As people flee intense heat in Arizona for gentler climes, rental and property values soar. But what about those left behind?

Only half-jokingly, some residents of a progressive city 300 miles north of the Mexican border have adopted the “build the wall” slogan in the face of a wave of newcomers. But these perceived interlopers are starkly different from Donald Trump’s imagination.

They are American, mainly white and are fleeing the unlivable heat.

Arizona’s vast sweep of landscapes stretches from the scorched western movie backdrop of the Sonoran desert in the south, past rusty red sandstone outcrops further north in Sedona until you ascend to Flagstaff, a pleasant city carved into the largest expanse of ponderosa pine trees in the world, at an elevation of 7,000ft.

Flagstaff, population 70,000, has long been a destination for people in southern Arizona looking for a cooling respite in summer or a spot of skiing on the nearby San Francisco Peaks in winter.

But rising temperatures, driven by human-induced climate change, mean that many in Flagstaff fret they are now being overrun by those fleeing sweltering cities such as Phoenix and Tucson. A pattern of climate-driven gentrification is taking hold across the US, as those who are able to retreat from floods, storms, heatwaves and wildfires shift to safer areas, bringing soaring property and rental values with them.

“As it gets hotter, we are getting a lot of climate refugees,” said Coral Evans, Flagstaff’s mayor. “We don’t mind people moving to Flagstaff at all. But about 25% of our housing is now second homes. The cost of living is our number one issue.

“We don’t talk much about what climate change means for social justice. But where are low-income people going to live? How can they afford to stay in this city?”

There are usually a tangle of reasons – jobs, love, education – as to why people decide to move, but Flagstaff’s agreeable climate is jostling towards the front. Last summer, Phoenix was so hot that road signs and mailboxes melted. Planes couldn’t take off or land. On a recent July day this year, when Phoenix hit 116F (47C), Flagstaff, a two-hour drive and a world away, was 80F (27C).

Facebook Twitter Pinterest Phoenix, Arizona, with its downtown lit by the last rays of sun at dusk. Photograph: Dreamframer/Getty Images/iStockphoto

Amanda Ormond moved to Phoenix in 1985, first working in bars after leaving college before becoming a clean energy consultant.

Ormond recalls stuffing her children into thick coats when trawling houses for trick or treating at Halloween. By the time the family moved permanently to Flagstaff three years ago, wearing anything warmer than shorts and T-shirts at that time of year was unthinkable. It will get worse – Phoenix, the fastest-warming large city in the US, could spend close to half of its year in over 100F (37C) heat within 30 years.

“If you choose to live in the desert you have to learn how to live in the desert,” Ormond said. “You worry about your car breaking down and so you have tons of food and water in it.

“But the heat used to break around September. Now, it’s October, sometimes November. We literally have six months of above 90F (32C). Mentally, you need a break. You can’t leave your house. It’s fatiguing.”

Ormond still owns her house in Tempe, which adjoins Phoenix. “We had this home and when I look around I think, ‘I just can’t see how this is gonna be a good investment for 20 years with climate change.’”

Phoenicians able to move, or even vacation, in cooler climes such as Flagstaff are usually older and wealthier. Those who still work can often do so remotely. The influx has aroused concerns in Flagstaff, where rents and property values have soared.

“The tenor in the town is ‘Stop building. Build a wall,’” said Jenny Niemann, a climate and energy specialist at the city of Flagstaff. “People joke about that. But I think it’s fair to say the town feels incredibly stressed by the increasing prices, as well as the development.”

While the western US is increasingly baked by heatwaves and choked by smoke from wildfires, the pressing concern in eastern states is that their coasts are being redrawn by sea level rise and pummeled by ever-stronger hurricanes. More than 300,000 homes near US coasts face being chronically flooded within 30 years.

This unfolding scenario is reshaping previous lines of segregation in coastal cities. As investors shift capital to higher ground and shoreline properties become costlier in terms of insurance and repairs, low- to middle-income people are squeezed out from both areas.

A recent study of the greater Miami area shows this process is already under way – properties at high elevations are experiencing rising values, while those situated just 3ft above sea level have declined in value, even when other factors are accounted for. This trend has largely taken hold since 2000.

“It’s a pretty clear signal and there’s evidence it’s happening across the US,” said Jesse Keenan, a climate adaptation expert at Harvard who authored the Miami report. “The very wealthy can afford to throw money away but moderate- to low-income people can’t, so there’s an inequality to living immediately on the coast.”

According to Keenan, climate gentrification is not just a supply problem – real estate developers actively marketing elevated areas as safe investments – but also a demand one – buyers are starting to swarm to higher ground.

“This is happening neighborhood to neighborhood, city to city, state to state,” he said. “It’s such a huge spectrum of geography that we are going to have make moral judgments about what to protect and what to let go. There’s not enough money to protect everyone. We need a complete mobilization, similar to the effort of putting a man on the moon, to adapt our coasts.”

Facebook Twitter Pinterest Residents of Little Haiti, Miami. Photograph: Alamy Stock Photo

Residents of the Miami districts of Liberty City and Little Haiti, traditionally African American and Hispanic areas, are seeing their neighborhoods transform around them. The districts, which sit a relatively safe 15ft above sea level, are currently having holes punched into them by bulldozers to make way for half a dozen apartment developments.

“We are already seeing low-income homes and businesses being evicted, the new developments are popping up everywhere,” said Valencia Gunder, a Liberty City resident turned activist who grew up hearing warnings about gentrification that are now being realized.

Previously blighted by poverty and crime, Liberty City is now seen as an attractive base for those worried their beachfront properties will soon be swamped. In 2000, no one in Liberty City paid more than $1,000 a month in rent – now it’s roughly one in six. Property prices have also risen sharply.

“People are being forced out to places like Georgia and Alabama, where it’s more affordable,” said Gunder. “It’s becoming so expensive. These developers aren’t making Liberty City better for the people who already live here.”

Even cities with cerebral approaches to climate change are at risk of upheavals that cut deepest in poorer, minority communities. Norfolk, Virginia, has reacted to some of the fastest sea level rises in the world with an ambitious plan that cedes some territory to the tides, while breaking up some housing projects and relocating residents. Local activists worry this will mean low-income, black communities will be displaced as their coastal neighborhoods are gentrified.

“This is a red alarm issue,” said Mustafa Ali, who spent 25 years at the Environmental Protection Agency’s office of environmental justice. “We need to make better decisions around resilience and vulnerable communities need to be brought into that conversation. A whole lot of folks are being left behind.”

In Flagstaff, the city is already straining to keep up. “Town gets crazy on the weekends when it’s 115F [46F] in Phoenix,” said Nicole Antonopoulos, Flagstaff’s head of sustainability. “Are we building our systems in a manner that can support a massive influx? No. Can our existing infrastructure support that? No.”

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Flagstaff also faces its own climate change threats – increased wildfires in the surrounding Coconino national forest, the associated risk of flooding rains washing freely down treeless slopes on to the city, pressure on the water supply. Growing numbers of homeless people are traveling to Flagstaff to camp in the woods, heightening local fears over unintended conflagration.

Antonopoulos, who has helped develop a draft climate plan for Flagstaff to confront this new reality, recalls the sky turning black from ash after the nearby Schultz fire, in 2010. “I was walking to work with a bandanna on and literally chunks of burning trees were falling everywhere,” she said. “When we’ve got climate refugees it’s going to put more stress not only on our infrastructure but also our natural resources.”

The hand of climate change is everywhere – from water availability to insurance markets to housing pricing – while rarely being identified as a culprit. As temperatures continue to escalate, prior inequities are likely to be exacerbated, injustices risk deepening.

“Whether it’s happening already is unclear but I think more and more people are going to be moving because of climate change,” said Brian Petersen, a climate change and planning academic at Northern Arizona University.

“The people marginalized already in society will bear the brunt of this. Poor people in Las Vegas or Phoenix who can’t get away from the heat are not going to be leaving to go to beautiful, expensive mountain towns.”

Even those who do make it to Flagstaff and other refuges, such as Oregon or near the Great Lakes, won’t be shielded from the transforming climate. Enough future warming has been locked into the world’s climate system to touch everywhere on Earth.

“At some point, Flagstaff’s going to be in the rear-view mirror,” said Petersen. “We’re going to be going to farther north places or other continents.”