A Return to the Eocene?

Global warming has been much in the news lately, as has debate over the extent of its anthropogenic nature. Worst-case scenarios envision a tipping point wherein a runaway accumulation of greenhouse gases triggers dramatic and irreversible temperature change. Huge concentrations of methane embedded in the tundra and elsewhere will be collaterally released, and these will dramatically accelerate the process. In a geological blink of an eye-a few generations or so-the ice caps will melt and global temperatures will not stabilize again until we will have reached those of the early Eocene epoch about 50 million years ago. How bad would that be, anyway? What was the Eocene like, and what would we go through to return there? As soldiers, what missions would we be likely to pick up en route?

Global temperatures averaged a dozen degrees or so warmer in the Eocene, but without permanent ice caps, the gradient across latitudes was nowhere near as pronounced as it is today. Thus, the tropics were not all that much hotter than now, but palm trees could be found as far north as Alaska. Dawn redwoods and swamp cypress trees prospered on Ellesmere Island, and rain forests in Antarctica. Moister air and a more homogenous climate enabled the spread of vast forests from pole to pole. Deserts were still present but less extensive. One presumes the reduced temperature gradients lessened the severity of storm systems that are dependent upon temperature differences, like hurricanes and tornadoes. Flowering plants came into their own in this lush era, multiplying in numbers of species and geographical extent across the biosphere.

Animal life was equally prolific. Herbivores ranging from massive Brontotheres to tiny Armintomys made themselves at home amid the luxuriant vegetation, occasionally fed upon by predators such as the Mesonyx, a flesh-eating ungulate. This is not to mention Titanoboa, a snake the size of a school bus. The oceans teemed with fish. Life flourished. A climate not unlike that of Virginia dominated where ice caps are today. What would be so bad about that?

What would be so bad about a return to the Eocene is not the relatively benign end state but rather the horrific hardships that would be endured while getting there. Sea levels would rise more than 200 feet. Florida, Denmark, the Po Valley, the Nile Delta and Bangladesh, along with many other places, would slip beneath the waves. Our own East Coast would retreat to the Fall Line, and China's to a line running from Taiyuan through Wuhan. More agreeable climates elsewhere would not immediately be accompanied by productive soils in regions that did not already have them. Rich, fertile soils built up through millennia of biological processes would disappear or turn brackish, taking with them the capacity that feeds half of the world's population today. Polar bears and Arctic wolves would become extinct outside of zoos, of course, and a major fraction of the biome would die offas each species struggled to accommodate radical changes in its habitat at an unprecedented pace.

There would be geostrategic winners and losers. Russia and Canada would be winners. Losing relatively little land that is particularly remunerative now, they would multiply their habitable areas several times over. They would also dominate the shores of a highly productive Arctic Ocean, with heavily trafficked sea lanes knitting the economies of the Northern Hemisphere together. Australia, New Zealand and Argentina might be winners as well, if they could make good their claims in Antarctica after it came out from under the ice. Egypt, Iraq, Paraguay, Bangladesh, Cambodia, Vietnam and Indonesia would number among the losers. They would be destroyed.

Brazil, China and the United States would come out somewhere in the middle. They could survive and perhaps prosper, but they would have to work hard and well to do so. An inland sea in the Amazon Basin might ultimately work in Brazil's favor. China's agricultural productivity could keep pace with land lost if the encroaching seas brought ever more moisture into central Asia. What the United States lost in its Southeast, it could perhaps make up in Alaska. Resources, social organization and political leadership would be severely taxed, but each of these nations could make it through. The European Community might make it through as well, if its members worked together and did not fragment along national lines. Perhaps the Danes could move to Greenland, inviting a great many Dutch, North Germans and Poles to go with them.

American soldiers would find themselves drawn into humanitarian relief on an unprecedented scale. Although the melting of the ice caps might take centuries, recurrent Hurricane Katrinas and Superstorm Sandys defined by ever higher sea levels would start immediately. A prolonged withdrawal from areas facing ultimate inundation would probably not be orderly. It can be hard to see the writing on the wall or to gauge how much time is leftbefore land is lost forever. A major fraction, although certainly not all, of the inhabitants of a severely flooded area would return to reoccupy and rebuild. If sea levels rose, they would be fighting a losing battle. Flood insurance would become impossible to obtain, government support for rebuilding on flood plains would dry up, and a smaller proportion of the population would return after each devastating event. Recurrent storm surges would clear land before it went permanently underwater. An incremental, generations-long retreat to several hundred feet above the present sea level could feature scores or even hundreds of Katrinas and Sandys. Our soldiers would be called upon to rescue and care for their stricken countrymen time and time again. The Chinese withdrawal would perhaps be more orderly, as they are already in the habit of relocating millions without debate and by decree.

Once the direction of climate change became clear, our country would face engineering tasks of unprecedented dimensions. Historically, only our U.S. Army Corps of Engineers has proven capable of managing projects of the scale and intricacy required. New ports would be built as old ports went under. Ports with a chance of reconfiguring and surviving-for example, New York and Boston-would be able to do so only after mammoth water-control projects. The hydrology of the entire country would change, and water management with it. Road systems would reroute, particularly those circuiting the Gulf of Louisiana-named after the state that would have disappeared underneath it. Soil would become a huge issue, with our nation and others seeking to infuse fertile soils into newly habitable locales at a pace faster than croplands were lost to the sea. Perhaps this would be as simple as dredging soil up in one place and depositing it in another. Perhaps it would involve the massive use of additives or mammoth investments in hydroponics. Much of our effort would be in cooperation with Canada as agricultural productivity migrated northward. The scale would necessarily be federal, and the agency of choice would be the Corps of Engineers.

As dramatic as potential instability in the United States might be as land was lost to the sea, it would be a pale reflection of instability overseas. Distressed populations would sweep away governments unable to meet the demands associated with the crisis, and pending doom would trigger wars of national survival. Two regions seem particularly vulnerable. Pakistan and Bangladesh would face national extinction unless they acquired sufficient land in nearby India or Burma. Nuclear weapons and centuries of ethnic enmity are already involved, so the situation could become explosive. Australia has faced recurrent threats, sometimes humanitarian and sometimes military, from Indonesia. This pressure would increase a dozenfold if sea levels rose appreciably. A score of other nations could present similar, albeit less historically entrenched, enmities. A safety valve could be some kind of multigenerational, United Nations-managed resettlement program. If Brazil, China, Europe and the United States took care of their own problems, this would still leave a billion people to relocate. The U.S. Army would inevitably become involved, either fighting wars in defense of its allies or assisting with the resettlement of millions.

No one knows if the Eocene is coming back, or when. Many believe we are moving in that direction, even if they don't particularly anticipate the end state. The Russians certainly are investing thought, energy and resources into their vision of a more temperate Arctic. Even if we moved only a tenth of the way to the Eocene, the results would be dramatic. One purpose served by the study of the past is to inform the present so that we can prepare for the future. It is not too early for our Army, particularly our Corps of Engineers, to give the long-term implications of global warming serious thought. The journey may take centuries, but the initial challenges will be encountered immediately-and will grow more formidable with time.

By BG John S. Brown

U.S. Army retired

BG John S. Brown, USA Ret., was chief of military history at the U.S. Army Center of Military History from December 1998 to October 2005. He commanded the 2nd Battalion, 66th Armor, in Iraq and Kuwait during the Gulf War and returned to Kuwait as commander of the 2nd Brigade, 1st Cavalry Division, in 1995. Author of Kevlar Legions: The Transformation of the U.S. Army, 1989-2005, he has a doctorate in history from Indiana University.