|Credit: Greg Hoxsie for ReWild Mission Bay.|
As sea levels rise, wetlands are encountering physical barriers to inland migration — a phenomenon known as "coastal squeeze." Wetlands are being squeezed between sea-level rise on one side and human development on the other, preventing their natural ability to adapt by moving inland to higher ground. To respond to these threats, there are two primary management responses state and local governments may consider: (1) maintaining existing or restoring coastal wetlands; and (2) facilitating their migration inland.See footnote 2 Each management response raises similar and yet distinct questions that decisionmakers will have to address to enhance wetlands and support their long-term viability. For example, maintaining existing or restoring coastal wetlands and adequate sediment supplies will require that decisionmakers evaluate water management requirements regarding allowable discharges and deposits to government-regulated water bodies (that can restrict sediment flows) and the use of clean fill in wetlands, including from dredging. Allowing the migration inland of wetlands raises different issues, since migrating wetlands may encroach on existing land uses, such as agriculture, forestry, and residential communities. As a result, decisionmakers will need to address additional questions about shifting economies, environmental justice and equity, and wetlands and private development regulations. Ideally, governments will develop comprehensive managed retreat strategies to implement both types of management responses. However, there is deficient information about legal and policy tools that state and local governments can use to adapt to sea-level rise and limit the impacts of coastal squeeze on migrating wetlands. This section attempts to fill that informational gap.
This section first provides a short background on the law and federal, state, and local actors that could impact state and local decisions, including considerations for wetlands on public versus private property. This section then identifies six components of a comprehensive wetland migration strategy as recommended practice tips for state and local coastal governments: (1) data; (2) planning; (3) voluntary land acquisitions; (4) legal tools; (5) community engagement; and (6) funding. This section concludes with case study examples to illustrate each of these six components. While other coastal ecosystems, like forests, and myriad species are also capable of and will need to shift their habitats to adapt to different climate threats, this section focuses on wetlands. This section will be broadened in the future as more on-the-ground actions occur.
It is important to note that, as multiple coastal ecosystems change and encroach on human development, land managers and communities will have to weigh decisions about whether to prioritize the conservation of some habitats or species over others. For example, in Dorchester County, Maryland, the inland migration of salt marshes is killing forests, resulting in a phenomenon known as “ghost forests.”See footnote 3 While sea-level rise may continue unabated, governments and people can take short- and long-term actions that affect the survivability of each habitat. For example, governments could help marshes migrate inland by removing roads or conversely, protect forests by erecting a flood barrier to keep marshes at bay. As people and ecosystems retreat away from the coast, land-use decisions should reflect human priorities for the environment.
A loblolly pine "ghost" forest in Blackwater National Wildlife Refuge in Dorchester County, Maryland (June 2018). Sea-level rise and land subsidence result in brackish water intruding on forested land and killing trees.
Credit: Will Parson, Chesapeake Bay Program, U.S. Fish and Wildlife Service.
Wetlands are regulated under a complex, and often overlapping jurisdictional framework at the federal, state, and local levels. At the federal level, the U.S. Army Corps of Engineers (Corps) is one of the primary agencies that regulate activities in intertidal areas that affect wetlands under two statutes, the Clean Water Act, 33 U.S.C. §§ 1251 et seq. and Rivers and Harbors Act of 1899, 33 U.S.C. §§ 403 et seq.).See footnote 4 States also regulate their coastal zones under the federal Coastal Zone Management Act, 16 U.S.C. §§ 1451 et seq. and may have special protections for wetlands, where certain actions conducted in or adjacent to wetlands may be prohibited or require specific mitigations through permits. Local governments have the primary authority to regulate land uses in their communities through zoning and floodplain ordinances. In particular, zoning ordinances provide the legal framework that governs the use and development of land in a municipality according to different districts based on the uses that are permitted (e.g., residential, commercial, industrial).See footnote 5 Overlay districts can impose additional regulations on an existing zone based on special characteristics in that zone, such as for natural resource conservation.See footnote 6 Before implementing any zoning or land-use changes, however, local governments must ensure that they have the authority to utilize a tool under state law, particularly in Dillon Rule states. In Dillon Rule states, state legislatures must delegate specific powers to local governments whereas, in home rule states, local governments generally have broader authorities.See footnote 7
Governments will have more control to actively manage wetlands and facilitate migration on publicly owned lands. In contrast, where wetlands are being affected by private development, governments will need to consider protections for private property rights. Most land in the U.S. is privately owned.See footnote 8 As wetlands migrate inland, governments will have to consider how development regulations intersect with private property rights.
The greatest concern for most decisionmakers will likely be potential conflicts with the U.S. Constitution’s Fifth Amendment prohibition against the “taking” of private property for public use without “just compensation.”See footnote 9 This protection for private property rights is also included in state constitutions. There are different types of takings that can result. Generally, courts apply a “per se” test to physical occupationsSee footnote 10 and regulations that deprive a private property owner of all or essentially all of his/her property’s economic valueSee footnote 11 but most regulations designed to protect wetlands will be evaluated under a case-by-case-specific balancing test.See footnote 12 Regardless, state and local governments have successfully navigated takings limits and protected sensitive ecosystems analogous to migrating wetlands. While state and local governments must consider constitutional and statutory protections for private property rights, policymakers can likely minimize their legal risk for implementing environmental regulations by being cognizant of existing federal and state takings law (for more information on takings law in a managed retreat context, see the Crosscutting Legal Considerations>Takings section of this toolkit).
As climate change impacts alter both built and natural landscapes, state and local governments should have proactive discussions about the conservation and protection of migrating wetlands. Any actions should be supported by public-private partnerships and communities to balance the tradeoffs and impacts of wetlands on human values and land uses. Policymakers can consider the following practice tips to facilitate wetland migration as a part of comprehensive managed retreat strategies:
1. Content in this section is adapted, in part from the following article: Katie Spidalieri, Where the Wetlands are—And Where They are Going: Legal and Policy Tools for Facilitating Coastal Ecosystem Migration in Response to Sea-Level Rise, Wetlands (2020), available at View Source. Please cite this article, in addition to the Georgetown Climate Center’s Managed Retreat Toolkit, when making references to this section. | Back to contentBack to content
2. A third possible management response is to allow wetlands to be lost. While some amount of wetlands and other coastal ecosystems will inevitably be lost to sea-level, that management strategy is acknowledged but will not be discussed herein. Instead, the focus of this section is to suggest legal and policy tools that can be used to facilitate wetland migration and conservation. Back to contentBack to content
4. The Clean Water Act enables the Corps to regulate the discharge of pollutants into “waters of the United States,” including those that involve the dredging or filling of wetlands or waterways. These types of activities precipitated by new development or redevelopment may require a permit from the Corps. Clean Water Act (or Federal Water Pollution Control Act), 33 U.S.C. § 1344 (“Permits for dredged or fill material”). Under the Rivers and Harbors Act, any activity that obstructs “navigable waters” requires a permit from the Corps. Back to contentBack to content
7. J. Peter Byrne & Jessica Grannis, Chapter Nine: Coastal Retreat Measures, in The Law of Adaptation to Climate Change: U.S. and International Aspects p. 297, n.23 (Michael B. Gerrard & Katrina Fischer Kuh eds., 2012). Back to contentBack to content
8. Excluding Alaska and some states out West, in nearly all states, most land is privately owned (i.e., greater than 50 percent of land in the state is privately owned). See, e.g., Katherine Sims, Jonathan Thompson, & Spencer Meyer, Can Protecting Land Promote Employment?, Route Fifty (July 17, 2019), View Source; Amos Eno, Willard Dyche, & Laura Mass, Res. First Found., State of the Land: A Brief Inventory of Public and Private Land in the United States (“The land surface of the United States covers 2.3 billion acres. Private owners held 61 percent in 2002, the Federal Government 28 percent, State and local governments 9 percent, and Indian reservations 3 percent.”). | Back to contentBack to content
9. U.S. Const. amend. V. Back to contentBack to content
10. J. Peter Byrne & Jessica Grannis, Chapter Nine: Coastal Retreat Measures, in The Law of Adaptation to Climate Change: U.S. and International Aspects 274–75 (Michael B. Gerrard & Katrina Fischer Kuh eds., 2012). Back to contentBack to content
11. Lucas v. S.C. Coastal Council, 505 U.S. 1003 (1992); J. Peter Byrne & Jessica Grannis, Chapter Nine: Coastal Retreat Measures, in The Law of Adaptation to Climate Change: U.S. and International Aspects 275–76 (Michael B. Gerrard & Katrina Fischer Kuh eds., 2012). Back to contentBack to content
12. Penn. Cent. Transp. Co. v. City of New York, 438 U.S. 104 (1978); J. Peter Byrne & Jessica Grannis, Chapter Nine: Coastal Retreat Measures, in The Law of Adaptation to Climate Change: U.S. and International Aspects 276–77 (Michael B. Gerrard & Katrina Fischer Kuh eds., 2012). Back to contentBack to content
13. See, e.g., J.G. Titus et al., State and Local Governments Plan for Development of Most Land Vulnerable to Rising Sea Level Along the U.S. Atlantic Coast, Envtl. Research Letters 4(4), doi: 10.1088/1748-9326/4/4/044008 (2009); Matthew L. Kirwan, David C. Walters, William G. Reay, & Joel A. Carr, Sea Level Driven Marsh Expansion in a Coupled Model of Marsh Erosion and Migration, 43 Geophysical Research Letters 4366–373 (2016), available at View Source; M. Mitchell, J. Herman, D.M. Bilkovic., & C. Hershner, Marsh Persistence Under Sea-Level Rise is Controlled by Multiple, Geologically Variable Stressors, Ecosystem Health & Sustainability 3(10):1379888 (2017), available at View Source. | Back to contentBack to content
14. 23 U.S.C. §§ 134(h)(1), 135(d)(1) (2020). Back to contentBack to content
16. It is important to distinguish that land acquisition programs can have different objectives for either open space or hazard mitigation. Some state and local governments have buyout and acquisition programs and policies for the primary purpose of acquiring land for open space or recreational purposes (e.g., parks, trails) or as working lands (e.g., agriculture, forest). This open space or natural resource management focus contrasts with programs and policies targeting lands for hazard mitigation purposes (e.g., to reduce flooding). Comprehensive approaches to facilitate wetlands migration and conservation would benefit from the development and implementation of both types of programs. For more information, see the Acquisition Tools section of this toolkit. | Back to contentBack to content
17. See, e.g., K. Tully et al., The Invisible Flood: The Chemistry, Ecology, and Social Implications of Coastal Saltwater Intrusion, 69 BioScience 368–78, doi: 10.1093/biosci/biz027 (2019). Back to contentBack to content