Part 4 of Earth as an Ecosystem
Looming climate-change-related water problems on land often play second fiddle to our most significant concern about water—rising sea levels. Under most current, realistic scenarios, the world’s two major ice sheets are engaged in a slow melt into oblivion. The Antarctic and Greenland ice caps are feeling the heat. It is true, a full meltdown is potentially hundreds of years out, but even in the early stages, the impact on coastal cities will be significant.
The threat of sea-level rise is disproportionately large for humans because of the way we have sought to settle near the oceans. About a third of the world’s population lives within 100 meters of sea level. Our return to an ice-free planet will submerge the first 66 meters of coastal land. In the USA alone, Houston, Miami, New Orleans, Charleston, New York, Boston, and Washington DC will all disappear beneath the waves.
Much of New Orleans already lies below mean sea level and is susceptible to small rises in the ocean. Other cities like Miami, perched at sea level, are already feeling the pinch from increased tidal and storm flooding. But the cities at highest risk are in Asia, not the Americas. With a 4 degree C global temperature rise, up to three-quarters-of-a-billion Asians will be living below sea level. In Shanghai, China alone, over 22 million people will be displaced by encroaching seas.
We have chosen to locate many of our major cities by the sea. These decisions have their roots in trade economics and a traditional reliance on shipping to build wealth and power. Despite the good reasons for locating near the sea, the threat remains. Our habitats have become fixed, and our ability to migrate to happier hunting grounds, as our ancestors did, is limited. When all land is occupied or owned, where do you migrate to? The only viable answer is to either new or existing cities above sea level. Coastal farmers will fare no better. It is not easy to take a 500-acre farming business and quickly relocate somewhere else.
Shelter becomes a priority as climate changes force mass migrations. These changes needn’t be just rising seas. As access to freshwater changes, the fortunes of populated areas will wax and wane. The Colorado River flows 1,450 miles from its headwaters in the Rocky Mountains to the Gulf of California, and it provides water for some 40 million people. Also, it provides irrigation for 5.5 million acres, and 4,200 megawatts of hydroelectric power generation capacity. But the demands on this river now exceed its annual flow capacity.
The 20th-century annual average river discharge was about 16.5 million acre-feet (MAF), but long-term drought conditions in the 21st century have reduced annual input, leading to lower river flows. However, demand for the Colorado river’s water is increasing and started seriously exceeding supply at the beginning of the 21st century. In 2009, for example, the yearly water recharge supplied through precipitation was about 12 MAF, and demand was just under 15 MAF.
Major cities like Phoenix, Tucson, Las Vegas, and Los Angeles depend on water from the Colorado River. The bottom line is, future aspirations for water use look unrealistic under current plans, because of their projected water demand of between 18 and 20 MAF per year, against a projected annual supply of 16 MAF. Water insecurity will curtail population growth at a minimum, but if conditions are severe enough, people may need to migrate to other locations. Such migrations are trying for those with wealth and devastating for those living on the financial edge.
Large human populations have become fixed in areas where climate change may affect their ability to survive. Complex relationships exist between ecosystems, food, water, and our habitats. We are right to be concerned about a future where these relationships change as the climate changes, forcing human migrations and the development of new agricultural strategies. But we shouldn’t fear climate change. Instead, we should concentrate our energy on devising solutions.
What we should fear is inaction and procrastination on the part of governments, both local and federal. A strategy to maintain the status quo is a road to failure. Climate change is not an existential threat unless we collectively decide to let it be.
Mapping Choices: Carbon, Climate, and Rising Seas, Our Global Legacy (By Benjamin Strauss, Scott Kulp, and Anders Levermann) – https://sealevel.climatecentral.org/uploads/research/Global-Mapping-Choices-Report.pdf
The Colorado River is running dry (Source: ArcheanWeb) – https://archeanweb.com/2020/03/03/the-colorado-river-is-running-dry/
Feature Image: DOMINICAN REPUBLIC. Desert island (By Ronald Saunders) (Modified) – This file is licensed under the Creative Commons Attribution-Share Alike 2.0 Generic license. – https://creativecommons.org/licenses/by-sa/2.0/deed.en