Restore Ecosystems - Algal Forests - Ocean Central
Algal forests, including kelp ecosystems, are dynamic coastal habitats that support rich biodiversity and play a central role in carbon and nutrient cycling.
They provide shelter and nursery grounds for fish and invertebrates, absorb CO₂, and buffer wave energy, helping to stabilize coastlines. These underwater forests are highly productive yet sensitive to ocean warming, marine heatwaves, and shifts in nutrient availability, making them vulnerable under climate change. Protecting and restoring kelp and algal forests is critical for biodiversity, carbon storage, and coastal resilience. To learn more, visit Blue Forests Project.
Key Stats
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25%
Source: Krumhansl, K.A. et al., 2016. Global patterns of kelp forest change over the past half-century. PNAS, 113(48), pp.13785–13790. https://www.pnas.org/doi/10.1073/pnas.1606102113Global coastal coverage of algal forests.
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$500-740 Billion/Year
Source: Beck, M.W. et al., 2018. The global flood protection savings provided by coral reefs. Nature Communications, 9, 2186. https://www.nature.com/articles/s41467-018-04568-zEcosystem services provided through coastal flooding, erosions, and storm protection.
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72,500
Source: Guiry, M.D. and Guiry, G.M., 2024. AlgaeBase. National University of Ireland, Galway. Available at: https://www.algaebase.orgKnown macroalgae species with many remaining to be discovered.
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2,900 tCO₂/km
Source: Krause-Jensen, D. and Duarte, C.M., 2016. Substantial role of macroalgae in marine carbon sequestration. Nature Geoscience, 9, pp.737–742. https://doi.org/10.1038/ngeo2790Carbon sequestration potential of algal forests.
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1,000+
Source: Teagle, H., Hawkins, S.J., Moore, P.J. and Smale, D.A., 2017. The role of kelp species as biogenic habitat formers in coastal marine ecosystems. Journal of Experimental Marine Biology and Ecology, 492, pp.81–98. https://research.aber.ac.uk/files/10952257/Teagle_et_al_2016_JEMBE_post_print.pdfSpecies of marine life that rely on algal forest habitats.
Jayathilake D.R.M, Costello M.J. (2020). A modelled global distribution of the kelp biome. Biological Conservation. https://doi.org/10.1016/j.biocon.2020.108815
Globally, algal forest ecosystems have decreased 67.6% between 1952 and 2014.
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Data Frequency
The number of years of available data.
1Year
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Data Quality
Sufficient – At least 2 data points available for trend analysis AND at least one data point in the last 7 yearsInsufficient – Does not have any data at all for analysis Expired – Does not have any data in the last 10 years Not Recent – At least one data point in the last 8 to 10 years Recent – At least one data point in the last 7 years Sufficient – At least 2 data points available for trend analysis AND at least one data point in the last 7 years
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Geographic Range
100% of global data avaliableThe percentage of the ocean represented by the available data
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Global Goal(s)
Global Goal(s)None – No Global Goal Established Low – The goal is broad Medium – The goal is specific High – The goal is measurable
There is still so much we do not know about our oceans.
Join us in filling critical gaps in ocean data.
Algal forests are increasingly recognized for their ecological and economic importance, yet global data on their extent, loss, and recovery remain patchy, limiting our ability to track trends.
Warming oceans and marine heatwaves are the leading causes of algal forest decline globally, particularly in kelp-dominated systems in temperate regions, and these impacts are often compounded by nutrient depletion and invasive species. In some areas, overgrazing by sea urchins—caused by the loss of natural predators—has transformed once-thriving forests into “urchin barrens,” where biodiversity and ecosystem function are severely diminished.
However, positive outcomes are emerging in regions where natural predators of urchins are recovering or where targeted urchin-removal programs are underway, demonstrating that effective interventions can reverse declines. Restoration efforts are rapidly gaining momentum, supported by new policies, financial incentives, and a growing recognition of their value to fisheries, coastal protection, and carbon storage. Many of these initiatives are guided by indigenous knowledge and stewardship.
Together, these actions show that targeted interventions—combined with adaptive management and community engagement—can successfully rebuild ecosystem resilience.
Explore where algal forests are most prevalent.
Jayathilake D.R.M, Costello M.J. (2020). A modelled global distribution of the kelp biome. Biological Conservation. https://doi.org/10.1016/j.biocon.2020.108815
Flanders Marine Institute (2024). The intersect of the Exclusive Economic Zones and IHO sea areas, version 5. Available online at https://www.marineregions.org/. https://doi.org/10.14284/699
Algal forest extent does not represent a single timepoint - a recent baseline was estimated using datasets from 1900-2017.
There are approximately 1,404,329 km² of algal forests globally—100% of which lie within national EEZs.
Track the pressures driving algal forest loss, from species at risk to disturbance alerts.
Jayathilake D.R.M, Costello M.J. (2020). A modelled global distribution of the kelp biome. Biological Conservation. https://doi.org/10.1016/j.biocon.2020.108815
National Oceanic and Atmospheric Administration (NOAA) Coral Reef Watch (n.d.) Daily Global 5km Satellite Marine Heatwave Watch (MHW) product. NOAA Coral Reef Watch. Available at: https://coralreefwatch.noaa.gov/product/marine_heatwave/
Globally, approximately 19.74% of algal forests lie within areas experiencing marine heatwaves in the past year.
Jayathilake D.R.M, Costello M.J. (2020). A modelled global distribution of the kelp biome. Biological Conservation. https://doi.org/10.1016/j.biocon.2020.108815
Gregor, L. and Gruber, N.: OceanSODA-ETHZ: a global gridded data set of the surface ocean carbonate system for seasonal to decadal studies of ocean acidification, Earth Syst. Sci. Data, 13, 777–808, https://doi.org/10.5194/essd-13-777-2021, 2021
NOTE: Negative pH values and trends indicate increasing ocean acidification
Significant Increasing Acidity Trend – Any pixel where the p-value of a linear trend line is less than 0.05, based on data over the period 1982-2022.
Globally, approximately 49.47% of algal forests lie within areas experiencing increasing acidification.
See where algal forests are safeguarded and how restoration efforts are expanding their coverage.
IUCN (International Union for Conservation of Nature) (2025) The IUCN Red List of Threatened Species. Available at: https://www.iucnredlist.org (Accessed: December 12 2025).
Globally, there are 82 species of kelp tracked by the IUCN out of which 11 are endangered meaning there's still a strong chance for recovery with timely action.
| Species | Status |
|---|---|
| Acrosorium papenfussii | VU |
| Ahnfeltiopsis smithii | DD |
| Alsidium pusillum | DD |
| Amphiroa compressa | DD |
| Amphiroa crustiformis | DD |
| Amphiroa galapagensis | DD |
| Antithamnion veleroae | DD |
| Archaeolithothamnion crosslandii | DD |
| Asparagopsis svedelii | DD |
| Austrofolium equatorianum | VU |
| Austrofolium howellii | DD |
| Bifurcaria galapagensis | CE |
| Botryocladia darwinii | DD |
| Callithamnion ecuadoreanum | DD |
| Callithamnion epiphyticum | DD |
| Ceramium hoodii | DD |
| Ceramium howellii | DD |
| Ceramium inkyui | DD |
| Ceramium prostratum | DD |
| Ceramium templetonii | DD |
| Chondria chejuensis | DD |
| Chondria flexicaulis | DD |
| Chondria pellucida | LC |
| Chondrus albemarlensis | DD |
| Chondrus hancockii | DD |
| Dasysiphonia chejuensis | LC |
| Desmarestia tropica | CE |
| Dictyopteris diaphana | DD |
| Dictyota galapagensis | CE |
| Dictyota major | DD |
| Ectochaete perforans | DD |
| Eisenia galapagensis | VU |
| Galaxaura barbata | CE |
| Galaxaura intermedia | DD |
| Goniolithon alternans | DD |
| Gracilaria ecuadoreanus | DD |
| Gracilaria skottsbergii | CE |
| Halymenia santamariae | DD |
| Kallymenia multiloba | DD |
| Kallymenia setchellii | DD |
| Laurencia congesta | DD |
| Laurencia densissima | DD |
| Laurencia intercalaris | DD |
| Laurencia ligulata | DD |
| Laurencia mediocris | DD |
| Laurencia oppositocladia | CE |
| Laurencia succulenta | DD |
| Lithophyllum amplostratum | DD |
| Lithophyllum complexum | DD |
| Lithophyllum mutabile | DD |
| Lithophyllum rileyi | DD |
| Lithophyllum sancti-georgei | DD |
| Lithothamnion cottonii | DD |
| Lithothamnion pocillum | DD |
| Martensia flammifolia | DD |
| Mesophyllum laxum | DD |
| Myriogramme kylinii | CE |
| Nitophyllum divaricatum | DD |
| Ochtodes crokeri | LC |
| Pachymenia saxicola | LC |
| Padina concrescens | DD |
| Phycodrina elegans | CE |
| Pleonosporium complanatum | LC |
| Prionitis galapagensis | DD |
| Prionitis hancockii | DD |
| Pseudolaingia hancockii | VU |
| Pterosiphonia paucicorticata | DD |
| Pugetia latiloba | LC |
| Rhizoclonium robustum | DD |
| Rhodymenia decumbens | DD |
| Sargassum albemarlense | DD |
| Sargassum galapagense | DD |
| Sargassum setifolium | EN |
| Sargassum templetonii | DD |
| Schizymenia ecuadoreana | CE |
| Sebdenia rubra | DD |
| Spatoglossum ecuadoreanum | DD |
| Spatoglossum schmittii | CE |
| Sporochnus rostratus | DD |
| Tenarea erecta | DD |
| Vanvoorstia bennettiana | EX |
| Zosterocarpus abyssicola | DD |
Jayathilake D.R.M, Costello M.J. (2020). A modelled global distribution of the kelp biome. Biological Conservation. https://doi.org/10.1016/j.biocon.2020.108815
UNEP-WCMC and IUCN (2026), Protected Planet: The World Database on Protected Areas (WDPA) and World Database on Other Effective Area-based Conservation Measures (WD-OECM) [Online], January 2026, Cambridge, UK: UNEP-WCMC and IUCN. Available at: www.protectedplanet.net.
Algal forest extent does not represent a single timepoint - a recent 2017 baseline was estimated using datasets from 1900-2017.
Globally, approximately 25.37% of algal forests lie within established protected areas.
Duarte, C.M., Agustí, S., Barbier, E., Britten, G.L., Castilla, J.C., Gattuso, J.-P., Fulweiler, R.W., Hughes, T.P., Knowlton, N., Lovelock, C.E., Lotze, H.K., Predragovic, M., Poloczanska, E., Roberts, C. and Worm, B. (2020) Rebuilding marine life. Nature, 580(7801), pp. 39–51. https://doi.org/10.1038/s41586-020-2146-7
Globally, there was an increase of 19 algal forest restoration projects between 1965 and 2020.
Algal forest recovery enhances habitat complexity, supports marine species, and sequesters carbon, strengthening coastal ecosystem health.
Taking Action
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Include Algal Forests in the Blue Carbon Scheme
Macro algae, such as kelp, are not yet officially recognized as a Blue Carbon ecosystem under UNFCCC policies due to limited scientific data, especially regarding carbon assimilation rates and the fate of exported macroalgae. Recent studies, however, challenge this view and suggest that seaweeds are globally significant contributors to oceanic carbon sinks.
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Protect Existing Algal Forests
The current percentage of macroalgae falling within marine protected areas remains unclear. To safeguard these ecosystems, expanding MPAs to include algal forests is essential. One effective approach is creating “no-take” zones where fishing and harvesting are prohibited, allowing predator-prey dynamics to stabilize and enabling natural regeneration. In certain cases, areas where some regulated activities are permitted may be more practical, avoiding intensified pressures on nearby areas outs
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Control Overgrazing by Sea Urchins
The excessive population of sea urchins, due to a decline in their natural predators, is a primary cause of algal forest degradation. Restoring populations of key predators like sea otters, lobsters, and large fish helps control herbivorous sea urchins, mitigating overgrazing. In regions with low predator numbers, direct sea urchin culling may be necessary to reduce the immediate threat to algal forests.
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Mitigate Climate Change Impacts
Climate change poses a significant threat to algal forests, particularly as warming waters and ocean acidification affect their health. Global efforts to reduce carbon dioxide emissions are critical. Additionally, identifying and protecting areas where algal forests show resilience to temperature changes will help target conservation efforts, securing ecosystems that are more likely to adapt to future conditions.
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Address Drivers of Algal Forest Loss
Sustainable practices in fishing, tourism, and agriculture are essential to minimize pollution and habitat degradation.
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Promote Seaweed Farming
Seaweed aquaculture provides an alternative source of macroalgae for industrial, pharmaceutical, and food purposes, alleviating pressure on wild forests. By expanding seaweed farming, coastal communities can simultaneously support economic development and reduce the exploitation of natural macroalgal forests.
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Active Restoration Efforts
In heavily degraded areas, active intervention may be required to restore algal forests. This can involve replanting or reseeding, either by transplanting healthy specimens or cultivating them in nurseries before outplanting. In cases where the natural rocky substrate has eroded, building artificial reefs or restoring natural substrates can encourage macroalgae to recolonize barren areas.
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Adopt Nature-Based Solutions
Nature-based solutions, such as using algal forests for coastal defense, can protect shorelines from erosion while restoring ecosystems.
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Marine Spatial Planning
Incorporating algal forest restoration into marine spatial planning, alongside managed retreat zones and dedicated areas for seaweed farming, can ensure that restoration goals are met.
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Engage Local Communities and Stakeholders
Involving local communities in the restoration process is key to long-term success.
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Support Research and Monitoring
Ongoing scientific research is vital to identify best practices for algal forest restoration. Large-scale mapping and long-term monitoring programs should track the success of restoration efforts, assessing factors such as plant growth, biodiversity recovery, sediment deposition, and the ecosystem services provided by restored algal forests.
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Reviving kelp forests in Port Phillip Bay rebuilds lost underwater ecosystems, restores climate-resilient blue forests, and demonstrates how science and community can bring back nature’s foundations for life and livelihoods. -
By restoring Cystoseira forests, this project is rebuilding one of the Mediterranean’s most valuable ecosystems for biodiversity and climate adaptation.
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View relevant data layers on the globe using the available map toggle in the top right of each card in the left panel.
View relevant data layers on the globe using the available map toggle in the top right of each card in the left panel.