As world leaders gathered Wednesday at the United Nations in New York to rally for more aggressive climate action, the heads of some of the most vulnerable nations met on the sidelines to highlight the daunting challenges they face as extreme weather forces millions of people to flee their homes. The problem is here already, they said, and it will only get worse unless governments slash emissions and prepare for what will effectively be a new world map.

Speaking at the Climate Mobility Summit, leaders from nations such as Guatemala and Somalia, which are seeing tremendous population shifts driven by climate change, projected a message that wealthy countries must work with developing ones to better manage a swelling flow of global migration. 

While the majority of the world’s migrants move within their own countries or regions, millions have also sought work and refuge in the United States and Europe in recent years, causing political upheaval and backlashes against immigration.

Amy Pope, director general-elect of the International Organization for Migration and a co-host of the summit, opened with a story about a recent trip to a refugee camp in Kenya, which she said had hosted more than 100,000 people who have fled Somalia, in large part because of a devastating drought there. Pope said she met people who had tried to return to Somalia, only to turn back after finding that the drought had made raising crops or livestock impossible. 

“At the global level, we are seeing slowly the recognition that climate change is displacing people at record levels,” Pope said.

There is wide agreement that climate change is becoming an increasingly important contributor to global migration. Climate disasters and extreme weather are now forcing more than 20 million people a year to leave their homes and relocate to other areas within their own countries, according to the U.N.United Nations High Commissioner for Refugees. Many researchers say that climate change has also worsened conditions in countries such as Syria and Honduras, where violence and repression have forced millions to flee across borders, increasing the flow of refugees and asylum seekers.

In the greater Horn of Africa region alone, tens of millions of people are expected to become climate migrants over the next few decades, potentially up to 10 percent of the area’s population, according to research by the Global Center for Climate Mobility, which organized the summit. The center is a partnership of U.N. member states with support from various international agencies, including the International Organization for Migration.

In some parts of the world, climate change will likely become the sole driver of migration. The archipelago of Tuvalu, for example, in the South Pacific, has an average elevation of just 2 meters and is already seeing the impacts of rising seas. 

“For Tuvalu, everything is at stake,” said Kausea Natano, prime minister of Tuvalu, a co-host of the summit. “Rising sea level endangers our homes and our way of life. It will undermine our territorial integrity and force us to defend our sovereignty.”

Talua Nivaga, a youth delegate from Tuvalu, added, “This for us is about our identity. Every inch of land that is flooded takes with it centuries of our heritage, of our traditions and our memories.”

Over the course of a breakfast session and several panels, many of the delegates stressed the need for governments to identify hotspots of climate mobility and prepare for migration flows by drafting newimplementing international agreements and government policies.

Colombia has seen decades of internal displacement driven by war, for example, and those migrantspeople had legal recognitions that allowed them to access government support, said Julia Miranda Londoño, a member of that country’s Congress. But there are no such recognitions for climate migrants in the country, she said.

María Susana Muhamad González, Colombia’s minister of environment and sustainable development, called on governments to develop international agreements to help manage the flows of climate migrants, rather than trying to force people to stay within their own borders.

She referred to the thousands of people who have been passing through Colombia to Panama daily this year, with many hoping to reach the United States, and said that route is currently controlled by criminal networks. Climate migrants will increasingly use this same route, Muhamad said, so governments have the choice to take control or allow gangs and organized crime to expand their influence.

“It is time to start understanding the science and start organizing the humanitarian agreements for a planned transition and migration,” Muhamad said.

While migration can strain local governments and communities, many of the speakers stressed that mobility can also be a tool for climate adaptation, and in some cases might be the only option. Swaths of low-lying coastal areas could become uninhabitable due to rising seas this century, while other areas may become unbearable due to extreme heat. But officials at the summit said that proper planning can help ensure that migrants can supply new pools of labor and economic growth in other regions that are struggling to adapt.

Saber Hossain Chowdhury, climate envoy for Bangladesh, described a program in his country that provides vocational training for new arrivals to cities so they can help strengthen the communities they are migrating to. Bangladesh is one of the most climate-vulnerable countries, with tens of millions of people living in low-lying areas that are at risk of inundation. It has already seen its population shift from rural to urban areas.

There are limits to this adaptation, however. Chowdhury said government research suggests the country can accommodate about 10 million migrants internally. After that, he said, people would have to leave the country. The World Bank projects that Bangladesh could see 13.3 million internally displaced climate migrants by mid-century. 

“This cannot be a permanent, sustainable solution,” Chowdhury said about mobility and migration. “If emissions continue to rise then it doesn’t matter what you do. Mobility simply will not work.”

Chowdury was followed by Esrom Immanuel, assistant minister of finance for Fiji, who said his country had identified 600 communities at risk from rising seas that will need to be relocated. Fiji is relatively better off than many other small island Pacific nations. Because of its relatively greater land area, Fiji will be able to absorb many migrants within its borders, he said.

But many smaller island nations will not, said Henry Puna, secretary general of the Pacific Islands Forum, an intergovernmental organization. For the people of those nations, he said, “we’re talking about something much more severe, much more permanent, and that is leaving your home, your ancestral home, to relocate somewhere else.”

Eventually, Puna said, these nations will struggle with how to maintain their sovereignty as their land disappears.

Puna’s message underscored a central theme of the leaders who attended the mobility summit. The day’s goal was to promote cooperation and new policies to better manage climate migration. But at best, those policies would work only if leading economies zero out their greenhouse gas emissions over the next few decades, a task well beyond the control of anyone in attendance.