Rising Sea Levels

Already the average global sea level has risen by 8 inches in the past century. By the end of this century, average global sea level could rise an additional three feet or more. The ecological consequences of these changes include worsening coastal erosion, habitat destruction, and saltwater encroachment into freshwater environments.

How are Sea Levels Changing?

Climate change accelerates sea level rise in two ways:

1. Rising temperatures are melting land-based glaciers and icepacks. This melt-water eventually makes its way to the oceans, where it contributes to sea level rise.
2. Water expands as it warms. Even if no glaciers were melting, sea level would still rise due to increasing water temperatures.

Melting glaciers and warming water contribute relatively equally to sea level rise. Additional factors may accelerate or slow regional sea level rise. For example, the subsidence of coastal land along the Chesapeake Bay — due partially to groundwater extraction — is accelerating the relative rate of sea level rise in the region.

Implications for Land Trusts

The environmental and economic impacts of sea level rise are potentially devastating. In the United States, a sea level rise of 3-4 feet could drown 25-80% of coastal wetlands, depending upon the ability of the wetland species to adapt to deeper water and/or to migrate inland. The rising waters could also inundate 5,000-10,000 square miles of currently dry land. One recent study suggests that the impacts of sea level rise — erosion and dry-land inundation, for example — could threaten 9% of the land within 180 U.S. cities by 2100.

The impacts of sea level rise include:

• Loss of coastal habitats, including wetlands, mangroves and beaches.
• Loss of currently dry land to advancing seas.
• Stronger, deeper and more destructive storm surges.
• Worsening coastal erosion.
• Disruption and destruction of shorebird and sea turtle nests.
• Population declines in fishes, shellfish and other species that rely on coastal wetlands for at least part of their lives.
• Population declines in migratory birds — including waterfowl — that rely on coastal habitats during seasonal migrations.

Sea level rise may also compound other climate change negative impacts, such as posing greater flood risk and presenting additional challenges to migrating species.

Tips for Planning: What Land Trusts Are Doing

Cooperatively Working Towards Conservation Goals.

Coastal land trusts are responding to on-the-ground impacts of changing sea levels in various ways. Some groups are implementing adaptation projects such as restoring sea grass ecosystems that attenuate wave impacts and removing hardened barriers that may exacerbate effects of erosion. In addition to employing strategic conservation planning to reduce risks and enhance resilience, some land trusts are also supporting efforts to mitigate greenhouse gas emissions to reduce the extent of future climate change.

Land trusts must determine the right planning approach for their organization, however, more and more, conservation organizations are working with their communities to identify opportunities to reduce vulnerabilities and prepare for changing temperatures. Agencies are making similar strides to implement projects that reduce risks and plan for resilience by incorporating adaptation, mitigation, and engagement into their strategic goals and objectives. For example, the U.S. Fish and Wildlife Service’s Strategic Plan for Responding to Accelerating Climate Change identifies seven planning and development goals to support sustainable landscapes. Conservation groups are increasingly partnering with agencies as well as other nonprofits and for-profit organizations to respond to this global challenge at local levels.

Building resilience for multiple management objectives.

Resilience describes the ability of a system to persist through extreme change. By working to identify and reduce potential threats land managers can build resilience and achieve multiple management objectives. Assessing vulnerabilities is a critical step in the strategic conservation planning process that helps land trusts identify key threats to resources. Adaptive management planning enables conservation practitioners to implement interventions to reduce vulnerabilities and to monitor and revise strategies as new information becomes available. There is no one-size-fits-all solution to addressing management challenges associated with warming average temperatures, however, planning that acknowledges vulnerabilities can help land trusts better achieve their conservation objectives.

Learn More

• Climate Change Indicators: Sea Level Rise, EPA
• Climate Ready Estuaries – Coastal Adaptation Toolkit, King Tides, Risk-Based Adaptation, EPA
• Coastal Sensitivity to Sea Level Rise, a Focus on the Mid-Atlantic Region, USGCRP
• Digital Coast – Data, Tools, Topics, Training, and Stories, NOAA
• Encroaching Tides, UCS
• Sea Level Rise, National Climate Assessment
• Sea Level Rise and Nuisance Flood Frequency Changes around the United States, NOAA
• Sea Level Rise Planning, USFWS
• Sea Level Trends, NOAA