Summer 2008

Given that May and June are usually our two driest and windiest months, it is not surprising that this time of year everyone's level of concern about the condition of our forests becomes paramount. Additionally, forest health is becoming more critical each year as several contributing factors (drought, fire, insects and climate change) come together often in compounding ways to affect the potential for unnaturally severe wildfires. The following is a summary of these contributing factors for the Southwest, and sources of more detailed information.

Wildfire

The National Interagency Fire Center Predictive Services center reports a large degree of green-up and above average fine fuel loading in Arizona. Effects of La Nina are expected to continue, though weakening, through summer in the Southwest, creating warmer and drier weather. The potential for significant wildfire activity during April is above normal for Southern and Southeastern Arizona, including Coronado National Forest lands and most of Pima, Santa Cruz, Cochise, Pinal, Graham, and Greenlee counties. Southern and eastern New Mexico and West Texas are also expecting elevated risk of significant fires in the near term. Thanks to high levels of winter snowfall and precipitation Northern and Western Arizona is facing normal fire potential early in the season. However, abundant fuels and persistent drought are leading to above-normal fire potential starting in May. The elevated fire danger will follow the typical pattern in the state throughout most of the summer until the monsoon moisture and rain decrease fire potential.

Bark Beetles

Since 2000, southwestern forests have experienced severe bark beetle epidemics that have killed many trees. Ponderosa and pinyon pine trees have been especially hard hit. By stressing individual trees, overly dense forest conditions have contributed significantly to the severity of the on-going bark beetle outbreak.

Unfortunately, there is a public perception that the bark beetle outbreak is over in the Southwest. Certainly tree mortality has slowed, but beetle populations have remained relatively stable during the last three years. Late winter snow storms last year contributed significant levels of moisture to Arizona’s forests, possibly staving off another major bark beetle outbreak.

The summer monsoon rains do not appear to affect bark beetle outbreaks. Arizona’s forests will continue to teeter on the brink of another outbreak so long as stand density is high and warmer, drier climatic conditions are the rule.

There needs to be a long-term trend toward wetter conditions for the relationship between the trees and the bark beetles to come into equilibrium, and according to the meteorologists, we are still on a drying trend. Therefore, trees are still at risk of a continuation of the bark beetle outbreak we have been witnessing these last four years, with the potential of bark beetles significantly increasing mortality in our forests only limited by the weather and the number of remaining live trees. To learn more about bark beetles and their relationship with trees, click on the following link for the FAQ about bark beetles.

Drought

Drought stresses the health of individual trees and increases overall forest susceptibility to severe fires and beetle infestations. The Southwest has been in the grip of drought since the mid-1990s. Recent trends described inClimate Assessment for the Southwest (CLIMAS) indicate that: “High temperatures and low precipitation have maintained drought conditions in much of Arizona, while the opposite conditions have helped most of New Mexico stay drought-free. Still, the southern portions of both states are projected to face above-normal fire risk through at least the end of May. The risk is greatest in lower and middle elevations where grasses can quickly dry into tinder.” The National Drought Mitigation Center issues regular updates on current conditions.

Climate Change

Human-caused emissions of carbon dioxide have been implicated in the warming of the global atmosphere, which is likely to have strong but varied affects on ecosystems everywhere. A recent report from the USDA Forest Service’s Pacific Northwest Research Station suggests that warming is likely to cause continued increases in the growth of woody vegetation in the western United States, while hotter, drier summers are likely to cause more and larger forest fires. As a result, the report concludes, managers may want to manage forests “to be more resilient to drought, long hot summers, and insect and disease outbreaks.”

Carbon sequestration in forests is one strategy for combating climate change. Read about its connection to southwestern forest restoration in the ERI white paper, Forestlands Health and Carbon Sequestration."

Policy

Homeowners

People who live in ponderosa pine or pinyon-juniper forests bear responsibility for fire readiness and forest health on the lands they own. For specific ideas on what to do around houses, read the ERI pamphlet Forest Restoration for Homeowners or the recently published Backyard Wildlife Habitat and Fire Safety: A Guide for Residents of Flagstaff. Planting native grasses, flowers, and shrubs in your yard can help conserve plant and animal species, cut down on water use, and create a beautiful home landscape. Read more in our pamphlet Restoring Native Plants and Landscapes: A Guide for Residents of Southwestern Ponderosa Pine Forests.

Forest Restoration

Southwestern ponderosa pine forests have become much denser, as shown by comparison photos and many other lines of evidence. Long-term research conducted by ERI and other researchers has shown that a combination of thinning and prescribed burning, developed as elements of a site-specific treatment, can effectively restore the structure and ecological functioning of southwestern ponderosa pine forests. Such treatments can:

• decrease the severity of natural or human-caused fires
• improve the health and growth rates of older trees
• increase the abundance and diversity of grasses, wildflowers, shrubs, and butterflies
• promote overall biodiversity
• contribute to the forest’s recreational and aesthetic attributes.

Read more about the basics of forest restoration here. For a more detailed overview, read excerpts from the Introduction to the Island Press book, Ecological Restoration of Ponderosa Pine Forests. Or check out what’s happening in collaborative forest restoration around the Southwest at the online Southwest Community Forestry Caucus.

For More Information

Two places on the ERI web site to find more information about many of the topics summarized above are the ERI recent publications page and the ERI library.