Table 3. Examples of agents of change and their effects in frequent-fire, old-growth conifer forests of the western United States Agent Examples of potential effects Reference Fire-regime disruption Fire exclusion Increase tree density Stephenson 1999 Increase fire severity Eradicate old trees Savage and Mast 2005 Ranching Livestock grazing Reduce palatable plants Clary 1975 Fragmentation Restrict wildlife movements Milchunas 2006 Watershed disruption Damage/eradicate springs Belsky and Blumenthal 1997 Wood harvesting Large-tree removal Reduce some wildlife habitat Tecle and Covington 1991 Road building Spread exotic plants Fornwalt et al. 2003 Fuelwood harvest Affect oak structure Fulé et al. 1997 Other Predator control Regional species extinctions Dahms and Geils 1997 Exotic plants Reduce some native plants Keeley 2006 Urban development Fragmentation Dale 2006 Climate change Increase tree mortality Breshears et al. 2005