Convention on Biological Diversity
The Convention on Biological Diversity was signed by over 150 governments at the Rio Earth Summit in 1992 and entered into force in 1993. It has become the centerpiece of international efforts to conserve the planet's biological diversity, ensure the sustainable use of biological resources, protect ecosystems and natural habitats, and promote the fair and equitable sharing of the benefits arising from the utilization of genetic resources. The convention was signed on June 4, 1993, but the United States has failed to ratified it.

Convention on Climate Change
Over 150 states signed the United Nations Framework Convention on Climate Change in June 1992 at the Rio Earth Summit, recognizing climate change as "a common concern of humankind." The convention aimed to reduce emission levels of greenhouse gases to 1990 levels by the year 2000 but failed to set binding goals. The United States signed the treaty on June 12, 1992, ratified it on October 15, 1992, and entered it into force in the United States on March 21, 1994.

Kyoto Protocol to the United Nations Convention on Climate Change
The agreement sets, for the first time, legally binding limits on the heat-trapping greenhouse gases that cause global warming. Under the protocol, 38 industrialized countries agreed to reduce their overall emissions to about 5% below 1990 levels by 2012, and a range of specific reduction requirements was set for other countries. The U.S. signed the protocol on November 12, 1998, but has not yet ratified it.

Convention to Combat Desertification
The Convention to Combat Desertification in Those Countries Experiencing Serious Drought and/or Desertification, Especially in Africa (CCD) promotes an integrated approach to managing the problems posed by dry-land ecosystems and encourages developed nations to support such efforts internationally. The convention came into effect in 1996 and has over 120 parties. The United States has signed but not ratified the convention.

Convention on International Trade in Endangered Species (CITES)
CITES establishes international controls on global trade in endangered or threatened species of animals and plants. For example, CITES prohibits all commercial trade in wildlife species threatened with extinction. CITES was ratified by the United States on January 14, 1974, and implemented as the Endangered Species Act. More than 125 countries are members.

Montreal Protocol on Substances that Deplete the Ozone Layer
The Montreal Protocol—and subsequent revisions—is the primary international regime for controlling the production and consumption of ozone-depleting substances such as CFCs, halons, and methyl bromide. As of June 1994, 136 states, including virtually all major industrialized countries and most developing countries, had become parties to the protocol. The United States signed the protocol on September 16, 1987, and ratified it on April 21, 1988. The protocol and its subsequent revisions modified the original 1985 Vienna Convention for the Protection of the Ozone Layer.