Forest fires: The scientists studied an area in northwestern Ontario. There, either because of natural climate variation or the greenhouse effect, average annual temperatures rose 4 degrees Fahrenheit from the mid-1960s to the mid-1980s. Droughts became more frequent and, as a result, so did forest fires. With less rainfall, runoff from the watershed was so reduced that it took lakes about 20 years to replenish their water instead of five. The more frequent fires reduced the number of trees, which ordinarily break up winds; the gusts drove cold layers of the lake deeper or eliminated them altogether. Some fish, such as lake trout, cannot live without these oxygen-rich layers. With fewer trout-friendly lakes, some of the world’s most valuable fisheries would disappear–bad news for fish, fishermen and other creatures caught in a greenhouse with no exit.
