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Social-Ecological Systems Meta-Analysis Database: Theory

Ecological effectiveness of MPAs

Variable relationship:

This theory is based on research assessing the ecological effectiveness of marine protected areas (MPAs). Most recently, a meta-analysis paper outlined five key features that contributed to the ecological effectiveness of MPAs. This text from the abstract of the Edgar et al 2014 paper summarizes the relationship: "Here we show that the conservation benefits of 87 MPAs investigated worldwide increase exponentially with the accumulation of five key features: no take, well enforced, old (>10 years), large (>100km2), and isolated by deep water or sand."

Marine protected areas
Scientific Field
Component Type(s)


VariableRoleRole ExplanationValue
External sanctionsProximate independent variable"Efficient enforcement" (the wording used by Edgar et al.) contributed to increases in fish biomass within MPAs.Yes
Governance system spatial extentProximate independent variableLarge (>100km2) MPAs increase ecological benefits.>100km2
Governance system ageProximate independent variableOlder MPAs (>10 years) are hypothesize to be more effective.> 10 years
External monitoringProximate independent variable"Efficient enforcement" (the wording used by Edgar et al.) contributed to increases in fish biomass within MPAs.Yes
PA IUCN strict zonesProximate independent variableNo-take areas were found to be more effective than partially closed areas.100%
MPA internal natural boundariesProximate independent variableThe paper states: "Isolation, a categorical factor that distinguished MPAs with reef habitat surrounded by deep (.25m) water or large expanses of sand from MPAs with shallow reef habitat extending to fished areas, seemed to exert a stronger influence for community level biomass and richness metrics than the other four features."Yes
Policy instrumentProximate independent variableThis theory describes marine protected areasProtected area
Transaction costsModerating independent variableEnforcement is much more effective if it is done in a way that keeps transaction costs low.Low
ComplianceIntermediate outcome Edgar et al. note that compliance may contribute to the isolation effect, in that "isolated MPAs are generally well demarcated for control purposes".Yes
Commons condition trendFinal outcomeThis is the outcome variable. MPAs that show improved condition (this outcome) are hypothesized to be influenced by the other variables. Condition is measured in the paper as increases in biomass.Remained the same or Improved

Related Theories

TheoryRelationshipCharacterizing Variables
Local livelihood and protected areasrelated
Centralized conservationrelated
Critique of fortress conservationcontradictory
CAR principles for conservation area designrelated

Related Studies


Edgar, G. J., R. D. Stuart-Smith, T. J. Willis, S. Kininmonth, S. C. Baker, S. Banks, N. S. Barrett, M. A. Becerro, A. T. F. Bernard, J. Berkhout, C. D. Buxton, S. J. Campbell, A. T. Cooper, M. Davey, S. C. Edgar, G. Forsterra, D. E. Galvan, A. J. Irigoyen, D. J. Kushner, R. Moura, P. E. Parnell, N. T. Shears, G. Soler, E. M. A. Strain, and R. J. Thomson. 2014. Global conservation outcomes depend on marine protected areas with five key features. Nature 506:216-220.