Nature provides protection to about 8.5 million of the 31 million people who live in coastal regions that are vulnerable to tropical storms. Coral reefs and mangrove swamps both form natural buffers that absorb a storm’s energy. But rising sea levels threaten the long-term future of these natural storm barriers.
Both coral reefs and mangroves work to reduce wave height by absorbing the incoming storm energy. Coral reefs buffer the coast by absorbing up to 97 percent of the wave energy, and a 100-meter-wide mangrove forest reduces wave height by up to 66 percent.
Storm damage
These natural storm barriers offer protection, but they are not a panacea for reducing all storm risk. Tropical storms, hurricanes, and cyclones all pose a series of threats to coastal populations. Direct wave damage is one of these threats, and these natural barriers effectively reduce the destruction caused by waves pounding directly on homes and infrastructure. But other threats accompany these storms. High winds and storm surges also bring disaster to coastal communities.
Damages from sustained high wind speeds, and even faster moving gusts, are relatively easy to understand as the winds rip away roofs, blow debris through windows, and uproot signs. However, storm surge is not understood as well and operates separately from wave damage. Hurricanes and cyclones form around low-pressure centers. The low pressures cause water to mound up in the center of the storm. A storm surge of 20 feet means that the water level in the center of the storm is 20 feet higher than normal water levels. This mounding effect is caused by the atmospheric pressure differential between the storm’s center and the storm’s outer edges.
Think of a straw in a cup of water. When you slightly suck on the straw, water inside the straw will rise above the cup’s average water level. This effect happens because you have reduced the air pressure inside the straw. The higher air pressure pushing on the water surface outside the straw is forcing the water higher on the inside.
As a storm comes inland, it drags the mound of water in its center with it, causing flooding. Mangroves and coral reefs may have some effect on how this mound of water moves, but they can’t effectively prevent the storm surge.
The last of the storm threats is heavy rain that causes coastal and inland flooding. But the mangroves and coral reefs can’t deter this threat either.
Preservation of natural storm barriers
The preservation of these natural storm barriers is a positive step in reducing the damaging impact of high-intensity tropical storms. However, these barriers are threatened by rapid climate change. Coral reefs suffer bleaching from ocean heat waves, and mangroves are in danger of drowning.
Mangroves have intricate root systems that stabilize the coastline and reduce erosion. They also form the backbone of coastal ecosystems that support a high level of biodiversity. Mangroves cope with gradually rising seas by building soil underneath and growing vertically, so their roots and trunks are adequately balanced between the water and air. However, a study of sediment data from the past 10,000 years indicates that mangroves can only sustain this strategy when the rate of sea-level rise is below 5 millimeters (0.2 inches) per year. When the oceans rise more rapidly, then mangroves must retreat inland and abandon the coast to the open ocean.
Sea levels are currently rising at a rate of 3.2 millimeters (0.125 inches) per year, but that rate is accelerating. It is a high priority for coastal communities that climate change is moderated, and the rate of sea-level rise stays near its current level. Regions that depend on mangroves and coral reefs for storm protection have the most to lose if greenhouse emissions continue at their current rates.
ArcheanWeb:
Hurricanes more dangerous than in the past (Source: ArcheanWeb) – https://archeanweb.com/2020/06/01/hurricanes-more-dangerous-than-in-the-past/ Also:
The Everglades water wars (Source: ArcheanWeb) – https://archeanweb.com/2020/04/09/the-everglades-water-wars/ Also:
Sources:
Two vital buffers against climate change are just offshore (By Tom Parisi, Tim Stephens, University of California – Santa Cruz; Phys Org) – https://phys.org/news/2020-06-vital-buffers-climate-offshore.html Also:
Mangrove TreesNature’s Hurricane Barriers Could Be Gone By 2050 Due To Sea Level Rise (Source: National Parks Traveler) – https://www.nationalparkstraveler.org/2020/06/mangrove-trees-natures-hurricane-barriers-could-be-gone-2050-due-sea-level-rise Also:
Feature Image: Damage caused by Ike in the Bolivar Peninsula (Modified) – By Unknown author (National Weather Service) – NOAA: Information, Direct, Public Domain, https://commons.wikimedia.org/w/index.php?curid=30286433