Carbon Sequestration Project Outline
Written by: Erin West and Luis Agurto
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Cedar Forest in Bonnieux (Provence, France)
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Carbon sequestration is one of the most promising ways for reducing the buildup of greenhouse gases in the atmosphere. Carbon sequestration is defined by the U.S. Environmental Protection Agency (EPA) as “the process through which carbon dioxide (CO2) from the atmosphere is absorbed by trees, plants and crops through photosynthesis, and stored as carbon in biomass (tree trunks, branches, foliage and roots) and soils”. The term “sinks” is also used to refer to forests, croplands and grazing lands, and their ability to sequester carbon. In terms carbon dioxides global impact, one unit of carbon dioxide released from a car’s tailpipe has the same effect as one unit of CO2 released from a burning forest. In the same way, CO2 removed from the atmosphere through tree planting can have the same benefit as avoiding an equivalent amount of CO2 released from a power plant (EPA, 2007). Forests of the world sequester and conserve more carbon than all other terrestrial ecosystems and account for 90% of the annual carbon flux between the atmosphere and the Earth’s land surface (Winjum et. al, 1993). Forests growing on abandoned agricultural land, such as the project site, accumulate biomass faster than other past land uses. Research has shown that tropical reforestation has the potential to serve as a carbon offset mechanism both above and below ground for at least 40 to 80 years, and possibly much longer. Enhancing the natural processes that remove carbon from the atmosphere is thought to be one of the most cost-effective means of reducing atmospheric levels of carbon dioxide. Practices that aim to reduce carbon losses and increase sequestration generally enhance the quality of air, soil, and water (EPA, 2007). Tree planting that restores fuller forest cover may not only sequester carbon but could improve habitat suitability for wildlife as well.
This project is a multi-phased plan that will reduce carbon dioxide emissions at each step. A variety of species of trees will be planted including Cedar, Roble, Caoba and Teak on a total of 130 acres in Los Espinozita San Rafael Del Sur in Managua, Nicaragua with the purpose of creating a surplus of stored carbon within the vegetation. The project site is located approximately fifty miles south of Managua on abandoned agricultural land. The warm, tropical climate of the area is an ideal site for such a project. Sequestration rates can vary depending on a number of variables including tree species, soil type, regional climate, topography and management practices but the highest of all sequester rates have been shown within these tropical climate zones. Trees growing in such a climate have shown to grow three times as fast compared to trees growing in temperate zones (Department of Energy). Each tree growing in tropical climates removes approximately 22 kilograms (50 pounds) of carbon dioxide from the atmosphere each year (Global Cooling Centers, 2006). After the trees reach maturity, they will be harvested and made into high-end furniture that will preferably be produced in Nicaragua. By creating furniture from the harvested trees the carbon stored within the wood will remain trapped for decades longer. Additional trees will be planted and again harvested at maturity to create more furniture.
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| Teak trees |
Another important aspect to this project is reducing carbon emissions produced locally by the wood burning stoves. Wood burning stoves will be subsidized for ones which are 75% more efficient. These stoves will preferably be built with local materials and provide work for the community. Other building supplies and farming equipment will be imported from the United States as well. Additional revenue will also be generated by the sale of the surplus carbon or, carbon credits. A carbon credit represents the sequestration of one ton of CO2 from our atmosphere. These carbon credits are then sold to companies, corporations and individuals that wish to offset their own carbon emissions.
With the revenue generated by the carbon sequestration project it will provide additional funds to expand the current project as well as explore other alternative projects that will further reduce carbon dioxide emissions. This project can be both beneficial for the environment by removing carbon dioxide from the atmosphere as well as generate revenue for all parties involved with the sale of the carbon credits, the manufactured furniture and the efficient stoves.
The Carbon Sequestration Debate
Sequestering carbon from the atmosphere has been a recent scientific research topic. Scientists have debated the costs and benefits of carbon sequestration from the beginning. Some call it a “feel good” solution that does little to reverse the effects of the increasing levels of atmospheric CO2. Others argue strongly that large scale planting to increase the number of carbon sinks is one of the most effective current strategies at our disposal. While both sides of the debate back up their arguments with years of research and experience those in favor of carbon sequestration projects have shown that when done correctly atmospheric CO2 removal is possible and can be very effective. Since these successful experiments have been published the debate has quieted but has not been extinguished.
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| Tropical forest |
The argument against carbon sequestration disagrees that planting trees can lower the global temperature and states that by planting trees in one part of the world to affect change in another is a wasted effort. However, both sides do agree that when planting trees in a tropical climate zone as opposed to a temperate climate the amount of carbon removed is dramatically more significant than in other climate zones. Research has indicated that in temperate climates, with long periods of snow cover and a high percentage of evergreen trees a warming effect has been documented. The rise in temperature is due to sunlight absorption by the forest’s dark surfaces which counteracts the global cooling effect of the carbon sequestration (Gibbard et. al, 2005). Some scientists feel that to prevent climate change we must radically alter our current energy policy rather than waste time, money and effort on planting trees.
Other research against terrestrial carbon sequestration has focused on the potential negative side affects of planting trees. Past projects have focused on planting fast growing, high yield species for maximum CO2 removal. These species tend to be non-native to the project area and thus can out-compete native species. These exotic species can also bring new diseases and pests which can devastate native plant communities. Introducing a new species to a plant community can severely disrupt the natural ecosystem and affect everything from biodiversity to soil composition. Only planting one species leads to monoculture areas with reduced biodiversity (Gibbard et. al, 200). Trees can also affect water levels and flow of above and below ground reservoirs and downstream ecosystems may have reduced water availability. Plantations can also increase soil salinity when species composition changes abruptly over a short period of time. Another problem is when ground is cleared for forest planting the rotting of organic matter in the soil can release a surge of excess carbon dioxide into the atmosphere. This CO2 release may exceed the amount of carbon removed by the trees for the first ten years (tiptheplanet.com, 2007). Another potential problem is that carbon accumulation in forests and soils eventually reaches a saturation point, beyond which additional sequestration is no longer possible. This happens, for example, when trees reach maturity, or when the organic matter in soils builds back up to original levels before losses occurred (DOE, 2007)). Yet another argument against plantations is that old forests absorb more CO2 than new ones, suggesting that protecting and preserving old forest is more effective than planting new ones. However, the problems with large scale planting that were mentioned previously usually results when planting isn’t done properly and the necessary research was not conducted or followed.
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| Tree Planting |
The research has shown that with the correct species, climate, topography and management practices it is possible to sequester a significant amount of carbon dioxide from the atmosphere. Using terrestrial carbon sequestration to reduce carbon dioxide emissions and global warming is a current method being used worldwide with promising results. There are several planting practices that will garner different carbon sequestering rates. Afforestation is one such method in which trees are planted in an area that had not previously held forest, such as agricultural land. Reforestation, another method, is re-planting trees in an area in which at one point in time had held forest but currently do not. Both methods have been studied and their sequestration rates compared. Afforestation practices were shown to have the highest increase in carbon sequestration compared to the baseline rate prior to planting (EPA, 2007). Forests growing on abandoned agricultural land accumulate biomass faster than other past land uses which explains the difference in sequestration rates between the two planting practices. In addition to acting as carbon sinks, forests also add water vapor to the atmosphere which increase cloudiness and therefore have a cooling affect. Research has shown that reforestation and afforestation projects both promote biodiversity and create additional wildlife habitat not previously available (Silver et. al, 2000). There are several other benefits of large scale plantation efforts in addition to the removal of carbon dioxide. Planting trees in an area previously devoid of any can stabilize soil and prevent runoff and erosion, thereby reducing losses of water, soil material, organic matter and nutrients. The presence of tree roots in a system can improve nutrient cycling which can decrease the amount of nutrients lost through the soil. Another potential benefit is the decomposition of tree litter and prunings can substantially contribute to the maintenance of soil fertility and therefore promote improved regeneration (DOE, 2007). All of these benefits directly improve the quality of the local ecosystem. By planting non-invasive species and carefully managing their progress most problems can be avoided and a successful program is possible.
Soil Composition and Tree Species
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| A typical tropical soil profile |
Four species of trees have been researched for this project. Of the four, three are native to Central America and tropical climates. The only non-native species is Teak. All four species have a high economic value and can be produced for upscale furniture, flooring, cabinets and so on. The species being used are mahogany (Swietenia macrophylla or humilis), caoba (Cedrela odorata), roble (Tebebuia heterophylla), and teak (Tectonia grandis). All four species have been grown together on commercial plantations.
Teak
(Tectonia grandis)
Teak is very fast growing, and on favorable sites may reach, at maturity, 40 to 50 meters in height. The trunks are cylindrical and may reach 1-2 meters in diameter. Teak can take 20-25 years to reach full maturity. Teak rapidly puts on height as well as diameter given the right conditions. The rate of growth and the quality of teak from plantations are largely dependent on the type and quality of the seeds; the physical and chemical characteristics of the soil, including topography and drainage and on the environmental variables such as rainfall, temperature and humidity; and on management techniques (Wikipedia, 2007).
Pure teak plantations are often prone to attack by defoliators, especially when planted on unsuitable soils, poor in nutrients. Attack by defoliators is less frequent and intense on sites where healthy growth is present and can be further reduced with the maintenance of a suitable under story. Teak is usually planted when the seedlings or clones are four to six weeks old. The usual 1,200 to 1,600 plants per hectare is a good range, with closure of the canopy commonly taking place between the third and fourth year. The first thinning should take place when the dominant height reaches 9 to 9.5 meters, and the second when the dominant height reaches 17 to 18 meters. Dominant height is the average height of the 100 largest diameter trees per hectare. A common strategy to grow long boles, clear of knots, is to keep the stand quite closed and high in number of trees during the first years of development, when rapid height growth occurs. This is meant to keep crowns small, and consequently the branches relatively small and thin (Centeno, 1995). Teak is used as a food plant by the larvae of moths of the genus Endoclita and other moths including the Turnip Moth (Wikipedia, 2007).
Caoba
(Swietenia macrophylla or Swietenia humilis)
Caoba is also known as mahogany. Due to its biological and commercial characteristics, mahogany has a large potential to become the basis for a sustainable use and management system of the tropical forest. It occurs in the neotropics, from southern Florida, the Caribbean, Mexico and Central America south to Bolivia. They are medium-to large sized trees growing 20-45 meters tall, and can have up to a two meter trunk diameter. Swietenia macrophylla, big leaf mahogany, occurs along the Atlantic coast of Central and South America. Swietenia humilis, Pacific coast mahogany, occurs along the Pacific coast of Central America and Mexico. In a natural forest, tree density is very low, often less than 5 individuals of any diameter class per hectare. Natural regeneration is dependent on canopy gaps, often caused by natural disturbances such as hurricanes that allow sufficient light (Wikipedia, 2007).
The average density of commercial-sized mahogany trees in Central America is about one tree per hectare, but densities can be higher when mahogany regenerates in post-disturbance clearings. It tolerates a variety of soil types but grows best on fertile, deep soils with a pH between 6.6 and 7.5. It does not grow well on rocky or waterlogged sites and does not tolerate frost or fires. Seeds do not require pre-treatment due to their high germination rates, although some authors recommend soaking seeds 24 hours at ambient temperature to improve germination. Seedling should be grown in full sun and only the vigorous, healthy plants should be taken to the field which means around 10% of the seedlings need to be culled. Trees should be planted at the beginning of the rainy season to maximize growth. Maximum growth can be one meter per year or more on good sites. Survival rates of big leaf mahogany vary greatly depending on the site, light availability and stock quality. Even on good sites, survival rates are approximately 80-90% (Valera et. Al, 2002).
The major pest of all mahoganies, as well as Cedar, is the mahogany shoot borer, Hypsipyla grandella, which bores in twigs and seed capsules of trees in the mahogany. In the tropics, mahogany shoot borers are active all year, with high shoot borer activity typically occurring with growth flushes of mahoganies subsequent to periods of high rainfall (Wikipedia, 2007). Mahogany shoot borers can also attack seed capsules. Young mahogany trees are susceptible to attack when they reach a height of 0.5 meter. The insect’s most severe damage to trees occurs when a larva bores into and kills the terminal shoot. A lateral branch grows upward to replace the lost terminal shoot, resulting in a crooked main stem. This insect is notoriously difficult to control because although some methods reduce the pest population considerably, even light populations can cause significant damage. There is still no reliable, cost-effective, and environmentally sound chemical control method available to prevent economic damage by these insects. It has been suggested, however, that chemical control of these pests might be applicable to nursery situations. Biological control of the mahogany shoot borer has been researched as a controlling agent and around 40 native species of insects have been identified as natural enemies of the mahogany shoot borer in the Americas. However, their effect is insufficient to prevent economic damage. The most promising strategy to control mahogany shoot borer populations is using integrated pest management options. The use of resistant genotypes, planting mahogany and cedar trees in mixed rather than pure stands and planting under an established canopy reduced shoot borer populations considerably reduces incidences of shoot borer attack. Additionally, growing young saplings in nursery conditions further diminished vulnerability (Valera et. Al, 2002).
Spanish cedar
(Cedrela odorata)
Known as Spanish cedar in English commerce, the wood is in high demand in the American tropics because of its natural termite and rot resistance. Cedro, another common name for Spanish cedar, is a semi-deciduous tree ranging in height from 10 to 40 meters. It can tolerate a long dry season but does not flourish in areas of rainfall greater than about 120 inches annually, or on sites with heavy or waterlogged soils. Cedro maximum growth potential is reached with 45 to 95 inches of rainfall annually with a dry season 2 to 5 months long. Individual trees are generally scattered in mixed semi-evergreen or semi-deciduous forests dominated by other species. Early development of the seedling is rapid as long as moisture and light are adequate. Natural cedro regeneration from seed is good in many parts of Central and South America, but good initial growth is often followed by dieback after 2 to 3 years. Fast-growing saplings develop straight, clean boles and narrow, thin crowns. Shade-grown seedlings are sensitive to sunscald after which they become more vulnerable to insect attack. Seedlings also have superficial root systems and may be sensitive to mechanical damage from weeding and other soil preparation activities. Cedro is also used for honey production in addition to replantation and agroforestry projects (Wikipedia, 2007).
Similar to caoba, the mahogany shoot borer is the most serious insect pest of cedro. The saplings can escape shoot borer attack in 3 to 4 years if robust, and subsequent growth is rapid on favorable sites. Plantations of cedro have also suffered snail damage in Malaysia and Africa and there have been reports of slug infestations killing some nursery stocks in the Virgin Islands. Beetle damage is a problem in some plantations in Africa, but evidently not in the Americas. Cedar wood and cedar oil is known to be a natural repellent to some species of moths (U.S. Forest Service, 2007).
Roble
(Tabebuia heterophylla)
Roble is often referred to as white cedar or roble blanco. It is a small to medium size tree with a height of 25 to 30 meters and a diameter of 60 cm. Roble is an aggressive pioneer in the seedling and sapling stages and is moderately resistant to white and brown rot fungi but it is susceptible to termite and marine borers (U.S. Forest Service, 2007). Plants in this genus are also notably resistant to honey fungus as well. It is a fast growing, shade intolerant tree and is often used as a hedge or windbreak. The crown is wide, stratified, and irregular, with a few thick, horizontal branches; the bole is straight, sometimes channeled at base. Seeds do not require special treatment for germination which occurs either in shade or in direct sunlight, provided humidity is kept stable. Roble grows best in open, moist, well-drained soils with a pH between 5 and 7. Roble regenerates well in open fields and develops into a dense stand of seedlings, after which it appears to stagnate. Transplanting of wild seedlings was found to be preferable to nursery stock due to their abundance and superior root systems. The trees do not require pruning, and no severe predator or parasite damage of seedlings have been reported (Flores et. al, 1999).
Measuring Carbon Sequestration Rate
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| Measuring carbon sequestration |
Several methods are available to measure carbon levels as well as the changes in carbon in above ground and below ground biomass, soils, and wood products. The methods vary in complexity, precision, accuracy, and cost. Regardless of what method is chosen, the baseline stored carbon amount must be measured in order to calculate the potential gains. The stored carbon must be measured in a readily understood and consistent manner so that potential buyers and sellers have a clear understanding of the product. A current method is to compare the amount of stored carbon in the soil, above and below ground biomass to one metric ton of atmospheric carbon dioxide that has been removed from the atmosphere or avoided from an emission source. This unit is commonly expressed in terms of a carbon emission reduction equivalent or CO2e (Butt & McCarl, 2004).
Direct on-site methods include field sampling and laboratory measurements of total carbon in the soil and biomass. Changes in carbon content resulting from changes in land management may then be expressed as the change in carbon amount on an area or volume basis (biomass would require volume calculations, vertical height included with acreage). The calculation is not difficult but requires awareness of the variability of soil properties. There is some uncertainty of how accurately and efficiently a routine soil carbon field monitoring program can be implemented, but research has suggested it can be done for a few dollars an acre, depending upon the desired degree of accuracy. Measurements may only need to be done once every 3 to 5 years, and in combination with satellite imagery and computer modeling could result in a more comprehensive assessment. Current forest carbon estimates are generally more accurate and easier to generate than soil estimates. Estimating changes in soil carbon over time is generally more challenging due to the high degree of variability of soil organic matter. Above-ground biomass may be easier to measure, where foresters have been measuring timber for years for wood production. These measurements, combined with biomass equations for a species of tree and shrub, can provide a fairly accurate estimate. Landowners themselves are capable of measuring tree dbh (diameter at breast height), where random trees can be sampled and with the species carbon default values, an average quantity of carbon stored can be estimated (Vincent et. al, 1999).
Because direct field measurements can be expensive, the use of indirect remote sensing techniques is an option worth exploring. High altitude or satellite imagery has been used to verify no-till conservation practices, cropping patterns, and biomass accumulation. In addition to cost, remote sensing may have several other advantages. For example, remote based data can be used for verification and comparison of carbon storage on a regional basis, while an individual inspection may see only a single field. Statistical sampling, computer modeling and remote sensing can be used to estimate carbon sequestration and emission sources at the global, national and local scales (Vincent et. al, 1999).
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| Flux tower and water fluxes are measured continuously to quantify carbon sequestration. |
Another approach to estimating carbon storage is the use of default values for certain land-based activities. A land-use based accounting system would focus on the changes in carbon stocks on managed lands during a defined time period. Default values would be assigned to a particular tract of land based upon county or regional level research on the average sequestration likely to result from specific agricultural or conservation measures in that area (Vincent et. al, 1999).
A distinct advantage of forest and agroforestry is the relative ease with which carbon accumulation can be measured and monitored. The baseline for agroforestry practices that involve tree planting could be assumed to be zero. Over time satellite imagery or aerial photos could be used to verify the continued presence and extent of a planting, such as a field windbreak. Statistical ground sampling methodology could be designed to document the amount of carbon accumulation over time for representative agroforestry practices across a range of site conditions (Vincent et. al, 1999).
Carbon credits
The set of buyers and sellers of emissions credits is largely constrained to the large greenhouse gas (GHG) emitting industries which tend to be power plants and other large industrial power generators. The strength of the United States GHG market, into which producers would sell, depends on the status of the GHG mitigation policy. Because federal policies currently do not mandate emission reductions, there is little stimulus in the United States for a broad carbon market to develop. However, it appears that many GHG-emitting industries believe that their assets could be at risk in a GHG-constrained world due to potential changes in emissions reduction policies in the near future as well as differences between national, international and state wide emissions policies. Companies which produce in multiple states or nations must cooperate with each entities emissions policy (Butt & McCarl, 2004). As emissions policies are almost certain to tighten the carbon credit market is equally certain to grow.
