DISORDERS IN SOUTHWEST FORESTS

Recent events in the forests of the Southwest have prompted scientists to consider the role of climate variability in insect and disease cycles. The ponderosa and piñon pine mortality due to bark beetles during 2002-2003 and the decline of aspen from 1999 to 2004 are examples of events that appear to be tied to recent climatic episodes (Breshears et al. 2005). Extreme to exceptional drought conditions in the Southwest in 2002 (U.S. Drought Monitor 2002) have plausibly tipped the balance towards bark beetle outbreaks in pine forests and woodlands. The ecological impacts of 2002 may not have been as severe if it had not been for the preceding six of seven years with below normal precipitation. Over 70 million pine trees along with millions of other conifers died in 2002-03 (USDA-FS 2002, 2003). Fluctuations in conifer mortality caused by bark beetles ca