Rethinking forest health
With the recent devastating fires in Mora, how we manage our forests is of the utmost importance, but are we addressing it from the wrong perspective?
Within our natural world we can see the cycle of birth, life, death, decay and renewal played out everywhere. Energy from the sun has driven this endless cycle for billions of years, sustaining life through the miracle of photosynthesis. The health of every ecosystem on the planet is intimately tied to this cycle, in which carbon from the atmosphere is transformed into plant bodies and then broken down by fungi and other microbes, ultimately returning to the soil, where it may remain for thousands of years.
In temperate forests, it is estimated that 40 percent of the biodiversity is dependent on dead wood — the biological capital of the forest. In fact, dead wood in the form of standing snags, fallen logs and coarse woody debris plays a critical role in water retention, nutrient cycling and overall forest health. One of the main drivers of forest degradation is the limited awareness about the range of ecological functions dead wood provides that are central to ecosystem health. It’s time to change our perception of dead wood.
First of all, it is important to understand that dead wood is a misnomer. Most dead wood has more living tissue than a live tree. This comes from the fungi, insects and the countless diversity of microorganisms that are directly or indirectly feeding on the wood. In addition, numerous species of birds and mammals utilize fallen logs or standing snags as habitat for their nests and homes. From the smallest microorganisms to some of the largest animals in the forest, dead wood is central to their life cycle.
As wood decomposes, it absorbs and retains a significant amount of moisture. Dead wood is increasingly recognized as a major part of the hydrology within forest watersheds. Water retention in our temperate forests is critical during the dry season, as it is linked to decreased soil erosion, reduced flooding and extended runoff, thus improving river health and water quality. Additionally, the shade provided by fallen branches helps seedlings regenerate by reducing soil temperature and lessening evaporation. In short, dead wood helps the forests stay hydrated.
A “clean” forest with only living trees is not a healthy forest. Maintaining sufficient dead wood is critical for supporting a highly biodiverse forest ecosystem. Biodiverse forests are more resilient to disease, and with increased moisture retention and species richness, less vulnerable to catastrophic fire. Thus, dead wood is the biological capital of a healthy forest.
A diverse forest with an abundance of aged dead wood in various forms retains more moisture and is thus more resistant to crown fires. The claim that dead trees increase fire probability, intensity or rate of spread has been strongly refuted by current science. In fact, forests with high levels of snags tend to burn less intensely. Shortly after trees die (the “red stage,” when reddish-brown dead needles are still on the trees), the combustible oils that naturally occur in their needles begin to dissipate, reducing potential fire intensity shortly after the trees die. A 2015 study published in the National Academy of Sciences concluded that recently-dead trees in the red stage were not more fire prone than live trees.
As dead wood decomposes it undergoes a process called humification, in which dead and decaying organic matter is converted to rich humus by bacteria, fungi and other microorganisms. Farmers will recognize humus (made up of the most complex organic molecules in soils) as the foundation of healthy soils, supporting their capacity to cycle nutrients and hold moisture. As dead wood decomposes and ultimately turns into humus, it supports an incredible diversity of organisms, increases water holding capacity, returns nutrients to the forest and sequesters massive amounts of carbon.
Legislation that eliminates environmental safeguards and prioritizes the removal of dead trees to ostensibly improve “forest health” or reduce fire risk is not good public policy. It does not safeguard the health of our public lands and precious watersheds. Recognizing the tremendous ecological value of dead wood is critical for the creation of evidence-based policy and forest management. Protecting the health of our watersheds and helping to reverse the biodiversity crisis starts with respecting the natural processes that have sustained the planet for billions of years. We must change our perceptions of death as an end. In the forest, it’s a beginning.