Key points, adapted from the 3rd and 4th National Climate Assessments
Climate-related changes in the ocean's physical and chemical properties are disrupting marine ecosystems. Unless carbon-based emissions are significantly reduced, changes already underway will result in transformative impacts on ocean ecosystems.
As oceans warm, the abundance and distribution of marine organisms and fish species are shifting. Such changes influence fisheries harvests, regional economies, aquaculture productivity, cultural heritage, recreational opportunities, and shoreline protection.
Along with human activities that have degraded coastal and marine habitat over time, ocean warming and acidification are causing the loss of two vulnerable habitats: coral reef and sea ice ecosystems.
Aquaculture already supplies half of all seafood produced for human consumption. Economically important species such as oysters, mussels, and sea urchins are highly vulnerable to the declining trend in pH of ocean waters.
Ocean heat waves—periods of very warm conditions that persist for several months or more—affect marine ecosystems and disrupt fisheries. Studies suggest that future marine heat waves will become more common, cover larger areas, and last longer.
Human use of living marine resources moves billions of dollars through the U.S. economy each year. Sustaining the fish and marine species that people depend upon for food and income requires proactive management that takes the multiple factors affecting these ecosystems into account.
The value of marine ecosystems
Oceans and coasts are among the nation’s most treasured and valuable resources. Americans rely on ocean ecosystems for food, jobs, recreation, energy, and other vital services. From fish and fisheries to whales, sea turtles, coral reefs, and oysters, many living marine resources and their habitats are at risk due to our rapidly changing and variable climate.
Climate-related changes in ocean and coastal ecosystems—including warming oceans, rising seas, ocean acidification, and coastal droughts—are impacting marine resources and, in turn, the people, businesses, and communities that depend on them. These changes affect jobs, impact economies, and disrupt traditional ways of life.
Changes to ecosystem productivity, species abundances, species distributions, and community interactions (including changes in predation or competition between species) are already being observed.. Less mobile species, such as corals, are not able to migrate with changing conditions to find suitable habitat. If conditions become unsuitable, some species will die off and no longer be a resource to help defend coastal communities from storms and inundation, or provide the foundation for tourism and recreation.
Businesses and communities that are dependent on particular fisheries and marine resources will need to find ways to adapt to the changes. Given the pace and scope of climate-related changes in marine and coastal ecosystems, decision makers need easy access to better information on what is changing, what is at risk, and what actions they can take to prepare for and respond to changing conditions. The tools and information provided here are intended to help people and communities take action to reduce climate-related impacts and increase resilience.
This section has been excerpted and abridged from the report Climate Change Impacts in the United States: The Third National Climate Assessment (Chapter 24: Oceans and Marine Resources) and Impacts, Risks, and Adaptation the United States: Fourth National Climate Assessment, Volume II: The Fourth National Climate Assessment (Chapter 9: Oceans and Marine Resources).
To learn more about the impacts of climate change and variability on marine ecosystems and resources, visit the subtopic pages: