Stuart H. M. Butchart

The IUCN Red List of Threatened Species, the most widely used global system for assessing species’ extinction risk, has become a foundational source of information for conservation management, policy and research. Since the adoption of quantitative extinction risk criteria more than three decades ago, the Red List has expanded substantially in scope and influence, informing decisions ranging from species conservation and protected area designation to international agreements, corporate risk assessments and global biodiversity indicators. Given its central role, maintaining scientific rigour, transparency and trust in the Red List system is essential. Feedback from users, emerging from evolving applications and scientific advances, has shaped the Red List throughout. At the same time, the Red List has been subject to recurring critiques, some of which stem from persistent misconceptions about its purpose, design and appropriate use. To address these, we review the history and development of the Red List system, clarify the strengths of its design, delineate the contexts for which the system was and was not intended, and elucidate the circumstances under which it may be modified. Finally, we outline pathways for researchers and users to contribute to ongoing improvements and discuss potential future directions for evolution of the Red List.

1. Aim: The Species Threat Abatement and Restoration (STAR) metric was developed to support setting and measuring progress towards science-based targets for species conservation, in alignment with the Kunming-Montreal Global Biodiversity Framework. The STAR metric quantifies the potential reduction in species’ global extinction risk achievable through actions to abate threats (STAR _T ) and restore habitat (STAR _R ). The STAR metric is used across multiple sectors to assess contributions to nature-positive species outcomes and implement action for biodiversity. Here we present a substantially enhanced global estimate of STAR _T for terrestrial vertebrates. Developed in response to user demand, this work integrates advancements in methodology and data quality, increased spatial resolution, and addition of reptile species. Location: Global Time Period: Current Major taxa studied: Terrestrial vertebrates Methods: STAR _T was estimated at 1km ² resolution for 9,100 species of threatened and Near Threatened birds, mammals, amphibians and reptiles, using IUCN Red List assessments (version 2025-1) and area of habitat (AOH) maps generated using an advanced data-driven methodology and satellite-derived land-cover data. AOH maps were validated using a two-stage protocol using species observation data. Results: The six countries with the highest estimated STAR _T scores, and therefore the largest individual potential to reduce global extinction risk via tackling threats nationally were Brazil, Madagascar, Indonesia, Mexico, Ecuador and Colombia (each contributing over 5% of global estimated STAR _T ). The threat with the greatest individual potential to reduce extinction risk was annual and perennial non-timber crops (21.2% of global STAR _T ). Main conclusions: Targeted actions to tackle a few high-impact threats in a few discrete locations, and cumulative effort across multiple areas with lower individual potential, are both required to meaningfully reduce species’ extinction risk through threat abatement. This global scale estimation of STAR _T enables consistent scoping of conservation opportunity over large areas and provides the critical initial data to support planning and action.

Target 4 of the Kunming–Montreal Global Biodiversity Framework (KMGBF) calls for urgent management actions to halt human-induced extinctions and enable species recovery. However, most Parties face substantial challenges in determining which species require urgent management actions. Here, we present a transparent, standardised protocol that identifies and ranks species most likely to need urgent management actions at the national level, using globally available data from the IUCN Red List of Threatened Species. The protocol integrates four criteria aligned with Target 4: global extinction risk, rate of decline, population or range restriction, and endemism, to generate a national ranked list of species. Species scoring highly on these four criteria, and therefore most in need of urgent management action, are ranked most highly. We applied this method to all 250 countries and territories listed in the IUCN Red List and pilot-tested national rankings with participants from eight diverse countries. Across pilots, participants reported that the ranked lists were scientifically robust, time-saving, and valuable starting points for national priority-setting, while stating the importance of national context, and the need for additional technical and financial support for implementation. Our results demonstrate that a science-based approach can meaningfully support Parties in identifying species requiring urgent action under Target 4, in a standardised way. With 2030 approaching rapidly, this protocol provides an immediate, practical tool to accelerate progress toward halting extinctions and advancing species recovery.

A global standard for the identification of Key Biodiversity Areas (KBAs) was published 10 years ago to provide a unified set of criteria for identifying ‘sites of significance for the global persistence of biodiversity’. We review the initiative's origins, the KBA identification process, characteristics of the current network, threats, policy uptake, private sector applications and future priorities. KBAs are identified using criteria with quantitative thresholds relating to threatened or geographically restricted species or ecosystems, ecological integrity, biological processes, or irreplaceability. These criteria can be applied in terrestrial, inland water, marine and subterranean environments, and to all taxonomic groups. A total of 16,596 KBAs covering 22.1 million km ² has been identified, with 29% of these sites in marine and 26% in freshwater ecosystems. KBAs range from 0.001 km ² to 712,457 km ² in extent, with a median size of 141 km ² and a mean of 1,364 km ² . Most (63%) qualify due to the globally threatened species they support, with 48% being important for biological processes and 39% for geographically restricted species. KBAs have been identified for 18,365 qualifying species in total, of which 37% are plants and 32% are birds. The most prevalent threats are biological resource use (hunting, logging, fishing, etc., impacting 40.8% of sites with available data), unsustainable agriculture (40.7%), human intrusions and disturbance (38.4%) and natural systems modifications (water management and fire; 33.4%). KBAs are important for delivering ecosystem services to people, both locally and globally. KBAs have had widespread impact in informing protected area designation in all regions. In total, 10,054 sites (62%) are covered completely or partially by protected areas. Hence, KBAs are highly relevant to Target 3 (and other targets) in the Kunming–Montreal Global Biodiversity Framework, and to Sustainable Development Goals 14.5, 15.1, and 15.4. Indicators based on KBA data are therefore being used by the Convention on Biological Diversity and United Nations to track progress towards these targets. Many companies and financial institutions use KBAs to assess their exposure to nature‐related risks and to identify opportunities for site‐level, nature‐positive actions. Future priorities include expanding and updating KBA assessments, and strengthening efforts to protect, conserve and safeguard these sites effectively.

Area of habitat (AOH) maps provide a high‐resolution representation of the habitat available in a species’ range and can support conservation policy and planning processes. However, until recently, there was insufficient knowledge on the distribution of inland wetlands and freshwater biodiversity to develop AOH mapping methods specifically tailored to inland wetlands. We used a combined empirical and thematic approach to translate inland wetland habitat classes in the International Union for Conservation of Nature (IUCN) Habitats Classification Scheme into spatially explicit wetland‐cover types derived from the Global Lakes and Wetlands Database 2 and the World Karst Aquifer Map. The AOH was subsequently estimated as the area in the mapped range that corresponded to each species’ habitat and elevation associations. We developed and tested the method with IUCN Red List assessment data, range maps, and point locality data for fishes, odonates, decapod crustaceans, and mollusks (22,876 species). The method performed well in comparison with similar methods already developed for terrestrial mammals, birds, amphibians, and reptiles. The mean map prevalence (proportion of area in a species’ range that was AOH) was 18–32% for each taxonomic group. Based on data on known localities of occurrence, 78–100% of species per taxonomic group had a higher classification accuracy than expected if AOH were distributed in the range at random. This represents an increased accuracy in the distribution of wetland species. Our study represents the first attempt to distinguish between inland wetland habitat subclasses and to include subterranean habitats in an AOH mapping method. Our method will facilitate the inclusion of previously underrepresented taxa in key conservation tools and analyses and is expected to increase the accuracy of AOH mapping for any species associated with inland wetlands.

The Kunming-Montreal Global Biodiversity Framework (GBF) is the most ambitious multilateral agreement on biodiversity to date. It calls for a whole-of-government and whole-of-society approach to halt and reverse biodiversity loss worldwide. The GBF’s monitoring framework lays out how Parties to the Convention on Biological Diversity are expected to report on their progress. An expert group convened by the Convention on Biological Diversity, the Ad Hoc Technical Expert Group (AHTEG) on Indicators, provided guidance on its implementation, including a gap analysis to identify the strengths and limitations of the indicators in the monitoring framework. We present the results of the AHTEG gap analysis and provide recommendations on implementing and improving monitoring of the GBF. We compare three implementation scenarios, from worst-case to best-case: (1) Parties only report on required headline and binary indicators; (2) Parties also report on all headline indicator disaggregations and (3) Parties additionally report on all optional component and complementary indicators. In each case, the monitoring framework covers (1) between 19–40%, (2) 22–41% and (3) 29–47% of the elements in the GBF’s goals and targets. Even in the best-case scenario (3), no indicators are available for 12% of the GBF’s elements. In practice, the coverage and thus effectiveness of the monitoring framework will depend on which indicators (required and optional) and disaggregations countries apply. Substantial investment is required to collect the necessary data to compute indicators, infer change and effectively monitor progress. We highlight important next steps to progressively improve the efficacy of the monitoring framework.

Understanding the consequences of past conservation efforts is essential to inform the means of maintaining and restoring species. Data from the IUCN Red List for 67,217 animal species were reviewed and analyzed to determine (i) which conservation actions have been implemented for different species, (ii) which types of species have improved in status and (iii) which actions are likely to have driven the improvements. At least 51.8% (34,847) of assessed species have actions reported, mostly comprising protected areas (82.7%). Proportionately more actions were reported for tetrapods and warm-water reef-building corals, and fewer for fish, dragonflies and damselflies and crustaceans. Species at greater risk of extinction have a wider range of species-targeted actions reported compared with less threatened species, reflecting differences in documentation and conservation efforts. Six times more species have deteriorated than improved in status, as reflected in their IUCN Red List category. Almost all species that improved have conservation actions in place, and typically were previously at high risk of extinction, have smaller ranges and were less likely to be documented as threatened by hunting and habitat loss or degradation. Improvements in status were driven by a wide range of actions, especially reintroductions; for amphibians and birds, area management was also important. While conservation interventions have reduced the extinction risk of some of the most threatened species, in very few cases has full recovery been achieved. Scaling up the extent and intensity of conservation interventions, particularly landscape-scale actions that benefit broadly distributed species, is urgently needed to assist the recovery of biodiversity.

The intensification and expansion of croplands are among the greatest threats to biodiversity, but the likely responses to these changes remain unknown for most species. Using data on responses of 862 bird species to changes in yields of arable crops, we extrapolate vulnerability to agriculture for the world’s other terrestrial birds based on their traits and taxonomy. We estimate that 74-78% of terrestrial bird species globally suffer population declines where natural habitats are replaced by croplands, and that over half cannot persist in cropland at even the lowest current yields. Past impacts of agriculture on birds have been greatest in the tropics, particularly in coastal forest regions of Central and South America and West Africa and in southern and South-East Asia. Using these estimates to model the impacts of future scenarios of agricultural change, we find that continuing current rates of cropland expansion and yield increases (i.e., extrapolating ‘business-as-usual’ trends to 2050) is expected to have more negative impacts on birds (particularly in Central and South America, Eastern Europe, sub-Saharan Africa and South and East Asia) than a potential alternative of a targeted strategy of closing yield gaps while limiting cropland expansion. However, we also identify biodiverse regions of the world where closing yield gaps may have more severe impacts on birds than business-as-usual, such as the Pampas of South America and parts of the Sahel region in West Africa. The strategy of least impact for a particular area can be predicted from the response characteristics of the communities of species present there, offering opportunities to take account of regional context for designing less damaging global food production systems.

The Red List Index (RLI) is an indicator of the average extinction risk of groups of species and reflects trends in this through time. It is calculated from the number of species in each category on the IUCN Red List of Threatened Species, with trends influenced by the number moving between categories when reassessed owing to genuine improvement or deterioration in status. The global RLI is aggregated across multiple taxonomic groups and can be disaggregated to show trends for subsets of species (e.g. migratory species), or driven by particular factors (e.g. international trade). National RLIs have been generated through either repeated assessments of national extinction risk in each country or through disaggregating the global index and weighting each species by the proportion of its range in each country. The RLI has achieved wide policy uptake, including by the Convention on Biological Diversity and the United Nations Sustainable Development Goals. Future priorities include expanding its taxonomic coverage, applying the RLI to the goals and targets of the Kunming–Montreal Global Biodiversity Framework, incorporating uncertainty in the underlying Red List assessments, integrating into national RLIs the impact of a country on species’ extinction risk abroad, and improving analysis of the factors driving trends. This article is part of the discussion theme issue ‘Bending the curve towards nature recovery: building on Georgina Mace's legacy for a biodiverse future’.