Any dry forest in the western US that has not experienced fire in the last 50 to 100 years probably has too many trees to maintain healthy conditions. Many dry forests are so overgrown that fire – whether from lightning strike, prescribed or cultural burn – can be unsafe. Thinning prior to burning is especially important in the wildland-urban interface, to keep communities safe during a burn. Thinning also helps land managers influence which trees will survive a fire.
Trees in these crowded forests are under stress because they are competing with their neighbors for light, water, and nutrients. Stressed trees are prone to insect attack and disease which can make them more flammable.
In these forests, thinning involves removing some trees from the landscape, allowing the remaining trees more room to grow, making them more resistant to drought, and increasing the likelihood that they will survive future fires.
Frequently Asked Questions
For many hundreds of years, dry western forests benefited from more frequent, low intensity fires which helped reduce the density of vegetation and dry fuels in forests. For the last 100 years, many forests have had no fire. This resulted in many forests becoming overcrowded. Thinning smaller trees to reduce fuels and create growing space for larger trees in these dry forests is generally thought to be a beneficial practice – especially when the thinning is followed up with prescribed fire.