Fire and disease have always been part of western forests.
Forces that appear destructive actually allow new life to generate where old trees fall. However, these same forces have become more frequent and more severe as the new threat of a warming climate has entered the scene. What kills trees now is out of balance with the ability of a forest to regenerate itself. Every year millions of acres of forest are lost and are not replanted by nature or people.
THE CONSEQUENCES OF THESE THREATS, WORKING IN CONCERT, WILL BE PROFOUND.
Fire is a natural and necessary part of forest ecology. For example, the world's largest tree, the mighty Giant Sequoia of California, cannot reproduce without the heat of a fire to open its pine cone. However, in the early part of the 20th Century, it became government policy to suppress fire as a way to "protect" forests. This unknowingly set the stage for the catastrophic fires that have become commonplace in the last few decades. Fire suppression prevented many, small, lower-intensity fires from removing the understory and deadfall common in a growing forest. Without the intermittent removal of this fuel, it accumulated, leading to very large, very intense fires that are changing the American landscape. In some locations, modeling software predicts natural reforestation will not occur for over 500 years as the forest slowly works its way in, over generations, from the edges of these fire scars.
Parasites and Disease
Like fire, the parasites and diseases that affect western forests are generally not new and are naturally part of the ecosystem. The most publicized, the Western Bark Beetle (pictured), is native to North America and has been here for eons, evolving with the forest. However, as the climate warms, the winters of western North America are no longer as cold as they once were. The beetle (and other parasites) no longer suffer from the same attrition from cold. Conversely, as the summers are longer, the beetle lives longer and breeds more prolifically. Millions of acres of forest have been killed when once only isolated stands used to be affected.
Increases in disease, parasites, and fire are indications that our forests have become unhealthy. While past policy decisions are greatly responsible for this, a warming climate is also a central enabler. Shorter, warmer winters combine with hotter, drier summer to create dangerously unhealthy conditions. It stresses trees for moisture, allows parasites to proliferate, and creates a longer, more intense fire season. As scientific predictions expect this trend to intensify in the coming decades, the worst effects are yet to come.