A thinned forest surrounded by untreated forest land.
The forest thinning campaign, promoted by the Forest Service, timber industry and politicians, uses terms such as "forest health" and "restoration" to persuade the public to support forest thinning. This misinformation has done irreparable damage to the last remaining remnants of our intact forests. When a forest is mechanically thinned, the canopy is severely altered, the forest floor is damaged by the equipment used and by mulch suffocating plant life. All the integral ecological relationships with lichen, fungus and mycelium are completely broken. Healthy forests need a vast network of living relationships to remain intact and healthy for the entire system to work. It is much healthier for a forest to burn than to have heavy equipment remove that fuel.
Thinning is another manipulative term used for logging forests. Logging means altering trees that were previously performing ecological functions in the forest and using that wood for profit, whether small logging outfits are making the money through forestry grants (thin and mulch) or large corporations through a combination of grants and wood salvage operations. Healthy forests are not ones that have been managed by the logging interests in the past, and research repeatedly shows that logging forests is the most damaging component of forest management.
Forests are complex interweavings between millions of life forms that depend upon each other for their existence. To approach forests with a one-size-fits-all solution to stop fires and improve health is an oversimplification of the incomprehensible interrelationships that create a healthy, vibrant forest. It is increasingly important that we understand forest systems are complex interrelationships between diverse parts before making decisions to alter forest ecology.
Effects of Thinning on Plant Life
Forest floor in thinned area completely taken over by Canadian Thistle
Mechanically thinning forests eliminates plant diversity throughout the forest floor. Plant life on the ground in a thinned forest usually consists of little diversity, and the species that come back in thinned areas are invasive weeds, non-native grasses and hardy plants. The ecologically rare native plants do not come back after thinning. Since thinning opens up the canopy, much more sunlight reaches the ground, completely altering the forest ecology in the area. Thistles, mullein and other invasive weeds occupy the disturbed ground of thinned forests taking over previously native plant habitat. The equipment used in thinning also carries invasive plant seeds on the tires, spreading those plants over the thinned area. When trees are masticated, especially in a dry climate such as Colorado's, that wood covers the ground and suffocates plant life so little remains. What comes back are plants that can grow through and around all the masticated wood. Canadian Thistle is most prominent on the front range. Adding insult to injury, the Forest Service recommends a class that instructs individuals who thin their lands to aggressively spray herbicides on the land they thinned. This poisons all the living beings in that area as well as the ground water making it difficult for native species to restore the disturbed ground.
The invasive plants and non-native grasses that predominantly colonize thinned areas happen to be more fire prone than the native grasses they replace. These new plants increase fire risk in the area and completely alter the ecology of the forested area removing the ability for the non native plants to come back. Thinning replaces delicate native plants and geographically suitable plant communities with fire-prone invasive plants and hardy non-native grasses.
Tree damage from mastication equipment
By encroaching into a delicate forest system, equipment and the mastication process is damaging to the ground in multiple ways. Fungus, lichen and mycelium are essential nutrient providers in a forest. Once mastication occurs along with the process of thinning, these important organisms are severely reduced and are unable to deliver necessary nutrients to trees and the forest floor. In the process of thinning forests, heavy equipment runs across the forest floor taking trees, ripping them from the ground and chopping them into pieces. Often times, many trees left standing bare scars from the process of this work. On the ground, the soil is compacted, delicate organisms are eradicated and the ground suffers from loss of nutrient carriers that were previously available for the forest community.
Effects of Thinning on Forest Canopy, Soil and Watershed
Ten years after thinning and very little new growth on the ground.
Thinning alters the canopy in the forest which raises soil temperatures in summer. These temperature fluctuations occur because shade in thinned forests is radically altered and sunlight hits the ground and begins to heat the once-insulated soils. By impacting the temperature in the forest and by altering the habitat of the organisms living there, thinning dramatically changes forest ecology and opens up habitat for invasive insects since tree boring beetles thrive in heat. Once you heat up the forest floor by removing the canopy, you invite heat-loving insects into a previously cool forest environment. In a report entitled Quietly Paving Paradise, research showed there was a higher rate of tree mortality from beetle infestations in thinned forests than in untouched areas. Untouched forests are much more resilient than thinned areas when left to their natural processes.
Because thinning damages the forest floor by removing native plants, mosses, fungus and mycelium, the ground is increasingly unable to support life, especially native plants and organisms historically adapted to that area. As the ground loses ability to absorb moisture, water runs off these areas at an increased rate creating erosion and damage to the forest floor. Prior to the thinning, water would have trickled down through the soil by the work of roots and ground cover of native plants. Once the soil has lost most of the roots from the plants and other living organisms, it dries out and has a difficult time absorbing moisture so that moisture runs off, erodes the landscape and damages watersheds in those areas.
In the dry West, the mastication process leaves a huge amount of wood on the ground which creates tinder for fires. The longer tinder is left on the forest floor, the dryer it becomes. These masticated pieces of wood do not decompose in Colorado as they would in a moist environment. For folks living in this area, I invite you to come on a tour of forest sites that were thinned by mastication 10 years ago and see how the wood did not decompose and is still suffocating the ground. It is clear by looking at the mess left behind that the pieces of wood are dry and highly flammable. By altering the canopy in our forests, we completely change the ecology of the forest, which radically alters the species that are living there.
Thinning Adversely Affects Wildlife Habitat
Along with the dramatic changes that thinning creates, the wildlife living in the forests are adversely affected. Forest Service "experts" tell people thinning increases wildlife habitat. It is important to ask whose habitat thinning expands. Thinning can potentially increase habitat for deer because they like to live on the forest borders; however, habitat for deer is not what should be expanded since the deer population is increasing and causing population stresses on the environment and the deer population itself. Other species, such as rare birds and mammals that were living comfortably in these untreated forests, must find new places to live. Not only do thinning projects occur when rare birds are nesting, thus killing young hatchlings in nests, the thinning process kills numerous organisms in forests at the time of treatment. The alterations from a moist cool forest to a hot dry one with a different set of plant life forces the animals to leave their homes. Thinning also increases visibility for predator and prey living in the forest. By opening up the canopy, animals do not have as many safe places to hide and predation increases by prey animals and humans because it is much harder to hide in a thinned forest.
Thinning Increases Carbon
Research shows that by thinning a forest, carbon release increases. When trees are removed in a forest system, stored carbon is released into the atmosphere and those trees are no longer able to sink ever-increasing carbon in the atmosphere. Add that to the impacts of increasing temperatures which reduces plant diversity and cooling shade, and you have a catastrophic situation. Altering the ecology of a forest has serious and widespread consequences.
Listen to the Forest
The most important action we can take in regards to understanding the damage thinning has on forests is to walk into a thinned forest and an untreated forest and see for ourselves the effects of thinning. In thinned forests, it is important to look at the ground cover and see what is growing there. Are diverse native plants thriving in that area? How much diversity of plants, besides weeds and hardy grasses, is growing in those areas? What wildlife sounds are you hearing in those forests? Before making any decisions to thin the land that you live on, please take the time to visit thinned forests, compare them to untreated areas and seriously consider the effects of those actions on the forest community.