Recent Evaluation of Rising Temperature and Oil Palm Extension to Higher Elevation in North Sumatra(evaluasi Terkini Kenaikan Suhu Dan Perluasan Tanaman Kelapa Sawit Ke Dataran Tinggi Di Sumatera Utara)

Implication of climate change on oil palm plantation in Indonesia generally not much known, which could be a threat that needs attention, or maybe an opportunity. Climate change could cause the rainy season more wet and dry season drier. At other side, climate change also caused the temperature increased, which could make an extension of oil palm plantation in higher altitude become possible. Nowadays, total area of oil palm plantation in high altitude in north Sumatera was 4.725 hectares. This paper describes recent evaluation of climate change in North Sumatera province and its relation with oil palm extension and the response of oil palm productivity in higher altitude.


INTRODUCTION
Science has proved that global temperature constantly increased after industry era. Global temperature has increased 0,6 o C for the last 100 years (Boer, 2001). It was estimated that if there is no effort to eliminate the increasing temperature, there will be a high CO2 concentration at the atmosphere which made the temperature increase until 4,5 o C for the next 100 years and this will cause global climate change.
Climate change was mainly forced by human activity, especially the use of fossil fuel and the change of land use. Those activities will produce gases which increased by the time at the atmosphere. The main gases are carbon dioxide (CO 2 ), methane (CH 4 ), and nitrous dioxide (N 2 O). These gases called green house gases which has character like glass that forward the short-wave radiation or sunlight, absorb and reflect the long-wave radiation or back-radiation from earth which is hot that caused earth temperature increased. Climate change caused the atmosphere condition change too, especially temperature and rain distribution which made wide implication to several human life sector at a long period of time.
Nowadays, climate change implications in Indonesia are the higher air temperature, drier drought at dry season, and higher floods intensity at rainy season. These are caused by the ability of the green house gases (GHG) emissions which accelerate radiation transmission from the sun to earth and become barrier for some radiation that leave the earth.
When the GHG concentration increased, radiation from the earth will obstructed that made earth temperature increased. The best estimation of temperature increase at this 21 st century is from General Circulation Models (GCMs), which is 2.5 -5.5 0 C follow with the increase of hydrology circulation rate equal to 5 -15 %, or as the effect of global climate change in Indonesia, made the rainfall increase especially at rainy season equal to 15 % for every 1 0 C temperature increase (IPCC, 1996).
It was estimated that the climate change has an important implication and serious threats, such as decreasing agriculture farm, decreasing plant productivity, changing forest use and function, decreasing water sources quality and quantity, increasing sea level which cause many coastal area sank and coastal area function change, and increasing certain disease like dengue fever.
Implication of climate change on oil palm plantation in Indonesia generally not much known, it could be a threat that need attention or an opportunity for agriculture development. When the climate change happened, it would made some land that formerly unsuitable for oil palm became suitable, or on the contrary. At one side, climate change that caused the rainy season more wet and the dry season drier can decrease oil palm productivity. At another side, climate change that caused the temperature increase, could made an extension of oil palm plantation in higher altitude (>600 meter above sea level (m asl) become possible.
This paper describes recent evaluation of climate change in North Sumatera province and its relation with oil palm extension and the response of oil palm productivity in higher altitude.

Climate Change in North Sumatra Province
The climate change and global warming has been proven happened in North Sumatra Province, even in Indonesia. The phenomenon like the long and often drought, and also an often flood that caused by rainfall above normal. Indonesian Meteorological, Climatologically, and  Based on perception result from several BMKG station in North Sumatra Province, Hutapea and Wiyoso (2003) explained that beside the tend of air temperature increase, there is also a tend of rainfall increase especially at rainy season. The temperature trend in North Sumatra generally indicate a significant increase which are 0.5 -1 0 C for 30 years (period 1974 -2002). This condition will cause the increase of air ability to intercept water vapor, which made the rainfall tend to increase and fluctuate during rainy season. This condition also cause the rainy season more wet and dry season more dry, that would make an increase of flood and dryness threat ( Figure 1).
Despitefully on rainy season, rainfall became higher and often cause flood at several places.
Other implication of the climate change was the change of cultivation system which made farmer adapted their cultivation due to that change. This change also could affect the strategy problem on maintaining food safety, because there is always threat of dryness and flood.
By the temperature increased, possibility that some of ice at pole would melt which caused the increase of sea level, so that the agriculture, resident settlement, and ecosystem around the coast will be threatened. The increase of sea level also could forced the water go forward to continent. The 10 cm increase of sea level would force the water as far as 1 km to the higher continent.

Extension of Oil Palm Plantation in Higher Altitude
Formerly, oil palm was not suitable being cultivated at higher altitude. Based on report analyze (Abraham, 1991 andAdiwiganda et al., 1999), the limited factor on cultivating oil palm at higher altitude were the annual minimum air temperature was < 18 0 C, sunshine intensity was ≤ 4 hours/day, and annual rainfall was > 2500 mm/year. Meanwhile, the main factor was the annual minimum air temperature < 18 0 C, due to minimum temperature at that altitude was < 18 0 C. This would causes oil palm growth get constrain because of oil palm metabolism and inflorescences process were disturbed which usually called "low air temperature stress". Effect of the low air temperature stress could analogue with "drought stress" such as (i) increase of abortion, (ii) failed or rotten bunch, (iii) fluctuated and low productivity, and (iv) long inflorescences (8 -9 months).
Prior study at higher altitude in North Sumatra proves that climate change was happened at North Sumatra as an impact of global warming in higher altitude (Table 1, Figure 2, 3, and 4). The study showed that during the last 30 years, there was an annual mean air temperature increased between 0.31 -0.47 0 C per 10 years, annual minimum air temperature increased between 0.25 -0.65 0 C per 10 years, and annual maximum air temperature increased between 0.20 -0.33 0 C per 10 years. All the air temperature parameters tend to increase, also followed by the increase of sunshine and rainfall parameter, but tend to not consistence ( Table 2).
Extension of oil palm plantation in higher altitude (> 600 m asl) is possible through three approaches, i.e. physical environmental factor, plant material genetic factor, and technical cultivation. The approach of physical environmental factor (soil and climate) was using recent superior plant material due to oil palm grow condition, which is the main limited factor in higher altitude is a minimum air temperature that < 18 0 C. The approach of plant material genetic factor use the cold tolerant plant material or altitude adapted oil palm hybrid (Blaak and Sterling, 1996;Chapman, Escobar and Griffee, 2003;Alvarado and Sterling, 2005). Meanwhile the technical cultivation approach due to an adjustment of oil palm technical cultivation in higher altitude like plant spacing arrangement that between 110 -120 palm/ha.
The increase of annual minimum air temperature as  18 0 C at North Sumatra after 1990 at 850 m asl has an implication to the extension of oil palm plantation in higher altitude (600 -850 m asl) becomes possible. Therefore, based on physical environmental factor, it was possible to extend oil palm plantation into higher altitude until 850 m asl.
Oil palm need growth space which could guarantees the availability of CO2, water, nutrient, and sunshine for oil palm growth. It was assumed that oil palm that growth in higher altitude will compete to have more sunshine, so that it will have greater height growth rather than oil palm that growth in lower altitude (Table 3). Productivity of D x P Yangambi (IOPRI plant material) in higher altitude tend to be lower than standard productivity of marginal land at 0-600 m asl ( Figure 5 and 6). Some bunch quality components of 9 years old oil palm showed quite similar in term of mesocarp to fruit (83.63-84.46%), oil to bunch (31.34-31.67%), and oil extraction ratio (26.79-27.08%) compared to those of low altitude (Figure 7). Nowadays, total area of oil palm plantation in high altitude in North Sumatra was 4.725 hectares, increased from 443 hectares in 1996 (Table 4). Most likely this condition becomes an important consideration to develop oil palm plantation at high altitude in other provinces.