What works to improve species conservation state? An analysis of species whose state has improved and the actions responsible
Ashley T. SimkinsiD, William J. SutherlandiD, Lynn V. DicksiD, Craig Hilton‐TayloriD, Molly K. GraceiD, Stuart H. M. ButchartiD, Rebecca A. SenioriD, Silviu O. PetrovaniD
Abstract
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 comprehensively assessed animal species were reviewed and analysed to determine (i) which conservation actions have been implemented for different species, (ii) which types of species have improved in state 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%), with more actions reported for both terrestrial 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 to less threatened species, reflecting differences in documentation and conservation efforts. Six times more species have deteriorated rather than improved in their Red List category. Almost all species that improved have conservation actions in place; species that improved in state typically were historically at high risk of extinction, have smaller ranges and lacked a range of reported threats, particularly hunting and habitat loss or degradation. All types of conservation action were associated with improvements in state, especially reintroductions and invasive species control, alongside, for amphibians and birds, area management. This suggests a range of conservation interventions have successfully conserved some species at greatest risk but have rarely recovered populations to resilient levels. 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.
02 /Specification & Classification
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In-depth summary
Claude Opus 5.5 · xhigh effort · 8 Nov 2026 · from the full text of version 1 (7 Aug 2024) · CC BY 4.0
Across 67,217 IUCN-assessed animal species, deteriorations in Red List category outnumber improvements sixfold; reintroductions and invasive species control are most consistently linked to recovery.
Evidence on which conservation actions work is scattered and skewed toward birds, mammals, North America, Europe and protected areas, and practitioners often lack the time or incentives to publish outcomes. Mining tabular and narrative IUCN Red List data, including genuine category changes and Green Status counterfactuals, gives a multi-taxon view of which actions accompany species recovery.
Key results
ShownRecovery is rare. Many more amphibians, birds and mammals have genuinely worsened than improved in Red List category, and very few species overall show increasing global populations.
Net deterioration in 1,220 vs net improvement in 202 species (amphibians, birds, mammals); 25 species moved from Least Concern to Critically Endangered, none moved the reverse way; 969 of 67,217 species (1.4%) have increasing population trends; 289 genuine improvements since 1980 across all groups. · Species with improvements in conservation state; How are species changing in Red List category?
ShownAbout half of comprehensively assessed animal species have any documented conservation action, and most of these records are occurrence in protected areas. Coverage favours terrestrial tetrapods and reef-building corals over fish, dragonflies and crustaceans.
34,847 of 67,217 species (51.8%) have actions; 7,380 of 12,574 threatened species (58.7%); protected areas 32,793 of 34,847 (82.7%); taxon effect X^2 = 15364, df = 12, p < 0.001. 5,194 threatened species lack actions (41.0% freshwater fish), and at least 778 of these need urgent management. · Numbers of conservation actions in place for…; Types of conservation actions in place for…; Which conservation actions have been implemented…
ShownNearly every species that recovered had conservation action in place. Assessors credited most bird and mammal improvements to conservation, often to a combination of actions.
Of 289 improved species, only 13 lacked tabulated actions and 11 of those had actions in narratives (two with none: Craugastor taurus, Notomys cervinus); 759 of 969 (78.3%) increasing species have actions; 91 of 128 bird and mammal improvements (71%) attributed to conservation, 58 (63.7%) with two or more actions. · Species with improvements in conservation state; Drivers of genuine improvements in Red List…
SuggestedReintroduction or translocation and invasive or problematic species or disease control were each associated with improvement on all three indicators; for amphibians, protected areas and area management plans tracked improving trends, while several actions were linked to deterioration overall.
Variables retained after backward selection in cumulative link mixed models (population trend, genuine category change) and a logistic GLMM of prevented declines across 35 Green Status species; legislation, awareness and species management plans were linked to deterioration overall; estimates are in Table S3 (not in the text). · Models of improvements in species conservation…; Actions; Actions with mixed associations with species…
ShownCredited actions differed from those merely in place: for birds, area management plans, reintroductions and invasive control were credited most often, though protected areas and species management plans were most common; monitoring was rarely credited, and mammal differences were not significant.
Birds and mammals combined X^2 = 71.739, df = 9, p < 0.001. Birds: in place, protected areas 86 and species management plans 69; credited, area management and reintroduction 30 each, invasive control 27, legislation/trade 6, monitoring 3 (X^2 = 75.418, df = 9, p < 0.001). Mammals X^2 = 9.509, df = 7, p = 0.218. · Drivers of genuine improvements in Red List…
Methods, data and reproducibility
Red List version 2023.1 data for comprehensively assessed animal groups were tallied by action, taxon and category and tested with chi-squared tests. Population trend and genuine category change were modelled with cumulative link mixed models, and Green Status prevented declines with a logistic generalised linear mixed model (GLMM), each using backward selection on traits, threats and actions.
- IUCN Red List version 2023.1 global assessments of comprehensively assessed animal groups (traits, threats, actions in place, population trend, range maps) · multiple animal groups (e.g. amphibians, birds, mammals, fish, corals) · n = 67,217 species
- Genuine Red List category changes from Red List Index data plus additional changes identified 2016 to 2022, with assessor justifications · animals (mainly amphibians, birds, mammals) · n = 289 species with genuine improvement since 1980
- Birds and mammals with genuine improvement whose credited actions were reviewed against action codes and narrative accounts · birds and mammals · n = 128 species (91 attributed to conservation)
- Green Status of Species assessments: current vs counterfactual (no-action) state for each spatial unit, plus past and current threats and actions · animals (incl. Trechus terrabravensis and Troides helena) · n = 35 species
- Mammal generation lengths from Pacifici et al. (2013), used to fill missing Red List values · mammals
- Bolam et al. (2023) list of species needing urgent management, compared against threatened species with no reported actions · animals · n = at least 778 overlapping threatened species
- Methods & tools
- IUCN Red List of Threatened Species (version 2023.1), Green Status of Species, Cumulative link mixed models, Logistic generalised linear mixed models, Chi-squared tests with post-hoc tests (chisq.posthoc.test), R 4.3.1 (RStudio), tidyverse, lme4, ordinal, ggplot2 / pheatmap / ggcorrplot, sf, QGIS Desktop 3.22.12
- Reagents & environment
- R 4.3.1 in RStudio with tidyverse, chisq.posthoc.test, lme4, ordinal, ggcorrplot, ggplot2, pheatmap and sf; QGIS Desktop 3.22.12; data downloaded from IUCN Red List version 2023.1
- Reproducibility gaps
- The text gives no code repository or data download links. Model outputs and chi-squared tables are in supplementary Tables S1 to S4, and taxonomic group definitions are in Text S1; none of these are reproduced here.
Limitations (6)
- Reporting actions in place is only recommended (and optional for Least Concern species), and narrative accounts may hold information missing from the tabular fields, so the count of species with actions is likely an underestimate. · stated by the authors
- Documentation differs by Red List authority: BirdLife assesses all birds, whereas mammals were comprehensively assessed only twice by over 35 Specialist Groups. Global databases may also over-represent protected-area and legislation records. · stated by the authors
- Genuine category change underestimates real change: categories are threshold-based, a species must qualify for five years before downlisting, and reassessment lags (e.g. the Iberian lynx not yet recorded). Justifications exist only for birds and mammals. · stated by the authors
- With only 33 improved mammals, differences in attribution among actions could not be resolved, and primary drivers could not be separated from all credited actions. · stated by the authors
- The Green Status data cover only 35 species with a coarse, expert-derived counterfactual, and these assessments rely on expert input and post-hoc counterfactual reasoning rather than empirical tests of action outcomes. · stated by the authors
- The analyses are correlative and actions are often deployed for species already in decline, so both negative and positive action associations may partly reflect targeting and documentation effort rather than effectiveness. · noted in this summary
Who should read:Read this if you evaluate conservation interventions or biodiversity indicators and want a multi-taxon, Red List based view of which actions accompany genuine species recovery.
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