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Continent-wide declines in shallow reef life over a decade of ocean warming


Human society is dependent on nature1,2, but whether our ecological foundations are at risk remains unknown in the absence of systematic monitoring of species’ populations3. Knowledge of species fluctuations is particularly inadequate in the marine realm4. Here we assess the population trends of 1,057 common shallow reef species from multiple phyla at 1,636 sites around Australia over the past decade. Most populations decreased over this period, including many tropical fishes, temperate invertebrates (particularly echinoderms) and southwestern Australian macroalgae, whereas coral populations remained relatively stable. Population declines typically followed heatwave years, when local water temperatures were more than 0.5 °C above temperatures in 2008. Following heatwaves5,6, species abundances generally tended to decline near warm range edges, and increase near cool range edges. More than 30% of shallow invertebrate species in cool latitudes exhibited high extinction risk, with rapidly declining populations trapped by deep ocean barriers, preventing poleward retreat as temperatures rise. Greater conservation effort is needed to safeguard temperate marine ecosystems, which are disproportionately threatened and include species with deep evolutionary roots. Fundamental among such efforts, and broader societal needs to efficiently adapt to interacting anthropogenic and natural pressures, is greatly expanded monitoring of species’ population trends7,8.

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Fig. 1: Populations of shallow reef species have generally declined over the past decade.
Fig. 2: Variation in population trends with species traits.
Fig. 3: Disproportionate declines in mobile invertebrate populations off Tasmania and southeastern Australia.
Fig. 4: Annual trends in species population density with latitude.
Fig. 5: Mean annual population trends for reef species with different biogeographic affinity in different regions.
Fig. 6: Mean annual population trends for reef species in different taxa in different regions.

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Data availability

Raw data from the Reef Life Survey and Australian Temperate Reef Collaboration programmes are accessible through a live data portal accessed via either the Reef Life Survey ( or Australian Ocean Data Network ( websites using the keywords ‘National Reef Monitoring Network’. Sea surface temperature data were obtained from Coral Reef Watch (available through, chlorophyll data were obtained from Bio-ORACLE (, fish trait data were obtained in part from Fishbase (, and invertebrate trait data from Sealifebase (, as described in Methods.

Code availability

Analytical computations were undertaken in R version 4.2.0 (using libraries tidyverse. janitor, zoo, magick, cowplot, scales, patchwork, ggplot, rag, gt, gtable, grid, nlme, here and kableExtra)57, as described in R markdown script available at


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Support for field surveys and analyses was provided by the Australian Research Council; the Australian Institute of Marine Science; the Institute for Marine and Antarctic Studies; Parks Australia; Department of Natural Resources and Environment Tasmania; New South Wales Department of Primary Industries; Parks Victoria; South Australia Department of Environment, Water and Natural Resources; Western Australia Department of Biodiversity, Conservation and Attractions; The Ian Potter Foundation; Minderoo Foundation; and the Marine Biodiversity Hub, a collaborative partnership supported through the Australian Government’s National Environmental Science Programme. We thank the many colleagues and Reef Life Survey (RLS) divers who participated in data collection. RLS and ATRC data management is supported by Australia’s Integrated Marine Observing System (IMOS)—IMOS is enabled by the National Collaborative Research Infrastructure Strategy (NCRIS).

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Authors and Affiliations



G.J.E. conceived the study. G.J.E., R.D.S.-S., N.S.B., E.T., H.S., M.J.E., D.J.B., J.H., B.F., S.C.B., S.A.H., A.J., N.A.K., P.M., A.T.C., E.S.O., G.A.S., C.M., S.D.L., J.W.T., P.B.D., M.F.L., Y.S., J.S.-S., E.C., T.R.D., J.S., D.S., O.J.J., Y.H.F., L.D.-R. and T.J. contributed to collection of field survey data. E.T. identified corals and digitized coral density data. J.C.D. led sea surface temperature analysis. G.J.E., A.E.B. and F.J.H. analysed data. All photographs were taken by G.J.E. G.J.E. wrote the initial manuscript draft and all authors contributed to the final version.

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Correspondence to Graham J. Edgar.

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Nature thanks Sergio Floeter and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Extended data figures and tables

Extended Data Fig. 1 Sites surveyed around Australia.

Sites visited on single occasions are shown in blue, and in at least two years in red. Most individual sites are overlapping.

Extended Data Fig. 2 Total number of sites surveyed with differing annual survey frequency.

Number of annual surveys undertaken at sites from 2008 to 2021.

Extended Data Fig. 3 Recent change in mean abundance around the Australian continent for different species groupings.

Major taxonomic and biogeographic groupings were assessed using data with different site sampling frequency. a. Full dataset, as shown in Fig. 1, that includes sites surveyed in at least two separate years. b. Reduced dataset that includes sites surveyed in at least 3 years. c. Reduced dataset that includes sites sampled in at least four years. Data relate to the 10-year period from 2011 to 2021. The number of species considered per grouping and 95% confidence intervals are shown. Images by GJE.

Extended Data Fig. 4 Mean annual population trends for reef species with different biogeographic affinity in different regions.

Species trends relative to 2008 were categorised within three biogeographic groupings (tropical >23 °C; warm-temperate >17.5 °C, <23 °C; cool temperate <17.5 °C) for six regions around Australia. a, Northwest: Northern Territory, Western Australian coast north of 27°S. b, Southwest: western coast south of 27°S. c, South: southern coast east to 148°S. d, Northeast: Queensland, Coral Sea. e, Southeast: New South Wales; Victoria west to 148°S; f, Tasmania. In contrast to data presented in Fig. 5, relative abundance for each species and site was calculated using Population Trend Assessment Method 2, as the log ratio relative to site mean across years, then averaged for sites within 1° x 1° grid cells. Shading indicates ±1 SE (assuming a normal distribution across species estimates).

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Edgar, G.J., Stuart-Smith, R.D., Heather, F.J. et al. Continent-wide declines in shallow reef life over a decade of ocean warming. Nature 615, 858–865 (2023).

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