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Large Marine Ecosystems (LMEs): Status and Trends

The Intergovernmental Oceanographic Commission (IOC) of UNESCO is leading the assessment of Large Marine Ecosystems (LMEs).


Volume four presents the results of the comparative assessment of LMEs, which was conducted by a working group of institutional partners and experts under the leadership of the Intergovernmental Oceanographic Commission (IOC) of UNESCO. It includes an assessment of the Western Pacific Warm Pool (WPWP), using a sub-set of the indicators used in the LME assessment. This first global comparative assessment of LMEs provides a valuable snapshot of LME condition with respect to a number of priority issues identified in Transboundary Diagnostic Analyses conducted as part of GEF LME projects – for example, unsustainable fishing, pollution, habitat destruction, and climate change. The patterns of risk among LMEs (based on single as well as multiple indicators for both the human and natural systems) have highlighted those LMEs at highest potential risk of degradation and the contributing factors, as well as where human dependence on LMEs services and vulnerability to LME degradation and natural phenomena are greatest.

The assessment explores the human–environment interactions, with a focus on human dependence on ecosystem services and vulnerability to environmental degradation and climate-related natural phenomena, reveals patterns that are relevant for management and provides a multidimensional basis for determining risk. Management and response options can be tailored to suit the specific socio-economic and environmental conditions in each LME.

Assessment results based on single indicators and indices, as well as on multivariate indicators, are fairly consistent. They show that, in general, LMEs in developing regions (GEF-eligible) are at highest potential risk. However, LMEs are impacted to different degrees by each issue assessed, and the factors accounting for high risk vary across LMEs. These factors are largely anthropogenic and local and regional in scale. But global threats (warming seas and acidification) are projected to play an increasing role in determining LME condition, as seen in changes in fish catch potential under future warming, Reefs at Risk with warming and acidification, and the CHI Index. Furthermore, in a business-as-usual scenario, risk levels in a number of LMEs are projected to rise in the future due to factors such as increasing nutrient inputs from watersheds and increasing coastal populations. While this assessment focuses attention on LMEs at relatively high risk, low and medium moderate risk LMEs should not be ignored, as appropriate actions will be necessary to ensure that the risk levels in them do not increase.

Because this was a global comparative assessment across all LMEs, it was not possible to examine cause and effect, which is likely to vary among and within LMEs. Detailed assessments, including at the sub-LME scale, are needed to link cause and effect in the conceptual framework for specific issues. More conclusive results can be obtained with improved data, including data at the sub-LME scale. While this assessment presents an approach for prioritization of LMEs based on multiple indicators, other types of indices can be created from the indicators based on stakeholder priorities and user-defined weightings.

Large Marine Ecosystems:Key messages

1. A wide range of natural and human stressors that have cumulative and synergistic environmental impacts are concentrated in LMEs, and underscores the need for integrated and multisectoral environmental management approaches. Human use of LME natural resources and activities on land and sea are putting LME health and productivity at risk.  Unsustainable fishing practices, floating plastic debris, persistent organic pollutants, nutrient inputs from watersheds, and coastal habitat destruction are some of the pressures experienced by LMEs around the world. This is compounded by climate change impacts, which are already evident in many LMEs. These pressures are projected to increase in the future under a business as usual scenario.  LMEs that are at highest relative risk are mainly those in tropical regions.  Addressing the diverse sources of pressures on LMEs requires, among others, integrated and multisectoral approaches and improvement in transboundary governance architecture.

2.  Ecosystem degradation has potentially severe consequences for the millions of people around the world who are dependent on LME ecosystem services for their survival and wellbeing.   Future deterioration of ecosystem health coupled with climate change will exacerbate an already precarious state for coastal populations of some LMEs. These populations particularly in highly populated tropical regions are the most at risk from the combined effects of environmental threats, dependence on LME resources, and shortfalls in their capacity to adapt. Based on indicators of LME human development status and of LME health, the LMEs at highest overall risk are those fringed by developing countries in Africa and Asia. Measures need to be urgently taken to mitigate the risks to human communities arising from the combination of environmental degradation and climate change impacts.

3. Management of LMEs can be considerably improved by improving the quality of data and information and by assessments at sub-LME scales. The assessment has been constrained by limitations in the availability and quality of data, which are variable amongst LMEs.  Much of the available data are characterized by varying levels of uncertainty as well as by spatial and temporal gaps, which can be addressed in the future through research and monitoring and observing programmes.  Assessments are also needed at sub-LME scales, so that actions can be taken to address pressures and impacts at the appropriate scale.  This requires the availability of data and information at the appropriate geographic scale.  In addition, there is need for maintenance and regular updating of the LMEs data portal developed under this phase of the TWAP so that interventions can be made in a timely manner as new data and information become available.  It is crucial that adequate financial resources are made available to improve data availability and quality.

LMEs Partners

A global partnership comprising recognized institutions, experts and data providers, among others, is responsible for carrying out the LMEs assessment.  A core partner is the National Oceanic and Atmospheric Administration (NOAA), United States, one of the leaders in the global LMEs movement. The other partners are:


For more information on the GEF TWAP LMEs Assessment:

LMEs map

Figure 1. The global ocean is divided into 66 Large Marine Ecosystems. Data source:







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