Younger forests are more efficient at fixing carbon than older forests because they grow at faster rates and not
as many trees are dying, rotting and thereby putting carbon back into the atmosphere. More of the energy in older forests is consumed by the functions of trees just staying alive--by transpiration and
respiration. More of the energy in younger forests goes to adding wood.
Forests in southern New England start to decline in net growth and carbon fixation at about 100-120 years old. From a
carbon point of view, it's at this age that decadent and declining trees need to be removed, and put into long-term carbon storage in the form of building materials and furniture, or used to replace fossil
Forest products also go into short-term carbon storage in shipping pallets. Some low grade hemlock and pine goes to pulp mills in New York and Maine. Some paper gets recycled.
This can stretch its carbon storage life.
Low grade and small diameter hardwoods go into fuelwood. Fuelwood burning of course doesn't store carbon at all. It puts it right back into the
atmosphere. But burning fuelwood substitutes for the burning of fossil fuels. It therefore prevents adding additional carbon to the atmospheric "reservoir." The more carbon that can be kept
undereground in the fossil fuel "reservoirs," the better.
Therefore any uses of forest products that put carbon into long-term storage, or substitute for fossil fuel burning, are good in terms of global
carbon cycles. Storing carbon in the forest is a good thing too, particularly where it's being stored in forms that can be later converted to timber/lumber and fuelwood products. Storing carbon
as pulpwood is a different question.
Much of the timber in old growth forests in the Pacific Northwest is unfortunately in this situation. Many trees can't meet lumber
specifications, so when they are harvested they just go into pulp. A good argument can be made on carbon conservation grounds that these forests should not be cut--in order to prevent release of
greater amounts of carbon into the atmosphere.
What typically happens with older forests is that they start to degrade and lose their commercial value for different reasons. Hemlocks will get
ring-shake. Pines will get red rot. Many hardwoods will get heartwood discoloration. Pines will also have their tops broken off or be uprooted by storms. All species will become more
susceptible to damage by storms, insects and diseases.
From a carbon management point of view, forests shouldn't be allowed to reach this stage. Of course carbon management is not the only criterion
to be used in making forest management decisions. But as climate change accelerates with more burning of fossil fuels, carbon management will be an increasingly important criterion in forest management
Storm Damage and Carbon Management
Climate change will require all forms of forest management to incorporate strategies for minimizing damages due to increasing frequencies and
severities of storms. With the increasing probabilities for severe ice storms, snow storms, wind storms (downdrafts, hurricanes, tornadoes), foresters and forest landowners will have to plan to
minimize the risk of damage.
Due to environmental regulations, we can't store logs in ponds and lakes any more the way loggers and lumber companies did after the 1938 hurricane, so if damaged timber isn't
sawn and dried by the onset of hot weather in June, some species will lose their value due to fungal discoloration and insect infestations.
Timber that isn't salvaged in time to retain its commercial value
will likely just stay in the forest and rot. This material will release even more carbon back into the atmosphere. The net effect is like a very slow burning fire. There is also increased
risk of fast-burning fires because of the increased fuel load from all the branches and stems that litter the forest floor after such storms.
Carbon risk management therefore involves identifying the
stands that are at higher risk of catastrophic storm damage. These risk factors are known for different species at different ages on different sites. There are also methods for reducing and
managing the risks to these stands. This usually involves some kind of selective cutting or sanitation cutting to remove the trees at higher risk.
Fires, Insects, Diseases and Carbon Management
All long-term forecasts of the effects of climate change on forests include projections of increased damages due to fires, insects and diseases--as well
as storms. Forests in the Northeast may avoid some of the fire damages expected in other parts of the world because of a wetter climate here, as well as better access for fire suppression.
a warmer, wetter climate will likely increase the incidence of fungal diseases, as well as the numbers of some insects which have historically been limited in their ranges by cold winters. Many insects
that damage forests overwinter as larvae in the upper soil layer. Winter freezing kills many of these larvae, but with shorter, milder winters this will change.
Trees and forests damaged by fire,
insects and diseases are like those damaged by storms. Damaged trees should be harvested and put into carbon storage as building materials or burned as fossil fuel substitutes (fuelwood). Trees
that are at high risk of damage by these agents should be evaluated for removal in advance of actual damages.
As the adverse effects of climate change become more
apparent throughout the world, awareness of the role of forests in storing carbon will increase. This awareness will alter the goals and methods of forest management. Our forests will undergo
changes as these goals and methods are integrated with other traditional goals such as timber production, wildlife habitat enhancement, watershed protection and recreational improvements.
Research is now underway to determine where, and under what conditions, carbon sequestration in trees and forest products is preferable to carbon substitution by fuelwood burning. Much
research has already been done to determine what types of forest compositions are more resistant and resilient to storm damages. Gradually the results of these research efforts will be applied to
It's difficult to say at this time what the carbon management forests of the future will look like, but we can assume that they will be more diverse in ages and species because
diversity generally confers resistance and resilience to storm damages and other damaging agents. They are likely to be younger, or at least of younger median ages, due to the greater carbon fixation
efficiency of younger forests.
Our forests will also be much more carefully tended and monitored as landowners and foresters realize the importance of their roles as carbon stewards. Time will
tell whether this transformation in the goals and methods of forestry will occur in time to be of significant value in mitigating the negative consequences of climate change.
Apps, M J and D T Price, eds. 1996. Forest Ecosystems, Forest Management and the Global Carbon Cycle: (Review of
conference proceedings with 30 papers).
Brown, Sandra. 1997. Forests and Climate Change: Role of Forest Lands as Carbon Sinks:http://www.fao.org/WAICENT/FAOINFO/FORESTRY/WFORCONG/PUBLI/V1/T4E/1-3.HTM.
Scholarly overview of global carbon sequestration by forests.
German Forest Management Council. 1998. Policy Statement: http://www.faf.de/position/engl_1.htm. The number one policy
issue (out of 10) is "Maintenance and appropriate enhancement of forest resources and their contribution to global carbon cycles."
Karjalainen, T. 1996. Model Computations on Sequestration of Carbon in
Managed Forests and Wood Products under Changing Climatic Conditions in Finland. Journal of Environmental Management: http://alpha1.joensuu.fi/~hstrand/silmu/timo2.html. Abstract of a very
comprehensive paper that evaluates different management strategies over a 300 year period.
Marland, G and B Schlamadinger. 1997. Forests for Carbon Sequestration or Fossil Fuel Substitution? A Sensitivity
Analysis: http://www.fao.org/WAICENT/FAOINFO/FORESTRY/WFORCONG/PUBLI/V1/T4E/3.HTM#TOP. A recent paper about a question that has received insufficient attention by researchers and the public.
Marland, Gregg and Bernhard Schlamadinger. 1998. Forest Management, Biomass Fuels, and CO2 Emissions to the Atmosphere: http://cdiac.esd.ornl.gov/pns/band.html.
Many scholarly references,
the latest ones focusing on questions of sequestration versus fossil fuel substitution. Cutting edge analysis.
Sedjo, Roger A. 1996. The Economics of Forest Management for Carbon Sequestration:
Http://info.metla.fi/iufro95abs/d6pap89.htm. Abstract of paper with information on how to get the full version from Resources for the Future.
Wong, Nelson. 1997. Message posted to forest.list:
Http://www.metla.fi/archive/forest/1997/05/msg00124.html. Short bibliography of references on carbon sequestration by forests.