by Ashley Tuggle

Having come from the dense pine forests of North Carolina, I prepared myself for downed trees and delays after a recent wind storm swept the coast of Southern California. Instead of crews of city workers clearing tree branches, I noticed the palms swaying precariously overhead, but never breaking. It prompted the question: Why don’t palm trees break and fall as easily as other trees in high wind?

Palms are not your average tree, and depending on your definition, might not be a tree at all. They’re monocots, which means they have more in common genetically with wheat than the sweetgum, maple, or oak in your backyard^[1]. What makes them so flexible is that palms lack secondary xylem, a tissue that carries water throughout plants along with some nutrients. As a result, palm trees are much less vulnerable to wind because they bend.

Nature provides a cornucopia of these types of adaptations that help plants and animals and the habitats that support them survive in extreme conditions. For example, many species of mangroves have an extensive network of roots that stabilize them in the face of oncoming storm surges, which protects the shoreline by slowing water down.

The U.S. experienced the most extreme weather events in 2012, the most since such record-keeping began in 1910. In thinking about designing for the future and restoring what might be lost from events like Superstorm Sandy, it’s important to build back better rather than just rebuild.

Coastal communities must be able to reduce the initial impact from extreme storms, resistance, and recover in their wake, resilience. While man-made structures can provide some resistance, they require maintenance and repairs. In addition, they may also not provide the same services that an equivalent natural system would in tandem with their protective abilities. A combination of man-made and natural structures, such as oyster reefs, will provide the optimal protection.

Oyster reefs provide natural protection against storms as well as critical ecological and economical benefits to our shorelines. Ecologically, oyster reefs improve estuary water quality by filtering nutrients and provide feeding grounds and habitat for commercially valuable fisheries. An oyster reef not only slows and absorbs wave energy, protecting a shoreline from erosion, but is also able to naturally and efficiently regenerate after an extreme weather event. One study found that after two back-to-back hurricanes in the Gulf of Mexico, oyster reefs recovered fully within only a year, providing the same level of ecological benefits as before. In addition to oyster reefs, barrier islands and coastal wetlands help slow down waves before they can reach habitats further inland.

Restoring and protecting our shorelines has become a central focus of restoration and resiliency efforts. The combination of natural habitats and man-made structures is essential for protecting our shorelines against future damage. This is particularly relevant to the current debate about how to address the aftermath of Sandy. We need to recognize that while enhanced ecological designs will not completely ameliorate the impacts of extreme weather events, communities designed to be more ecologically sound may reduce the initial impacts and contribute to a swifter recovery.

Like the palm tree, we need ecological designs that aren’t going to be swept away by storms, but move with and protect our shorelines.

References:

[1] Haynes, J.L. The Palm Encyclopedia.

National Climatic Data Center. Climate Extremes Index

Alves, L.F. F.R. Martins, and F.A.M. Santos. Allometry of a neotropical palm, Euterpe edulisMart.

Livingston, R.J., R.L. Howell IV, X. Niu, F.G. Lewis III, and G.C. Woodsum. Recovery of oyster reefs (Crassostrea virginica) in a Guld estuary following disturbance by two hurricanes.