1999: Canada and the United States sign a treaty governing the conservation and sharing of the Pacific salmon that migrate between waters of the two nations.
1992: Start of Rio Summit or Earth Summit held by the UN. See also Ozone Layer clip for @Issue.
1989: A natural-gas pipeline explodes in Russia, just as two trains pass, killing more than 500 people. Although pressure in the pipeline had dropped, a sign of a possible leak, instead of following procedures and checking for leaks, pipeline workers instead pumped in more gas to keep the pressure up. The gas leaked and ignited when the trains passed by.