Evaluating restoration success using metric-based indicators of ecosystem recovery in tidal marshes along the northern Gulf of Mexico

Habitat restoration is commonly used to recover ecosystem services, but
due to resource constraints, post-project monitoring often fails to fully
evaluate the recovery of important ecosystem functions. Metric-based
indicators use simple-to-measure variables to assess ecosystem health and
function, thereby providing a time- and cost-effective method to improve
monitoring. We used a tidal marsh dataset to develop metric-based
indicators of ecosystem recovery. In 2021 and 2022, we surveyed eight
restored/created and three natural reference tidal marshes in the northern
Gulf of Mexico to assess recovery of ecosystem attributes [e.g., above-
and below-ground biomass, soil organic matter (SOM), and sediment total
carbon (C) and total nitrogen (N)]. To determine what combinations of
variables best predicted recovery, we split our data into model training
and testing datasets, used backward model selection, and then created and
tested a metric-based indicator of ecosystem recovery. Recovery of plant
above- and below-ground biomass and sediment structure (i.e., SOM, C, and
N)—important measures of wetland carbon sink capacity and biogeochemical
functioning—could be predicted through a combination of simpler-to-measure
variables, such as time since restoration, percent plant cover, and
sediment bulk density. The indicator constructed from these relationships
was highly effective in predicting the development of ecosystem attributes
(r = 0.85, p < 0.001). This indicator approach provides an
effective but simple method to assess the recovery of ecosystem attributes
in tidal marshes, and it can be used to develop similar indicators in
other ecosystems. By overcoming resource constraints of post-project
monitoring, metric-based indicators of ecosystem recovery may serve as a
key strategy to improve restoration outcomes.