Duluth, the New Jerusalem

This warming has contributed to falling crop yields, which have in turn driven mass migration around the world. Those no longer able to scratch out a living in the drought-ravaged Sahel wind up fleeing across, and often drowning in, the Mediterranean on their way to Europe, while those from Central American communities no longer able to feed their families wind up on the U.S. southern border.

As always, where you stand depends upon where you sit. This reviewer, for example, sits in Portland Oregon, which on June 28, 2021, saw a temperature of 116^o, fully nine degrees hotter than the previous record, killing an estimated 70 local residents. The year before, wildfires spiked the city’s atmospheric particulate levels (PM_2.5) to an unheard-of 500 μg/m3, preventing all but the foolhardy from venturing outside.

ProPublica reporter Abrahm Lustgarten sits not far away from me in Northern California, where his formerly idyllic outdoor lifestyle evolved over the past few decades into a nightmare of choking smoky skies and near-constant fire warnings, often forcing his evacuation. A few years back, his friend Ellen Herdell wrote him a panicked email that described raising a family against a background of chronic existential insecurity. In October 2017, the Tubbs fire destroyed 5,500 homes and killed 22 people. As it burned, she and her husband listened to the police scanner and the popping of propane tanks; the blaze stopped just near their house. Herdell’s nine-year old daughter sobbed uncontrollably with each new fire warning. The family contemplated the difficult decision of whether to move, and Herdell wistfully emailed Lustgarten, “It didn’t used to be like this.”

Lustgarten’s conversations with Herdell inspired him to write On the Move: The Overheating Earth and the Uprooting of America, a cold-blooded examination of the world’s climate-induced migrations from the five horsemen of climate change – heat, falling crop yields, fire, storm-related flood, and sea-level rise – and attempts to forecast how these migrations will evolve in the coming decades.

The book features ground-level reporting from climate change hot spots such as the disappearing coastline of the Mississippi delta and the drought-stricken highlands of Guatemala. It combines these narratives with econometric analysis by leading academics like Tulane’s Jesse Keenan, Stanford’s Marshall Burke, and Princeton’s Michael Oppenheimer, who was in turn inspired to examine climate-induced migration by the late, fabled Alan Kreuger.

Lustgarten freely admits that accurately forecasting migration patterns, let alone their social, political, and economic effect, faces a computational impasse. That said, he is confident about two basic conclusions.

The first prediction is that rising temperatures will soon render increasing parts of the world uninhabitable, a conclusion that’s inescapable from projections of local “wet-bulb temperatures.”

This parameter is measured by passing a cooling breeze over a muslin-soaked thermometer bulb: a value above 35^oC (95^oF) prevents humans from cooling themselves through skin evaporation and is thus incompatible with life. Although lethal wet-bulb temperatures currently occur on only one percent of the earth’s land surface, by 2070 they are likely to afflict nearly all of the Sahel, India, and SE Asia, which together are home to more than a quarter of the world’s population.

Immigration is a major source of developed-nation political discord, but you ain’t seen nothing yet: One economic model suggests that each 0.1^oC rise in mean global temperature results in 140 million additional migrants.

When an unprecedented wildfire destroyed the northern California city of Paradise in 2018 and killed 85 people, nearby Chico received the largest share of the displaced. Although Chico’s citizens initially supplemented the FEMA tents and portable showers with spare rooms and baked goods, as the weeks turned to months and the city choked with traffic, increased crime, and an overloaded sewage system, the welcome wore out. Writ large, the same thing happened with the initially generous German responses to Syrian refugees and Texan generosity to Central Americans.

The book’s coverage of emigration from Central America will make border-security hawks squirm. Lustgarten exquisitely documents how rural inhabitants are forced towards the U.S. in stepwise fashion. People do not on their own free will all at once decide to up sticks, leave their farms, and head directly for the U.S. Rather, their first move, after the land can no longer support them, is to a neighboring town, and after that becomes non-viable, to a nearby major city. Only when those overcrowded cities become too economically depressed and dangerous do they head for the U.S. southern border. This stepwise sequence is a hopeful sign, since it means that it’s likely cheaper and more effective to aim economic assistance to Central American nations than to pay for expensive, aggressive, and often inhumane border security.

Lustgarten’s second major point pertains specifically to the U.S. The nation precisely straddles the north-south climatic sweet spot, but in the coming decades that optimal climate zone will gradually shift north towards Canada. In other words, short Arizona, Texas, Florida, and the Gulf Coast, and go long Duluth and Maine. (Fun fact: The Great Lakes hold 20% of the planet’s increasingly scarce commodity necessary for human life: fresh water.)

The U.S. population will not only shift north, but as drought-stricken rural communities empty out, it will be drawn to large urban areas; Lustgarten forecasts that Atlanta, despite its subtropical temperatures, will likely see millions of climate refugees.

Thus far this process, mediated mainly by fire in the west, flooding in the Midwest, and sea level rise in Florida and the Gulf Coast, has been largely blunted by government insurance subsidies and mandates. When Florida Governor Ronald DeSantis attempted in 2022 to indulge his small-government libertarian instincts by trimming back flood insurance supports, he was forced to back down by a tsunami of opposition from folks who presumably shared his politics, just not when those politics affected their wallets. (The same had happened to a previous Florida governor, Democrat Charlie Christ, in 2006. Even Friedrich von Hayek advocated for government flood and earthquake insurance in Chapter 9 of The Road to Serfdom.)

Within a decade or two, federal, state, and local budgets will not be able to afford subsidies against fire in California, hurricanes in Florida and Louisiana, and 50-inch downpours in Houston; houses lost to these calamities will not get rebuilt, buyers unable to insure their homes will not purchase them, and developers will not build them. (As a stopgap measure, state and local governments have found that buying out the owners of homes threatened by floods and rising sea levels is cheaper than repeatedly paying to rebuild them.)

The book bursts with vignettes and incisive analysis that will surprise even the best-informed reader, and it contains more than a few gems for the financial professional. For example, Lustgarten highlights the research of Keenan, who coined the term “underwaterwriting” to describe the reluctance of insurance companies to provide coverage to the uninsurable. He observes that even more important than the behavior of insurance companies is that of banks: In recent years, they’ve begun to quickly unload their mortgages to large financial institutions for securitization, a sign that their on-the-ground knowledge of their local markets forecasts trouble ahead. In Keenan’s words, “in a game of musical chairs, it is likely the market that will start and stop the music sooner than people might realize.”

Most impartial readers will find Lustgarten’s treatment of climate change-induced migration convincing, though at times his Democrat-leaning sympathies get in the way, as for example when he discusses the disproportionate burden borne by the poor and minorities. Presumably his readers will be familiar with the economic damage inflicted upon today’s African Americans by slavery, Jim Crow laws, and redlining, but his several-page history of these events constituted overkill. And while he is careful to describe the uncertainty of the book’s socio-economic and demographic projections, at times he lets down his guard to project more certainty than warranted. He discusses at some length Marshal Burke’s GDP estimates for the year 2100, which forecast per capita GDP declines in the 50% range for all of Africa and India, much of SE Asia, and most of South America. While published in Nature, one of the world’s most prestigious and aggressively peer-reviewed journals, Lustgarten neglected to sprinkle that 75-year forecast with the requisite bucket of salt.

That said, this book’s evenhanded and compelling description of the coming world of climate-driven mass migration should be read by both climate believers and skeptics – before it’s too late.

William J. Bernstein is a neurologist, co-founder of Efficient Frontier Advisors, an investment management firm, and has written several titles on finance and economic history. He has contributed to the peer-reviewed finance literature and has written for several national publications, including Money Magazine and The Wall Street Journal. He has produced several finance titles, and four volumes of history, The Birth of Plenty, A Splendid Exchange, Masters of the Word, and The Delusions of Crowds about, respectively, the economic growth inflection of the early 19th century, the history of world trade, the effects of access to technology on human relations and politics, and financial and religious mass manias. He was also the 2017 winner of the James R. Vertin Award from the CFA Institute.

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