A Systematic Review of Facilitation in Intertidal Habitats

Abstract

Recent decades have seen an increase in research on positive species interactions, and it is now known that they are ubiquitous in nature. However, these interactions were never intentionally used in beneficial ways. This changed in 2015 when a study revealed that positive species interactions could aid in salt marsh restoration. Since then, the restoration paradigm has shifted from systematically suppressing negative interactions to harnessing nature’s positive interactions, including ecological facilitation. This review investigates the facilitative interactions that have been observed in intertidal habitats, including salt marshes, mangroves, and oyster reefs. I performed a systematic review to highlight the general trends and research gaps in the study of facilitation across these three intertidal habitats. Seventy-eight studies were included in the database, and the earliest study was published in 1984 in a salt marsh. Since then, studies have increased exponentially. The majority were located in mid-latitudes but were spread across six continents and 18 countries. The 78 studies revealed 212 unique, facilitative interactions. One hundred and thirty-two of these interactions were in salt marshes, 77 were in mangroves, and only 3 were in oyster reefs. The majority of interactions involved autotrophs and lower trophic level species. In addition, the majority of facilitative interactions were direct, interspecific, non-trophic, and involved a primary foundation species. The 78 papers in this database revealed some previously unknown trends in intertidal facilitation which can actively be incorporated into restoration projects. However, this study also revealed the major research gaps in the field that need to be filled in order to more thoroughly establish facilitative theory and most effectively include facilitation in intertidal restoration design.