Global success in oyster reef restoration despite ongoing recovery debt

Abstract

Habitat destruction and biodiversity loss from exploitation of ecosystems have led to increased restoration and conservation efforts worldwide. Disturbed ecosystems accumulate a recovery debt - the accumulated loss of ecosystem services - and quantifying this debt presents a valuable tool to develop better ecosystem restoration practices. Here, we quantified the ongoing recovery debt following structural restoration of oyster habitats, one of the most degraded marine ecosystems worldwide. We found that whilst restoration initiates a rapid increase in biodiversity and abundance of 2- to 5-fold relative to unrestored habitat, recovery rate decreases substantially within a few years post-restoration and accumulated global recovery debt persists at >35% per annum. Therefore, while efficient restoration methods will produce enhanced recovery success and minimise recovery debt, potential future coastal development should be weighed up against not just the instantaneous damage to ecosystem functions and services but also the potential for generational loss of services and long-term recovery.

Reef design influences habitat provision on a restored oyster reef

“…For example, given a limited amount of restoration substrate, restoration designs could be prioritized by their ability to meet criteria such as maximizing reef area available to be settled by oysters, or increasing reef height to potentially avoid deleterious conditions (e.g., hypoxia) and be exposed to favorable conditions (e.g., increased food quality) associated with deeper water (Breitburg et al, 2000). Whereas low-relief reef designs can be beneficial in increasing the restoration footprint and meeting largescale ecosystem restoration goals (e.g., La Peyre et al, 2022;Hemraj et al, 2022), decreasing the areal footprint in exchange for increasing reef height can enhance ecological benefits and habitat resilience (Lenihan, 1999;Tolley and Volety, 2005;Powers et al, 2009;Gregalis et al, 2009;Schulte et al, 2009;Powell et al, 2012;Colden et al, 2017;Peters et al, 2017). In this study, we evaluate habitat provision for oysters and motile reef-resident fauna on highand low-relief restored oyster reefs for 36 months after reef construction.…”