Habitat and Biodiversity Loss

A new version of this report with updated data is available. Link to the 2021 edition.

Data Highlights

Implemented MPAs

5.7% of ocean (2020)

MPAtlas, 2020

Avg. growth rate of MPA coverage

8% per year

Duarte et al, 2020

Global mangrove loss

0.1%–0.4% per year (2000–2012)

Hamilton and Casey, 2016

Jump to:


    Direct and indirect human pressures are leading to the unprecedented loss of marine biodiversity across all levels. The primary drivers of biodiversity loss include overexploitation, human pressures in coastal environments (habitat loss, development, and pollution), and increasingly, climate change and ocean acidification.1 Marine ecosystems, from coastal to deep sea, show the influence of human activity; in particular, coastal ecosystems exhibit large historical losses in both extent and condition.2

    Marine biodiversity provides a critical set of ecosystem services and resources to society, from moderating climate to providing food, medicine, and jobs for millions of people. Biodiversity decline has tangible impacts on ecosystem functioning, human health, livelihoods, and food security. In the coastal zone itself, over 500 million people worldwide benefit from protection by ecosystems including coral reefs, mangroves, kelp forests, and seagrass beds. The natural capacity of the ocean to provide these ecosystem services and goods will continue to weaken without action to maintain and restore marine habitats and biodiversity.

    It is estimated that an average of 30 to 50 percent of vulnerable marine habitats have been lost,3 even as biodiversity losses in the ocean are considered less pronounced than on land.4 The degradation and loss of marine habitats are not uniformly distributed and tend to face cumulative, yet poorly understood, interactions between multiple threats.5

    A key challenge in understanding trends for marine biodiversity and ecosystem integrity include the lack of baseline data and long-term monitoring of the status of species and habitats.6 There has been a lack of global coordination to gather baseline data and support ongoing monitoring, in spite of recommendations to do so for the past several decades. While the IUCN Red List includes relatively decent coverage of extinction risk assessments for marine vertebrates—including fish, seabirds, and marine mammals—there is inconsistent coverage in particular of marine invertebrates.7 As a result of this incomplete data picture, there are discrepancies and biases in understanding particular geographic areas, habitat distribution, species groups, and performance trends.

    Estimating the loss of marine biodiversity is as much about what we do not know as what we do know. It is estimated that only 10-25 percent of marine species have been described globally.8 Among the least known groups, there could be thousands to over a hundred thousand undescribed species. Still, researchers estimate that half of the major taxonomic grouping include identification of more than 50 percent of known species.9 Within the IUCN Red List to assess extinction risk, only about 3 percent of roughly 240,000 described marine species have been assessed. Research suggests that species loss often does not manifest as the complete extinction of individual species, but instead as changes in the composition of ecosystems and the relative abundance and ecological status of individual species, coupled with more regional or local extirpations.10 Even absent an assessment of global extinction, a species could have marked influence through ecological extinction, local extinction, or commercial extinction.

    Trends in habitat degradation

    According to the most recent assessment by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES), the influence of human activities on marine ecosystems has expanded significantly in recent years. The IPBES assessment and other studies have found that marine habitats have changed in the following ways:11

    • Over 66 percent of the ocean experienced increasing cumulative impacts in 2014 (up from 40 percent in 2008).
    • Live coral cover on reefs has nearly halved since the 1870s, with the rate of decline most pronounced over the past 2 to 3 decades due to increased ocean acidification and water temperature (combined with other drivers of loss). Projections for coral reef loss are particularly dire: it is anticipated that a majority (70 to 99 percent) of corals on Earth may die off in the coming decades due to rising temperatures.12
    • Seagrass meadows decreased in extent by over 10 percent per decade from 1970 to 2000.
    • Global coverage of mangroves has declined by roughly 40 percent, while saltmarsh coverage has declined an estimated 60 percent.
    • Kelp forests have shown significant declines in certain regions, including in the Great Southern Reef of Australia. Global patterns are more nuanced as kelp forests are declining in some areas but expanding in others.

    Coastal habitat conversion

    Human pressure on the marine environment is most acute along the world’s coastlines. Roughly 40 percent of the global population lives within 100 km of a coastline. This proportion is expected to rise to 50 percent by 2030.13 From draining wetlands and clearing mangrove habitat, to filling in estuaries and hardening shorelines, the conversion of coastal ecosystems has made them one of the most modified and threatened ecosystems globally.

    Shoreline hardening reduces the ecosystem services that support coastal populations, including protection from sea-level rise and storm surge. A meta-analysis found that engineered seawalls support 23% lower biodiversity and 45 percent fewer organisms than natural shorelines.14 Global data on overall trends in shoreline hardening are not available, but it is well known that the amount of hardened coastline continues to grow in many ecologically-important coastal regions.15

    In major coastal cities such as Hong Kong, Sydney, and New York, more than half of the shoreline is hardened.16  In the United States alone, over 22,000 km (approximately 14 percent) of shoreline have been hardened. In coastal China, the trend of shoreline hardening increased sharply in the early 2000’s, in close correlation with rising GDP per capita in the country.17

    Satellite Imagery of Coastal Reclamation in Nahui Shore near Shanhai, China

    map image

    Source: Tian, B., W. Wu, Z. Yang, and Y. Zhou. “Drivers, Trends, and Potential Impacts of Long-term Coastal Reclamation in China from 1985 to 2010.” Estuarine, Coastal, and Shelf Science 170 (2016): 83–90.

    The expanding footprint of human development in the coastal zone has been evident in the loss of mangrove forests worldwide. At least 35 percent of mangrove area was lost globally during the 1980s and 1990s alone; in some regions, the rate of loss was as high as 50 to 80 percent.18 The rate of global mangrove deforestation has declined significantly in recent years; during 2000–2012, the global deforestation rate was between 0.16 to 0.39 percent per year.19 While the rate of deforestation has stabilized or declined in many countries, Southeast Asia remains the epicenter of mangrove loss, with deforestation rates between 3.6 to 8.1 percent.20 Aquaculture and agriculture have been the principal drivers of mangrove loss in recent decades.21

    Although the global rate of mangrove loss has been declining over the past three decades, several mangrove species remain at high risk of extinction. Mangrove forests make up the economic foundation of many tropical coastal regions, providing roughly USD 1.6 billion in ecosystem services worldwide.21 An estimated 80 percent of global fish catches are directly or indirectly dependent on mangroves.22 In recent years, mangrove management has received significant attention as a climate adaptation and mitigation strategy: though mangroves account for only 0.7 percent of the world’s tropical forest area, they contribute 10 percent of total global emissions from tropical deforestation.23

    The conversion and degradation of wetlands has also continued at a global level, though there are important regional variations.24 In Europe and North America, the rate of wetland loss has largely declined in recent decades. In contrast, the conversion of coastal and inland natural wetlands has continued at a high rate in Asia.

    Tidal flats—defined as sand, rock, or mud flats that experience regular tidal inundation—are one of the most extensive coastal ecosystems, yet their distribution and status has been relatively unknown until recently. A team of researchers used satellite images to map the global distribution and change in tidal flats during 1984–2016. Nearly 50 percent of the global extent of tidal flats is concentrated in just eight countries—Indonesia, China, Australia, the United States, Canada, India, Brazil and Myanmar.25 At least 16 percent of tidal flats were lost globally between 1984–2016.26 Trends suggest continued declines in coverage due to coastal development, reduced sedimentation from major rivers, subsidence of riverine deltas, and increased coastal erosion and sea-level rise.27

    Portion of the ocean protected

    To address losses in biodiversity and marine habitat, the international community has increasingly focused on the protection of marine areas. Global coordination to protect biodiversity for the next decade is gaining momentum and will be an area of heightened focus as countries gather at the Conference of the Parties to the Convention on Biological Diversity in Kunming in May 2021. A growing coalition of scientists, Indigenous peoples, and advocates are calling for an updated global target to protect at least 30 percent of the ocean by 2030.

    As of late 2020, 5.7 percent of the world’s ocean was protected in implemented marine protected areas (MPAs).28,29 Roughly half of this amount, 2.6 percent of the ocean, was protected as “highly protected marine reserves.” Implementing proposed or officially announced MPAs would increase the overall level of protection to 8.0 percent of the ocean.

    The United Nations’ target for global ocean protection is 10 percent of the coastal and marine areas in MPAs by 2020, as set forth by Aichi Target 11 under the Convention on Biological Diversity (CBD). The U.N. Sustainable Development Goal 14 (SDG 14) reaffirms this commitment. According to the most rigorous projections, collective commitments are not currently on track to meet the 10 percent global target by 2020, although numerous countries will meet the 10 percent target for areas within their Exclusive Economic Zone (EEZ).30 Many scientists emphasize, however, that the 10 percent target is intended as a first milestone for global ocean protection, rather than an endpoint.31

    MPA progress toward Aichi Target 11

    The MPA coverage statistics presented here are based on data from the Atlas of Marine Protection (MPAtlas.org), a project of the Marine Conservation Institute, which conducts research and follow-up verification to capture the actual level of MPA protection. Other sources, including the World Database on Protected Areas (WDPA) upon which the Atlas of Marine Protection uses for baseline records, may overestimate the extent of protected area due to reliance on self-reported data from governments, NGOs, and other stakeholders. In the lead-up to the 2020 deadline, several leading marine scientists have called for definitional clarity and improved accounting to ensure that coverage statistics honestly and accurately reflect what is protected on the water.32

    In 2020, the global community is expected to adopt a new 10-year global biodiversity framework with a new global target for ocean protection. Stakeholders are currently holding discussions about potential conservation goals. The International Union for Conservation of Nature (IUCN) initially proposed the most ambitious target, calling for the protection of at least 30% of the ocean by 2030.33

    Recent trends in MPAs

    Several trends stand out as the global community has sought to achieve 10 percent protection of coastal and marine areas. At a high-level, those trends include: 1) an accelerated rate of MPA declarations in anticipation of 2020 targets, 2) a rise in designating large-scale marine reserves in remote areas, 3) an underperformance in ensuring ecological connectivity and representation, 4) a varied pattern of protection by ocean basis, and 5) increased attention on the protection of the high seas.

    Accelerated rate of MPA declarations

    The rate of MPA coverage has increased rapidly in recent years as governments race to meet coverage targets by 2020.34 For several decades, MPA coverage hovered around 1 percent. During 2006–2015, the increased interest in designating very large MPAs (over 100,000 km2) and meeting Aichi targets accelerated the rate of MPA designations. Since 2015, MPAs have been designated at an even faster rate in anticipation of the 2020 target deadlines.35

    Map of MPAs by recentness of implementation

    Marine Conservation Institute, MPAtlas (Seattle, 2018), www.mpatlas.org

    According to current projections, MPA commitments are not on track to meet the 10 percent global target by 2020. Although the global community may fall short of reaching the 10 percent target, several countries (e.g., Palau, United States, Great Britain) are poised to exceed the 10 percent protection target for areas within their EEZ.36,37

    Scenarios of MPA progress toward global targets

    Rise in large-scale marine reserves in remote areas

    The past decade in particular has seen a rise of large MPAs in remote areas of the ocean, usually in locations with low human density and low levels of commercial use and industrial fishing. Protecting remote areas which are far from human-use conflicts is generally more politically expedient and less likely to encounter resistance from resource users.38

    On one hand, large remote MPAs provide several benefits, including protecting the entire home ranges of individuals, maintaining ecological functions over larger spatial scales, and safeguarding the most pristine expanses of the ocean. At the same time, MPAs in densely-populated coastal zones play an important role in negotiating access among resource user groups. Both approaches are necessary to ensure ecological functioning and minimize human impact on the marine environment.

    Map of MPAs by protection level and implementation status

    Marine Conservation Institute, MPAtlas (Seattle, 2018), www.mpatlas.org

    Underperformance in ensuring ecological connectivity and representation

    Aside from including the target of 10 percent coverage by 2020, Aichi Target 11 also includes language which calls for ecologically representative and well-connected systems of protected areas. As shown in Figure 6.5, there is a high frequency of red polygons, which indicates the lowest level of protected area coverage within marine ecoregions. The ideal scenario would be for all ecoregions shown in the teal category on this map, representing 10 percent or greater coverage within MPAs.

    The full target goal for Aichi Target 11 is: “By 2020, at least 17 per cent of terrestrial and inland water areas and 10 per cent of coastal and marine areas, especially areas of particular importance for biodiversity and ecosystem services, are conserved through effectively and equitably managed, ecologically representative and well-connected systems of protected areas and other effective area-based conservation measures, and integrated into the wider landscape and seascape.”39 While countries race to reach overall coverage targets, it appears that the ability to ensure ecological connectivity and representation has fallen short—which is partly due to the political capital required and intricacies of implementing large-scale systematic conservation planning processes.40

    Map of MPA coverage by ecoregion: Biogeographic representation

    Marine Conservation Institute, MPAtlas (Seattle, 2018), www.mpatlas.org

    Varied patterns of protection by ocean basin

    The Southern Ocean has the highest level of protection among all ocean basis, followed by the South Pacific Ocean and the South Atlantic Ocean. If current proposals by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) are adopted and implemented (including the East Antarctic and Weddell Sea proposals), the Southern Ocean would achieve 20 percent MPA coverage. Oceania also has a high level of MPA coverage due to a combination of factors: numerous large-scale MPAs; several remote and uninhabited islands and atolls where pelagic fishing effort is limited; and a strong cultural heritage for marine protection given the inextricable link to livelihoods in the region.41

    Map of MPA coverage across ocean basins

    Marine Conservation Institute, MPAtlas (Seattle, 2018), www.mpatlas.org

    MPA coverage across ocean basins

    Increased attention on the protection of the high seas

    As of January 2019, 1.2 percent of the high seas were protected in MPAs. Of this amount, 0.8 percent of the high seas were highly protected.42 Several stakeholders are calling for increased and coordinated protection of the high seas, which are beyond the control of any one state.

    Level of marine protection in the high seas

    Marine Conservation Institute, MPAtlas (Seattle, 2018), www.mpatlas.org

    The high seas, which comprise 60 percent of the expanse of the ocean, lie beyond national EEZs. In September 2018, the United Nations held the first session to negotiate a treaty to improve management of the high seas to protect biodiversity. It is anticipated that the U.N. process may lead to a new treaty in 2020, though it will likely take several additional years to fully ratify and implement the treaty. While the global community is not expected to achieve 10 percent MPA coverage in the high seas by 2020, it is anticipated that the UN treaty process will streamline currently disconnected management and regulatory processes.43 As such, actions to protect the high seas are expected to accelerate over the next 5 to 10 years.

    MPA management and governance

    As MPAs have rapidly expanded in number and coverage to represent a leading conservation tool for ocean protection, the level of success among MPAs has been varied and uneven. 44 Research associating the efficacy of MPA management processes to conservation outcomes has traditionally been limited to theory and local-scale case studies. However, a recent global study by Gill et al. (2017) suggests staff capacity and budget capacity are the strongest predictors in explaining fish biomass responses to MPA protection.45 MPAs with adequate staff and budget capacity had fish recoveries which were nearly three times as large as those without adequate capacity.46

    Relationship between MPA management processes and ecological impact

    Relationship between MPA management processes and ecological impact

    Random forest variable importance measures for management and other variables as they related to ecological effects in 62 MPAs. Adapted from source: Gill, D.A. et al. “Capacity shortfalls hinder the performance of marine protected areas globally.” 2017. Nature (543): 665-671.

    The study found that only 35 percent of MPAs surveyed had a sufficient budget to manage their protected area, while only 9 percent had adequate staff capacity.

    As this research highlights, the rapid expansion of protected areas without corresponding investment in capacity is not poised to yield positive conservation outcomes. Particularly as anthropogenic pressures on marine resources increase, it is critical to ensure adequate capacity for MPA management, monitoring, and finance.

    Reported level of MPA staff capacity

    Reported level of MPA staff capacity

    MPAs reporting adequate (dark blue), inadequate or below optimum (blue) and no (light blue) staff capacity in their most recent management assessments where spatial data were available [n=243 MPAs; excludes MPAs with intermediate scores (n=5)]. Adapted from source: Gill, D.A. et al. “Capacity shortfalls hinder the performance of marine protected areas globally.” 2017. Nature (543): 665-671.


    1. Rogers, A., O. Aburto-Oropeza, et al. 2020. “Critical Habitats and Biodiversity: Inventory, Thresholds and Governance.” Washington, DC: World Resources Institute. Available online at www.oceanpanel.org/blue-papers/critical-habitats-and-biodiversity-inventory-thresholds-and-governance.
    2. IPBES. “IPBES Global Assessment Summary for Policymakers.” https://www.ipbes.net/news/ipbes-global-assessment-summary-policymakers-pdf (2019).
    3. IPBES. “IPBES Global Assessment Summary for Policymakers.” 2019.
    4. McCauley, D. J. et al. Marine defaunation: animal loss in the global ocean. Science 347, 1255641 (2015).
    5. Halpern, B.S., M. Frazier, J. Afflerbach, J.S. Lowndes, F. Micheli, C. O’Hara, C. Scarborough, and K.A. Selkoe. 2019. “Recent Pace of Change in Human Impact on the World’s Ocean.” Scientific Reports 9 (August): 11609. https://doi.org/10.1038/s41598-019-47201-9.
    6. Ibid.
    7. Ibid.
    8. Ibid.
    9. Ibid.
    10. Rogers, A., O. Aburto-Oropeza, et al. 2020. “Critical Habitats and Biodiversity: Inventory, Thresholds and Governance.”
    11. IPBES. “IPBES Global Assessment Summary for Policymakers.” 2019.
    12. IPCC. “Summary for Policymakers. In: Global Warming of 1.5°C. An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty.” [Masson-Delmotte, V., et al. (eds.)]. World Meteorological Organization, Geneva, Switzerland, 2018, 32 pp.
    13. Neumann, B., Vafeidis, A.T., Zimmermann, J., Nicholls, R.J. “Future Coastal Population Growth and Exposure to Sea-Level Rise and Coastal Flooding – A Global Assessment.” PLOS ONE 10 (2015). e0131375. https://doi.org/10.1371/journal.pone.0131375.
    14. Gittman, Rachel K, F.J. Fodrie, A. M Popowich, D.A. Keller, J.F. Bruno, C.A. Currin, C.H. Peterson, and M.F. Piehler. “Engineering Away Our Natural Defenses: An Analysis of Shoreline Hardening in the US.” Frontiers in Ecology and the Environment 13, no. 6 (August 2015): 301–7. https://doi.org/10.1890/150065.
    15. Ibid.
    16. Ibid.
    17. Tian, B., W. Wu, Z. Yang, and Y. Zhou. “Drivers, Trends, and Potential Impacts of Long-term Coastal Reclamation in China from 1985 to 2010.” Estuarine, Coastal, and Shelf Science 170 (2016): 83-90.
    18. Romañach, Stephanie S., Donald L. DeAngelis, Hock Lye Koh, Yuhong Li, Su Yean Teh, Raja Sulaiman Raja Barizan, and Lu Zhai. “Conservation and Restoration of Mangroves: Global Status, Perspectives, and Prognosis.” Ocean & Coastal Management 154 (March 2018): 72–82. https://doi.org/10.1016/j.ocecoaman.2018.01.009.
    19. Hamilton, S. and Casey, D. “Creation of a high spatio-temporal resolution global database of continuous mangrove forest cover for the 21st century (CGMFC-21).” Global Ecology and Biogeography 25 (2016): 729–738. DOI: 10.1111/geb.12449.
    20. Ibid.
    21. Polidoro, Beth A., Kent E. Carpenter, Lorna Collins, Norman C. Duke, Aaron M. Ellison, Joanna C. Ellison, Elizabeth J. Farnsworth, et al. “The Loss of Species: Mangrove Extinction Risk and Geographic Areas of Global Concern.”
    22. Ibid.
    23. Ibid.
    24. Davidson, Nick. “How much wetland has the world lost? Long-term and recent trends in global wetland.” Marine and Freshwater Research (2014). http://dx.doi.org/10.1071/MF14173.
    25. Murray N. J., Phinn S. R., DeWitt M., Ferrari R., Johnston R., Lyons M. B., Clinton N., Thau D. and Fuller R. A.. “The global distribution and trajectory of tidal flats.” Nature 565 (2019): 222-225. https://doi.org/10.1038/s41586-018-0805-8.
    26. Ibid.
    27. Ibid.
    28. Marine Conservation Institute, MPAtlas (Seattle, 2020), www.mpatlas.org
    29. The definition of ‘Marine Protected Area’ is adopted from Lubchenco and Colvert (Science, 2015): “lightlyprotected” MPAs reference MPAs in which some protection exists but significant extractive activity is allowed;“highly protected” MPAs permit only light recreation and subsistence fishing (all commercial activity is prohibited);and “fully protected” MPAs are those for which no extractive activities are allowed. The term “Marine ProtectedArea” encompasses all three categories.
    30. Sala, Enric, Jane Lubchenco, Kirsten Grorud-Colvert, Catherine Novelli, Callum Roberts, and U. Rashid Sumaila.“Assessing Real Progress towards Effective Ocean Protection.” Marine Policy 91 (May 2018): 11–13. https://doi.org/10.1016/j.marpol.2018.02.004
    31. Ibid.
    32. Ibid.
    33. “IUCN Members Approve 30%-by-2030 Goal for MPAs — Most Ambitious Target So Far for MPA Coverage,”MPA News, October 27, 2016. Accessed December 28, 2018. https://mpanews.openchannels.org/news/mpa-news/iucn-members-approve-30-2030-goal-mpas-%E2%80%94-most-ambitious-target-so-far-mpa-coverage
    34. Worm, Boris. “How to Heal an Ocean: Marine Conservation.” Nature 543, no. 7647 (March 2017): 630–31. https://doi.org/10.1038/nature21895
    35. Marine Conservation Institute, MPAtlas (Seattle, 2018),
    36. Sala, Enric, Jane Lubchenco, Kirsten Grorud-Colvert, Catherine Novelli, Callum Roberts, and U. Rashid Sumaila.“Assessing Real Progress towards Effective Ocean Protection.” Marine Policy 91 (May 2018): 11–13. https://doi.org/10.1016/j.marpol.2018.02.004
    37. Marine Conservation Institute, 2018.
    38. Luiz Rocha, “Bigger is not better for ocean conservation,” The New York Times, March 20, 2018. AccessedDecember 28, 2018. https://www.nytimes.com/2018/03/20/opinion/environment-ocean-conservation.html
    39. Convention on Biological Diversity, “Target 11 – Technical Rationale.” CBD Strategic Plan 2011-2020. AccessedDecember 28, 2018. https://www.cbd.int/sp/targets/rationale/target-11/
    40. Russell Moffitt, Marine Conservation Institute, personal communication, October 19, 2018.
    41. Ibid.
    42. Marine Conservation Institute, MPAtlas (Seattle, 2018),
    43. Russell Moffitt, Marine Conservation Institute, personal communication, January 11, 2019.
    44. Gill, D.A. et al. “Capacity shortfalls hinder the performance of marine protected areas globally.” 2017. Nature (543):665-671.
    45. Ibid.
    46. Ibid.