CLIMATE CHANGE INFORMATION AND LINKS
Maine Forests and Carbon Sequestration
by Jonathan Carter
Forests are critically important in the fight to reduce greenhouse gases and mitigate climate change. Forests are part of the human-generated carbon footprint because stored carbon is released as a result of harvesting, forestland development, and soil damage. On the other hand, the ability of forests to sequester carbon (capturing carbon through the process of photosynthesis) is of major importance in removing human-caused emissions. In the United States forests absorb about 12% of the carbon from fossil fuel emissions. On a global basis, forest carbon sequestration may be as much as 30%.
Maine, as the most forested state in the nation, has the potential to make a significant contribution in the effort to mitigate global warming. In order to maximize this contribution, it is not only necessary to stop high carbon-releasing forest practices, but it essential that best management practices foster carbon sequestration. Unfortunately, current forest practices in Maine are designed to maximize bottom-line profits, and not bottom-line carbon sequestration. This must change
Negative Carbon Forest Practices
Clearcutting has the greatest negative impact. Recent research indicates that for up to twenty years after a forest has been clearcut there is a net carbon loss to the atmosphere. While some of the biomass from the wood may be tied up in wood products, the vast majority is turned into paper products and wood chips which have a very short carbon retention time frame landfills, biomass plants and incinerators. Normally 30% of the biomass is left behind (roots and slash) for soil microbes to decompose. This results in an increase in carbon dioxide release. The most recent data indicates about 18,700 acres are clearcut each year.
Shelterwood cuts involve the removal of biomass through multiple harvests over time. Ideally, shelterwoods would be practiced over the natural life cycle of a stand (100-200 years) However, in Maine the logging industry has redefined shelterwood harvest to mean total forest removal over a 5-10 year period really nothing more than a clearcut over a short period of time. This type of shelterwood is the dominant forest practice utilized in the Maine Woods today. Data from 2006 indicates that 5-10 year shelterwood cuts are undertaken on about 233,000 acres annually. Industry has simply renamed a clearcut a shelterwood cut. The CO2 releases, while reduced, still are huge.
Overcutting is defined as cutting more than is growing back on an annual basis. Theoretically, if the volume cut is equal to the volume grown, then the carbon tied up in the harvested forest biomass would be equal to the carbon sequestered in the annual growth. Maine forests are currently being cut faster than they are growing back. Recent data indicates that the overcut annual may be as much as a 100 million cubic feet. Therefore, carbon loss is significant.
Pre-commercial thinning is a practice used to enhance merchantable timber growth rates. By thinning a stand, this allows the remaining trees to grow faster This results in an immediate reduction in carbon stored and can also have a negative impact on biodiversity.
Plantation forestry involves the clearcutting of a forest and the planting of a monoculture of native or exotic tree species. Carbon loss from the initial clearcut is huge. The plantation virtually eliminates natural biodiversity and reduces potential carbon sequestration. Plantation forestry also often requires the application of pesticides and herbicides. Plantations have declined significantly in recent years (due in large part to the high costs and slow growth rates), but still three to four thousand acres are planted each year.
Herbicides are use to kill regenerating hardwoods so that softwood species can dominate a site. These poisons are not only a threat to humans, but also may have negative impacts on the soil microbes a key indicator of below ground carbon storage potential. While herbiciding has declined in recent years, 11,700 acres are still sprayed annually.
Forests store about twice as much carbon below ground as above. Soil compaction, reduced soil oxygen levels, and reduced water percolation all result from current logging activities. Erosion from logging roads damages aquatic systems and reduces their carbon storage capacities. The loss of carbon and the potential to store carbon in soils as a result of logging damage has not been quantified, but there is no question that it must be immense, perhaps even greater than all the carbon lost from harvest practices.
Development/Land Use Changes
Development and land use changes result in significant reductions in carbon storage capacity. Between 1982 and 2003 over 800,000 acres of forests were converted to a non-forested state. Plum Creeks plan for the Moosehead Lake Region would have a large carbon footprint not just from the 11,000 acres of development sites converted from forest to non-forest, but also from the carbon released as a result of construction, increased traffic, and higher energy demands.
Positive Carbon Forest Practices
Selective cutting is the only harvest practice that has the potential to increase and maximizing carbon storage. Selective cutting involves a tree-by-tree choice. It involves lighter harvesting over the normal life cycle of a particular forest stand. Selective cutting could be designed to maximize carbon storage capacity. Growing forests for high quality timber would result in significantly greater amounts of carbon being tied up longer in the resultant wood products. While most small landowners already practice selective cutting, large industrial and non-industrial landowners, by and large, view selective cutting as labor intensive and expensive. Using selective cutting requires foresters to practice forestry assessing each tree rather than making decisions on a stand or landscape scale.
Because of the massive amount of clearcutting and overcutting during the last several decades, Maine forests have been severely depleted. The most recent data suggests that over 500,000 acres are poorly stocked and even a larger number of acres only moderately stocked. Increased stocking levels equates directly into higher carbon storage levels. While the presence of such vast under stocked acreage is a sad indictment of logging practices, the potential for increasing carbon storage by allowing natural restocking to proceed is huge.
Reduced Erosion/Soil Disturbance
Since maintaining soils is key to enhancing carbon storage in forests, reducing the current level of erosion and disturbance is of great importance. The expansion of permanent logging roads (over 30,000 mile in the last 25years) needs to be halted. Not only should the current road network be evaluated for road removal, but any future harvests plans should be required to include reclamation of road ways.. In addition, logging activities should only be allowed when the ground is frozen, which will minimize soil disturbance
Increased Rotation Length
The average age of Maine forests is declining. This means that Maines forest carbon sink is being reduced. It has been well documented that forests increase carbon uptake with age. This uptake continues well into maturity. Currently less than .1% of the forest in Maine can be classified as old growth and less than 3% as late successional. The large landowners harvest on 30 year cycles well before any tree species in the forest have come close to reaching their maximum carbon uptake rates as well as their carbon storage potentials.
Uneven Aged Management
Due to the cutting regimes of the past several decades and the desire for shorter and shorter rotations, Maine forests have become not only younger, but more even aged. This is particularly true in the softwood component. Multi-age stands not only enhance biological diversity and enhance forest health, but the increase in the average age results in greater carbon uptake and storage. Selective cutting can be used to move the forest toward a natural mutli-aged condition.
Non-Manipulation Forest Stands
One of the biggest goals of forest managers has been to manipulate the composition of a natural forest to one that has more commercial value not necessarily more carbon sequestration value. This has been particularly true in terms of hardwood forests where a tremendous acreage of beech/maple/birch has been destroyed in order to promote softwoods. Carbon densities by stand type indicate that on a per acre basis beech/maple/birch forests store at least 20% more carbon than a spruce/fir forest. The more fertile soils and longer lived species in northern hardwood stands would favor greater carbon storage capacity.
Conservation and wildlands restoration pose the greatest opportunity for increasing carbon sequestration in Maine forests. The longer forests grow, the more carbon they store. It is critical to preserve all our old growth and late successional forests. It is equally critical to promote the recovery of the forest, which has been severely depleted in recent years. On public lands the state should halt all logging activities which do not enhance carbon storage. While this represents a drop in the bucket, it sends a strong message that the policy makers in Augusta understand the dire consequences of global warming and that they recognize that forest protection, restoration, and conservation are critical in the fight to mitigate the crisis. Business as usual is not the solution. In addition, forest practices need to be regulated so that all harvesting enhances carbon sink capacity. While financial incentives/compensation may be worth considering, there needs to be a mandatory participation requirement.
The Maine Woods have the potential to play a significant national role in carbon reduction not as offsets or carbon credits which allow big carbon emitters to continue to pollute. It is time for the federal government to recognize that the preservation and restoration of wild forests is one of the most important tools for dealing with climate change. Designating the Maine Woods as a National Carbon Sequestration Forest and supporting the creation of the 3.2 million acre Maine Woods National Park and Preserve would result in a vast carbon sink capable of storing millions and millions of metric tons.