Seagrass meadows can help fight climate change and biodiversity loss - if we can learn how to restore them

Seagrass habitats provide essential ecosystem functions, improving water quality, supporting biodiversity, and mitigating climate change through carbon storage and ocean acidification amelioration. However, they are declining worldwide. Eelgrass (Zostera marina) is the dominant seagrass along the U.S. west coast, and its lush meadows are threatened by conflicting human uses and global change, resulting in significant protections and efforts to restore areas where habitat is extant or degraded. Despite a history of eelgrass restoration in this region spanning nearly 60 years, very little work has been published on the subject, making it hard to know if we are succeeding in our goals to protect and restore these essential habitats. Drs. Melissa Ward and Kathryn Beheshti conducted a review of all available literature on eelgrass restoration projects conducted in California, Oregon, and Washington. Their paper, “Lessons learned from over thirty years of eelgrass restoration on the U.S. west coast”, was recently published in Ecosphere.

Of the 82 restoration projects included, which occurred from 1989 to 2020, only 6 were published in peer-reviewed journals. Dr. Melissa Ward, the corresponding author of the synthesis notes that “despite the precedent for conducting restoration, the lack of available data makes assessing regional success, drivers of failure, and best practices extremely difficult”. 

From this synthesis, they found that the majority of restoration projects (73%) occurred for mitigation (compliance) purposes (i.e., to account for human-induced habitat losses). This contributes to habitat acreage goals, but results in little dissemination on the subject or lessons learned. While eelgrass mitigation policies serve to maintain eelgrass structure and regional acreages, they do not facilitate assessments of habitat function or incentivize advancements in regional best practices. The authors also found that when they could evaluate project outcomes, 32.3 to 59.6% of restoration plots failed by the end of the project - highlighting the need for advances in restoration practices. Dr. Kathryn Beheshti, co-first author on the publication adds, “these estimates of plot failure are highly dependent on how success or failure are defined, a long debated subject in the field of restoration ecology”. According to restoration practitioners, failure was likely to result from environmental factors such as light or excess nutrients, but was occasionally due to logistical factors such as restoration method or approach. Drs. Ward and Beheshti recommend a standardized, evidence-based approach to restoration, improved data sharing practices, and careful consideration of existing eelgrass mitigation practices. 

Marine habitat restoration is entering a new global stage - backed by public and private investment, burgeoning carbon markets, and global biodiversity initiatives, including California’s carbon reduction targets and 30x30 initiatives, among others. It is essential to learn from past work to understand and improve seagrass conservation and restoration success, making syntheses such as theirs, recently published in Ecosphere, a necessary step for progress.

Read the full article here.

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