Introduction
The United States, Canada, and Mexico share more than long borders; they also share guardianship of a common environmental heritage. At times they have worked together to deal with transborder problems such as air and water pollution and disposal of hazardous wastes. At other times, differences over resource management (especially water) have raised sovereignty concerns and provoked fractious disputes.

Not surprisingly, the proposal a two decades ago to advance regional integration by negotiating a North American Free Trade Agreement (NAFTA) provoked sharp reaction by the environmental community. US environmental groups argued that increased industrial growth in Mexico, spurred by trade and investment reforms, would further damage Mexico’s environmental infrastructure; that lax enforcement of Mexican laws would encourage “environmental dumping”; and that increased competition would provoke a “race to the bottom,” a weakening of environmental standards in all three countries. They demanded that any new trade pact include safeguards against real or potential abuses.

• Since it entered into force in January 1994, the NAFTA

has become one of the world’s best-known free trade agreements. In many respects, the NAFTA represents the most environmentally conscious trade pact. Public concerns about the interplay between trade and the environment pushed the NAFTA’s architects to pursue a “parallel track” that incorporated environmental sensitivities into the agreement it self where trade environment tensions were inescapable and dealt with other matters in side agreements. The NAFTA explicitly addresses environmental issues in its preamble and in five of its 22 chapters. A number of other chapters deal with environmental issues indirectly.

• The NAFTA’s preamble ensures that the goals of the

agreement are attained “in a manner consistent with