Since the first serious discussion about climate change in the last half of the 20th century, the prevailing political and social attitude has been “Why do today, what you can put off until tomorrow?” The impacts of climate change are often seen as future threats, not present-day ones. The tides are shifting, however, as climate change at the margins creeps in.
Many aspects of climate change are currently in play, but sea-level rise is a highly visible one. Mean sea level rose 6 to 8 inches between 1880 and now. Meltwater from ice and thermal expansion of seawater feed the rising oceans (water expands as it heats up).
I understand that 8 inches doesn’t seem like much, but change always starts at the margins. In the case of sea-level rise, it literally starts at the margins of the oceans. Key West made the news recently as one of its neighborhoods reached the three-month milestone of continuous flooding. Granted, the “king tides” of South Florida historically cause nuisance flooding, but three months seems a bit closer to permanence than to nuisance.
One of the issues emerging from recent research is that sea levels are not simply rising at a steady rate. The rate of sea-level rise is accelerating. Over the past 20 years, sea-level rise has moved from 2.5 mm/year to 3.4 mm/year, an average rate increase of 0.045 mm/year. The practical implications of climate change acceleration are significant. Over 100 years, the present-day acceleration almost doubles the change in sea-level rise compared to a steady-rate assumption.
More change is happening
Key West is not alone. Venice suffers from increased flooding. The Maldives (a string of atolls in the Indian Ocean) is the lowest-lying country in the world. The average elevation above sea level for the country is 1.3 meters (4 feet). The Maldives will be one of the first nations to disappear under rising seas.
The Sundarbans in the southwest portion of the Bengal delta are also feeling the pressure. Subsistence farmers there are on the margins of change. The obvious casualty is productive land lost to the rising sea, but there are other more insidious problems the farmers face.
One of these problems is increasing saltwater contamination. The salinity of shrimp ponds increases when saltwater penetrates the farmlands and mingles with the freshwater supplies. While this doesn’t kill the shrimp outright, it does decrease the productivity of the farms. Farmers are a versatile group of people, and a shift from shrimp farming to the less profitable crab farming business is in progress for some of them.
Rice farming is also falling prey to rising salinity. High yield rice varieties, the crops that bring maximum value, are not tolerant of high salinity. Farmers compensate by returning to native rice species that tolerate the saltwater encroachment into the rice paddies. This change in crops decreases already meager profits but keeps them in business for the time being.
Thinking that climate change is a problem for the distant future is only a luxury for those not already living on the margins of climate change.
Climate Change: Global Sea Level (Rebecca Lindsey – NOAA) – https://www.climate.gov/news-features/understanding-climate/climate-change-global-sea-level
New Study Finds Sea Level Rise Accelerating (NASA) – https://www.nasa.gov/feature/goddard/2018/new-study-finds-sea-level-rise-accelerating
82 Days Underwater: The Tide is High, but They’re Holding On (Patricia Mazzei – The New Your Times) – https://www.nytimes.com/2019/11/24/us/florida-keys-flooding-king-tide.html