Coral reefs may not relate to people’s daily lives, but their role in nature cannot be dismissed. They provide habitats for various types of animals and offer fishing and tourism resources. They also serve as natural embankments to protect land against big waves, including tsunami. However, the ecosystems that embrace coral reefs are under threat from the serious danger of coral bleaching — apparently due to rising sea water temperatures linked to climate change. The government and the public should realize that a key component of measures to protect coral reefs is the fight against global warming, and act accordingly.
According to the Environment Ministry, coral reefs from the Amami Islands of Kagoshima Prefecture to the Yaeyama Islands of Okinawa Prefecture suffered large-scale bleaching last summer. In the Sekisei lagoon lying between Ishigaki Island and Iriomote Island, both in Okinawa, more than 90 percent of the coral was found bleached, and 70 percent of the coral was found to be dead. The ministry says that the current situation affecting coral in the sea off southern Japan is the most serious since large-scale bleaching in 1998. High temperatures prevailed in seawater around the world in 1997 and 1998, killing 16 percent of reef-building coral worldwide.
As the extensive coral damage in the late 1990s shows, bleaching of coral reefs is a global phenomenon. The Environment Ministry cites the U.S. National Oceanic and Atmospheric Administration (NOAA) as saying that El Nino events — warming of surface waters and reduced upwelling of cold, nutrient-rich water off the western coast of South America — from 2015 to 2016 have caused unprecedented widespread and long-running coral bleaching, leading to the worst damage ever in the Great Barrier Reef of Australia and Kiribati in the central Pacific Ocean. This coral bleaching mentioned by NOAA continues to this day.
The ministry also quotes a report by the Intergovernmental Panel on Climate Change that a rise in seawater temperature by 2 degrees Celsius can cause large-scale coral bleaching every year, inflicting devastating damage to coral reefs.
While rising water temperatures are causing coral bleaching, it is believed that acidification of the ocean caused by higher concentration of carbon dioxide in the atmosphere may also damage coral. There is a forecast that unless stronger measures to mitigate the effects of global warming are taken, rises in seawater temperatures coupled with acidification could cause the total disappearance of coral near Japan by the 2070s.
In view of this serious situation, the government convened a meeting of experts in late April in Onna on Okinawa Island. The participants adopted an “emergency declaration” calling for accelerated measures to protect coral against bleaching. Proposed measures include correctly ascertaining the facts about the coral bleaching that occurred in 2016, continual and effective monitoring of the ecosystems of coral reefs with particular attention on their diversity, and sharing information on the conditions of coral reef ecosystems on a global scale through international networks such as the International Coral Reef Initiative.
As measures more directly related to protecting the environment in which coral lives, the experts at the meeting proposed long-term nationwide observation and forecasting the impact of rising seawater temperatures, acidification of the ocean and social and economic changes. They recommended identifying areas where healthy coral reef ecosystems can be maintained with a view to designating them as protected areas and reducing pollution there. They urged development of coral transplant and culturing technologies to revive dying coral reefs, reducing the flow of red clay, soil and sand, and polluted water into coral habitats, measures to prevent a mass generation of crowns-of-thorns starfish — a natural enemy of coral — and the promotion of ecotourism designed to educate people on coral.
The crucial thing that people can and need to do to protect coral is to reduce carbon dioxide emissions to prevent rises in seawater temperatures. The ability of coral to survive will increase if reefs are given time to adjust to environmental changes by reducing as much as possible increases in temperature and acidification. Japan and other countries must spare no efforts to achieve the goals set by the 2015 United Nations climate change conference in Paris: limiting rises in global temperatures from pre-industrial levels to below 2 degrees and closer to 1.5 degrees.