Over the past 20 years, an extraordinary number of international environmental agreements have been concluded. More than 200 multilateral environmental agreements—defined in this book as those involving more than two countries—are known to exist. Some of these are global treaties, open to any country. The number of bilateral agreements is unknown, but is thought to be well in excess of a thousand. The result is an international structure for environmental management that was not premeditated, and that reflects the extraordinary diversity of issues and interests involved.

Very few MEAs actually regulate trade or contain trade provisions. Of the 20 or so that do, even fewer are of notable significance to the environment-trade interface. Seven of the most important are discussed in greater detail below.

Increasingly, the complex of institutions and organizations that develop around international environmental agreements are referred to as "regimes," expressing the reality that they involve a number of constituencies and actors, and no longer reflect the dynamics of power between sovereign states alone. The rules governing these regimes differ from one to another reflecting the provisions of the relevant agreement. But all draw on customary international law and a range of practices and principles that have become widely accepted.

The international structure of environmental management is extremely dynamic. The various regimes address a wide variety of issues, ranging from toxic substances to the protection of elephants, from air pollution to biodiversity. As well, they must respond to changing scientific information about the environment, changing perceptions of the significance of this information, and the constant feedback from the successes and failures of the measures adopted in support of their objectives.

2.4.2 MEAs: The principal MEAs