World's coral reefs could be lost by century's end, U.N. report says

Dec. 22 (UPI) -- The world's coral reefs could be lost by the end of the century due to bleaching caused by carbon emissions, a new U.N. environment group report warns.

Corals reefs sustain a variety of marine life and protect coastlines from erosion from waves and storms, and their loss could be devastating for a billion people globally who benefit directly or indirectly from them, according to a U.N. statement released Tuesday.

"In the face of inaction, coral reefs will soon disappear," Leticia Carvalho, head of the United Nations Environment Program's Marine and Freshwater Branch said Monday. "Humanity must act with evidence-based urgency, ambition and innovation to change the trajectory for this ecosystem, which is the canary in the coal mine for climate's impact on ocean's, before it's too late."

Researchers looked at coral bleaching, a phenomenon that can result from warmer water temperatures.

"When water is too warm, corals will expel the algae living in their tissues causing the coral to turn completely white," according to the National Ocean Service. "This is called coral bleaching."

Although bleached corals are still alive and can recover their algae if conditions improve, they are under increased stress and "if bleaching persists, the corals die," a U.N. statement on the new report noted.

Two possible scenarios were analyzed for the report. One was based on the world economy being heavily driven by fossil fuels. The second was based on a "middle of the road" approach where countries exceed their current pledges to limit carbon emission by 50% under the Paris Climate Agreement, which would still lead to more than 2 degrees Celsius warming by century's end.

Under the first scenario, all of the world's reefs will bleach by the end of the century with annual severe bleaching occurring by 2034. In the second, the severe bleaching would be delayed by 11 years.

"Coral reef adaptation to the changing climate, continued ecosystem service provision, and recovery of the areas that have already been or will inevitably be lost, require greatly increasing efforts to reduce direct stress on reefs, as well as more ambitious climate change mitigation than is committed to within the Paris Agreement," the report said.

Since 1998, there have been three major global bleaching events, including the most recent and longest on record, which started in 2014 and extended into 2017.

According to the new report, such bleaching events could become the norm in coming decades.

The report's lead author, Ruben van Hooidonk, a coral researcher with America's National Oceanic and Atmospheric Administration said "the sad part is that the projections are even more dire than before."

"It means we really need to try to reduce our carbon emissions to save these reefs," Hooidonk said. "This report shows that we need to do it even more urgently and take more action because it's even worse than what we thought."