Carbon Sequestration Capability Analysis of Urban Green Space Using Geospatial Data

Indonesia is the world’s sixth largest producer of Carbon Dioxide (CO 2 ) emissions. Jakarta is one of the cities in Indonesia with the highest amount of CO 2 emission, due to the growing number of population within the city. Anthropogenic activities in the form of industry, transportation, and housing have become one of the primary sources of CO 2 emission. The emission is an urban natural hazard, and it needs to addressed immediately. Green open space is the fundamental solution to this problem. The presence of urban green space will reduce the amount of CO 2 emission. Unfortunately, the extent of reduction remains unclear, especially in South Jakarta. The study aims to analyze the capability of urban green space in sequestering CO 2 from anthropological aspects such as some population and vehicle in South Jakarta. The sequestration capability of each green open space is measured using the Leaf Area Index generated from remote sensing imagery. The CO 2 emission was calculated from some population and the number of vehicles collected from statistical data and ground measurement, respectively. The result shows that green open space distribution significantly correlated with the CO 2 sequestration (with the value of 0.79). This study shows that the number of urban green space is one of the solutions to reduce CO2 emissions.


Introduction
Global warming is a phenomenon of rising earth temperatures due to the production of Greenhouse Gases (GHG) one of the CO2 [1]. In the 1990s about two-thirds of CO2 emissions came from developed countries, but CO2 emissions come from developing countries such as Indonesia, which is the world's sixth largest emitters [2].
Jakarta is the capital of Indonesia which is one of the urban areas. The city of Jakarta which is the capital makes it a center of government and economic activity [3]. The city of Jakarta is the center of activity to make the city of Jakarta has a large population and amount of vehicles, so they make the amount of carbon dioxide emissions getting risen. Large amounts of carbon dioxide emissions can be absorbed with green open space. Green space is a land that consists mostly of surfaces such as grass, shrubs, and trees [4]. Open space defined as part of an urban area that contributes to its ease, both visually by positively contributing to the urban landscape, or based on public access, so that green open space is a combination of green space and public space [4]. South Jakarta is the largest open green city with the widest area of 398.2197 Ha [5]. Also, South Jakarta has the best green open space regarding its utilization in Jakarta [6].

The Study Area
South Jakarta located at 106 ° 22''42 'East Longitude s.d. 106 ° 58''18 'east, and 5 ° 19''12 South Latitude. The total area by the Decision of the Governor of KDKI No. 1815 of 1989 is 141.37 km 2 or 22.41% of the total area of Jakarta [7].

Green Open Space Distribution
The distribution of green open space can know through the fragmentation index [8] with the equation below: n: the total number of polygons in the sub-district analysis unit The fragmentation index value is between 0 and 1. 0 -0,5: the distribution of green open space tend to gather. 0,6 -1: the distribution of green open space tend to spread.

Vegetation Index
The vegetation index is the greenish vegetation value obtained from the digital signal processing of the brightness value data of several satellite sensor data channels. Vegetation index data obtained from SPOT 6 that have processed Method of vegetation index conducted in this research is using the Leaf Area Index (LAI). LAI defined as the leaf area of each unit of surface area covered by a tree canopy [9]. LAI used through the approach of EVI value. EVI (Enhanced Vegetation Index) is an index developed by MODIS data as an improvement of NDVI. EVI showed by equation [10]: L = 1, C1 = 6, C2 = 7.5, and G (factor gain) = 2.5 The value of EVI obtained is then entered into the LAI equation [11]. Vehicle volume data obtained based on the survey. A survey conducted that is taking ten samples according to the number of sub-districts in South Jakarta. Selection of sample using purposive sampling by determining one street that has traffic using Waze application in each subdistrict at peak hour that is from 06.30 until 08.00 on weekdays. The road samples presented in figure 2.

Carbon dioxide emissions from anthropogenic
Calculation of emissions of carbon dioxide from anthropogenic emissions released by human respiration. The amount of carbon dioxide emitted during the respiratory process is assumed to be the same for every human [13].

Absorption of Carbon Dioxide Emissions
The absorption capacity of carbon dioxide obtained through the equation (Prasetyo, 2002 cited in Rawung, 2015): The absorption of carbon dioxide (ton/year) = CO2 absorption by type of vegetation x vegetation cover area (7)

Residual of Carbon Dioxide Emissions
The residual carbon dioxide emissions obtained from the equation [14]: Residual emissions = Total emissions of CO2absorption of CO2 emissions (8)

Analysis
The analysis used is descriptive analysis and correlation analysis to determine the strength of the relationship between green open space distribution and the absorption of carbon dioxide emissions by vegetation. Correlation analysis used in this research is the Spearman rank.

Green Open Space Distribution
The fragmentation index can know the distribution of green open space in each sub-district of South Jakarta. Fragmentation index in ten sub-districts in South Jakarta has a value less than 0.5 which means green open space tend to gather in each sub-district.

Transportation and Population Data
Transportation data divided into two data, motorcycle and car (see Table 5). Population data divided into ten according to the number of sub-districts in South Jakarta (see Table 6).

Fig.4. Total Emissions in South Jakarta
Total carbon dioxide emissions divided into three levels. The low level is the total value of carbon dioxide emissions from 40.000 tons/year to 60.000 tons/year. The middle class is the total value of carbon dioxide emissions from 61,000 tons/year to 80,000 tons/year. The high level is the total value of carbon dioxide emissions from 81,000 tons/year to 140,000 tons/year.

Absorption of Carbon Dioxide Emissions
The

Residual of Carbon Dioxide Emissions
The highest residual carbon dioxide emissions in Kebayoran Lama Sub-district are 68,674.51 tons/year, and the lowest in Jagakarsa Sub-district is 15,808.43 tons/year. The residual of carbon dioxide emissions divided into three levels. The low level is the value of residual of carbon dioxide emissions from 15,000 tons/year to 30,000 tons/year. The middle class is the value of residual of carbon dioxide emissions from 31,000 tons/year to 50.000 tons/year. The high level is the residual value of carbon dioxide emissions from 51,000 tons/year to 70,000 tons/year.

The Relationship between The Characteristics of Green Open Space Distribution and The Absorption of Carbon Dioxide Emissions
The distribution of green open spaces in South Jakarta tends to gather based on fragmentation index that has a value less than 0.5 in ten sub-districts.

Conclusion
Distribution of green open space in ten districts in South Jakarta tends to cluster with fragmentation index value less than 0.