Climate change is already contributing to an increase in migration around the world, a report released Wednesday shows, as events ranging from rising seas to droughts make parts of places like coastal Bangladesh and Pacific Island nations uninhabitable.

There is no widespread consensus on how many climate refugees will be created in the coming decades. The United Nations estimates 200 million by 2050, while other estimates run as high as 1 billion.

Last year natural disasters — 90 percent of them related to weather events — forced 20 million people to leave their homes, according to data from the Geneva-based Internal Displacement Monitoring Center, a nonprofit organization that tracks migration.

Millions from that total were internally displaced within Bangladesh, which is already densely populated and stands to lose much of its coastal land to rising sea levels. Farmland and freshwater supplies in the South Asian country have already been threatened increasingly in recent years by saltwater intrusion.

In the South Pacific, residents of the Marshall Islands — an atoll nation plagued by floods, rising seas and drought — have already begun to emigrate to the United States. About 10,000 of the country’s 70,000 people now live in Springdale, Arkansas, with many citing climate change as the reason for leaving their homeland.

Marshallese remaining in the islands have reported damage to their homes and land from increasingly severe flooding, and some entire atolls have become uninhabitable because of saltwater tainting agricultural land and precious freshwater supplies.

The Marshallese aren’t the only Pacific islanders abandoning their homes because of climate change, according to the U.N. report on climate migration released Wednesday.

Most households in the island nations of Kiribati, Nauru and Tuvalu said rising sea levels, saltwater intrusion, cyclones and droughts have already prompted them to seek new places to live in their home countries or abroad, according to another new report by the Bonn, Germany-based U.N. University Institute for Environment and Human Safety (UNU-EHS) and the Bangkok, Thailand-based U.N. Economic and Social Commission for Asia and the Pacific (UNESCAP).

Some 23 percent of migrants in Kiribati and 8 percent in Tuvalu cited climate change as their reason for moving, said the institute’s report, titled, “Climate Change and Migration in the Pacific.”

“The results from this unprecedented survey show us empirically what we already know. Pacific islanders are facing the brunt of climate change impacts and are increasingly finding themselves with few options," Tuvalu’s Prime Minister Enele Sosene Sopoaga, said in a news release.

Many more in Kiribati, Nauru and Tuvalu have been internally displaced by the effects of global warming, the report said, adding that migration is not a workable solution to the problem because many who move end up in already overpopulated cities with high unemployment — and eventual vulnerability to climate change.

About 10,000 people in the three nations tried to emigrate between 2005 and 2015 but were unable to do so, mostly for financial reasons, the report said.

That’s why leaders from some small island states are calling for developed nations — deemed most responsible for climate change — to donate to funds including the U.N.’s Green Climate Fund, which helps developing countries adapt to the adverse effects.

The U.S. has promised $3 billion to the Green Climate Fund, but that contribution is subject to Congressional approval. President Barack Obama met with leaders from small island states on Tuesday in Paris, where world leaders are gathering and are expected to sign a global climate treaty meant to avert the worst effects of global warming.

One of the sticking points in the Paris negotiations, called COP21, is how much responsibility the world’s wealthy countries owe to developing nations dealing with climate change.

Obama on Tuesday called for global financing for countries that have polluted far less than others and thus contributed little to climate change, but are “among the most vulnerable” to its effects.

“In Paris, we call on world leaders to address climate change and human mobility in the new climate agreement,” Koko Warner, senior expert at UNU-EHS, said Wednesday in the news release. “This issue is not only a Pacific issue; it is a global issue. All countries will be affected by people on the move in relation to climate change, whether they are origin, transit or destination countries.”

With wire services