Assessment of Carbon Sequestration Potential and Management Strategies on Philippine Forests: Implications to Global Warming

The study was conducted to assess the carbon sequestration potentials of major DENR programs (Community-Based Forest Management (CBFM), Timber License Agreement (TLA) and the Integrated Forest Management Agreement (IFMA)), and the secondary forest and two agroforestry systems in Mt. Makiling Forest in Los Baños, Laguna.

In assessing the carbon sequestration potential of major DENR programs, biomass and carbon densities derived from the previous studies conducted were used.  Based on calculations made, the three DENR programs were able to store a total of 133 Tg of carbon  and sequester 6.9 Tg of carbon per hectare per year.  Among the three programs evaluated, CBFM stored and sequestered the biggest amount of carbon.  With a total of 495 hectares, CBFM was able to store 56 Tg C and sequestered 2.6 Tg C/ha/year.  This represents 42% of the total amount of carbon stored by the DENR programs (133 Tg C).  Rate of carbon sequestered per year by CBFM is 2.6 Tg/ha/year. 

Total biomass (above and below ground) of the secondary forests in Mt. Makiling Forest Reserve was 576 Mg/ha with an annual tree biomass accumulation of 12 Mg/ha/yr.  At an average of 43% carbon content of biomass, the total carbon stocks was 418 Mg C/ha including soil organic carbon (SOC) which comprised about 40% of the total.  Carbon sequestration rates were estimated at 5 Mg C/ha/yr.

Multistorey system on the other hand had a mean biomass of 258 Mg carbon/ha and a carbon density of 185 Mg carbon/ha/yr.  Carbon was stored in the various pools in the following order of magnitude: soil > tree biomass (above ground)> necromass>understorey vegetation > roots.  The Gliricidia hedgerow had a biomass density of 3.8 Mg C/ha.  Total carbon density was 93 Mg C/ha of which 92 Mg C/ha was in the soil.

The main usefulness of the results of the study is in the conduct of Greenhouse Gas Inventory (GHG).  Carbon storage and sequestration rates of secondary forests and agroforestry systems will help reduce error in national estimates as mandated by the UN Framework Convention on Climate Change (UNFCCC).  In addition, the data from this study will be beneficial in quantifying carbon benefits of Clean Development Mechanism (CDM) projects involving Philippine forests.  

Carbon Dioxide (CO2) Absorption and Sequestration in the PNOC-Leyte Geothermal Reservation

Climate change or global warming due to the rise in greenhouse gases, primarily CO2, is one of the most urgent environmental problems of our day.

Because of their lower CO2 emission, the PNOC-EDC received a GEF grant to develop 601 MWe geothermal power plants in Leyte.  As part of the grant privisions, the PNOC must determine the C sequestration of the study area.  Thus, the main objective of the study was to estimate quantitatively the absorption index and the amount of C sequestered by the different vegetative cover in the study area in Leyte.

Five major land cover were identified and studied: natural forests, tree plantations, brushlands, agricultural farms and grasslands.  in each of these cover, monitoring plots were established to determine current C stored as well as C sequestration for one year.  On the basis of the data gathered, the C storage and sequestration of the entire reserve was calculated.  The study was conducted from March 1998 to June 1999.

In terms of C storage capacity, the various vegetative cover ranked as follows: natural forests (392.96 tC/ha) > tree plantations (253.89 tC/ha) > coconut (196.75 tC/ha) > brushlands (186.31 tC/ha) > banana/abaca (114.72 tC/ha) > grasslands (10.09 tC/ha/yr) > coconut (4.78 tC/ha/yr) > brushland (4.29 tC/yr) natural forest (0.92 tC/ha/yr).

For the 20,438 ha watersheds of the study area, the total C storage is 3.84 Mt C (14.10 Mt CO2) while C sequestration based on biomass change was 47.35 Kt C (173.77 Kt CO2).  Relative to power plant emission, the C stored in the reserve is equivalent to more than 22 years of CO2 emission.  Annual C sequestration is 27% of CO2 emission per year.

For the next 25 years, two scenarios were projected.  Under Scenario I ("Business as usual"), the reserve will be able to store and sequester, more than 32 years of CO2, emission from the power plants.  Under Scenario II (Accelerated Reforestation), the reserve can store and sequester about 34 years of CO2 emission which corresponds to the life of the project.

In terms of cost, the PNOC is spending P1.22 per t CO2 (P4.46 per tC) for every year of C storage and sequestration.  For 25 years, the total cost is P30.40 per tCO2 (P111.58/US$2.94 per tC) which is comparable to the cost of C offset in other tropical countries.

Carbon Stocks Assessment of Philippine Tropical Forest Ecosystems

Climate change or global warming is one of the most urgent environmental issues of our generation.  Land-use change and forestry (LUCF) activities are important contributors to the problem as well as its solution.  A vital information necessary in assessing the role of LUCF in climate change is an accurate estimate of carbon (C) stocks and rate of C sequestration of forest land uses.  The paper reviews the various methods available in obtaining an accurate estimate of C stocks and sequestration based on the experiences of the Environmental Forestry Programme (ENFOR).  In addition, the results of the APN supported field study on C stocks assessment is presented.

There are two general methods: estimating C stocks based on existing information and estimating C stocks based on field data gathering.  The indirect estimation of C stocks in the forest is premised on the fact that about half of biomass is C.  There are already existing "default" values for all the major ecosystems in the tropics.  The paper provides an example of how these can be used to estimate national C storage and sequestration in LUCF.  Field measurements of C involve destructive sampling or combining destructive sampling with the use of allometric equations for large trees.  ENFOR has developed and/or adopted methods for the following forest land uses: natural tropical forests, tree plantations, agroforestry, brushlands, and grasslands.  The following C pools have been monitored: aboveground biomass (trees, understorey vegetation, herbaceous plants), litter/necromass, belowground biomass (roots) and soil organic C.

The field study showed that the various forest ecosystems have the following amount of C stocks: old-growth forests > secondary forests > mahogany plantation > dipterocarp plantation > tree legumes plantation > mossy forest > mangrove forest > A. auriculiformis plantation > pine forest > teak plantation.

Finally, important issues and concerns that need to be addressed in relation to the Clean Development Mechanism (CDM) of the Kyoto Protocol are discussed.

Carbon Stocks Assessment of a Selectively Logged Dipterocarp Forest and Wood Processing Mill in the Philippines

Tropical forests have an important role in climate change as sources and sinks of carbon. Forestry activities such as selective logging and wood processing affect the carbon balance of terrestrial ecosystems. The objective of this study was to determine the effects of selective logging on carbon stocks of a Dipterocarp forest in the Philippines. In addition, the total carbon budget of the concession including the wood processing mill was analyzed. Biomass carbon was determined from data from fixed plots using a 1-21 years after logging.  

Unlogged forests had mean C stocks of 298 MgC/ha, of which 34% was in soil organic carbon. For above-ground biomass carbon, about 98% was in trees ³ 19.5 cm dbh. After logging, above-ground carbon stocks declined by about 50% (100 MgC/ha). In between the cutting cycle of 35 years, logged forests sequester carbon at the rate of about 3 MgC/ha/yr. Before the next harvest, forests recovered about 70% of the original biomass carbon. SOC showed no correlation with the number of years after logging. About 40% of woody above ground biomass carbon was converted to lumber and veneer/plywood or sold as logs. Most of the remaining 60% was emitted to the atmosphere as CO₂ through burning as fuel and decay.

Carbon Stock Assessment of Secondary Forest and Tree Plantations in the Philippines: Towards Improving the GHG Inventory

This study was conducted in Subic Bay Freeport Zone in Subic, Zambales, Mt. Makiling Forest Reserve (MFR) in Laguna, Quezon National Park in Atimonan, Quezon, and Southern Luzon Polytechnic College Forest Reserve (SLPCFR) in Lucban, Quezon.  In general, the study was designed to generate biomass and carbon density data that will be useful in refining the national GHG inventory in the LULUCF sector.  Specifically, it aimed to: (a) establish monitoring plots for the collection of data on annual biomass increment of secondary forest ecosystems and tree plantations of various ages and at different sites (agroclimatic and soil types) in the Philippines; (b) collect data on forest above-ground biomass of the mentioned secondary forests and tree plantations in the Philippines; and (c) collect site-specific or species-specific wood density data from literature and monitoring plots. 

Results of the study showed that combined biomass and necromass density for all study sites have a range of 154-727 Mg/ha.  In terms of biomass alone, the study sites have biomass density ranging from 133-569 Mg/ha.  About 84.10% of the biomass are found in large trees.  This is consistent with the general pattern that ³ 96% of forest biomass are found in trees ³ 10 cm dbh.   

Understorey biomass was highest in the mossy forest of Mt. Banahaw but low in the lowland forests.  This is more likely due to the more open canopy in higher elevation so that there are more understorey vegetation.  

Second largest component was the coarse woody debris (CWD).  This comprises about 148 Mg/ha.  Coarse litter on the other hand, ranges from 5.15 to 7.37 Mg/ha while fine litter ranged from 0.68 to 3.07.   

Carbon analysis of the plant tissues revealed that the mean carbon content is 45.07%.  Between plant types and plant parts, there is slight variation in carbon content.  Quezon National Park and the Makiling Forest reserve have the highest carbon density while Lucban had the lowest. 

Soil organic carbon ranges from 1.47% to 4.35% while bulk density ranges from 0.42 in Lucban to 1.1 in MFR.  Mean SOC density ranges from 45.19 to 116.05 MgC/ha. 

New data generated from this study was used to recalculate GHG uptake/emissions. Compared with the GHG inventory done in 1994 where the LUCF sector has an almost negligible net CO₂ absorption (0.126 Mt CO₂ equivalent), it can be observed that in this inventory LUCF became a significant sink of carbon (127 Mt CO₂ equivalent).  This result indicates that forest lands may be able to sequester the equivalent amount of CO₂ emitted per year which is equivalent to 101 Mt CO₂/year.  

Based on the results, it can be concluded that second growth forests when left undisturbed for a number of years may yield almost the same amount of biomass as that of old growth forests.  Thus, a more careful method of logging in this type of forests must be pursued to avoid large carbon emission.

Tropical forests have an important role in climate change as sources and sinks of carbon.  Forestry activities such as selective logging and wood processing affect the carbon balance of terrestrial ecosystems.  The objective of this study was to determine the effects of selective terrestrial ecosystems.  The objective of this study was to determine the effects of selective logging on carbon stocks of a Diperocarp forest in the Philippines.  In addition, the total carbon budget of the concession including the wood processing mill was analyzed.  Biomass carbon was determined from fixed plots using a chronosequence of 1-21 years after logging.

Unlogged forests had mean C stocks of 298 MgC/ha, of which34% was in soil organic carbon.  For above-ground biomass carbon, about 98% was in trees >= 19.5 cm dbh.  After logging, above-ground carbon stocks declined by about 50% (100 MgC.ha).  In between the cutting cycle of 35 years, logged forests sequester carbon at the rate of about 3 MgC/ha/yr.  Before the next harvest, forests recovered about 70% of the original biomass carbon.  SOC showed no correlation with the number of years after logging.  About 40% of woody above ground biomass carbon was converted to lumber and veneer/plywood or sold as logs.  Most of the remaining 60% was emitted to the atmosphere as CO2 through burning as fuel and decay.

Guidelines for Watershed Management and Development in the Philippines

The need to properly manage our watersheds are more pressing now than it has ever been.  The increasing demand for water, timber, land, and other valuable watershed resources alongside the worsening negative impacts of local and global phenomena such as the El Niño, La Niña, and global warming have brought the necessity for sustainable watershed management to a higher level.

Excessive soil erosion and siltation, floods, droughts, shortages of water supply, the diminishing forest cover and declining land productivity are just a few but telling signs of the adverse effects of watershed resource utilization and the ever-changing local and global climate.

Without appropriate interventions, our watersheds which are mostly now in varying degrees of degradation will be in a greater risk of being permanently impaired to deliver many goods and services vital to society.  The task of steering watershed management into the roads of sustainability is daunting but not impossible.  It will take concerted, determined, and deliberate actions not only of the Department of Environment and Natural Resources and Department of Agriculture but of all concerned public and private sectors to attain sustainability of watershed resources.

This project presents the general and specific guidelines for the preparation and implementation of watershed management plans consistent with the current thrusts of the DENR and as embodied in the Philippine Strategy for Improved Watershed Resources Management crafted through the Watershed Management Improvement Component of the Water Resources Development Project.

Development of Water Budget Model(s) on Selected Major Watersheds in the Philippines

This study project aims to test appropriate model(s) for assessing the water budget of watersheds and to have detailed projections on the direction and magnitude of impacts of the said phenomenon on surface water resources of major watersheds in the Philippines.  This is essential in making appropriate actions to mitigate the adverse impacts of El Niño.  In this project, the water budget of the four selected major watersheds in the Philippines namely, Angat watershed, Bayongan watershed, Mananga watershed and Manupali watershed was assessed and evaluated using hydrologic models that are capable of simulating run-off as affected by rainfall and other factors.  These models are BROOK 5 Hydrologic model and WAT-BAL model.  BROOK 5 model is a lumped parameter model that uses physically-based equations in predicting hydrologic processes while WAT-BAL model is designed as integrated water balance model in assessing climate impacts on river basins.

Based on the study, it was found that El Niño is likely associated with a marked decrease in rainfall in some watersheds while in other watersheds, rainfall can remain unaffected.  During La Niña periods, rainfall increases in some watersheds while no change in rainfall was observed in other watersheds.  This could mean that other watersheds may not have been affected seriously by El Niño or it is possible that in other watersheds the sample of El Niño years excluded the years when El Niño was pronounced.  There are watersheds where total rainfall may not change due to El Niño or La Niña but changes in the variability or distribution of rainfall may take place and can have equally damaging if not more damaging impacts than changes in total amount of rainfall.  El Niño generally brings about a reduction in evaporation and run-off.  However, it was found in this study that evaporation and run-off either increase or decrease during La Niña years.  Run-off efficiency either increases or decreases during the El Niño and the La Niña years.

Based on the findings. Most impacts of El Niño and La Niña on various hydrologic processes are nonlinear.  The assessment of the directions and magnitude of impacts could possibly be enhanced by integrating the influences of other factors that affect the different hydrologic processes.

Caliraya-Lumot Watershed Land-Use Development Plan

The energy crisis that has hit almost all countries of the world has sent the Philippine government scampering to search for indigenous sources of energy to cushion the impacts of the spiraling cost of fuel oil.  The National Power Corporation (NPC) responded by constructing additional generating plants - hydroelectric, geothermal, thermal and coal-fired plants.  The NPC's Power Development Program directly addresses the country's escalating energy requirements and reduces to a minimum the dependence on oil imports.  The Kalayaan Pumped Storage Power Plant (KPSPP) is a realization of this important goal.

A compilation of relevant policies were formulated which will serve as a 25-year land-use plan for the Caliraya-Lumot Watershed.  This will the guide for future decision and action in the watershed.