What Nature-Based Solutions Can And Cannot Do

COASTAL RESILIENCE SERIES  ·  ARTICLE 2 OF 5

Daniel Pingaro, MLA  ·  Ocean Conservation & Coastal Resilience

The professionalization of nature-based solutions in coastal practice has been one of the more significant shifts of the past decade and more. Living shorelines, oyster reef restoration, mangrove rehabilitation, coastal wetland restoration/creation have moved from ecological aspiration to mainstream practice in many contexts. The evidence base for their effectiveness has grown substantially. Funding mechanisms have expanded. Agency and community familiarity has improved. By most measures, this is genuine progress.

But there is a tendency in any maturing field to develop a preferred solution typology and then apply it too broadly to let the enthusiasm for a genuinely good approach outpace the honest accounting of its limits. Nature-based solutions are now at risk of this. The field needs a clearer-eyed conversation about where these approaches work, where they don't, and what the boundaries between those two conditions reveal about our assumptions.

Where the Evidence Is Strong

Living shorelines, the family of approaches that use marsh vegetation, oyster reefs, beach nourishment, and sometimes low-profile structural elements to stabilize shorelines and attenuate wave energy, perform reliably well in specific conditions. Sheltered embayments, low-to-moderate wave energy environments, and transitional zones between upland and subtidal habitat are where the biological and hydrological dynamics align with what these systems are designed to do.

The ecological co-benefits in these settings are real and measurable: improved water quality through filter feeding and nutrient uptake, habitat provision for juvenile fish and invertebrates, carbon sequestration in marsh soils, and shoreline stabilization that typically outperforms hardened structures over a ten-to-twenty year horizon — particularly since hardened structures age, require increasingly costly maintenance, reduce biodiversity, and usually eliminating accessibility to the coast. On a lifecycle cost basis, in the right contexts, nature-based approaches are not just ecologically preferable, they are economically superior.

Mangrove and coastal wetland restoration has similarly strong evidence base in tropical and subtropical contexts. Restored mangrove systems provide measurable storm surge attenuation. Studies from the 2004 Indian Ocean tsunami and Hurricane Irma in 2017 both documented significantly lower damage rates in areas with intact or restored mangrove cover. Tidal wetland restoration as a carbon sequestration strategy, blue carbon, is now sufficiently well-documented to support emerging voluntary carbon market mechanisms, which creates a potentially transformative funding pathway for coastal restoration at scale.

Where the Limits Are Real

The picture changes significantly in high-energy coastal environments. Outer coast exposures, inlet mouths, and headland settings subject to persistent wave attack, storm surge, and longshore sediment transport present conditions that exceed the engineering capacity of most biological systems. Marsh grass does not stabilize a shoreline experiencing two feet of episodic wave runup during storms. Oyster reefs do not significantly attenuate energy on exposed coastlines. The biology is not the limiting factor, the physics are.

In these settings, the appropriate response is often a hybrid approach: structural elements that absorb the high-energy events, combined with biological systems in the lower-energy zones between those events. The design challenge is not choosing between hard and soft infrastructure but calibrating the relationship between them across a dynamic energy gradient. This requires integrated design thinking that most disciplinary silos with engineering on one side, ecology on the other struggle to produce.

There is a third category that is harder to discuss, because it involves not the limits of the solutions but the limits of the coastline itself. In communities facing the most acute near-term risks, low-lying barrier islands, subsiding communities, urban waterfronts with a century of armoring and fill, communities facing consistent wave energy action year-round, the honest technical assessment increasingly points toward managed retreat as the only approach genuinely responsive to what the next fifty years will deliver. No nature-based solution, and no engineered solution, changes the fundamental physics of a coastline losing elevation relative to sea level faster than any intervention can compensate. The profession does communities a disservice when it designs around this reality rather than engaging it directly.

The Assumption Problem

Underlying the limits of nature-based solutions is a deeper assumption worth examining. Much of coastal resilience practice including nature-based approaches is implicitly designed for the coast we have now, with incremental adjustments for projected change. The designs assume that the primary challenge is to attenuate the impacts of increasingly frequent and intense storms on a shoreline that remains more or less where it is.

The science no longer supports this assumption in many coastal contexts. The projections for sea level rise along the entire U.S. coastline, which is experiencing both global sea level rise and regional subsidence in specific locations, describe a future in which large portions of the current coastal landscape are periodically or permanently inundated within the planning horizon of infrastructure being designed today. Nature-based solutions can extend the functional life of a coastline under moderate scenarios. They cannot reverse the fundamental trajectory under high-end scenarios.

Designing for adaptive capacity, building systems that can evolve as conditions change, rather than systems that assume stable conditions, is the more honest framework. This means designing living shorelines with the understanding that the marsh platform may need to migrate landward. It means siting coastal wetland restoration with attention to future accommodation space. It means being explicit, in every design, about the climate scenario it is designed for and the conditions under which it will need to be reassessed.

The profession's credibility in coastal resilience work depends on being clear about this. Deployed as a universal answer, nature-based solutions become a way of avoiding the harder conversation about what the coast is actually becoming. Deployed with rigor and intellectual honesty, they are among the most important tools available.

NEXT IN THE SERIES

Article 3: Trust as infrastructure — why community engagement in coastal resilience is not a process step but a foundational design condition, and what it requires.

Daniel Pingaro, MLA

Ocean conservation and coastal resilience executive. Former USEPA, CEO of Sailors for the Sea & Ocean Institute, Executive Director Laguna Beach Community Foundation.

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