By Richard Wildermann for The Island Connection
Small, low-lying islands in the open ocean are like canaries in the coal mines, warning of the dangers of sea level rise. There are thousands of such islands in the western Pacific Ocean, and sea level has been rising faster there, especially over the last couple of decades, than many places on the planet. Kiribati, a Pacific Island nation about halfway between Hawaii and Australia, is made up of 33 coral reef atolls, 21 of which are inhabited, with a total land area of 313 square miles.
Because of severe erosion and saltwater intrusion, more of the islands are becoming too narrow to be livable. Storm surges occur more frequently, washing over shoreline barriers, turning wells brackish, and flooding villages and crops. Warming seas bleach and kill the coral that has afforded some protection from waves and storms.
The 1,190 islands of the Republic of Maldives lie southwest of the southern tip of India. It is the lowest lying island chain in the world. Because 80 percent of the land area is below 3.3 feet, the Maldives are especially vulnerable to flooding and sea level rise. Over the last six decades, sea level around the Maldives has been rising at a rate of 0.03 – 0.06 inches per year. Given mid–level scenarios for global warming emissions, the Maldives is projected to experience sea level rise on the order of 1.5 feet, and to lose some 77 percent of its land area, by around the year 2100.
The most obvious evidence of sea level rise in more populated areas is the increasing frequency and extent of tidal flooding. In coastal communities, tidal waters will inexorably reach further inland twice a day, flooding areas that were dry a few months before. Using data from tidal gauges at 27 coastal locations in the U.S., one study has shown that the number of flood days along the coast has increased steadily since the mid-1950s due primarily to human-caused sea level rise. Over 100 million people in the U.S. live in coastal counties. The five states with extensive low-lying areas that are most vulnerable to rising seas are Louisiana, Florida, North and South Carolina, and California.
South Florida is called ground zero for sea level rise. The average elevation of Miami-Dade County is just six feet. In recent years, sea level has been rising at almost an inch a year in the Miami area, many times greater than the average global rate. There is speculation that this is due in part to changes in near-shore ocean currents. In Fort Lauderdale, just north of Miami Beach, water regularly spills over sea walls, lapping against foundations every few weeks. During king tides, which are the very highest predictable tides that occur twice a year, whole streets and neighborhoods are inundated.
The 165 miles of canals in the city once effectively drained storm water into the ocean. Now seawater backs up through drain pipes into the canals and floods city streets. One-way valves are being installed in the drainage pipes to prevent the back up.
But during high tides or heavy rain, the valves can’t open and the streets flood. In an article in March 2016 for Inside Climate News, Katherine Bagley stated, “Scientists, city officials, planners and policymakers say that in the coming decades, climate change will impact nearly every aspect of life in Fort Lauderdale and the rest of South Florida, from the price of flood insurance to home values, drinking water supplies, infrastructure, the economy and health.”
The City of Charleston, South Carolina is one of the most popular places in the country to live and visit. It’s a challenge for the city to effectively deal with the growth and congestion that come with such popularity. But flooding from more intense storms and sea level rise is already compounding Charleston’s problems, and in the next few decades it could overwhelm the city’s capacity to keep its head above water. During spring tides, the highest tides that occur regularly about twice a month, flooding is becoming more common and more severe.
In the 1970s tidal flooding occurred about twice a year in Charleston. Now it occurs about 11 times a year, and the number of daily floods is projected to increase rapidly in the next few decades. Sea level could rise 3.9 feet by 2100, according to one conservative estimate from Climate Central. The South Carolina Department of Natural Resources warns that the Charleston area will experience increasing habitat loss, seawater encroachment, flooding and water quality degradation from sea level rise.
Throughout geologic time, movement of the plates that make up the earth’s outer shell has been the primary cause of long term sea level fluctuations, those that occur over tens of millions of years. More short-term changes in sea level are attributed primarily to fluctuations in the Earth’s temperature. At the end of the last ice age (about 21,000 years ago), sea level began to rise gradually until it stabilized about 2,000 years ago. Then at the beginning of the 20th century, just as greenhouse gas emissions and temperatures began to increase, sea level began to climb at an average rate of 0.07 inches per year. Expansion of warming ocean waters and glacier melting have been the dominant contributors to global sea level rise for the last hundred years. Over the past 25 years or so, global sea level rise has accelerated to a rate of about 0.12 inches per year and is expected to rise at an even greater rate this century because the Antarctic faster rate than anticipated.
Sea level is rising at different rates around the world. For example, the waters surrounding the Solomon Islands in the Western Pacific have risen at 0.33 inches per year since 1994, almost three times faster than the global average. Over the past 150 years, sea level has risen about 12 inches in southeast Florida compared to about 8 inches on average globally. Various ocean processes, such as changes in ocean currents, contribute to the variations in the rate of sea level rise.
Coastal areas in Louisiana and elsewhere are sinking, which also causes higher than average sea levels. Even the shape of the land and seafloor are factors in these regional and local variations.
What is being done to slow or stop rising seas?
Governments at all levels have made meaningful efforts to stop or slow warming of the atmosphere and oceans. But the problem is global and needs a cooperative international effort to succeed. One of the first major international conferences on climate change was held in February 1979 in Geneva, Switzerland. Since 1995 United Nations Climate Change Conferences have been held annually. The fundamental purpose of these international efforts is to reduce global greenhouse gas emissions.
But after decades of meetings, reports, resolutions, agreements and promises, the rate of greenhouse gas emissions is actually increasing, and as a result Earth’s warming and the rate of sea level rise is accelerating.
Carbon dioxide emissions have increased by about 90 percent since 1970. This trend is likely to continue as fossil fuels continue to drive economic growth.
Even if international cooperation eventually results in modest reductions in greenhouse gas emissions, it is too late to measurably slow global warming and sea level rise during this century. The Earth’s temperature reacts slowly to the mechanisms that drive climate change, and climate models predict the Earth’s average temperature will continue to rise over the next century. So if we are unable to effectively treat the cause of the problem, we need to adapt to it.
In part II Mr. Wildermann will address how we adapt to rising seas. Mr. Wildermann, a resident of Seabrook Island, was an environmental specialist and manager with the federal offshore oil and gas program for over 25 years. He directed agency compliance with environmental laws, conducted public hearings, and managed the analyses for proposals to lease to oil companies the rights to drill in federal waters. During his tenure, his agency received a Presidential award for its commitment to interdisciplinary environmental analysis. In 1997 Mr. Wildermann was the sole U.S. member of an international team that wrote the Guidelines for Environmental Impact Assessment in the Arctic. While in the private sector, Mr. Wildermann managed an environmental assessment for a proposed wind farm off the coast of Long Island, New York. He currently works with nonprofit organizations in the Lowcountry in opposition to offshore seismic surveys and oil drilling. Mr. Wildermann has a graduate degree from the Yale School of Forestry and Environmental Studies.