The Impacts of Global Warming on the World's Coral Reefs

By Karen Dougherty

Coral reefs are some of the world’s most fragile ecosystems and are particularly vulnerable to the effects of global warming. According to a World Resources Institute report in 2008 by Matt Kallman, “coral reefs are often referred to as “rainforests of the sea” because they are home to more than 25 percent of all marine species."

Healthy coral reefs can only survive within a very narrow range of temperatures and pH levels, two factors that are being negatively impacted by global warming. Coral reefs are usually found off continental coasts in clear, shallow water. The sensitivity of these ecosystems makes them an excellent barometer of our marine health. Since they are located adjacent to coastlines, they are affected by “coastal development, pollution, irresponsible fishing practices, and runoff”, according to Kallman.

The oceans absorb up to 50 percent of all man-made CO₂; due to this, the pH in the oceans is becoming more acidic. Historically, the oceans have had a slightly alkaline pH level around 8.2. During the last century, pH levels have dropped to 8.1 and are predicted to drop to 7.8 in the next century. Kallman calls it “the largest change in more than 20 million years.” Many scientists feel that coral may not survive such a dramatic increase in acidity.

Many of the world’s coral reefs are already exhibiting signs of “bleaching” due to increased sea temperature and acidification, a sign that they are in poor health and consequently prone to disease. Recently, the journal Science assessed the health of the world’s coral reefs. “Approximately one-third of the over seven hundred species studied are listed as Critically Endangered, Endangered, or Vulnerable… In 1998, El Nino weather patterns led to a mass-bleaching event, destroying approximately 16 percent of the world’s coral reefs.”

Coral reefs are important not only for their rich biodiversity, which houses many of the world’s commercially important food sources, but also as buffers that protect fragile coastlines. How many more ecosystems and species will succumb to man’s irresponsible behavior towards our planet? We must deal quickly and decisively with the issue of global warming; if not, coral reefs, like so many other endangered ecosystems will cease to exist.