A centuries-old legal principle guaranteeing public access to coastal shorelines is facing an unprecedented challenge from climate change. As global warming accelerates sea-level rise, the ambulatory high-tide line—the legal boundary between private property and public land—is steadily moving inland. This migration of the tidal boundary is shrinking sandy beaches, intensifying conflicts between private landowners and the public, and forcing a legal and societal reckoning over who has the right to the coast.
The core of the issue lies in a phenomenon known as “coastal squeeze,” where the rising sea pushes the public portion of the beach inland, only for it to be blocked by man-made structures like sea walls. This traps the beach between a rising ocean and an unyielding barrier, leading to the erosion and eventual disappearance of the sandy public space that provides recreation, economic benefits, and ecological habitats. As the ocean claims more of the shore, the legal framework that has long preserved public access is being tested, raising difficult questions about property rights, environmental protection, and the future of coastal communities.
The Shifting Sands of Legal Ownership
The right of the public to access and use coastal areas is rooted in the public trust doctrine, a legal concept with origins in Roman law that was later adopted into U.S. common law. This doctrine holds that certain natural resources, including tidelands, are held in trust by the state for the benefit of the public. In most coastal states, the boundary between private property and these public trust lands is the mean high-tide line, a scientifically determined average of high tides over a specific period. This line is not fixed; it naturally moves seaward and landward with the erosion and accretion of sand.
Historically, this ambulatory boundary has allowed for a dynamic but generally stable system of shared coastal use. However, with sea levels rising, the mean high-tide line is now on a long-term inland trajectory. This means that, over time, land that was once considered private can become public trust land as it is submerged by the rising tides. This has created a legal gray area and a source of increasing tension, as private property owners see their land being subsumed by the sea, while public access advocates fight to preserve the public’s right to the shore.
A Legal Framework Under Pressure
The legal and regulatory frameworks governing coastal management are struggling to keep pace with the rapid changes brought on by sea-level rise. In California, for example, the Coastal Act of 1976 enshrined public access rights and gave the California Coastal Commission broad authority to regulate coastal development. However, the act also includes provisions that allow for the construction of sea walls to protect homes built before 1977, creating a direct conflict with the goal of preserving public beaches. As the sea continues to rise, these legal frameworks are being tested in courtrooms and legislative chambers across the country, forcing a re-evaluation of long-held assumptions about property rights and public access in the face of a changing climate.
A ‘Coastal Squeeze’ on Public Space
The primary threat to public beach access from rising seas is a process known as “coastal squeeze.” This occurs when the high-tide line moves inland due to sea-level rise, but is prevented from migrating naturally by a fixed, hard structure like a sea wall, revetment, or building. The result is a narrowing of the sandy beach, and in many cases, its complete disappearance. When waves hit a sea wall, the energy is reflected, scouring sand from the base of the wall and accelerating erosion. This process, combined with the rising water levels, effectively “drowns” the beach, eliminating the public space between the high and low tide lines.
Coastal armoring is a widespread practice, with scientists estimating that about a third of the world’s sandy coastlines have already been hardened. While these structures may protect individual properties in the short term, they often do so at the expense of the broader community and the environment. The loss of sandy beaches not only curtails public access and recreational opportunities but also destroys critical habitats for coastal wildlife and reduces the natural buffer that beaches provide against storm surge. The choice facing many coastal communities is becoming a zero-sum game: protect the private property or protect the public beach.
California’s Proactive Stance
In response to the growing threat of beach loss, some states are taking proactive measures to address the issue. California, a state with an iconic coastline and a strong legal tradition of public access, has been at the forefront of this effort. In May 2023, the California Coastal Commission unanimously adopted a new Public Trust Guiding Principles and Action Plan, which provides a framework for managing the state’s coastal resources in the age of climate change. The plan explicitly recognizes the ambulatory nature of the public trust boundary and aims to ensure that public access is preserved as sea levels rise.
Navigating a Changing Coastline
The new guidance in California does not expand the Coastal Commission’s authority, but it does provide a clear direction for how the commission should make decisions regarding coastal development. It emphasizes the need to consider the long-term impacts of sea-level rise and to prioritize solutions that allow the beach to migrate inland, a strategy often referred to as “managed retreat.” This may include limiting the construction of new sea walls, requiring setbacks for new development, and exploring nature-based solutions to coastal erosion. The goal is to avoid a future where California’s famed beaches are replaced by a line of armored properties with no public access to the shore.
The Science of Rising Tides
The threat to public beaches is driven by the inexorable rise of the world’s oceans, a direct consequence of global warming. The primary drivers of sea-level rise are the thermal expansion of seawater as it warms and the melting of land-based ice sheets and glaciers. Current projections indicate that global sea levels could rise by 3 to 6 feet by the end of the century, with some scenarios suggesting an even more dramatic increase if the Antarctic and Greenland ice sheets melt more quickly than anticipated. A 3-foot rise in sea level would have a profound impact on coastlines worldwide, leading to increased flooding, erosion, and the permanent inundation of low-lying areas.
In addition to the long-term trend of sea-level rise, other factors can exacerbate the problem. For example, a natural phenomenon known as the “moon wobble,” a cyclical shift in the moon’s orbit, can amplify high tides, leading to more frequent and severe coastal flooding. This effect, combined with the steady rise in sea level, is projected to cause a significant increase in the number of high-tide flooding days in the coming decades.
Economic and Environmental Consequences
The loss of public beaches has far-reaching consequences that extend beyond the loss of recreational space. Coastal tourism is a multi-billion dollar industry in many parts of the world, and sandy beaches are often the main attraction. As beaches disappear, so too will the economic activity they generate, leading to job losses and a decline in property values. A 2022 report by the California State Lands Commission estimated that the economic damages and replacement costs for vulnerable assets on just a fraction of the state’s public trust lands could exceed $19 billion by 2100, with an additional $5 billion in lost value for natural resources and recreational amenities.
The environmental impacts of beach loss are equally severe. Beaches provide a critical habitat for a wide variety of species, from shorebirds and sea turtles to the tiny invertebrates that form the base of the coastal food web. As beaches are squeezed between rising seas and coastal armoring, these habitats are lost, leading to a decline in biodiversity. Beaches also serve as a natural defense against coastal storms, absorbing wave energy and protecting inland areas from flooding and erosion. The loss of this natural buffer will leave coastal communities more vulnerable to the impacts of climate change.
The Inevitable Trade-offs Ahead
The conflict over public beach access in an era of rising seas highlights the difficult choices that coastal communities must make in the coming years. The traditional approach of armoring the coast to protect private property is becoming increasingly untenable, as it often leads to the destruction of the very beaches that make the coast a desirable place to live. As Richard K. Norton, a professor of urban and regional planning, has stated, “Are you going to save the beach house, or do you want to save the beach? Because you cannot save them both.”
Moving forward, a new paradigm for coastal management is needed, one that recognizes the dynamic nature of the shoreline and prioritizes the long-term health of the coastal ecosystem. This may involve a combination of strategies, including managed retreat, the restoration of natural coastal habitats, and the development of innovative engineering solutions that can protect coastal communities without destroying public beaches. The decisions made in the coming years will determine the future of our coastlines and the public’s right to access and enjoy them for generations to come.
