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Live Coral Cover

Key indicator facts

Indicator type

State

Applicable for national use

Yes (find out more)

Indicator classification

Operational and included in the CBD's list of indicators

Indicator type

State

Applicable for national use

Yes (find out more)

Indicator classification

Operational and included in the CBD's list of indicators

Last update

2000

Coverage

Global

Availability

Data freely available

Partners

Gcrmn

Global Coral Reef Monitoring Network

Goos

Global Ocean Observing System

Mbon

Marine Biodiversity Observation Network

Contact point

David Obura, on behalf of the Global Coral Reef Monitoring Network (GCRMN) Steering Committee, dobura@cordioea.net

Key resources

Indicator description

Live hard coral cover is the primary indicator of the health of coral reefs, from local to larger scales, including national, regional and global. Hard coral cover is measured in situ or from images or sensors, as the percentage cover of hard corals of the surface area of coral reef habitats. The indicator directly addresses the health of the ecosystem, and thus of management and policy measures taken to protection, maintain or restore the health of coral reefs. It answers questions such as ‘what is the status or health of coral reefs?’, ‘what is the impact of a certain management or policy intervention?’.

The percent cover of hard corals has been measured in coral reef science and monitoring for over 100 years, recognized as a key variable for distinguishing a coral community from a community dominated by other species (eg. algae, other invertebrates). It has been the primary measure for reef monitoring and reporting, in the early scientific literature, and adopted into the GCRMN (Wilkinson 2000). It is identified as one of the two most advanced Essential Ocean Variables in 2016 and as an ecosystem structure Essential Biodiversity Variable (Obura et al. 2019, Muller-Karger et al. 2018). The GCRMN Implementation and Governance Plan (2019) defines it as the core variable, supported by algal cover and fish diversity and biomass, for global monitoring and reporting of coral reef health.

Related Aichi Targets

Primary target

10

Target 10:

By 2015, the multiple anthropogenic pressures on coral reefs, and other vulnerable ecosystems impacted by climate change or ocean acidification are minimized, so as to maintain their integrity and functioning.

Primary target

10

Target 10:

By 2015, the multiple anthropogenic pressures on coral reefs, and other vulnerable ecosystems impacted by climate change or ocean acidification are minimized, so as to maintain their integrity and functioning.

10

Related SDGs

E sdg goals icons individual rgb 14

GOAL 14 - Conserve and sustainably use the oceans, seas and marine resources for sustainable development.

Target 14.2| Relevant indicator

By 2020, sustainably manage and protect marine and coastal ecosystems to avoid significant adverse impacts, including by strengthening their resilience, and take action for their restoration in order to achieve healthy and productive oceans.

E sdg goals icons individual rgb 14

GOAL 14 - Conserve and sustainably use the oceans, seas and marine resources for sustainable development.

E sdg goals icons individual rgb 14

Themes

Marine

Marine & freshwater habitats

View related indicators >
Marine

Partners

Gcrmn
Goos
Mbon

Key indicator facts

Indicator type

State

Applicable for national use

Yes (find out more)

Indicator classification

Operational and included in the CBD's list of indicators

Indicator type

State

Applicable for national use

Yes (find out more)

Indicator classification

Operational and included in the CBD's list of indicators

Last update

2000

Coverage

Global

Availability

Data freely available

Indicator description

Live hard coral cover is the primary indicator of the health of coral reefs, from local to larger scales, including national, regional and global. Hard coral cover is measured in situ or from images or sensors, as the percentage cover of hard corals of the surface area of coral reef habitats. The indicator directly addresses the health of the ecosystem, and thus of management and policy measures taken to protection, maintain or restore the health of coral reefs. It answers questions such as ‘what is the status or health of coral reefs?’, ‘what is the impact of a certain management or policy intervention?’.

The percent cover of hard corals has been measured in coral reef science and monitoring for over 100 years, recognized as a key variable for distinguishing a coral community from a community dominated by other species (eg. algae, other invertebrates). It has been the primary measure for reef monitoring and reporting, in the early scientific literature, and adopted into the GCRMN (Wilkinson 2000). It is identified as one of the two most advanced Essential Ocean Variables in 2016 and as an ecosystem structure Essential Biodiversity Variable (Obura et al. 2019, Muller-Karger et al. 2018). The GCRMN Implementation and Governance Plan (2019) defines it as the core variable, supported by algal cover and fish diversity and biomass, for global monitoring and reporting of coral reef health.

Contact point

David Obura, on behalf of the Global Coral Reef Monitoring Network (GCRMN) Steering Committee, dobura@cordioea.net

Graphs / Diagrams

Sample graphs of coral cover trend from regional GCRMN assessments in the Pacific (2018) on the below top, the Western Indian Ocean (WIO, 2017) in the below middle, and the Caribbean (2014) on the below bottom. Showing means (main dots) and 95% confidence limits of the mean (shaded area), standard error of the mean bars (Caribbean), and individual reefs and linear trend line (Pacific), and fleshy algae cover (WIO).

Live Coral Cover 1

Live Coral Cover 2.0








Live Coral Cover 3

Coral cover has been relatively stable in the Pacific, declined moderately then shows an increase in the WIO (the last year is of limited sampling) and declined strongly in the Caribbean. Considering the size of the ocean basins and reef systems, this may illustrate the high vulnerability of Caribbean reefs where multiple threats are large enough and aggregate to overwhelm regional recovery processes. In WIO reefs, the impact of a major regional mass bleaching event (1998) then varied recovery and minor bleaching and other impacts until 2015 illustrates a degree of resilience to date. The size and scale of Pacific reefs masks the effect of major mass bleaching events significant at national and even sub-regional scales, and intact resilience to date.


This graph of mean global coral reef cover 1972 – 2016 shows data submitted to the BIP to date, compiled from over 30 countries, more than 470 reefs and 1509 records (compiled by Pete Mumby & George Roff,Marine Spatial Ecolog Lab, U. Queensland, Australia). It shows a linear decline in live coral cover of 2% per decade.

Current storyline

Flat or increasing coral cover is indicative of stable or improving reef condition – ecosystem support for biodiversity may be maintained, though a masked decline in coral diversity may also result in/reflect loss in other associated species. A decline in coral cover at large scales is indicative of widespread loss of functioning reef communities and concomitant loss in habitats and interactions supporting the diverse coral reef-associated community.

Fluctuations in coral cover in aggregated time series reflect coral cover loss from disturbances and gain from coral growth and recovery, aggregated from highly variable and dynamic changes at local and sub-national scales, to national and regional. The full time series are difficult to interpret partially due to limited sampling in early years in all regions. Due to regional aggregation, sharp declines in coral cover from mass bleaching events and other threats are masked by growth in coral growth across regional scales – and the difference between regions appears to relate to the scale and diversity of a region and a diversity or mosaic of responses at scale. Further, aggregate coral cover masks shifts in community composition, and this is tending towards slower growing and lesser structural corals dominating and thus slower growth in reef framework. The increasing frequency and intensity of large mass bleaching events may result in a threshold being passed where recovery aggregated across sites to the regional level is not sufficient to mask the downward signal of larger and more numerous mortality events. The differential responses shown by the series Caribbean – WIO – Pacific is indicative of this trend.

Data and methodology

Coverage:

Global: Coral cover information is aggregated from all tropical coral reef regions by the GCRMN through regional networks. These regional networks operate through national and other ad hoc members, compiling coral reef monitoring data from individual sites and institutional monitoring programmes. Thus, data can be aggregated at any level from the site to global.

GCRMN regions (tentative): Caribbean, Brazil/SW Atlantic, Western Indian Ocean, Red Sea and Gulf of Aden, ROPME Sea Area, South Asia, East Asian Seas, Australia, Pacific Islands, Eastern Tropical Pacific.

Scale: The primary area for data collection is the local reef unit, down to scales of 30-100 m depending on the sampling protocol. This may be aggregated via local, sub-national, national and regional to global levels.

Time series available: Late 1970s in the Caribbean and early 1990s in the WIO and Pacific. Earlier records from research projects will be added to the time series over time.

Next planned update: 2020

Possible disaggregations: By genus (level 3) or growth form (level 2). Additional sub-variables are relevant for most efficient use of coral cover as an EOV, including diversity, condition (disease, bleaching, etc.), colony recruitment and size classes, and substrate variables (e.g. rugosity, hard substrate, etc.)

Metadata used: A metadata standard for the GCRMN is being established to confirm to Darwin Core and EML global standards

Methodology: Coral cover can be measured by a variety of tools that assess spatial cover of corals in relation to the total surface of a reef : • Point and line-intercept transects use a linear sample, where the cover under individual points (at varying separation distances) or continuous under a line (usually to 1 cm resolution or slight coarser) are aggregated and divided by the total sample size (number of points or length of line) to give percent cover of each class recorded. • Quadrats us two-dimensional samples in the same way aggregating the cover of individual classes recorded ot the total area sampled. Methods include in situ observation, and observations from photographic and video records. Automated tools are under development, to both record images using underwear drones and analyse cover through algorithms. • Techniques to document coral cover from aerial or satellite sensors re under development, requiring sensitive multi-spectral sensors to different coral from algal surfaces. These are not yet operational on meaningful scales.

National use of indicator

Producing this indicator nationally: Live coral cover is a highly standardized and simple indicator, and the GCRMN has aggregated it from national to regional and global levels since 2000. At present a renewed Implementation and Governance Plan is being implemented that will facilitate data aggregation through national and regional networks using online repositories. This is intended to make the submission of updated data from monitoring programmes a regular/ongoing process, so that national updates can be obtained simply by reprocessing the relevant analysis code.

This will be operational through the global 2020 report, such that annual national reporting on coral reef health can be done ‘at the push of a button’.

Examples of national use: NOAA/USA and Australia

Availability of global data for national use: Regional repositories will be operational during 2019-2020 under the GCRMN which can be used for national purposes and/or national networks may establish their linked/compatible national repositories/databases.

The indicator methodology can be applied with in-country data to develop a national indicator. Guidance on how to produce the indicator at the national level can be found on the GCRMN website.

Further resources

Key indicator facts

Indicator type

State

Applicable for national use

Yes (find out more)

Indicator classification

Operational and included in the CBD's list of indicators

Indicator type

State

Applicable for national use

Yes (find out more)

Indicator classification

Operational and included in the CBD's list of indicators

Last update

2000

Coverage

Global

Availability

Data freely available

Partners

Gcrmn

Global Coral Reef Monitoring Network

Goos

Global Ocean Observing System

Mbon

Marine Biodiversity Observation Network

Contact point

David Obura, on behalf of the Global Coral Reef Monitoring Network (GCRMN) Steering Committee, dobura@cordioea.net

Key resources