The positive effects on the environment may however be weakened at the global level by possible cross-border leakage and increased emissions from international transport (OECD, 2010d), as some of the economic activity is shifted to countries with less strict environmental standards and enforcement (Box 2.2). Finally, in some cases new or higher environmental taxation would replace or make redundant environmental regulations already in place, limiting the positive effects on environment. Of the countries with a recommendation to rely more on such tax sources, France, Belgium and the United States tend to have relatively low environmentally-related revenues (both with respect to total revenues and to GDP), with Finland, Estonia and Korea at the other end of the spectrum. The effects on the environment will depend on the nature of exemptions that are scrapped.