Fifth National Climate Assessment: Chapter 10 - Ocean Ecosystems and Marine Resources

Abstract

The ocean supports diverse and productive marine ecosystems that provide innumerable benefits to the United States. Fishing, recreation and tourism, energy, shipping, and transportation in the ocean and Great Lakes sustain a marine economy that contributed over $781 billion (in 2022 dollars) to the US economy in 2021. Ocean resources support human health and well-being in communities throughout the US, and sustained connections to the ocean are foundational to cultures and identities. This chapter assesses climate impacts and risks to US marine ecosystems, and to the communities and industries that depend on them, as well as ocean-based measures for climate change adaptation and mitigation.

Across the globe, climate change is altering marine ecosystems and connected social systems at a scale and pace that is unprecedented in recent millennia. The combination of long-term changes in physical ocean conditions—such as warming, sea ice loss, acidification, and deoxygenation (KMs 2.1, 3.3)—and short-term extreme events (KM 2.2) such as marine heatwaves threatens marine ecosystems and human communities (Focus on Compound Events). Numerous marine species, from phytoplankton to whales, are altering their distribution, seasonal activities, and behaviors to align with suitable ocean conditions. These changes ripple through the food web, affecting species interactions, ecosystem functions, and biodiversity, as well as conservation, management, and uses of valuable ocean resources. Climate-driven changes to marine ecosystems significantly affect ocean-dependent livelihoods and, in some communities, threaten food supplies and ways of life.

In affected communities, the magnitude of climate impacts and levels of adaptive capacity vary with marine resource dependence, socioeconomic status, and historical and institutionalized inequities. Some individuals, communities, and industries are adapting to changes, largely through reactionary responses and, in some cases, through coordinated resilience planning. However, responses are uneven across communities and sectors, and they remain insufficient to meet mounting challenges and costs. Global policy choices regarding greenhouse gas (GHG) mitigation govern the intensity and trajectory of future climate impacts and the diversity and effectiveness of adaptation options. Mitigation and adaptation efforts require explicit accountability in social equity, sustainability goals, and fairness in governance and finance to address entrenched inequities that increase climate change risks and adaptation burdens.

This chapter draws on global insights to address climate-related changes and challenges in US marine areas. It largely focuses on continental shelf waters, with some discussion of topics that extend shoreward to intertidal areas, and it complements Chapter 9 (Coastal Effects), which extensively covers the topic of sea level rise. The chapter builds upon the climate-related physical oceanographic changes discussed in Chapters 2 (Climate Trends) and 3 (Earth Systems Processes) to highlight some of the unprecedented ecological changes taking place in US marine waters and their impacts on social, economic, and governance systems. Policy directions, planning efforts, and investment decisions being made now will affect mitigation and adaptation options and timelines and will determine the future of our ocean and social and economicsystems that rely on it.

Citation

Mills, K. E., Osborne, E. B., Bell, R. J., Colgan, C. S., Cooley, S. R., Goldstein, M. C., Griffis, R. B., Holsman, K., Jacox, M., & Micheli, F. (2023). Ocean ecosystems and marine resources. In A. R. Crimmins et al. (Eds.), Fifth National Climate Assessment (Ch. 10). U.S. Global Change Research Program.

https://doi.org/10.7930/NCA5.2023.CH10