Hi Stephane:

You can download protected areas data from some sources as:

http://staff.glcf.umd.edu/sns/branch/htdocs.sns/data/wdpa/

http://www.protectedplanet.net/help#question3

http://data.unep-wcmc.org/datasets/17

http://geocommons.com/datasets/143679/data

http://gcmd.nasa.gov/KeywordSearch/Metadata.do?Portal=esip&KeywordPath=Parameters%7CHUMAN+DIMENSIONS%7CENVIRONMENTAL+IMPACTS%7CCONSERVATION&OrigMetadataNode=GCMD&EntryId=GLCF_WDPA&MetadataView=Full&MetadataType=0&lbnode=mdlb2

These data files contain information about extension and you can use it to make the statistic job you need. I suggest you can import the datafiles into a spatial database, this allow you to make all kind of analysis

I hope you find it usefull

Hi,

I advice you to see this work: "Ocean yearbook, 27. Dalhousie University, Leiden (2013)" its a very interesting publication about the numerical coverage of Marine Protected Areas (MPAs) over the world, and especially the chapter of Spalding et al. "Protecting Marine Spaces: Global Targets and Changing Approaches" this one is available online from: http://www.cbd.int/doc/meetings/mar/cbwsoi-seasi-01/other/cbwsoi-seasi-01-protecting-marine-spaces-en.pdf

I hope this can help you.