1870-3550 1870-3550 S1870-35502018000200009 10.20999/nam.2018.b001 United Kingdom 00 12 2018 00 12 2018 13 2 9 35

1999 2012 BECC (Border Environment Cooperation Commission) 2009 1998 32 1591-617 2000 1993 291-341 2009 2008 2016 133-53 2007 2017 12 1 1 157-75 1996 27 4 4 1027-56 2001 44 3 3 773-98 2014 185-204 2010 21-40 2011 19-36 2009 1997 28 24-48 1996 2001 39 395-482 2004 26 3 3 359-88 2003 1-21 2003 2008 219-38 2005 30 4 4 759-93 2004 26 341 1998 2015 17-26 2000 2006 264-303 1998 2016 1999 1992 2012 2004 26 389-413 2003 256-73 1996 36 3 3 721-63 2015 53 4 4 723-30 2003 147 147 1993 271-94 Statistics Canada 2013 2007 U.S. Census Bureau 2013 U.S. Department of State 1998 U.S. GPO (U.S. Government Printing Office) 2013 U.S. GPO (U.S. Government Printing Office) 1993 2009 2003 47-56 1990 2004 1998 2008 40 93-140