Targeting ocean conservation outcomes through threat reduction

Global biodiversity loss is accelerating despite efforts like expanding protected areas. Marine ecosystems are particularly vulnerable due to human activities and climate change, leading to extinction rates far exceeding natural levels. Existing metrics for measuring marine biodiversity impact are insufficient, hindering accountability and progress toward conservation goals such as the Kunming-Montreal Global Biodiversity Framework (GBF) and Sustainable Development Goals (SDGs) 14 and 15. The Species Threat Abatement and Restoration (STAR) metric, already used in terrestrial contexts and adopted by the private sector, provides a solution by quantifying the impact of threat reduction on extinction risk. This study adapts the STAR metric (specifically the threat abatement component, STARt) to the marine environment to address this gap, aiming to provide a tool to inform conservation planning and action at multiple levels.

The literature highlights the continued biodiversity loss in both marine and terrestrial environments despite the growth in protected areas. Studies show that protected area designation often prioritizes ease of establishment over effectiveness in reducing species extinction risk. The challenges of measuring marine biodiversity, due to data scarcity and a lack of appropriate metrics, are also discussed. The Kunming-Montreal Global Biodiversity Framework and Sustainable Development Goals underscore the need for improved metrics to track progress towards conservation targets. Existing studies point to the significant threats to marine biodiversity from overfishing, habitat loss, pollution, and climate change, impacting various species groups.

This study develops a marine version of the threat abatement component of the STAR metric (STARt). It included 1646 marine species assessed by the IUCN Red List as Near Threatened or threatened (Critically Endangered, Endangered, Vulnerable). The STARt scores were calculated using a 5 km x 5 km grid cell resolution, summing the proportion of each species' area of habitat (AOH), weighted by its IUCN Red List category and threat contribution. The methodology involved identifying species for inclusion, removing species with inadequate range data, assessing threats using the IUCN Threat Classification Scheme, and prioritizing threats based on their impact on species extinction risk. Data sources included the IUCN Red List database, the World Database on Protected Areas (WDPA), Key Biodiversity Areas (KBAs), Important Marine Mammal Areas (IMMAs), and Large Marine Ecosystems (LMEs). The analysis involved geospatial analysis in R using packages like ‘terra’, ‘exactextractr’, ‘tidyverse’, and ‘sf’ to extract global and regional statistics for countries, protected areas, and other designated areas.

The study found that reducing unsustainable fishing offers the greatest opportunity to lower marine species extinction risk (43% of the marine STARt score). A significant portion (75%) of the global marine STARt score lies outside protected areas, with only 2.7% within no-take protected areas. Indonesia, Australia, Mexico, the Philippines, Brazil, and China hold the largest percentages of the global marine STARt score. The Indonesian Sea had the highest STARt score among LMEs. Areas with high STARt scores outside protected areas include Taiwan and Cabo Verde. Climate change, invasive species, and pollution also contribute substantially to the global marine STARt score. The study also highlighted the importance of considering STARt density to identify smaller areas with high extinction risk such as Singapore, Belize, and Gibraltar. The analysis shows the complementary nature of the STARt metric with other conservation planning tools like KBAs, EBSAs, and IMMAs. The limitations of available data, particularly for deep-sea and Arctic regions, are also noted, affecting taxonomic coverage.

The findings demonstrate the need for effective placement and design of marine protected areas to protect biodiversity. The significant contribution of overfishing and climate change to extinction risk highlights the importance of targeted management strategies beyond protected areas. The spatial disaggregation of STARt scores by threat and geography helps identify areas and threats requiring priority attention. The metric’s application in conservation planning is illustrated by its complementary use with existing biodiversity designations (KBAs, EBSAs, IMMAs). The study acknowledges limitations in data availability, particularly for understudied regions and taxa, but emphasizes the value of STARt as a tool for prioritizing conservation actions.

The extension of the STAR metric to the marine realm provides a valuable tool for guiding ocean conservation efforts. The findings emphasize the need for a shift beyond solely relying on protected area expansion to address the major threats to marine biodiversity, particularly unsustainable fishing and climate change. Future research should focus on improving data availability, particularly for understudied areas and taxa, and refining the STAR metric to incorporate temporal changes in threats and habitat restoration potential. Harmonizing marine, terrestrial, and freshwater STAR scores will also enhance its comprehensive application.

The study acknowledges several limitations. Data availability for marine species is limited, particularly for deep-sea and Arctic regions, potentially leading to geographic biases in STAR scores. Taxonomic coverage could also be improved as further IUCN Red List assessments are completed. The spatial footprint of threats is derived from species ranges, assuming uniform threat distribution, which may not always reflect reality. The restoration component of the STAR metric was not incorporated in this study. The study does not capture immediate and long-term severity of the accelerating impacts of climate change on species.