Living in a material world: Support for the use of natural and alternative materials in coastal restoration and living shorelines

The size and expense of coastal restoration efforts are increasing exponentially to mitigate anthropogenic environmental impacts and achieve international conservation goals. As part of these efforts, a variety of conventional materials including plastic, metal, and concrete are used in breakwater, settling substrate, vegetation stabilization, and sediment retention structures because of their availability, inexpensive purchase price, and predictable properties. However, questions regarding sustainability arise given the adverse environmental impacts of the life cycle processes for each material. Life cycle impacts from production, transportation, installation, and degradation should be key considerations in material selection, with criteria that allow decision makers an opportunity to evaluate less impactful alternative materials. Natural and reduced-impact alternative materials include natural elements such as plant fibers and rock as well as reduced-impact materials such as bio-based and biodegradable plastics. These items may have comparable availability and functionality and exhibit reduced carbon, chemical, and particulate emission impacts. However, they are often not selected for full-scale restoration applications due to uncertainties regarding their financial cost and ability to replace conventional materials. Here, we compare conventional and reduced-impact alternative materials for use in coastal restoration applications. The function, engineering performance, and life cycle environmental impacts are reported for each material followed by a presentation of case studies that illustrate the value of appropriate material selection. We then compare the impacts of material sourcing and product lifespan to develop a material selection framework enhancing the selection process of reduced-impact alternatives. This study reveals a need for more detailed and standardized life cycle information about the materials used in the coastal environment. The proposed framework allows more emphasis on material life-cycle implications in the design process, which could lead to enhanced use of alternative over conventional materials and improved project value and outcomes.