reclamation from the sea. It works for some islanders who have the money to buy new properties and adopt a new way of life. They are working hard to bring new forms of tourism to the region through low-carbon transport. Some islanders could not wait and moved, with the support of the United Nations displacement mechanism.
These islanders send money back and remain citizens of their original island as well as their new country. They return for cultural festivals and see themselves as belonging to the island while making new connections elsewhere. They call the country a “networked nation” – linked to the sea and many new areas of land and opportunity like the spokes of a wheel.
These thought experiments raise vital questions that we, as individuals, as communities, and as voters, must consider. There are also choices for citizens of countries that could host migrants and for governments that consider their interests in the regional or international system.
There is no single answer and many choices have high short-term political costs, but we will have to face these difficult choices to find a way to live well in the face of climate change.
From Sink or swim: how the world must adapt to climate change by Susannah Fisher, on sale November 4 from Bloomsbury Publishing. Copyright © 2025 by Susannah Fisher. All rights reserved.
