0740-B1
Bruce C. Larson[1]
Forest management has historically been based on a "single objective with constraints" paradigm. It is necessary to change the paradigm to one of truly multi-objective management. The sale of carbon credits might make the transition easier in some areas leading to development of new management tools.
Many silvicultural tools exist that can be used to increase carbon sequestration. Under the Kyoto Protocol it should be possible to sell carbon credits for some forest management activities in Annex I nations. This presents an unprecedented opportunity for synergy between carbon sequestration, management for forest health, and the economic development associated with harvest and production of wood products. The boreal region of western North America has attributes that make this a particularly attractive place to develop such an integrated stewardship plan. Revenue from the sale of carbon credits would enable the implementation of the plan, but should not be considered in and of itself the primary source of economic gain.
This paper reviews the factors relating silvicultural activity to increased carbon sequestration, which would be eligible for credit transfer under the Kyoto Protocol and presents an example from the boreal region on how this plan could be constructed.
The possibility of receiving monetary return through a carbon credit trading mechanism creates an opportunity to the change some of the basic premises under which we conduct silvicultural activities throughout the developed nations of the world. It has been difficult to shift our management philosophy from a paradigm of managing for a single objective with constraints to one of truly multiple objectives. Sale of carbon credits may provide the incentive to change more quickly this paradigm.
Under the provisions of the Kyoto Protocol, Annex I nations (the most developed) can receive credit for forest management activities that increase carbon sequestration. These activities must be in addition to usual forest management activities ("additionality"), must represent a real monetary investment, must not move sequestration activities from one place to another ("leakage"), and must be accurately measured and accounted.
The opportunities for moving beyond simple lengthening of rotations or creation of preserves (neither of which may satisfy the condition of leakage) to designing more innovative silvicultural activities become more obvious when all forestry related carbon pools (Kurz, 1992), not just the standing biomass, are considered. The linchpin to the design of these activities is the ability and willingness to change the natural disturbance regime that normally returns large amounts of CO2 to the atmosphere.
Forestry can be described using five pools of carbon (Burschel et al. 1993). The major direct pools are: (1) standing biomass, (2) dead material - both standing and forest floor, and (3) soil. The major indirect pools are (4) products made from harvested material, and (5) petroleum - both used and not used because of forest management activities.
Four natural disturbance types lead to major transfers of carbon between pools; windstorms, insect attacks, disease infections, and fires. The first three move carbon from the living biomass pool to the dead pool and then decomposition releases the carbon into the atmosphere through microorganism respiration. Fire, however, as well as killing some trees that will decompose, also directly transfers carbon to the atmosphere through combustion.
Wind disturbances range from single tree, gap forming, events to major stand replacement events (Oliver and Larson, 1996). Many factors contribute to wind firmness of a tree and some of them can be influenced silviculturally (Mitchel, 1998). Likewise, the ability of a stand to withstand wind can be influenced by management. The single greatest impact of management is to reduce the height of the trees (harvest and regenerate). In other words, short, young, individual trees are quite windfirm as are young stands of trees. The effect of windthrow on the carbon budget is highly variable. Downed trees will decompose at some rate largely dependent on the climate of the area. Meanwhile the opening (large or small) will regenerate at some rate dependent on both the climate and the availability and mechanisms of regeneration of the species at the site. The forest floor will be exposed to heat and decomposition rates may change (Prescott et al 2000). The forest floor and the soil will be mixed to some extent depending on the uprooting process, affecting the amount of soil carbon.
Both insects and diseases kill trees by an identical process, forcing respiration to exceed photosynthesis. Photosynthesis can be reduced directly by reduction of the foliage, or indirectly by restricting water supply to the foliage, closing the stomates. The latter effect can be either through tree root death or destruction of the xylem. The trees die basically in place with little displacement of the forest floor. The wood and the forest floor decompose as described above.
Fires are one of the most complex disturbances with regard to carbon pools. Fire moves carbon from the living to dead pool similar to insects and diseases, but also moves carbon directly to the atmosphere. Carbon will be released both from the burning of standing biomass and from the forest floor (dead pool). After the fire, the remaining forest floor decomposition rate will again change as described above.
There are a number of silvicultural activities that can affect the amount of carbon that moves in or out of the five pools. Seven general categories are listed here.
Regeneration processes can be accelerated. Many disturbances lead to wide scale death of the trees in a forest. Given enough time, most places will revert back to forest. The invasion time may be short or long depending on the harshness of the site and the scale of the disturbance (Oliver and Larson, 1996). Accelerating regeneration and dominance of tree species through silvicultural activities such as planting can significantly increase the amount of carbon sequestration on a site.
The species (genetic) composition of a stand can be controlled through weeding, direct planting, or a combination of techniques. Species differ in both wood formation rate, in allocation between above- and below-ground and between harvestable and non-harvestable wood (Keyes and Grier. 1981, Smith et al 1997). Shade tolerance, drought tolerance and branch angle are examples of genetically controlled attributes that directly influence carbon fixation per hectare.
Tree and stand growth rates can be increased through site amelioration (Smith et al. 1997). The most common technique is fertilization, although drainage and irrigation techniques can be used. In terms of carbon sequestration it is important to account for all the energy inputs associated with use of these techniques.
Tree harvest and manufacture of products moves carbon from the standing biomass pool to the product pool where the rate that at which it is released back into the atmosphere depends on the product and its service life. The harvested land will begin storing carbon again.
Thinning, as well as moving carbon into products, can increase the vigor of the unharvested trees. Thinning can also change the dominant species.
Mitigation of insects or disease outbreaks can reduce CO2 released. A variety of silvicultural tools can be used to mitigate the carbon release associated with tree mortality following insect or disease infestation. The silvicultural tools for mitigation fall into 3 classes: those that make the stand less susceptible, those that reduce outbreak effects once the pathogen or insect attack has begun, and those that can be used after trees have been killed. Before a stand is attacked the trees can be made more vigorous by thinning, weeding, or perhaps fertilization. The stands can also be made less susceptible to specific agents if the species composition is changed through thinning. After the infestation or infection has begun, affected trees can be removed to reduce the amount of insects or inoculum. Sometimes insecticides can be used to reduce or isolate insect attacks. After tree mortality has occurred dead trees can be harvested and processed before they decompose. Accelerated regeneration techniques can be used.
Impact from catastrophic disturbances can be reduced through accelerated regeneration and by directly reducing carbon sequestration impacts. One example is the frequent harvest of trees which reduces susceptibility to blowdown (reduction of top height). Another example is to harvest trees to reduce standing biomass before fires.
It is possible to manipulate forest fire impact and frequency in a number of ways. Two specific standing biomass characteristics that affect fires can be adjusted by tree harvest are the structure and amount. The quantity and quality of fuel directly controls fire behavior and the amount of standing biomass will limit the total amount of combustion that can release CO2 into the atmosphere. Harvesting directs the stand development pathway; standing biomass is not only adjusted at the time of harvest, but for many decades into the future. Prescribed burning parts of the landscape in concert with natural features, such as water bodies, can be used to direct or isolate wildfires. Combining the activities, (i.e. preharvesting trees in prescribed burn areas) will lead to major decreases in combusted carbon. Harvesting activities can also be designed such that access for fire suppression activities after ignition will be enhanced in some unburned stands. Using all three actions would result in fewer fires (including those prescribed), smaller fires, and less carbon combusted (from the combination of less acres burned and less average biomass on the acres that do burn).
Given the expected range of carbon credit exchange values, setting a forest aside for just carbon storage will always be of less monetary value than managing for other products (although non-monetary values may be significant).
The boreal areas of Annex I nations are some of the best places for a multi-objective plan. Although this area has relatively low forest productivity (Apps et al. 1991, Lautenschlager, 2000), the conditions are very favorable to achieve the greatest gains through the sale of carbon credits. The region has large-scale fires offering a major mitigation opportunity. Although standing biomass is generally low, large amounts of carbon can be combusted from the thick forest floor. Comparatively little forest industry exists in many parts of the boreal (exceptions to this exist, in parts of Canada a flourishing forest industry exists). The remoteness of many areas, such as interior Alaska, combined with the scarcity of forest industry represents an opportunity for wooden product substitution. Remote areas also represent an opportunity for wood energy. Since much of the boreal is quite flat, there is little hydroelectric production; presently most is fossil fuel.
Wildlife habitat is a major concern in the boreal. Wildlife species require a wide variety of different habitat requirements and many require a variety of conditions simultaneously occurring across the landscape. Many boreal management plans simply attempt to mimic the outcome of natural fires (maintaining the natural range of variability). The natural variability is broad leading to "boom and bust" conditions for many species. An integrated plan could add a degree of control to the frequency, location, and scale of forest fires. Landscape level maps of future desired conditions could be constructed and a plan designed to achieve this set of conditions through harvesting, prescribed burns, and naturally occurring wildfires. The harvesting and the prescribed burn plans must be adaptable to compensate for unpredicted variations in the natural fires.
Key habitat structures could be protected through a combination of separating them from the rest of the landscape by "pre-burning" and increasing fire suppression activities in these areas. Stand structures that require fire (particularly some types and frequencies of snags) could be constructed by leaving unharvested patches to burn in the areas that are prescribe burned.
An important part of the plan is the harvesting of trees before large broadcast prescribed burns are set. To increase sequestration (rather than just substituting slow decomposition for rapid combustion) either products must be produced or the wood must be used to substitute for petroleum (wood energy). To avoid leakage, the products must not directly substitute for wooden products produced from forests not included in the carbon accounting area. Remote rural areas with low levels of economic development are well suited to meeting these restrictions. If local industry could be stimulated to produce small household products (e.g. furniture, wooden trim) these will substitute for many plastic and metal products currently used because they are easily transported. Another carbon saving is the petroleum based energy used to transport the products to the remote areas.
Wood energy is appealing for two reasons. Firstly, this represents an important addition to carbon sequestration if a direct replacement for oil or coal based systems. Secondly, wood energy plants have a low degree of economy of scale so they are appropriate as a decentralized energy source (ideal for rural, sparsely populated areas).
The key element of the plan is economic synergy leading to economic efficiency. Harvesting trees in order to either increase carbon sequestration or to increase local economic activity, including jobs, could be prohibitively expensive in remote boreal areas if either objective had to carry the cost alone. However, if the costs are borne by two objectives, meeting both can be affordable. The carbon sequestration goals can only be met by harvesting trees. Meeting both goals leads to income from the trade of carbon credits. The revenue from the carbon credits alone will not only fail to pay for the harvesting but the trees must be used, not decompose, otherwise carbon sequestration gains will be small. Likewise, it is doubtful that small local forest enterprises will develop if the full cost of harvesting trees must be met by wood prices. If the harvest and transportation costs are at least partially borne by carbon credit revenues it is much more likely that these local industries can develop. The economic gain from this plan is measured by the jobs, product revenue, and energy that are produced because the sale of carbon credits offsets forest management and operating costs.
Historically, forest management has been faced with situations of competing interests for forests. This has led to management for a single objective with other objectives being treated as constraints (Smith et al. 1997). A new multi-objective paradigm must be adopted that leads to more innovative silviculture based on developing synergies and overlap between objectives. It is no longer sufficient to manage for single objectives merely with the goal to minimize the detrimental impact on other objectives. The revenue that can be generated from the sale of carbon credits presents a unique opportunity in some cases to make these synergies possible.
Landscape level stewardship plans need to be developed that directly address wildlife objectives, bioconservation objectives, aboriginal values, and economic development including safe, well paying job creation (Johnson, 1992). Increased carbon sequestration and the revenue that can be generated from this process can become the tool that takes the plan above the economic threshold needed for implementation.
Revenue generated from the sale of carbon credits can move forest management to a paradigm of true multi-objective management. The sale of credits is somewhat unique because, although revenue is generated, the amount is not sufficient to shift management from timber to a system dominated by carbon sequestration as a goal, but the management necessary to create credits can satisfy other unmet objectives. Most other objectives such as recreation and bioconservation do not create an economic return and have been treated as social constraints.
One region where this may work is boreal North America. Here there is often low economic development, timber productivity is marginal and the infrastructure for management seldom exists. It is possible to develop a synergistic plan where these areas are not managed solely for carbon sequestration, but this objective meets other objectives.
One characteristic of this region is that much CO2 is released from catastrophic disturbances. This allows for silviculture to increase the net flux by reducing emissions rather than just to increasing productivity. These activities are more to meet the conditions of the Kyoto Protocol.
Research must be organized to accurately measure the baseline carbon fluxes and predict the impacts of silvicultural intervention. The research must then lead to efficient and effective monitoring plans to be implemented after a landscape stewardship plan is implemented.
Apps, M.J., W.A. Kurz, and D.T. Price. 1991. Estimating carbon budgets of Canadian forest ecosystems using a national scale model. In: Carbon cycling in boreal forest and sub-arctic ecosystems: Biospheric responses and feedbacks to global climate change. In: Proceedings of the international workshop. EPA Publication 600R930-84. p. 243-252.
Burschel P., E. Kursten, B. C. Larson, and M. Weber. 1993. Present role of German forests and forestry in the national carbon budget and options to its increase. Water, Air and Soil Pollution. 70: 325-340.
Keyes, M.R., Grier C.C. 1981. Above- and belowground net production in 40-year-old Douglas-fir stands on low and high productivity sites.. Canadian Journal for Forest Research. 11:599-605
Kurz, W.A., M.J. Apps, T.M. Webb, and P.J. McNamee. 1992. The carbon budget of the Canadian forest sector: Phase I. Natural Resources Canada Information Report NOR-X-326, 1992.
Johnson, E.A. 1992. Fires and vegetation dynamics: Studies from North American boreal forest. Cambridge University press, Cambridge, U.K.
Lautenschlager, R.A. 2000. Can intensive silviculture contribute to sustainable forest management in northern ecosystems, Forestry Chronicle 76:283-295
Mitchell, S.J. 1998. A diagnostic framework for windthrow risk estimation. Forestry. Chronicle 74:100-105.
Oliver, C.D., and B.C. Larson. 1996. Forest Stand Dynamics (Updated Edition). Wiley, Inc. 488p.
Prescott C.E., L.L. Blevins, and C.L. Staley. 2000. Effects of clear-cutting on decomposition rates of litter and forest floor in forests of British Columbia. Canadian Journal for Forest Research 1751-1757.
D.M. Smith, B.C. Larson, M. Kelty, and P.M.S. Ashton. 1997. The Practice of Silviculture: Applied Forest Ecology, (9th edition), Wiley, Inc. 550p.
| [1] FRBC Professor of Silviculture,
Forest Sciences Department, Faculty of Forestry, University of British Columbia,
2424 Main Mall, Vancouver, BC V6T 1Z4, Canada. Tel: (604) 822-1284; Fax:
(604) 822-8645; Email: [email protected] |