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next_migrationAs we will see, the entire world is facing problems due to the collision of skyrocketing population and consumption with falling global resources and increasing pollution costs. Many parts of the U.S. will suffer directly from climate change, but even the lucky places that see relatively little climate disruption will find their economic arrangements more and more affected by what is happening to everyone else. Thus, there are no really safe zones.
However, there are definitely less safe zones. My view of these is informed by three major sources: The U.S. Global Change Research Program’s (2018) Climate Report, John W. Day and Charles Hall’s (2016) analysis of regional economic dependencies and climate effects on water and sea level in America’s Most Sustainable Cities and Regions, and Julie Kurtz and colleagues’ (2020) present-day foodshed mapping, which analyzed how possible it was for America’s urban centers to be fed by the farmland of the surrounding region. These sources generally point in the same directions. While the latter two suggest that any large, densely populated urban areas are questionably sustainable, three regions are particularly problematic due to the severity of the problems they will face and the huge numbers of people involved. These are the Southwest, southern Florida, and the highly urbanized eastern coasts. Unfortunately, as reported by the U.S. Census Bureau (2021), all of these regions are continuing to grow in population. All of them are sure to see serious disruptions, but the Southwest is going to be first. In fact, it has passed its tipping point into crisis and the disasters are already beginning.
The entire southwestern quarter of the United States, from western Texas up to the southwestern corner of Oklahoma and west to the Pacific coast, including all or almost all of the Four Corners states, Nevada, and California, is expected to face severe disruptions. Continued warming in this region appears increasingly likely to result in a long-lasting “megadrought”, in which what we now think of as extreme drought conditions and heat waves become commonplace. The last time this region faced a centuries-long hot and dry period, in the precolonial era, it resulted in starvation, warfare, and the outright collapse of a culture that was far more modest in size and consumption habits than ours. Connie Woodhouse and colleagues, experts on historical climate, reported in 2010 that the worst period of 12th-century drought “far exceeded the severity, duration, and extent” of any drought seen in the post-colonial era, although the high temperatures at the peak of that drought were not as high as those already created by climate change.
We have already been seeing inexorable increases in droughts and heat waves. As of August 24, 2021, the U.S. Drought Monitor reported that almost 95% of the Western region (including Montana and New Mexico, but not Wyoming or Colorado), with a human population over 60 million, was experiencing some level of drought, with 60.68% in “extreme or exceptional” drought. A few years ago we were being told that droughts in the area were the worst in centuries; the 2021 drought was worse than those. Although heavy rains the following winter improved matters somewhat, so that the numbers now look much better with only 74.4% in drought, this relatively wet year is unlikely to represent a lasting change in the overall trend towards greater drought.
Fossil fuels gave us the necessary resources to build, water, and power cities in desert or near-desert regions that are far larger than the Ancestral Pueblo could have imagined. The Los Angeles megalopolis is the biggest of these, but other major cities including Phoenix and Las Vegas are also threatened. Water supplies for these cities and for other uses, such as irrigated agriculture and manufacturing, can be predicted to decline as climate change progresses. The two major reservoirs created by damming of the Colorado River, Lake Powell and Lake Mead, are running dry. The former is created by Glen Canyon Dam; the latter, farther downstream and at lower elevation, is created by the Hoover Dam. Both had water levels at historic lows in 2021, with Lake Mead almost two-thirds empty and Lake Powell three-quarters empty, the lowest it had ever been since it was filled.
The Guardian reported that in July 2021, Lake Powell had a record low water level of 3554 feet, at which level it was three-quarters empty. This was ruinous for the local economy, with tourism businesses, such as houseboat rentals, being left literally high and dry. (The water level when full is 3700 feet; the level of the surface of the water in these reservoirs is measured as elevation above sea level, not elevation above the bottom of the reservoir.) On March 16, 2022, the level had dropped below 3525 feet. For the first time, a water shortage on the Colorado River was declared, which meant cuts to the water Arizona, Nevada, and Mexico would receive in 2022. The Lake Powell Water Database reports that as of July 11, 2022 the water level had rebounded to 3539 feet. Nevertheless, it reported at the same time that at that point, approaching the last two months the 2022 “water year,” total outflows had exceeded total inflows by over 750,000 acre-feet, even though the wet year had meant that inflows were 50% greater than in 2021. In other words, even in a good year, consumption exceeds replenishment.
As for the even larger Lake Mead, an online graph tracking Lake Mead levels, created by Paul Lutus based on monthly U.S. government data, shows that the level declined sharply from over 1210 feet in 2000 to little over 1080 feet in 2011. During the next few years, the level rebounded slightly but then retreated to a bumpy plateau around 1080 for several years and in 2021 declined below 1070 feet, triggering a declaration of shortage. It has now dropped below 1050 feet, shortage condition II, like Powell approaching three-quarters empty. Continuing or, worse, escalating drought could allow further rapid declines in future, unless water supplies were cut severely to maintain lake levels. Moreover, if Lake Powell were to drop too low, to the so-called “deadpool” level, it could become impossible to release water through Glen Canyon Dam to replenish Lake Mead.
So far urbanites and farmers in California, which has senior water rights, have largely been asked nicely to conserve (and they’re not doing a very good job of that!), while a few who are directly affected by the physical reality of the situation, like Lake Powell houseboat owners, get hit hard. The drying up of these huge lakes has been devastating tourism-based businesses, with boats unable to enter and leave the lake using boat ramps that no longer reach the water. But the far bigger concern is the tens of millions of people who depend upon these critically important reservoirs for farming, industry, or drinking water.
Reporting by The Guardian in 2021 laid out the next steps for Lake Mead: The water level, which would be about 1221 feet above sea level when completely full, triggered tier 1 water restrictions, which hit primarily Arizona farmers, when it dropped below 1075 feet. Tier 2 restrictions would be imposed after the level drops below 1050 feet, and were expected by 2023, unless 2022 were an unusually wet year. You can see from this that the disaster is outrunning the predictions: 2022 has been a good year for precipitation, and yet, Mead is already below 1050 feet. Tier 2 restrictions will hit farmers in states with junior water rights much harder. (If you live in one of those states but aren’t worried because you aren’t a farmer and can afford imported food, you may have noticed that when farmers fail economically, especially when it can be blamed on “the government,” support for political extremism increases.) At 1025 feet, tier 3 restrictions would reduce supplies to cities and Native American reservations.
Lake Mead’s original intakes are at 1000 feet, meaning that when the lake dropped below that level they could not supply water. A third intake was tunneled into the center of the lake at 860 feet to supply Las Vegas with drinking water so long as any water at all was left; that represents the last-drop level. Since the bottom of a reservoir (formerly a river canyon) is narrower than the top, a layer ten feet deep of water at the top contains much more water than the ten feet nearest the bottom. Therefore, the amount of water that must be consumed to reduce the reservoir from 1050 to 1025 feet is less than the amount consumed to reduce it from 1075 to 1050. The more the level drops, the faster it could drop in future—unless consumption is forcibly restrained.
A continuing future of less precipitation in the Southwest, hotter temperatures, and less snowpack will mean less water entering the reservoirs. If a historic period of drought is in the near-term future, Lakes Mead and Powell and the region’s smaller reservoirs will never be replenished fully nor for long. Instead, even if an occasional wet year raises the water level, they will continue usually to decline in volume. Great political pressure will be placed on their managers to maintain water allocations to both populous cities and the politically powerful and economically important farming sector, but there simply will not be enough water to meet everyone’s needs.
Communities that are not fed by those reservoirs or other freshwater sources often depend upon other sources that will become less reliable in drought. Groundwater in some areas is already becoming less reliable, because it too is replenished by rainfall and snowmelt that are lacking in droughts. For example, the tourism-dependent town of Mendocino, California has already been forced to purchase water delivered by truck, as its wells ran dry.
Most of the West is too dry, without irrigation, for agriculture other than livestock grazing. Bridget Scanlon and colleagues (2012) analyzed the sustainability of irrigation in key western regions. While irrigation with freshwater from surface sources is threatened by drought, 60% of American irrigation comes from groundwater sources. Much of the Great Plains draws water from the huge Ogallala Aquifer, which in its southern portion is “fossil water” that is no longer substantially replenished through rainfall. California’s bountifully productive but naturally dry Central Valley is also underlaid by a large aquifer that provides pumped water. Scanlon et al. concluded that there were centuries’ worth of water left in both aquifers considered as a whole, but that depletion was patchy, both regionally and more locally. Some localities could start running out of groundwater within the next few decades. Meanwhile, two large aquifers in California proper, Lakes Shasta and Oroville, are also seeing their levels plummeting. Both of these have been an important water supply for California farmers, and both are being forced to slash their outputs.
The wildfire season in the West is already longer and more severe than in the past, with the destruction of whole towns despite heroic firefighting efforts increasingly common: in 2021, Lytton, British Columbia, and Greenville, California were lost. During the last megadrought, much more of the Southwest was desertified. Conversion of a forested area to a desert or semidesert will probably involve the burning of most of the forest, sooner or later. Drier foliage in hotter weather burns more easily. If the trees avoid fire long enough to die of drought, they become standing dry fuel easily ignited by lightning. The fact that traditional Native American forest management practices, which resulted in forests that could better survive fires, were suppressed long ago doesn’t help.
With hotter and drier or dying forests, forest fires may continue to worsen until most of the forest is gone in large parts of both the Southwest and Northwest. The affected states certainly will try to control fires, but already the longer fire season and larger fires are putting a strain on firefighters and firefighting resources. It is all too easy to imagine a scenario in which there might be more fires threatening populated areas than can be fought at once.
Long-term severe drought will have other consequences. Increases in extreme summer heat, as well as particulate air pollution from fires, will worsen health, cause deaths, and shorten life expectancy. If the two great Colorado River reservoirs drop too low, their dams will be unable to generate hydropower; however, they supply a small fraction of the region’s electricity so it is not clear how disruptive its loss would really be. Economically, much employment in the Southwest depends on non-essential economic sectors (e.g., tourism, gambling, and entertainment), which are vulnerable to economic decline occurring regionally, nationally, and/or globally. A California farmer who has lost his almond trees because he couldn’t get water for them will not be vacationing in Vegas that year.
Day and Hall (2016), in their book analyzing the relative sustainability of various regions of the U.S., considered the entire Southwest, including the large areas that are rural and sparsely populated, to be at extreme risk for climate disruption. Their grim conclusion was: “The current human population of the Southwest is probably just too large ... and systemic failure in the region seems likely.” If you live in that region, you should memorize that sentence and contemplate it daily for a few weeks—assuming that systemic failure is not already in progress by the time you read these words, a possibility that seems increasingly likely.
