Marine boundaries

Exclusive Economic Zones Boundaries (EEZ)

This dataset represents Exclusive Economic Zones (EEZ) of the world. Up to now, there was no global public domain cover available. Therefore, the Flanders Marine Institute decided to develop its own database. The database includes two global GIS-layers: one contains polylines that represent the maritime boundaries of the world countries, the other one is a polygon layer representing the Exclusive Economic Zone of countries. The database also contains digital information about treaties.

Please note that the EEZ shapefile also includes the internal waters of each country


Download EEZ Boundaries | Methodology

Remarks and corrections can be sent to info@marineregions.org.

Preferred citation:
VLIZ (2014). Maritime Boundaries Geodatabase, version 8. Available online at http://www.marineregions.org/. Consulted on 2014-11-01.

IHO Sea Areas

This dataset represents the boundaries of the major oceans and seas of the world. The source for the boundaries is the publication 'Limits of Oceans & Seas, Special Publication No. 23' published by the IHO in 1953. The dataset was composed by the Flanders Marine Data and Information Centre.

NB: The Southern Ocean is not included in the IHO publication and its limits are subject of discussion among the scientific community. The Flanders Marine Institute acknowledges the controversy around this subject but decided to include the Southern Ocean in the dataset as this term is often used by scientists working in this area. For more information, please refer to the Disclaimer.


Download IHO Sea Areas | View Metadata

Remarks and corrections can be sent to info@marineregions.org.

Preferred citation:
VLIZ (2005). IHO Sea Areas. Available online at http://www.marineregions.org/. Consulted on 2014-11-01.

Links:
Limits of Oceans & Seas, Special Publication No. 23

Marineregions: the intersect of the Exclusive Economic Zones and IHO areas

The maritime boundaries provide a useful tool to limit national marine areas, but do not include information on marine regional and sub regional seas. This hampers the usage of these boundaries for implementing nature conservation strategies or analyzing marine biogeographic patterns. For example, a species occurring in the German EEZ can live in the North Sea, the Baltic Sea or Kattegat area. Each of these different marine areas has very distinct hydrological, oceanographic and ecological conditions.

Therefore, by combining the information on regional seas and national maritime boundaries, we can include both a environmental and managerial factor. We propose to overlay the information from the maritime boundaries (the Exclusive Economic Zones) with the IHO Sea Areas (IHO, 1953). This map including the global oceans and seas, has been drafted for hydrographic purposes, but also gives an unequivocal and acceptable distinction of the regional seas and oceans from an oceanographic point of view. The combination of these two boundaries allows us for example to create national regional sea areas for the global ocean.

Methodology

We digitized the IHO Sea Areas using the publication 'Limits of oceans and seas (IHO, 1953). The dataset, available as ArcGIS Shapefile (polygons), represents the boundaries of the major oceans and seas of the world. For the maritime boundaries, we worked with the MarBound-layer version 1 or 2, with the low resolution coastline, that matches the ESRI Country shapefiles but implemented the change history file of the latest version. Since the third version onwards, the Marbound polygon layer has a high resolution coastline (GSHHS), which has advantages, but on the other end, the size of the file makes it difficult to handle for calculating the intersections. In addition, using two shapefiles with a different resolution creates a lot of small polygons that should have been checked to decide to which Marine Area it belonged. This would have been a very time-consuming task and the result would have been an enormous file, difficult to work with within an acceptable period of time.

We used the software ArcMAP 9.3 to make the new national sea boundaries intersect was, with several additional tools. The Analysis Tools Intersect to, Graphics and shapes, Calculate Geometry to, Field Calculator (ArcGIS), used to define the names and ID's using Visual Basic Expressions and the ET GeoWizards to remove multiple fields in the attribute table, to perform an Erase, Merge Layers.

If one uses the intersect method and both shapefiles are not exactly the same, in this case for instance for the coastline, we would create again lots of small polygons to analyze one by one. Although we did our best to minimize this, by using a lower coastline resolution, the small parts still appeared. If one uses the Intersect Tool, the result contains only the overlapping parts of both shapefiles. In the output of the Intersect Tool, only the EEZ features remain (Figure 6), but we also need the open sea oceans. Therefore the ET Geowizards Erase Tools was used, to delete from a rectangle all land and EEZ areas, so only the 'open seas' remained. This layer, with the result of the intersect were merged (Figure 8). Areas with the same Exclusive Economic Zone and the same sea basin were merged (with the Editor in ArcMap, except when both features are not connected to each other (single part features).

The last step was calculating the surfaces of each Marine Area. Different coordinate systems exist to perform geometric calculations, some are more precise then others, we opt for the method proposed by Jenness Enterprises to calculate surfaces on a sphere.

Nomenclature

SEA EEZ Marine Region
Mediterranean Sea - Western Basin Italian Exclusive Economic Zone Italian part of the Mediterranean Sea - Western Basin
Mediterranean Sea - Eastern Basin Italian Exclusive Economic Zone Italian part of the Mediterranean Sea - Eastern Basin
Ligurian Sea Italian Exclusive Economic Zone Italian part of the Ligurian Sea
Tyrrhenian Sea Italian Exclusive Economic Zone Italian part of the Tyrrhenian Sea
Adriatic Sea Italian Exclusive Economic Zone Italian part of the Adriatic Sea
Ionian Sea Italian Exclusive Economic Zone Italian part of the Ionian Sea
Creation of names for the Marine Areas. As example, the ones for the Italian EEZ have been chosen.

Polygon creation by merging of both layers


The result of all this is a shapefile with 525 features.
Download intersect IHO/EEZ

Remarks and corrections can be sent to info@marineregions.org.

Preferred citation:
VLIZ (2010). Intersect of IHO Sea Areas and Exclusive Economic Zones (version 1). Available online at http://www.marineregions.org/. Consulted on 2014-11-01.

VLIZ (2012). Intersect of IHO Sea Areas and Exclusive Economic Zones (version 2). Available online at http://www.marineregions.org/. Consulted on 2014-11-01.

Marine and land zones: the union of world country boundaries and EEZ's

This dataset combines the boundaries of the world countries and the Exclusive Economic Zones of the world. It was created by combining the ESRI world country database and the EEZ V7 dataset.


Download union land/EEZ

Remarks and corrections can be sent to info@marineregions.org.

Preferred citation:
VLIZ (2014). Union of the ESRI Country shapefile and the Exclusive Economic Zones (version 2). Available online at http://www.marineregions.org/. Consulted on 2014-11-01.

The SeaVoX Salt and Fresh Water Body Gazetteer

The data set consists of a polygon file defining the limits of water bodies from the SeaVoX Salt and Fresh Water Body Gazetteer. SeaVoX is a combined SeaDataNet and MarineXML vocabulary content governance group, it is moderated by BODC. This data set defines the geographic extent of the terms specified by the SeaVoX vocabulary governance to describe coherent regions of the hydrosphere. Includes land masses enclosing freshwater bodies. The coastline data set used in the shapefile is taken from the World Vector Shoreline data set (scale 1:250,000).

The data set was developed as a means of defining the geographic extent of the water bodies defined in the SeaVoX salt and fresh water gazetteer. (source: Metadata)


Download Seavox Sea Areas

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References:

OSPAR Boundaries and Regions

A shapefile containing the external boundary and internal region boundary lines to describe the OSPAR area and a shapefile to describe the OSPAR Regions.


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Statistics on Marbound and IHO (Costello et al., 2011) (Not integrated in gazetteer)

Depth and topography directly and indirectly influence most ocean environmental conditions, including light penetration and photosynthesis, sedimentation, current movements and stratification, and thus temperature and oxygen gradients. These parameters are thus likely to influence species distribution patterns and productivity in the oceans. They may be considered the foundation for any standardised classification of ocean ecosystems, and important correlates of metrics of biodiversity (e.g. species richness and composition, fisheries). While statistics on ocean depth and topography are often quoted, how they were derived is rarely cited, and unless calculated using the same spatial resolution the resulting statistics will not be strictly comparable. We provide such statistics using the best available resolution (1-minute) global bathymetry, and open source digital maps of the world's seas and oceans and countries' Exclusive Economic Zones, using a standardised methodology. We created a terrain map and calculated sea surface and seabed area, volume, and mean, standard deviation, maximum and minimum, of both depth and slope.
Download the results

References:

  • Costello, M.J.; Cheung, A.; De Hauwere, N (2011). The surface area, and the seabed area, volume, depth, slope, and topographic variation for the world's seas, oceans and countries. Environmental Science & Technology http://www.vliz.be/imis/imis.php?module=ref&refid=202017
  • The surface area, and the seabed area, volume, depth, slope, and topographic variation for the world's seas, oceans and countries. Available online at http://www.marineregions.org/. Consulted on 2014-11-01.

Ecological classifications

Large Marine Ecosystems of the World

This dataset represents the Large Marine Ecosystems of the world. It was composed by the National Oceanic and Atmospheric Administration (NOAA). The dataset exists as a polygon and as a polyline layer.


Go To LME-website | View Metadata

Links:
Large Marine Ecosystems of the World

Longhurst Biogeographical Provinces

This dataset represents a partition of the world oceans into provinces as defined by Longhurst (1995; 1998; 2006), and are based on the prevailing role of physical forcing as a regulator of phytoplankton distribution. The dataset represents the initial static boundaries developed at the Bedford Institute of Oceanography, Canada. Note that the boundaries of these provinces are not fixed in time and space, but are dynamic and move under seasonal and interannual changes in physical forcing. At the first level of reduction, Longhurst recognised four principal biomes (also referred to as domains in earlier publications): the Polar Biome, the Westerlies Biome, the Trade-Winds Biome, and the Coastal Boundary Zone Biome. These four Biomes are recognisable in every major ocean basin. At the next level of reduction, the ocean basins are partitioned into provinces, roughly ten for each basin. These partitions provide a template for data analysis or for making parameter assignments on a global scale. Please refer to Longhurst's publications when using these shapefiles.

A summery table has been prepared by Mathias Taeger and David Lazarus, Museum für Naturkunde, Berlin (2010-03-26). This table makes it easier to relate the classification of Longhurst to the the original quantitative parameters used to create it. Productivity values are from the table in Longhurst, 1995, Chlorophyll values; photic depth and mixed layer depth originate from graphs in Longhurst, 1998. The sea temperature at 0 and 50 m are from the World Ocean Atlas (2005), average values were calculated in ArcGIS. Each parameter value was set into 5 equal intervals. Download summary table.


Download Longhurst Areas Shapefile | View Metadata

Remarks and corrections can be sent to info@marineregions.org.

Preferred citation:
VLIZ (2009). Longhurst Biogeographical Provinces. Available online at http://www.marineregions.org/. Consulted on 2014-11-01.

References:

  • Longhurst, A.R et al. (1995). An estimate of global primary production in the ocean from satellite radiometer data. J. Plankton Res. 17, 1245-1271
  • Longhurst, A.R. (1995). Seasonal cycles of pelagic production and consumption. Prog. Oceanogr. 36, 77-167
  • Longhurst, A.R. (1998). Ecological Geography of the Sea. Academic Press, San Diego. 397p. (IMIS)
  • Longhurst, A.R. (2006). Ecological Geography of the Sea. 2nd Edition. Academic Press, San Diego, 560p.

Marine Ecoregions of the World, MEOW (Spalding et al., 2007)

MEOW is a biogeographic classification of the world's coasts and shelves. It is the first ever comprehensive marine classification system with clearly defined boundaries and definitions and was developed to closely link to existing regional systems. The ecoregions nest within the broader biogeographic tiers of Realms and Provinces.

MEOW represents broad-scale patterns of species and communities in the ocean, and was designed as a tool for planning conservation across a range of scales and assessing conservation efforts and gaps worldwide. The current system focuses on coast and shelf areas (as this is where the majority of human activity and conservation action is focused) and does not consider realms in pelagic or deep benthic environment. It is hoped that parallel but distinct systems for pelagic and deep benthic biotas will be devised in the near future.

The project was led by The Nature Conservancy (TNC) and the World Wildlife Fund (WWF), with broad input from a working group representing key NGO, academic and intergovernmental conservation partners.
(source: http://www.worldwildlife.org/science/ecoregions/marine/item1266.html)

Read the article


Download MEOW | View Metadata

Links:

References:

  • Spalding, M. D. Fox, H. E. Allen, G. R. Davidson, N. Ferdana, Z. A. Finlayson, M. Halpern, B. S. Jorge, M. A. Lombana, A. Lourie, S. A., (2007). Marine Ecoregions of the World: A Bioregionalization of Coastal and Shelf Areas. Bioscience 2007, VOL 57; numb 7, pages 573-584.

ICES Ecoregions

ICES EcoRegions are large-scale management units for the ICES regional seas and are used in advisory reports to segment advice into the different sea areas. The EcoRegions were first referenced by the predecessor to ACOM (Advisory Committee) in 2004 (source: http://www.ices.dk/sites/pub/Publication%20Reports/Advice/2004/Book%201%20-%20Part%201.pdf)


Download ICES Ecoregions | View Metadata

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Fishing zones

ICES Statistical areas

The ICES Statistical Areas delineates the divisions and subdivisions of FAO Major Fishing area 27. The Areas are used as bounding areas for calculation of fish statistics, e.g. catch per unit effort (CPUE) and stock estimates.


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The NAFO Convention Area

The NAFO Convention Area encompasses a very large portion of the Atlantic Ocean and includes the 200-mile zones of Coastal States jurisdiction (USA, Canada, St. Pierre et Miquelon and Greenland). The total area under NAFO's Convention is 6,551,289 km2. Geographic delineations of the NAFO Convention Area are described in the NAFO Convention and are included in Marine Regions.

FAO Fishing Areas

The dataset represents the boundaries of the FAO Fishing Areas. The source for the boundaries is the description that can be found on the FAO website. The dataset was composed by the Flanders Marine Data and Information Centre.


Download FAO Fishing Areas Shapefile | View Metadata

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FAO Fishing Areas

(Historical) fishing areas of Belgian sea fisheries

The project 'A century of sea fisheries' brings together data and information from different, fragmented sources into an integrated database. The historical Belgian fishing grounds are included in Marine Regions.

Thematic gazetteers

Marine Natura 2000 Sources

The source of Natura 2000 sites is the GIS shapefile made available for download by the European Environment Agency. Natura 2000 sites span over the European Union (EU) territories both on land and on sea. This dataset compiles marine Natura 2000 sites. Although there isn't a defined criteria by the EU for what constitutes a Marine Natura 2000 site nor does the original dataset contain information on this matter, we defined a selection criteria to sort between marine and terrestrial sites. Thus, this dataset encompasses all sites that fall (partly) within the Exclusive Economic Zone of countries of the European Union, based on the high resolution EEZ GIS cover, V7. It might occur that a terrestrial site with marine importance, e.g. inland nesting ground for seabirds, is excluded from the selection of Marine sites or that a site with only a small marine proportion is included in this selection. This selection identifies 2,894 (partly) marine Natura 2000 sites

One of the attributes of the dataset is the site type. Site type values range from A to K and indicate whether a site belongs to:

  • 1 - Natura 2000 Special Protection Area (SPA, EU Birds Directive); OR/AND
  • 2 - Natura 2000 Site of Community Importance (SCI, EU Habitats Directive);
as follows: A, B, D, F, H, J: belongs to category 1 - E, G, I, K: belongs to category 2 - C belongs to both categroies.

Original bilingual denominations were accounted for and correctly included in marineregions.org, however, for sites named in one single language, it was assumed that the language of appellation was the main official language of the corresponding country.

World Marine Heritage Sites

This file contains the 46 World Marine Heritage Sites. Launched in 2005, the mission of the world Heritage Marine Programme is to establish effective conservation of existing and potential marine areas of Outstanding Universal Value to make sure they will be maintained and thrive for generations to come.
In order to create the data, information from the UNESCO World Heritage Marine Programme and Protected Planet were collected and compiled.


Download the World Marine Heritage Sites

Remarks and corrections can be sent to info@marineregions.org.

Preferred citation:
VLIZ (2013). World Marine Heritage Sites (version 1). Available online at http://www.marineregions.org/. Consulted on 2014-11-01.

Global contourite distribution

To create a global overview of contourite distribution, a literature study was performed. This task fits in the IGCP- and INQUA-project (http://www.contourites.org). Both projects want to facilitate research and increase knowledge about these sediments deposits.

Definitions:
Contourites are sedimentary units which are deposited or substantially reworked by alongslope bottom currents. They refer to the lithological unit and the terminology reflects the grain size of the sediment. Drifts refer to the same sedimentary unit as a contourite, but the word 'drift' reflects the morphological appearance of the sedimentary unit. Their terminology reflects the external shape, and the internal shape, which is determined by seismography. If drifts are clustered into a local area of certain size, we call the clustered sediment group a Contourite Depositional System (CDS).
These sedimentary units are generally, but not exclusively, found in the deep sea (>2000m depth). They are a useful tool for determining paleoceanic and paleoclimatic changes, since their distribution is linked to bottom currents. They have gained interest from the hydrocarbon industry, since accumulation of source rocks may be influenced by bottom currents. Slope instability is also an area of interest for further research.

Source methodology:
For acquisition of the resulting information, several hundreds of papers on the relevant subject were read. Firstly, abstracts, introductions and conclusions were read for a general view on the article. Then further reading on the relevant chapters provided the presented information.

In 2013, 166 records with the place type Drift were added to the Marine Gazetteer. These are linked to one of the 24 Contourite Depositional Systems, if they make part of such a system. Each drift is also influenced by a water mass or current. This water mass or current determines the sedimentation, erosion and movements of these sediments.

In 2014, the list was extended with 81 records of the place type Drift. No Contourite Depositional Systems were added. The search process was identical to 2013, only this time a summary paper was the starting point (Rebesco et al., 2014). In this publication, the major drifts were listed with their most relevant sources along with them. These listed sources were then sought after and read. Not all papers were accessible at the time of this process, and thus it is advised to read these publications in the future as well.

When there were maps or similar images about contourites included in the paper, shapefiles were created by georeferencing them in QGIS, which were then uploaded into the Marine Regions website. If the articles did not provide such a map or image, the drifts or CDS's were marked by a single point with its set of coordinates.

Regional gazetteers

Placenames Southern Bight of the North Sea and Scheldt Estuary

Different sources have been used to describe the Southern Bight of the North Sea region. The Interreg SAIL project provided geographic information on coastal regions, districts and communes bordering the Southern Bight of The North Sea. The Scheldemonitor project mapped in detail the Scheldt estuary, including the names of different mudflats and sandbanks.
Also various atlases have been used to describe in detail this area.

SCAR Composite Gazetteer of Antarctica

The SCAR Composite Gazetteer of Antarctica (CGA) has been compiled over a period of 20 years (commenced 1992) and consists of 36857 names that correspond to 18858 features. The SCAR gazetteer is available for download.

Bulgarian Antarctic Gazetteer

Bulgarian place names in Antarctica are approved by the Antarctic Place-names Commission, and formally given by the President of the Republic according to the Bulgarian Constitution and the established international practice. The Commission maintains international coordination with naming authorities of other Antarctic nations, and with the Scientific Committee on Antarctic Research (SCAR). Names given by Bulgaria are incorporated in the SCAR Composite Antarctic Gazetteer.

Four Maps representing Belgian toponyms in Antarctica

Four maps with the Belgian Toponyms of the following Antarctic regions:

  • Queen Fabiola Mountains
  • Sør Rondane
  • Gerlache Strait
  • Belgica Mountains
View the poster

Australian Antarctic Gazetteer

The Australian Antarctic Names and Medal Committee (AANMC) is the authority on Australian names in the Australian Antarctic Territory, and the Territory of Heard Island and the McDonald Islands. It is responsible for the investigation and acceptance or rejection of all names proposals following prescribed procedures. These proposals must meet certain criteria in order to be accepted.

GIS meteorology of Azov and Black Seas author Vladimir Belokopytov

Global gazetteers

GEBCO Gazetteer of undersea feature names

The undersea feature names shown on sheets and products of GEBCO and Regional International Bathymetric Charts (IBC) projects, and on international (INT) nautical charts are selected by the GEBCO Sub-Committee on Undersea Feature Names (SCUFN).
SCUFN maintains and makes available the names information in the form of a digital gazetteer. The October 2012 version of the gazetteer is available to download.

ASFA thesaurus

Aquatic Sciences and Fisheries Abstracts (ASFA) is an International Cooperative Information System which comprises an abstracting and indexing service covering the world's literature on the science, technology, management, and conservation of marine, brackish water, and freshwater resources and environments, including their socio-economic and legal aspects.

Distribution records from WoRMS

The aim of a World Register of Marine Species (WoRMS) is to provide an authoritative and comprehensive list of names of marine organisms, including information on synonymy. The register contains distribution information on marine species, which is linked with Marine Regions allowing to display all species occurring is a specific biogeogrpahic region.

Others

ETOPO1 Global Relief Model (Not integrated in gazetteer)

ETOPO1 is a 1 arc-minute global relief model of Earth's surface that integrates land topography and ocean bathymetry. It was built from numerous global and regional data sets, and is available in Ice Surface and Bedrock versions. Historic ETOPO2v2 and ETOPO5 global relief grids are deprecated but still available. Available Versions of the Grid (relief for the rest of the world is the same in both versions.):

  • ETOPO1 Ice Surface: Grid of Earth's surface depicting the top of the Antarctic and Greenland ice sheets.
  • ETOPO1 Bedrock: Grid of Earth's surface depicting the bedrock underneath the ice sheets.

More information and the grid files can be found on: http://www.ngdc.noaa.gov/

References:

  • Amante, C. and B. W. Eakins, ETOPO1 1 Arc-Minute Global Relief Model: Procedures, Data Sources and Analysis. NOAA Technical Memorandum NESDIS NGDC-24, 19 pp, March 2009.

General Bathymetric Chart of the Oceans (GEBCO) (Not integrated in gazetteer)

The General Bathymetric Chart of the Oceans (GEBCO) consists of an international group of experts who work on the development of a range of bathymetric data sets and data products, including gridded bathymetric data sets, the GEBCO Digital Atlas, the GEBCO world map and the GEBCO Gazetteer of Undersea Feature Names. They make the following gridded bathymetry data sets available:

  • The GEBCO_08 Grid: a global 30 arc-second grid
  • The GEBCO One Minute Grid: a global one arc-minute grid

More information and the grid files can be found on: http://www.gebco.net/

References:

  • For the GEBCO_08 Grid: The GEBCO_08 Grid, version 20091120, http://www.gebco.net
  • For the GEBCO One Minute Grid: 'The GEBCO One Minute Grid, version 2.0, http://www.gebco.net

Continental margins between 140m and 3500m depth (IFREMER - COMARGE, 2009) (Not integrated in gazetteer)

This shapefile has been prepared in the framework of COMARGE, one of the field project of the Census of Marine Life. It is intended to represent continental margins worldwide, with the exclusion of the continental shelf. The continental margins have been defined based on bathymetry and expert opinion. The upper margin of the boundary has been set at 140 m depth, which is the average depth of the shelf break, except in Antarctica where the shelf break goes deeper and the upper boundary has been set up at 500 m. The lower boundary has been set at 3500 m depth. Both isobaths were extracted from S2004 Bathymetry (a global bathymetry at 1 arc-minute resolution). The upper and lower boundaries were manually edited to follow the contour of continental margins in particular cases.

Please note that some but not all margins around island are included in this shapefile. (source: Metadata)


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References:

  • IFREMER (Vion, A.; Menot, L.), (2009). Continental margins between 140m and 3500m depth. Available online at http://www.marineregions.org/ Consulted on 2014-11-01.

TDWG Geography shapefiles (Not integrated in gazetteer)

This scheme meets the need for a standard yet adaptable system of geographical units for use in recording plant distributions and arranging specimens. Because a purely political arrangement cannot meet all the needs of botanists, the scheme's arrangement compromises between a politically and a phytogeographically oriented system. It identifies geographic units worldwide in a four-level hierarchy, incorporating continents, regions, provinces and countries. Each geographical unit at each level has its own numeric or alphanumeric code.

More information and the shapefiles can be found on: Kew GIS Unit

References:

  • R. K. Brummitt with assistance from F. Pando, S. Hollis, N. A. Brummitt and others. Plant Taxonomic Database Standards No. 2.ed. 2. World Geographical Scheme for Recording Plant Distributions, ed. 2. 2001. xv, 137 pp.; 17 maps. Available online at http://www.kew.org/gis/tdwg/index.html

Terrestrial Ecoregional Boundaries Shapefile (TNC) (Not integrated in gazetteer)

Global Ecoregions, Major Habitat Types, Biogeographical Realms and The Nature Conservancy Terrestrial Assessment Units as of December 14, 2009
Developed originally by Olson, D. M. and E. Dinerstein (2002), Bailey (1995) and Environment Canada (Wiken, 1986), these data layers were modified by The Nature Conservancy (TNC) to be used in its Biodiversity Planning exercises in the process known as Ecoregional Assessments. Several Ecoregions were modified from the originals by TNC staff developing the aforementioned assessments. The modifications are based on ecological, bio-physical and political rationales; most changes are noted in the accompanying documentation (attributes). Ecoregions in Canada and Mexico were modified mainly at the border with US territory, where TNC modified-Bailey (1995) ecoregions crossed over the country boundaries and the Olson, D. M. and E. Dinerstein (2002) and (Wiken, 1986) were replaced where the TNC modified-Bailey (1995) overlayed them. This layer was split from the terrestrial ecoregional assessment layer in June 2008.