Eco-physiological indicators (Table 1) show that oil palm plantations and forests have similar characteristics. Seen from the water cycle function, such as evapotranspiration, groundwater reserves, rainfall catchment and water storing, the capacity of tropical forests is similar to that of oil palm. The strength of the tropical forest lies in its capacity to store carbon (total biomass) which is four times as high as the stock of carbon in the oil palm plantation. This high level of carbon storage reflects the bio-diversity of the tropical forest. This is why the function of the forest is the preservation of biodiversity and storage of carbon.
Table 1 Comparison of Eco-Physiology of Oil Palm and Tropical Forests
|Indicator||Tropical Forests||Oil Palm Plantations|
|Gross assimilation (Tonnes CO2/ha/Year)||163.5||161.0|
|Total Respiration (Tonnes CO2/ha/Year)||121.1||96.5|
|Net Assimilation (Tonnes CO2/ha/Year)||42.4||64.5|
|Efficiency of Photosynthesis (%)||1.73||3.18|
|The Conversion Efficiency of Radiation (g/mj)||0.86||1.68|
|Total Biomass (Tonnes/ha)||431||100|
|Incremental Biomass (Tonnes/ha/Year)||5.8||8.3|
|Productivity Dry Matter (Tonnes/ha/Year)||25.7||36.5|
|Production of Oxygen (O2) (Tonnes O2/ha/Year)||7.09||18.70|
|Groundwater Reserves, 0to 200 cm depth (mm)||59-727||75-739|
|Rainfall to the Soil Surface (%)||85||87|
|Infiltration Rate of Solum 0-40 cm (ml/cm3/minute)||30-90||10-30|
|Air Humidity (%)||90-93||85-90|
Source: Henson (1999)
However, the rate of absorption of CO2 from the atmosphere of the earth by oil palm plantations is in fact higher than that of the forest. Various indicators of absorption of CO2 from the atmosphere, such as efficiency of photosynthesis, efficiency of conversion of solar energy, net assimilation, and production of oxygen, show that oil palm plantations in this respect are superior to forest. As a result, the incremental biomass and the annual productivity of dry substance of oil palm plantations are higher than those produced by the forests.
With the strength of their ecological functions, oil palm plantations and forests benefit the sustainability of the global ecosystem. Forests function as the preserver of biodiversity and stock of carbon, while oil palm absorbs CO2, stabilizing the concentration of GHG in the atmosphere. Thus, forest and oil palm are two sub-ecosystems that both contribute to preserving the global ecosystem.
Global warming is a phenomenon of increasing temperature of the atmosphere resulting in a greenhouse effect. The greenhouse effect is caused by the increase in concentration of greenhouse gases (GHG) beyond the natural concentration, so that the radiation of the sun is increasingly trapped in the atmosphere (IPCC, 1991, 2001, 2007; World Bank, 2010). Greenhouse gases are among others Carbon Dioxide (CO2), Methane (CH4), Nitrogen Oxide (NO2), and man-made gases. The concentration of CO2, which is the largest component of greenhouse gases in the atmosphere, has increased from 280 ppmv in around 1800 to 353 ppmv in the 1990s (IPCC, 1991), and to 379 ppmv in 2005 (IEA, 2011).
The emission of CO2 is caused by human activities, namely energy (56 percent), agriculture (13.8 percent), industry (14.7 percent) and land use change (12.2 percent), and waste (3.2 percent) (IEA, 2011). The top ten contributors to emissions are: China, USA, India, Russia, Japan, Germany, Iran, Canada, South Korea and England. These countries contributed 65 percent of the total global CO2 emissions in 2010. Indonesia’s share in total global emissions of CO2 is only 1.3 % (IEA, 2011).
Agriculture is also a source of global CO2 emissions and CO2 equivalents, from fertilization, NO2; from livestock, CH4, and from land use change, CO2 and others. The global top six emitters (FAPRI, 2012) are China, Brazil, India, USA, the European Union and Argentine with a contribution of 70 percent of total global agricultural GHG emission. The contribution of Indonesia was only about 2.7 percent.
Naturally, plants growth constitutes an essential part of the recycling of carbon dioxide (CO2), oxygen (O2) and water (H2O) in the ecosystem of the planet. In other words agriculture has an ecological function. The ecological function of agriculture is part of the multi-functionality of agriculture that has always existed (OECD, 2001; Huylenbrock, et al,2007).
Oil Palm is the ideal plant for conversion of energy into biomass (Fairhurst and Hardter, 2005). During the process of assimilation, oil palm absorbs carbon dioxide from the atmosphere and releases oxygen into the atmosphere. During respiration, oil palm releases CO2, (photosynthesis/assimilation minus respiration). Oil Palm is a net absorber of CO2 from the atmosphere (Hansen, 1999; Fairhurst and Hardter, 2005).
The net fixation of CO2 from the atmosphere converts into biomass of oil palm. Chan (2002) measured the production of biomass in oil palm plantations (standing biomass) and the amount of bound carbon in the oil palm by age group as given in Table 6.4.
The amount of carbon bound in biomass of tropical forest and oil palm, in circulation and annual increment, are relatively similar. The difference is in the annual increment of carbon fixation. This is higher in oil palm than in tropical forests, because tropical forests are in steady state, which means that respiration and assimilation are equal, while oil palm is growing, so that the assimilation is higher than respiration. In other words, in reabsorbing CO2 from the atmosphere, oil palm plantations are far superior than the tropical forests.
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