Defining desired state of seagrass as a management target to support ecosystem resilience in the Great Barrier Reef

The Great Barrier Reef supports extensive, diverse and essential seagrass ecosystems. What should they look like? Do desirable states vary among the diverse communities found on the reef? These are fundamental questions when setting ecological targets and assessing management success. For complex and dynamic habitats, the answer is not simple. We present a framework to define seagrass desired state for the Reef and adjacent estuaries. This ambitious project included: (1) synthesizing 35 years of survey data with >81,000 observations, (2) predicting potential seagrass habitat, (3) defining 36 seagrass communities within that habitat, and (4) determining the desired state of a key seagrass health indicator – biomass – for each community. This resulted in defining what seagrass habitat within the Reef should look like and where it should occur. In the process, we identified environmental thresholds that define seagrass communities and knowledge gaps. There has been a decadal cycle of decline and recovery for some coastal communities, but other coastal and estuarine communities have not recovered to their desired states in recent years. These research outputs can be used for marine spatial planning and management, including zoning in “representative areas”, hierarchical monitoring design (e.g. RIMReP) and setting ecologically relevant load targets.