Guidelines for evaluating performance of oyster habitat restoration

Abstract

Restoration of degraded ecosystems is an important societal goal, yet inadequate monitoring and the absence of clear performance metrics are common criticisms of many habitat restoration projects. Funding limitations can prevent adequate monitoring, but we suggest that the lack of accepted metrics to address the diversity of restoration objectives also presents a serious challenge to the monitoring of restoration projects. A working group with experience in designing and monitoring oyster reef projects was used to develop standardized monitoring metrics, units, and performance criteria that would allow for comparison among restoration sites and projects of various construction types. A set of four universal metrics (reef areal dimensions, reef height, oyster density, and oyster size-frequency distribution) and a set of three universal environmental variables (water temperature, salinity, and dissolved oxygen) are recommended to be monitored for all oyster habitat restoration projects regardless of their goal(s). In addition, restoration goal-based metrics specific to four commonly cited ecosystem service-based restoration goals are recommended, along with an optional set of seven supplemental ancillary metrics that could provide information useful to the interpretation of prerestoration and postrestoration monitoring data. Widespread adoption of a common set of metrics with standardized techniques and units to assess well-defined goals not only allows practitioners to gauge the performance of their own projects but also allows for comparison among projects, which is both essential to the advancement of the field of oyster restoration and can provide new knowledge about the structure and ecological function of oyster reef ecosystems. Implications for Practice• Requests from restoration practitioners for a set of specific monitoring guidelines tiered to account for limitations in budgets and expertise in oyster restoration projects have been fulfilled by a panel of scientific experts and restoration practitioners. • Oyster restoration projects should monitor established universal metrics primarily focusing on structural attributes (vertical relief of oyster reefs, oyster density, and spatial footprint over time); specific minimum requirements for timing of monitoring are essential. • Measurement of broader ecosystem-based metrics would allow for more thorough examination of specific ecological benefits of restoration projects. • Detailed methodology provided publicly through a workshop report gives restoration practitioners access to training material and reporting information.

Integrating Larval Dispersal, Permitting, and Logistical Factors Within a Validated Habitat Suitability Index for Oyster Restoration

“…In this study, we used oyster density normalized by reef age for model validation. The utility of an index of normalized density is several-fold: (1) ease of calculation based on values that are often known (i.e., age of restoration) and values that are often collected post-monitoring (i.e., density Powers et al, 2009;Baggett et al, 2015), (2) ability to account for observed peaks and declines in density over time (e.g., Figure 1), and (3) relevance to common density-based restoration targets that can be set over a time period (i.e., 100 oyster m −2 over a 20 year period = normalized density of 2000). Normalized density was a statistically-significant exponential function of HSI, providing validity of the HSI as a robust predictor of suitable habitat for oyster sanctuary restoration in Pamlico Sound.…”

Guidelines for evaluating performance of oyster habitat restoration should include tidal emersion: reply to Baggett et al.

“…Monitoring restoration projects is essential to evaluate the success of restoring degraded ecosystems. Thus, we read with interest and appreciation Baggett et al (), as they suggest a common set of metrics with standardized techniques for judging oyster habitat restoration efficacy regardless of initial project goal(s). As oyster reef construction is a rapidly growing field within restoration ecology, such a “lingua franca” is important from a practitioners point of view as it allows better evaluation of individual projects but also enables scientists to draw comparisons among diverse projects and environmental contexts.…”

Shells from aquaculture: a valuable biomaterial, not a nuisance waste product

“…; Baggett et al . ). Restoration programmes and research typically use dredged shells or calcium carbonate‐based structures (concrete reef balls, for instance) to create a suitable settlement site for oyster larvae, then either let the natural larval stock settle if present or seed the reef structures from hatchery stock.…”