Biodiversity and Ecosystem (EO 1)

Common Indicator 4: Population abundance of selected species - Marine Reptiles

Geographical scale of the assessment:
Regional, Mediterranean Sea
Contributing countries:
Mid-Term Strategy (MTS) Core Theme:
2-Biodiversity and Ecosystems
Ecological Objective:
EO1: Biological diversity is maintained or enhanced. The quality and occurrence of coastal and marine habitats and the distribution and abundance of coastal and marine species are in line with prevailing physiographic, hydrographic, geographic and climatic conditions.
IMAP Common Indicator:
Common Indicator 4 (CI4): Population abundance of selected species (related to marine turtles)
Indicator Assessment Factsheet Code:

GES Definition: The population size allows to achieve and maintain a favourable conservation status taking into account all life stages of the population.

GES Targets:

  • State: No human induced decrease in population abundance.
  • State: Population recovers towards natural levels where depleted.



This assessment presents a brief overview of the known abundance of loggerhead and green sea turtles at breeding, foraging and wintering grounds, based on published data, to determine what knowledge gaps need to be filled to realise the objective of this indicator. The objective of this indicator is to determine the population status of selected species by medium-long term monitoring to obtain population trends for these species. This objective requires a census to be conducted in breeding, migratory, wintering, developmental and feeding areas.

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Assessment methods               

This assessment presents a brief and general overview of the distributional range of two marine turtle species to identify existing knowledge and knowledge gaps for use in elaborating the national monitoring programmes for biodiversity. Published information by regional and national surveys and research projects were used to compile the review, but this overview does not present a comprehensive assessment of existing knowledge.

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Results and Status, including trends

This general overview indicates that over 100 sites around the Mediterranean have scattered to stable (i.e. every year) nesting of loggerhead turtles. Greece and Turkey alone represent more than 75% of the nesting effort in the Mediterranean. Information on the size structure and abundance of individuals at oceanic and neritic marine areas has proven difficult. Most green turtle nests are laid in Turkey, Cyprus and Syria, with the remainder being found in Lebanon, Israel and Egypt. Information about the numbers of green turtles in various developmental, foraging and wintering habitats is limited.

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This general overview indicates that overall, programs at nesting sites need to place a strong focus on ensuring long-term recognition of unique female individuals and incorporate counts of males. The monitoring based on Common Indicator 1 will help with delineating developmental, foraging and wintering sites to make counts of adult vs. juvenile turtles and fluctuations in numbers over time. Information obtained through Common Indicator 2: Condition of the habitat’s typical species and communities will be intrinsically linked with Common Indicator 3: Species distributional range.

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Key messages 

  • This general overview indicates that major gaps exist in estimating the population abundance of sea turtles.
  • Programs at nesting sites need to place a strong focus on ensuring long-term recognition of female individuals and incorporate counts of males.

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