Environmental: Wetlands Migration

Introduction^{See footnote 1}

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.

Summary of Primary Actors and Laws Affecting Wetland Migration

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 occupations^{See footnote 10} and regulations that deprive a private property owner of all or essentially all of his/her property’s economic value^{See 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). 

Practice Tips

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:

• Invest in data: To effectively evaluate and make legal and policy decisions that facilitate wetland migration and conservation, governments must start with data. Successful strategies must be built on and informed by the best available, high-quality data at a local or place-based scale. The potential for wetland migration is highly variable based on different place-based physical factors, such as topography and relative sea-level rise, in addition to information about current and future zoning and land uses and the location of current and proposed structures and infrastructure on or near the coast that can act as barriers to inland wetland migration.^{See footnote 13} Data and information can come from a variety of sources like the federal and state governments, educational institutions, and nonprofit organizations. For example, some jurisdictions can utilize the U.S. Fish and Wildlife Service’s Sea-Level Rise Affecting Marshes Model (SLAMM), an online modeling tool that allows users to visualize and assess the impacts of sea-level rise on coastal areas under different scenarios out to the year 2100, including predicted impacts to coastal wetlands and shorelines. Nonprofits like the National Audubon Society and The Nature Conservancy have collaborated with various partners to create different mapping layers and sea-level rise vulnerability assessments for coastal habitats, species, and protected lands in different regions on both the East and West coasts of the U.S. Collectively, these types of tools and studies can be used to supplement other local data on zoning, land use, and development to support robust decisionmaking efforts. Still, governments have to account for staff time and training requirements to utilize data and to develop new partnerships for any of these examples. 
• Plan for wetland migration: Effective, proactive planning built on data, implemented through land acquisitions and legal tools, and supported by public-private partnerships and community engagement can better ensure that government actions are coordinated, efficient, and maximize benefits for humans and the environment in light of climate change impacts. Governments should consider wetland migration both across different temporal scales and types of plans. First, wetland migration will impact communities differently in the short- (five years or less) and long-term (greater than five years). Governments should incorporate management objectives and priorities for wetlands into both short- and long-term plans to preserve future wetland corridors or establishment areas now before the rate of sea-level rise escalates and potentially hinders migration. Second, a variety of plans at the state and local levels can impact wetland conservation. These include plans for: coastal management; open spaces and parks; natural resources or protected areas; hazard mitigation; floodplain management; zoning and land use (i.e., local comprehensive plans); transportation (e.g., long-range planning); and climate adaptation (e.g., Punta Gorda, Florida).
  
  Decisionmakers can leverage the benefits of wetlands that cut across different sectors and agencies to align planning efforts and coordinate actions that can affect these coastal habitats. For example, federally mandated statewide and metropolitan long-range transportation plans must consider projects and strategies that will “protect and enhance the environment . . . and promote consistency between transportation improvements and State and local planned growth and economic development patterns” and that “improve the resiliency and reliability of the transportation system and reduce or mitigate stormwater impacts of surface transportation.”^{See footnote 14} Nature-based solutions, such as wetland preservation, can help transportation agencies meet these planning requirements and provide a means of protection for coastal roads with high adaptive capacity and numerous environmental co-benefits.^{See footnote 15} Governments can also develop wetland-specific management or strategic plans (e.g., Blackwater 2100) that can provide the necessary specificity to evaluate potential management responses on an appropriate place-based scale; these plans can feed into broader state and local plans to account for wetlands adaptation on both site-specific and landscape-scale planes.
• Acquire land to protect and conserve wetland migration corridors and higher ground establishment areas: Land acquisitions can occur through either the purchase of properties in fee simple or development rights (to part of or an entire property) through easements.^{See footnote 16} Governments can consider different approaches for how to prioritize wetland migration in land acquisitions and maximize the expenditure of limited public funding. Florida and Maryland present examples of state-level legislation and data and tools that account for wetland migration in land acquisition programs, respectively. Governments can also acquire land voluntarily through the in-kind exchange or “swap” of publicly owned land for privately owned land in strategic conservation areas (e.g., Los Cerritos Wetlands, Long Beach, California). Generally, unobstructed land without any structures on it and restricted to human uses compatible with conservation will provide the simplest means and greatest potential for wetland migration. Land in both priority wetland migration corridors and upland establishment areas should be the aim of comprehensive land acquisition strategies for managed retreat. Regardless, land acquisitions present governments with tradeoffs that require substantial investments in funding both in the short-term to purchase land and use rights and the long-term to manage, monitor, and potentially enforce conservation restrictions. Moreover, as land is converted to public ownership, local governments may face revenue decreases due to a loss of private property taxes. Additionally, to voluntarily acquire property, governments must often overcome common barriers to working with landowners, including government distrust and educating residents about the benefits of wetland conservation. 
• Develop complementary legal tools: Supplementing acquisitions with regulatory or market-based tools for managed retreat can aid in implementing comprehensive strategies to maximize ecosystem benefits. A non-exhaustive list of legal tools that state and local governments could consider include zoning; setbacks; living shorelines/hard armoring restrictions; and Transfer of Development Rights/Purchase of Development Rights programs. As stated above, state coastal zone management regulations and local government zoning, floodplain, and land-use ordinances will likely be the primary instruments for implementing these tools. Maine’s Sand Dune Rules and a natural resource overlay district from Yankeetown, Florida present two respective examples. Again, governments should implement any actions in partnership with the federal, state, and local actors and per applicable laws and private property considerations to minimize potential legal risk.
• Engage communities and diverse stakeholders: Comprehensive wetland conservation strategies should include community engagement throughout their development and implementation. Wetlands — and the environment and natural resources more broadly—are a part of and not a distinct, isolated element of people’s communities. Wetlands provide several quantitative and qualitative benefits for humans (in addition to other species) including reducing flood damage, improving water quality, supporting fishing, recreation, and tourism economies, and serving as tangible refuse and escape. Residents in local communities should be included in decisions regarding wetland conservation from the outset. Educating residents about the value of wetlands can create local stewards, in addition to enhancing the benefits that can be attained for both people and the coastal environment. Moreover, communities can help state and local governments set management objectives in response to data to determine priority actions, like where to establish wetland migration corridors. As previously stated, not all wetlands can and will be saved, so community input should be sought on these potentially life-impacting decisions.
  
  Of particular note, some property owners in rural areas are concerned that wetland migration or “encroachment” could impact existing and future land uses and development. For example, owners of working lands, like farmers and forest managers, could have their revenue-generating acreage decrease when productive lands are naturally converted into wetlands.^{See footnote 17} In addition, private property owners facing wetland migration could unknowingly (due to a lack of education and awareness about this phenomenon) become subject to federal and state regulations that protect wetlands and limit development (e.g., Corps Clean Water Act Section 404 permits, state coastal zone management regulations). This can raise questions about how to balance environmental protection and community needs (especially for frontline, underrepresented communities). As sea levels continue to rise, communities and policymakers will have to evaluate how to protect and preserve wetlands and address private property and community concerns. In order to minimize potential conflicts and maximize benefits, governments should engage community members throughout all stages of these decisionmaking processes from planning development to post-implementation monitoring and evaluation. This should include those who own properties, frequently use, or operate businesses in or adjacent to wetlands or areas identified as potential wetland migration corridors.
• Evaluate diverse funding opportunities: Voluntary land acquisitions will necessitate funding, in addition to restoration and conservation activities associated with land management. Governments should seek different types of federal, state, and local funding that can be used for these purposes, and leverage public-private partnerships with conservation nonprofits and land trusts. Governments can also evaluate the potential for generating revenue for holding land in a conservation status, such as a wetland or carbon offset bank (e.g., Los Cerritos Wetlands, Long Beach, California, Greens Bayou Mitigation Bank, Harris County, Texas). This could be supplemented by in-kind exchanges of land (i.e., through a land swap) and other types of in-kind support, like volunteer time for citizen science or restoration activities or the donation of space to hold community meetings. For more information on available funding and financing options, see the Crosscutting Policy Considerations>Funding section of this toolkit.