When Does Timbering Become Land Disturbance?

The cover photo shows Richland Country Club’s course, one of Contineo Group’s success projects. 

Timber harvesting may often seem like a process that is destructive of the natural environment, but it actually has a number of ecological benefits. When responsible timbering is done properly,  it can improve the health of the forest and the ecosystem. When done poorly, however, it can have a negative impact. The question arises, when does timbering become a land disturbance?

The Benefits of Responsible Timbering

When sustainable methods are employed, timbering can promote the growth of crucial species that would otherwise struggle under a dense canopy. Oaks, hickories and black walnut trees are some that benefit from the harvesting of mature trees.

Beyond the trees themselves, responsible timbering also has a positive impact on biodiversity in the forest. Harvesting large trees promotes the growth of lower growing plants, which in turn provide essential habitat for a broader array of insects, mammals and birds. This biodiversity improves the overall ecosystem health of the forest, improves resilience against diseases and pests.

Timbering is an effective tool in mitigating wildfire risk, as well. It is estimated that over 80 million acres of national forests are at risk of severe wildfire, largely due to a large number of diseased, insect ridden trees and standing dead timber. Aggressive wildfire suppression has negatively impacted nature’s primary means of renewal in forests, actually allowing more and more fuel to be available. Active forest management through timbering and thinning can help.

Of course, there are also economic benefits to timbering. The U.S. is the largest producer and consumer of wood for industrial manufacturing. Over $200 billion in wood products are produced by the U.S. forest products industry annually. Nearly a million workers are employed by the industry. 

The Negative Side of Timbering

Timbering, especially when not done with sustainability in mind, can have a negative effect on the environment. The removal of too much forest cover can severely impact the forest ecosystem and biodiversity. This often happens when areas are completely deforested rather than responsibly harvested.

A major problem with timbering comes with the effect that it has on the soil health in the area. Land disturbance is a significant concern that arises from timber harvesting. Soil compaction, displacement and erosion, and pooling water on the soil surface are all potentially harmful types of land disturbance caused by the methods and equipment used in timbering.

Soil Compaction

When the ground is compressed to the point that pore space between soil particles is reduced, soil compaction occurs. This affects the amount of water, air and nutrients that can permeate the soil, as well as limiting the ability of plant roots to penetrate. All of this has a negative effect on plant growth and forest regeneration. Pooling water also results when water cannot soak into the soil efficiently.

Soil texture, soil structure, the type of machinery used, the number of passes machinery makes, the time of year and the slope all determine the extent of compaction that results from timbering. Moderately textured loamy soils are more susceptible to compaction than sandy and clayey soils and wet soil will compact faster than dry soil. Heavier machinery and more passes result in more compaction. Machinery used on slopes will also cause a higher rate of compaction.

The use of heavy equipment is a necessity in timbering operations. Machinery used in logging operations can weigh from 11,000 to 121,000 pounds. The pressure on the soil depends on the number and size of wheels or tracks, the weight of the machine and the load of harvested timber. As few as three passes can have a severe compaction effect on the soil, making it nearly impenetrable for plant roots.

Erosion From Timbering

Trees and healthy soil help to mitigate the runoff of water in forested areas. When trees are removed and the ground is disturbed, the erosion of soil can accelerate. Compacted soil can increase the downhill flow of water, further exacerbating the issue. 

Erosion becomes a major problem when soil particles end up as sediment in waterways. Increased sediment in streams and waterways can affect water quality, wildlife habitat and drinking water supplies. A hydrology study found that up to 50% more sediment was transported to waterways in timber harvested areas. What’s more, it can take up to two decades for the watershed sediment to return to normal levels. 

Avoiding the Harmful Effects of Timbering

Limiting the land disturbance associated with timbering involves analyzing the land where harvesting will take place, incorporating the least damaging harvesting methods and planning for proper project closeout.

Understanding Conditions

An important early task is to gain an understanding of the soil composition and topography of the area where timbering will take place. The impact caused by timber harvesting is very site specific, and it’s important to analyze soil condition before, during and after harvesting activities. Ideally, soil properties such as particle size, distribution and structure will be measured throughout the project. A USDA report entitled, Soil Sustainability and Harvest Operations: A Review provides a wealth of detailed information on the topic.

Limiting the Impact of Heavy Equipment

Best management practices (BMPs) can help limit the land disturbance caused by logging equipment. BMPs provided by the Alabama Cooperative Extension System are a good example. These contain guidelines for temporary or permanent forest road construction that can significantly decrease erosion and runoff. For instance, applying slash and brush mats on skid trails can reduce compaction. Limiting the use of heavy machinery on steep slopes and in wet areas is also part of the BMPs.

Protecting Waterways

Another important topic covered in BMPS is the protection of waterways in or around the timbered area. Streamside management zones (SMZs) are 35-foot buffers on both sides of a stream. They are left relatively untouched so that vegetation can filter and trap erosion before it reaches the waterway. It is also recommended that machine traffic is minimized near ephemeral streams that only flow during rainfall events.

Constructing crowned roads, ditches with turnouts and cross-drain culverts can help to limit runoff issues. Gravel on logging roads, particularly near paved exit points, can limit the amount of dirt tracked out of the logging area. Properly closing out skid trails, installing waterbars and applying grass seed, straw and logging slash can help mitigate future erosion.

Particular attention must be paid to properly engineering water crossings. Culverts, bridges, log crossings and fords are all viable solutions that can be either temporary or permanent. It is critical that fish and aquatic organisms are not prevented from passing freely through these crossings. Temporary crossing must be removed at the end of the project and additional steps may need to be taken to protect water quality.

The Engineering Behind Responsible Timbering

When does timbering become a land disturbance? When best practices aren’t followed and mitigation solutions are not implemented. 

Responsible timbering can be a beneficial endeavor, but there is a lot more to it than just cutting and hauling trees. Loggers are expected to implement best practices to make the process as environmentally responsible as possible. The health of the land, waterways and the industry itself are at stake. At Contineo Group, we have the expertise available to analyze soil conditions and properly engineer solutions to prevent a timbering project from becoming a major land disturbance.