Rising Sea Levels and the Future of Human Chain Migration
March 07, 2016
By Amy Seidl
Scientists have confirmed that sea levels are likely rising at a faster rate than at any point in twenty-eight centuries because of greenhouse gas emissions from human activity. In the coming decades, American coastal cities will be at risk of continual tidal flooding. If emissions keep up, many coastal cities could be abandoned by the twenty-second century. What does this mean for human migration when land grows scarce? In this excerpt from Finding Higher Ground: Adaptation in the Age of Warming, ecologist Amy Seidl takes a look at the impacts of rising sea levels on human populations in the last century to project the future of our increasingly complicated migration patterns.
Sixty percent of the world’s population lives along a coast. The people in Bangladesh’s deltas, on Florida’s developed coastlines, and on islands everywhere are at tremendous risk as sea levels rise. For instance, the Intergovernmental Panel on Climate Change predicts up to half a meter (18-59 cm) average sea-level rise by 2095, but others have found these projections conservative. The revised models that account for more rapid input from glaciers in Greenland and Antarctica blow away the IPCC estimates and calculate up to a two-meter rise. To put these figures in a relevant context, when Hurricane Gustav hit New Orleans in 2008, the accompanying storm surge came within one-third of a meter of the top of the levees. By the end of the century it is very possible that similarly strong storms hitting the Gulf of Louisiana would crest the levees, given the one to two meter higher seas.
Rising and falling water has historically been a catalyst for human migration. For eastern Europeans living near the Caspian Sea, fluctuating water has dictated their ability to use alternating wet and dry lands; people migrate when the waters inundate them and return when the water levels fall. Beginning in the 1930s, water in the Caspian Sea, the largest inland body of water in the world, fell by three meters. This created large new areas of coastal lands, especially in Russia’s rich Volga delta.
“The change of the Volga River discharge depends principally on precipitation in the catchment area, which is controlled by climate change,” writes C. X. Li, a researcher who has studied the hydrology and dynamics of the Caspian Sea. During hot, dry periods in Europe and Asia, there is increased evaporation, and water flowing into the sea from the Volga River decreases. Alternately, increased water runoff and decreased evaporation makes waters rise, but can also bring on catastrophic flooding. When waters began to rise in 1978, including a thirty-meter rise in a single year, twenty thousand square kilometers were inundated. Villages along the Caspian were drowned, and mosques, churches, bazaars, and Soviet-era apartment buildings were buried at sea.
And the people living there? Thousands resettled inland. Others migrated to America and Europe. “Migration tends to perpetuate itself, what is known as ‘chain migration.’ The first migrants serve as bridges between the original populations and their eventual destination,” write the anthropologists Sabine Perch-Nielsen, Michèle Bättig, and Dieter Imboden. Families follow families, neighbors follow neighbors. In the Age of Warming, whole populations will migrate, seeking asylum from the rising tide, river, or, ironically enough, lack of fresh water.
Demographers predict that people will move inland or within their home countries first. Then, as land grows scarce and as populations become too dense, people will look to permanently resettle elsewhere, distant from their homelands. Cities like Burlington, Vermont, have already agreed to take them in.
Once upon a time on Earth, human migrations networked the planet the way songbird populations do today. Settlements varied with the seasons and what could be planted. People traveled in small bands in search of what they needed, and moved on again when the harvest ended or another harvest began somewhere else. Then, as agriculture took hold, fewer migrations took place. People settled, crops grew, and children were weaned on cultivated grains, allowing their mothers to have more children spaced more closely together.
Now, migration numbers are on the rise. People are searching for landscapes where resources are abundant, or at the very least, where land is available. There is a momentum behind these migrations but is more complicated than in the past. Now there are political boundaries, quotas, and immigration offices to contend with. And yet the push is building, as more people are moving out of coastal zones, upslope, and away from floodplains. One estimate is that one hundred million people will be affected by sea-level rise of a single meter, a scenario we are likely to reach by midcentury. Like organisms everywhere, human migrants are looking for space, an unoccupied niche, a place where there is still room.
About the Author
Amy Seidl is an ecologist and teaches at the University of Vermont. She is the author of Early Spring: An Ecologist and Her Children Wake to a Warming World and Finding Higher Ground: Adaptation in the Age of Warming.