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How does climate change affect coral reefs?

The varied effects of climate change are changing the ocean; these changes dramatically affect coral reef ecosystems.

infographic showing relationship between coral and climate

Climate change poses a major threat to coral reefs. Download this infographic | Infographic Text

Climate change is the greatest global threat to coral reef ecosystems. Scientific evidence now clearly indicates that the Earth's atmosphere and ocean are warming, and that these changes are primarily due to greenhouse gases derived from human activities.

As temperatures rise, mass coral bleaching events and infectious disease outbreaks are becoming more frequent. Additionally, carbon dioxide absorbed into the ocean from the atmosphere has already begun to reduce calcification rates in reef-building and reef-associated organisms by altering seawater chemistry through decreases in pH. This process is called ocean acidification.

Climate change will affect coral reef ecosystems, through sea level rise, changes to the frequency and intensity of tropical storms, and altered ocean circulation patterns. When combined, all of these impacts dramatically alter ecosystem function, as well as the goods and services coral reef ecosystems provide to people around the globe.

Infographic Text

Threats to coral reefs: climate change

Increased greenhouse gases from human activities result in climate change and ocean acidification. Climate change = ocean change. The world's ocean is a massive sink that absorbs carbon dioxide (CO2). Although this has slowed global warming, it is also changing ocean chemistry.

Climate change dramatically affects coral reef ecosystems

Contributing factors that increase greenhouse gases in the atmosphere include burning fossil fuels for heat and energy, producing some industrial products, raising livestock, fertilizing crops, and deforestation. Climate change leads to:

  • A warming ocean: causes thermal stress that contributes to coral bleaching and infectious disease.
  • Sea level rise: may lead to increases in sedimentation for reefs located near land-based sources of sediment. Sedimentation runoff can lead to the smothering of coral.
  • Changes in storm patterns: leads to stronger and more frequent storms that can cause the destruction of coral reefs.
  • Changes in precipitation: increased runoff of freshwater, sediment, and land-based pollutants contribute to algal blooms and cause murky water conditions that reduce light.
  • Altered ocean currents: leads to changes in connectivity and temperature regimes that contribute to lack of food for corals and hampers dispersal of coral larvae.
  • Ocean acidification (a result of increased CO2): causes a reduction in pH levels which decreases coral growth and structural integrity.

How you can help

Shrink your carbon footprint to reduce greenhouse gases.

  • Drive less.
  • Reduce, reuse, or recycle.
  • Purchase energy-efficient appliances and lightbulbs.
  • Print less. Download more. Use less water.

Do your part to help improve overall coral reef condition.

  • Reduce the use of lawn and garden chemicals.
  • DO NOT dump household chemicals in storm drains.
  • Choose sustainable seafood. Visit FishWatch.gov.
  • Learn about good reef etiquette and practice it when in the water.
  • Volunteer for beach and waterway clean ups.