The climate is changing globally due to huge concentration of Greenhouse Gases, carbon dioxide (CO2) in particular, that traps outgoing long wave infra-red radiations into the atmosphere. Such gases contribute to higher global temperatures that could increase the frequency of extreme weather events and have a reflective impact on human health, glaciers, sea levels, natural habitats, and agriculture. Taking such cases in account, Kyoto Protocol was prepared in December 1997that recognizes human-induced carbon sequestration as a way of meeting legally binding greenhouse gas emissions targets. This protocol specifically point out emissions from different sources and related removals by sinks resulting from direct, human-made land-use change and forest-related activities (deforestation, reforestation, and afforestation) undertaken since 1990. Forest sinks are particularly attractive, since no new technologies need to be developed and forests also generate other social benefits.
Forests plays a critical role in climate change by sequestering, or storing, large quantities of carbon (by absorbing CO2) as they grow and releasing it when they die. Photosynthesis and respiration are the crucial mechanism by which forests accumulate and release carbon. A growing tree absorbs CO2 from the air during the process of photosynthesis, uses solar energy to store carbon in its roots, stems, branches, and foliage. When trees decay and die, they become a carbon source, releasing more carbon than they can absorb. And when forests are harvested, burned, or cleared by humans, or in the event of a natural disturbance such as fire or disease, some of the carbon stored in the trees’ cells is released into the atmosphere. Stored carbon, however, can be transferred into forest products—for example, wood used for lumber, furniture, and other durable goods can seize its carbon for decades or even centuries in case of well maintained.
One that occupies carbon is called a “sink” and that releases carbon is called a “source.” Shifts of carbon over time from one stock to another—from the atmosphere to the forest, for example—are referred as carbon “fluxes.” Over time, carbon may be transferred from one stock to another. For example, burning of fossil fuel moves carbon from fossil fuel deposits to the atmosphere. Physical processes also gradually convert some atmospheric carbon into the ocean stock. Biological growth in plants fixes atmospheric carbon in cell tissues, thereby transforming carbon from the atmosphere to the biotic system.
The total carbon supply of an old-growth forest may be large as they experiencing little net growth that means changes in that storage are small or negligible. In case young, fast-growing forests the stock may be small while the fluxes may be significant. There is potential for agricultural crops and grasses to act as a sink and sequester carbon but it appears to be limited due to their short life and limited biomass accumulations. Even so, agricultural and grassland soils have sufficient potential to sequester carbon.
The well known approach of carbon sequestration is probably the role of forests besides oceans, and carbon storage arrangement in forests is large enough that forests offer the high probability of sequestering considerable amounts of extra carbon in relatively short periods, such as decades. However, during burning of forest carbon release fairly quickly.
In a forest ecosystem there are five storages of carbon. These are as follows;
· Above-ground biomass(canopy),
· Below-ground biomass,
· Litter,
· Dead wood, and
· Soils organic carbon
In forests, carbon is sequestered in the process of plant growth as carbon is captured in plant cell formation and oxygen is released. As the forest biomass experiences growth, the carbon held captive in the forest stock increases. Concurrently, plants grow on the forest floor and add to this carbon store. In due course, branches, leaves, and other materials fall to the forest floor and may store carbon until they decompose. Moreover, forest soils may sequester some part of the decomposing plant litter in the course of root/soil interactions. In addition, carbon may be sequestered for extensive periods in long-lived wood products resulting from forest harvests.
The change of forest from one ecological form to another will generate large carbon surges, forests can be a carbon source or a sink. It is important to evaluate carefully exactly what is happening to the carbon as the forest changes to establish the forest’s sink/source contribution. Seeing that the forest as a source net carbon released is due to biomass reductions from fire, tree decomposition, or logging. In the case of decomposition or fire, forest carbon is released into the atmosphere. However, the forest may again become a carbon sink as it is restored through forest re-growth.
Widely on earth, wood is consumed as a source of energy and burning wood releases carbon into the atmosphere. Where the fuel wood is taken from a forest and re-growth occurs, no net carbon is emitted. Furthermore, to the extent that biofuels are produced sustainably and used as a substitute for fossil fuel energy, fossil fuel emissions are avoided and no new net carbon emissions are created, since biofuels re-growth offsets the initial biofuels emissions,
The terms Deforestation, Reforestation and Afforestation are often used in case of forest management so to the carbon sequestration management scheme. It is in the state of deforestation when forest land is cleared and reforestation does not take place. Usually, land clearing is connected with the everlasting conversion of forest lands to other uses, for instance croplands, ground or urban land. Once forest is changed to some other purposes, there is a net loss of carbon in the normal storage since most other land uses will sequester less carbon than the forest. Under such situations, net carbon transfers occur. If the place is cleared and the vegetation burned, most of the carbon is freed into the atmosphere. However, to the extent that the vegetation is converted into long-lived wood products or substituted for fossil fuel energy, only a part of the carbon in the forest will be a net release into the atmosphere.
Even if reforestation typically refers to the practice of reestablishing a forest on a site that has been recently harvested, it also may refer to the reestablishment of forest on a site that has been cleared for some period of time. In either case, reforestation acts as a carbon sink since it results in the build-up of carbon stocks in the recently established biomass.
The formation of a forest on land never forested or not forested for a very long time is called afforestation. Often the distinction between afforestation and reforestation shapes as the period during which the forest has been missing from the land extend. Afforestation arises when forests are established on grasslands never previously forested. Rehabilitation of different lands into forest will consume additional amount of carbon in trees and other components of the forest ecosystem.
In tropical regions, it is common that natural or human-induced conversion of land into reforestation of commercial timber harvests. When such harvests are accompanied by reforestation, the land-clearing effects of the harvest on the forest carbon stocks are offset, in the long term, by carbon sequestration and the build-up of carbon stocks in the newly regenerated forest. The long-standing alternation in carbon storage will depend directly on the type and scale of forest harvested and regenerated. In some cases, second-growth forest will not sequester as much carbon as the original forest. For instance, when old-growth forest is harvested, the replacement forest typically will involve less volume, especially if it is being managed for timber harvests. However, when storage in long-lived wood products is considered, the net carbon of the managed replacement forest and its products will more closely approach, and perhaps exceed, that of the initial forest over a longer period.
Forest management can contribute to carbon sequestration by promoting forest growth and biomass accumulation. Additionally, management can choose to widen the harvest rotation, thereby increasing the average forest stock and hence the average carbon sequestered in a forest
Finally, natural disasters can affect forest stocks and often result in forests becoming a carbon source—at least for a time. Large fraction of the world’s forests is subject to natural instability that occurs occasionally as part of natural cycles. Forest are subject to substantial carbon-releasing disturbances, particularly in the form of wildfires, that often occur after the forest is first disturbed by other forces, such as drought, disease, or pests. Natural disasters may discharge large amounts of carbon in a short period of time. On the other hand, where land is not changed to other uses, the forest classically re-establishes itself and again begins to hold carbon. In many forests, natural disturbance systems create a cyclic model of growth (sequestration), disturbance (emission), and re-growth (sequestration) over a period of years.
In case of Nepal, forests are the most important natural resources after water. Majority of people use forest products as firewood, food, fodder, timber and medicines. Wide-ranging utilization of and growing demands for forest products have led to its declining both in area and quality. Further, Global Warming may cause forest damage through migration towards the polar region, changes in their composition, extinction of species etc. The outcome of this situation could affect directly not only the environment of Nepal but also lives of majority of the people
According to Holdridge model there are 39 vegetation zones out of which Nepal has 15 types under the existing (CO2) condition. There would be only 12 types under 2xCO2 climatic condition as depicted by the model. In the same way tropical wet forest and warm temperate rain forest would vanish, and cool temperate vegetation would turn into warm temperate vegetation under double CO2 condition. As per the IPCC Guidelines, though Nepal lies among the tropical countries with six forest categories namely wet lands, moist with short dry season, moist with long dry season, dry, montane moist, and montane dry, the study has found only three of them as relevant to Nepal
The Department of Forest Research and Survey (DFRS, 1999) has estimated at 4,268.8 thousand hectares of forest area in 1994/95, which is about 29 % of the entire territory of the country. The forest cover in 1978/79 was about 5,616.8 thousand hectares, covering around 38 % of total territory of Nepal (LRMP, Land Utilization Report, 1986). The dissimilarity has been cited for deforestation or reduction rate of forests, which amounts to 1.7 % between the periods of 1978/79 and 1994/95. In total 1,348 thousand hectares of forest land i.e. more than 9 percent of the total forest covers had been transformed to the other land-use/land cover categories. During that phase, shrub land doubled from 689.9 thousand hectares (4.7 %) to 1,559.2 thousand hectares (10.6 %). Combining the forests and shrub lands (woody vegetation) as one, yearly about 29 thousand hectares of woody vegetation areas can be found converted to non-woody vegetation areas. This is a clear indication that forest resources were subjected to exploitation beyond its sustainable growth and use.
About 80 % of total energy consumption in Nepal is obtained from fuel wood, of which about 63 % comes from forestland (WECS, 2001). Of the total fuel wood consumption, only 27 % is estimated to have been extracted on a sustainable basis, and the remaining from over- cutting.. The actual annual growth rate is below the standard growth rate and varies from 0.59 to 2.34 tons dry matter per hectare per year (WECS, 2001).
Indigenous practices like Agro-forestry in the hilly region of Nepal and private plantations in Terai and community forest management have resulted in positive impact on tree-stock. Especially the fodder species and plantation for timber in the farmlands and in the non-cultivated land are common. Agriculture Census of Nepal (1991) has revealed that the woodlands and forest have increased from 15,000 hectares in 1981 to 109,000 hectares in 1991 (Environment Statistics, 1998) in private lands. On considering the average number of 408 trees per hectare from National Forest Inventory (NFI), it is estimated that 300 million trees exist outside the forest area in Nepal. Annual carbon removal due to the growing stock is obtained by multiplying the carbon content factor by net biomass growth. Calculation shows that about 14,737 Gigagram of CO2was removed from the atmosphere due to the growing stock in Nepal’s forest.
Biomass stock per hectare in Nepal’s forestland varies from 115 to 178 tons (WECS 2001). Entirely, about 14,006 kilo tons of biomass are removed from the different forestlands and other lands by cutting the trees. In Nepal, commercial harvest is not in practice. Forestland, in general, is changed in two-step process, the first from forestland to shrub land and the second from shrub to cultivation. The biomass in shrub land after conversion is assumed to be 16.1 tons per ha (WECS, 2001) whereas average biomass in the cultivation land is assumed to be 10 tons per ha (IPCC, 1996).
All the biomass removed from the forest is not consumed as fuel wood. Out of the total biomass loss from the forest clearing, 20 % is estimated for the purpose of using them for timbers (DFRS, 1993) that last up to few decades. During the period of 1978/79 to 1994/95, altogether 1.3 million hectare of forest was cleared (74 thousands hectare per year). In total 14 million tons of wood was removed from forest clearing releasing more than 18,547 Gigagram of CO2 to the atmosphere.
Conversion of forests to other land-use type affects the soil carbon. Forest soils are rich in organic matter than the land used for other purposes. Once deforestation occurs, the soils gradually lose its carbon content over the time. In such condition, temperature also disturbs the process of decomposition. In the higher altitude area (cold climate) the decay process is slower than in the Terai and Siwaliks regions (tropical climate). There is no thorough information of soil carbon content. Land system map prepared by LRMP has estimated organic matter content in the various lands and physiographic regions of Nepal. Soil carbon release estimation, as per IPCC Guidelines, is found altogether 23.71 Terragram (23.71 million tons) during the period from 1974 to 1994 (20 years) which is due to change in land-use from high carbon content soils (forest/shrub soils) to low carbon content soils (cultivation).
For a number of countries, carbon sequestration through forestation or retarded deforestation may be a cost-effective approach to contributing to reduced global atmospheric concentrations of CO2. So a variety of sustainable management approaches can improve carbon sequestration in existing forests. Allowing trees to grow for longer periods between harvests, planting longer-lived tree species (e.g., red oak, white pine, red spruce, hemlock), and setting aside wider buffer zones around streams and rivers have all been shown to increase carbon storage in forests.
References:
1. Ministry of Agriculture and Cooperatives, June 2007, Government of Nepal, “Melting Ice: A Hot Topic?”, The Journal of Agriculture and Environment,Vol:8.
2. MOPE/UNEP, June 2004, First Initial National Communication to the Conference of the Parties of the United Nations Framework Convention on Climate Change, Nepal.
3. Union of Concerned Scientists Citizens and Scientists for Environmental Solutions Catalyst,Vol.3 No.2 Fall 2004,http://www.ucsusa.org/
4. US Department of Energy, Office of Science,Science for America’s Future, http://www.science.doe.gov/
5. Wikipedia,Carbon capture and storage, Available at: http://en.wikipedia.org/wiki/Carbon_capture_and_storage
· Below-ground biomass,
· Litter,
· Dead wood, and
· Soils organic carbon
In forests, carbon is sequestered in the process of plant growth as carbon is captured in plant cell formation and oxygen is released. As the forest biomass experiences growth, the carbon held captive in the forest stock increases. Concurrently, plants grow on the forest floor and add to this carbon store. In due course, branches, leaves, and other materials fall to the forest floor and may store carbon until they decompose. Moreover, forest soils may sequester some part of the decomposing plant litter in the course of root/soil interactions. In addition, carbon may be sequestered for extensive periods in long-lived wood products resulting from forest harvests.
The change of forest from one ecological form to another will generate large carbon surges, forests can be a carbon source or a sink. It is important to evaluate carefully exactly what is happening to the carbon as the forest changes to establish the forest’s sink/source contribution. Seeing that the forest as a source net carbon released is due to biomass reductions from fire, tree decomposition, or logging. In the case of decomposition or fire, forest carbon is released into the atmosphere. However, the forest may again become a carbon sink as it is restored through forest re-growth.
Widely on earth, wood is consumed as a source of energy and burning wood releases carbon into the atmosphere. Where the fuel wood is taken from a forest and re-growth occurs, no net carbon is emitted. Furthermore, to the extent that biofuels are produced sustainably and used as a substitute for fossil fuel energy, fossil fuel emissions are avoided and no new net carbon emissions are created, since biofuels re-growth offsets the initial biofuels emissions,
The terms Deforestation, Reforestation and Afforestation are often used in case of forest management so to the carbon sequestration management scheme. It is in the state of deforestation when forest land is cleared and reforestation does not take place. Usually, land clearing is connected with the everlasting conversion of forest lands to other uses, for instance croplands, ground or urban land. Once forest is changed to some other purposes, there is a net loss of carbon in the normal storage since most other land uses will sequester less carbon than the forest. Under such situations, net carbon transfers occur. If the place is cleared and the vegetation burned, most of the carbon is freed into the atmosphere. However, to the extent that the vegetation is converted into long-lived wood products or substituted for fossil fuel energy, only a part of the carbon in the forest will be a net release into the atmosphere.
Even if reforestation typically refers to the practice of reestablishing a forest on a site that has been recently harvested, it also may refer to the reestablishment of forest on a site that has been cleared for some period of time. In either case, reforestation acts as a carbon sink since it results in the build-up of carbon stocks in the recently established biomass.
The formation of a forest on land never forested or not forested for a very long time is called afforestation. Often the distinction between afforestation and reforestation shapes as the period during which the forest has been missing from the land extend. Afforestation arises when forests are established on grasslands never previously forested. Rehabilitation of different lands into forest will consume additional amount of carbon in trees and other components of the forest ecosystem.
In tropical regions, it is common that natural or human-induced conversion of land into reforestation of commercial timber harvests. When such harvests are accompanied by reforestation, the land-clearing effects of the harvest on the forest carbon stocks are offset, in the long term, by carbon sequestration and the build-up of carbon stocks in the newly regenerated forest. The long-standing alternation in carbon storage will depend directly on the type and scale of forest harvested and regenerated. In some cases, second-growth forest will not sequester as much carbon as the original forest. For instance, when old-growth forest is harvested, the replacement forest typically will involve less volume, especially if it is being managed for timber harvests. However, when storage in long-lived wood products is considered, the net carbon of the managed replacement forest and its products will more closely approach, and perhaps exceed, that of the initial forest over a longer period.
Forest management can contribute to carbon sequestration by promoting forest growth and biomass accumulation. Additionally, management can choose to widen the harvest rotation, thereby increasing the average forest stock and hence the average carbon sequestered in a forest
Finally, natural disasters can affect forest stocks and often result in forests becoming a carbon source—at least for a time. Large fraction of the world’s forests is subject to natural instability that occurs occasionally as part of natural cycles. Forest are subject to substantial carbon-releasing disturbances, particularly in the form of wildfires, that often occur after the forest is first disturbed by other forces, such as drought, disease, or pests. Natural disasters may discharge large amounts of carbon in a short period of time. On the other hand, where land is not changed to other uses, the forest classically re-establishes itself and again begins to hold carbon. In many forests, natural disturbance systems create a cyclic model of growth (sequestration), disturbance (emission), and re-growth (sequestration) over a period of years.
In case of Nepal, forests are the most important natural resources after water. Majority of people use forest products as firewood, food, fodder, timber and medicines. Wide-ranging utilization of and growing demands for forest products have led to its declining both in area and quality. Further, Global Warming may cause forest damage through migration towards the polar region, changes in their composition, extinction of species etc. The outcome of this situation could affect directly not only the environment of Nepal but also lives of majority of the people
According to Holdridge model there are 39 vegetation zones out of which Nepal has 15 types under the existing (CO2) condition. There would be only 12 types under 2xCO2 climatic condition as depicted by the model. In the same way tropical wet forest and warm temperate rain forest would vanish, and cool temperate vegetation would turn into warm temperate vegetation under double CO2 condition. As per the IPCC Guidelines, though Nepal lies among the tropical countries with six forest categories namely wet lands, moist with short dry season, moist with long dry season, dry, montane moist, and montane dry, the study has found only three of them as relevant to Nepal
The Department of Forest Research and Survey (DFRS, 1999) has estimated at 4,268.8 thousand hectares of forest area in 1994/95, which is about 29 % of the entire territory of the country. The forest cover in 1978/79 was about 5,616.8 thousand hectares, covering around 38 % of total territory of Nepal (LRMP, Land Utilization Report, 1986). The dissimilarity has been cited for deforestation or reduction rate of forests, which amounts to 1.7 % between the periods of 1978/79 and 1994/95. In total 1,348 thousand hectares of forest land i.e. more than 9 percent of the total forest covers had been transformed to the other land-use/land cover categories. During that phase, shrub land doubled from 689.9 thousand hectares (4.7 %) to 1,559.2 thousand hectares (10.6 %). Combining the forests and shrub lands (woody vegetation) as one, yearly about 29 thousand hectares of woody vegetation areas can be found converted to non-woody vegetation areas. This is a clear indication that forest resources were subjected to exploitation beyond its sustainable growth and use.
About 80 % of total energy consumption in Nepal is obtained from fuel wood, of which about 63 % comes from forestland (WECS, 2001). Of the total fuel wood consumption, only 27 % is estimated to have been extracted on a sustainable basis, and the remaining from over- cutting.. The actual annual growth rate is below the standard growth rate and varies from 0.59 to 2.34 tons dry matter per hectare per year (WECS, 2001).
Indigenous practices like Agro-forestry in the hilly region of Nepal and private plantations in Terai and community forest management have resulted in positive impact on tree-stock. Especially the fodder species and plantation for timber in the farmlands and in the non-cultivated land are common. Agriculture Census of Nepal (1991) has revealed that the woodlands and forest have increased from 15,000 hectares in 1981 to 109,000 hectares in 1991 (Environment Statistics, 1998) in private lands. On considering the average number of 408 trees per hectare from National Forest Inventory (NFI), it is estimated that 300 million trees exist outside the forest area in Nepal. Annual carbon removal due to the growing stock is obtained by multiplying the carbon content factor by net biomass growth. Calculation shows that about 14,737 Gigagram of CO2was removed from the atmosphere due to the growing stock in Nepal’s forest.
Biomass stock per hectare in Nepal’s forestland varies from 115 to 178 tons (WECS 2001). Entirely, about 14,006 kilo tons of biomass are removed from the different forestlands and other lands by cutting the trees. In Nepal, commercial harvest is not in practice. Forestland, in general, is changed in two-step process, the first from forestland to shrub land and the second from shrub to cultivation. The biomass in shrub land after conversion is assumed to be 16.1 tons per ha (WECS, 2001) whereas average biomass in the cultivation land is assumed to be 10 tons per ha (IPCC, 1996).
All the biomass removed from the forest is not consumed as fuel wood. Out of the total biomass loss from the forest clearing, 20 % is estimated for the purpose of using them for timbers (DFRS, 1993) that last up to few decades. During the period of 1978/79 to 1994/95, altogether 1.3 million hectare of forest was cleared (74 thousands hectare per year). In total 14 million tons of wood was removed from forest clearing releasing more than 18,547 Gigagram of CO2 to the atmosphere.
Conversion of forests to other land-use type affects the soil carbon. Forest soils are rich in organic matter than the land used for other purposes. Once deforestation occurs, the soils gradually lose its carbon content over the time. In such condition, temperature also disturbs the process of decomposition. In the higher altitude area (cold climate) the decay process is slower than in the Terai and Siwaliks regions (tropical climate). There is no thorough information of soil carbon content. Land system map prepared by LRMP has estimated organic matter content in the various lands and physiographic regions of Nepal. Soil carbon release estimation, as per IPCC Guidelines, is found altogether 23.71 Terragram (23.71 million tons) during the period from 1974 to 1994 (20 years) which is due to change in land-use from high carbon content soils (forest/shrub soils) to low carbon content soils (cultivation).
For a number of countries, carbon sequestration through forestation or retarded deforestation may be a cost-effective approach to contributing to reduced global atmospheric concentrations of CO2. So a variety of sustainable management approaches can improve carbon sequestration in existing forests. Allowing trees to grow for longer periods between harvests, planting longer-lived tree species (e.g., red oak, white pine, red spruce, hemlock), and setting aside wider buffer zones around streams and rivers have all been shown to increase carbon storage in forests.
References:
1. Ministry of Agriculture and Cooperatives, June 2007, Government of Nepal, “Melting Ice: A Hot Topic?”, The Journal of Agriculture and Environment,Vol:8.
2. MOPE/UNEP, June 2004, First Initial National Communication to the Conference of the Parties of the United Nations Framework Convention on Climate Change, Nepal.
3. Union of Concerned Scientists Citizens and Scientists for Environmental Solutions Catalyst,Vol.3 No.2 Fall 2004,http://www.ucsusa.org/
4. US Department of Energy, Office of Science,Science for America’s Future, http://www.science.doe.gov/
5. Wikipedia,Carbon capture and storage, Available at: http://en.wikipedia.org/wiki/Carbon_capture_and_storage
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