沙漠研究 22-1, 69 -72 (2012 )"ICAL 1 / DT X"

Journal of Arid Land Studies－Refereed Paper－Estimation of Carbon Sequestration Potential of Arid Land Afforestation
Using Satellite Image Analysis and Ground Truth
Hideki SUGANUMA*1), Toshifumi ITO1), Hiroyuki TANOUCHI2), Yasuyuki EGASHIRA3),
Katsuhiko KUROSAWA1) and Toshinori KOJIMA1), 4)
Abstract: As a countermeasure to the greenhouse effect, afforestation in arid areas has been proposed and tested in an arid area ofWestern Australia. According to the CDM/JI guidelines set by UNFCCC, the sequestered carbon amount accountable as carbon
credit was estimated in this study. First, the sequestered carbon amount by planted trees was measured by repeated tree censuses.
Second, the land use type (vegetation type) was estimated using LANDSAT images by statistical methods. Third, by repeated tree
censuses, the Mean Annual Increment (MAI) at natural vegetation monitoring sites of each vegetation type was estimated, and thisMAI data were used as the baseline of each type of vegetation. Fourth, the present biomass distribution was estimated using theSAVI index calculated from LANDSAT image, since the original vegetation must be clear-cut before afforestation sites wereestablished. At last, the sequestered carbon amount accountable as carbon credit was estimated inside 45×50 km area, and this result
revealed that carbon mitigation amount by this arid land afforestation was equivalent to 0.88% of Japanese CO2 emission in 2008.
Key Words: Acacia aneura, CDM/JI, Eucalyptus camaldulensis, LANDSAT, Western Australia.

1. Introduction
As countermeasures against the greenhouse effect, twotypes of strategies can be used. One is emission reduction,and the other is Greenhouse Gas (GHG) capture. Typicalexamples of emission reduction are improving energy-saving
technology and renewable energy development, and those of
GHG capture are Carbon Capture and Storage (CCS) andafforestation. Afforestation and forest management wereconsidered as effective countermeasures against global
warming, thus many attempts were tested in the literatures(Moor et al., 2001; Grünzweig et al., 2003; Yamada et al.,
2003; Ravindranath et al., 2006; Roxburgh et al., 2006).
To evaluate the amout of effective carbon sequestered fromatmosphere by afforestation or reforestation activity, CleanDevelopment Mechanism / Joint Implementation (CDM/JI)
framework was decided by United Nations Framework
Convention on Climate Change (UNFCCC, 2006).
According to UNFCCC (2006), accountable carbon amount(carbon credit) by afforestation, which is effective for carbon
mitigation, was roughly described as follows.
Theaccountable carbon amount should be calculated as the “actualnet GHG removals by sinks” minus the “baseline net GHG
removals by sinks” minus “leakage” in five carbon pools(above-ground biomass, below-ground biomass, litter, deadwood and soil organic carbon). Of these five carbon pools,

the above-ground biomass and below-ground biomass willchange rapidly after afforestation.
In this study, as a first step, accountable carbon amount in
two types of carbon pools (above-ground biomass andbelow-ground biomass) by arid land afforestation wasestimated using satellite image analysis and ground truth.
The afforestation test site was established in 1999 and has beenmonitored at regular intervals (Yamada et al., 2003).

2. Materials and Methods
2.1. Research area
The research area of this study is Sturt Meadows (28°40'S,120°58'E) near Leonora, located about 600 km from Perth, theprovincial capital of Western Australia. The range of ourresearch area is approximately 45 km from east to west and 50
km from north to south. This research area belongs to theMurchison region of Interim Biogeographic Regionalization ofAustralia (IBRA) Version 5.1 (Environment Australia, 2000).
The mean annual rainfall is about 200 mm in this area, thus
categorized as an arid area (Yasuda et al., 2001). The
Murchison environment was described as having Mulga(Acacia aneura) low woodlands, often rich in ephemerals, onoutcrop hardpan wash plains and fine-textured quaternary
alluvial and eluvial surfaces mantling granitic and greenstone
strata (Environment Australia, 2000). From the vegetation
classification results (Suganuma et al., 2010), this research area

* Corresponding Author: h.suganuma.yf19.frx99@gmail.com
3-3-1, Kichijoji-kitamachi, Musashino, Tokyo, 180-8633, Japan
1) Department of Materials and Life Science, Faculty of Science and Technologies, Seikei University3) Graduate School of Engineering Science, Osaka University, Japan

2) Forestry and Forest Product Research Institute, Japan

4) School of Natural Sciences, Edith Cowan University, Australiaconsisted of 5 types of vegetation, i.e., Acacia forest andwoodland, Eucalyptus forest and woodland, bare ground,
halophyte, and hydrosol (salt lake).
Afforestation test site named site C, which is the largest site,
consists of 12 sub-plots, and each sub-plot adopted
hardpan-blasting afforestation method (Yamada et al., 2003;
Kojima and Egashira, 2011) and water-harvesting method.
Many kinds of trees were planted in each sub-plot with 7 × 7 m
spacing, and planted tree species were Acacia aneura, A.
tetragonophylla, Casuarina obesa, Eucalyptus camaldulensis,
E. salubris, E. torquata, E. lesouefii and E. striclandii. The
dominant tree species was E. camaldulensis.
2.2. Estimation of accountable carbon amount
According to the assessment method by UNFCCC (2006),
the accountable carbon amount resulted from afforestation inthis research area was calculated using following equation.
AC = [{(MAIA-MAIB)×N-B}×0.5×(44/12)-E]×Area (1)Where AC is accountable carbon amount (Mg-CO2); MAIA is
Mean Annual Increment (MAI) in afforestation sites (Mg ha-1year-1); MAIB is MAI in natural vegetation (Mg ha-1 year-1); Nis afforestation duration (year); B is biomass loss amount byclear-cut of natural vegetation (Mg ha-1); 0.5 is carbon
conversion factor from biomass; 44/12 is CO2 conversion
factor from carbon; Area is afforestation applicable area (ha); E
is CO2 emission of afforestaion site creation (Mg-CO2 ha-1).
MAIA was estimated from repeated tree census from June
2000 to August 2009 using allometric equations reported by
Suganuma et al. (2006). Among tree species planted inside
Site C, some trees grew poor or dead but some trees grew well,thus MAIA should become low value, thus we calculated
another MAIA value assuming that this afforestation site
consisted of single species which has the highest growth ratewith the highest survival ratio.
MAIB in each vegetation was estimated from tree census
data from 1997 to 2007 using allometric equations reported by
Suganuma et al. (2006). Vegetation (Acacia woodland, bareground and vegetation transition area) was classified by
Suganuma et al. (2010).
N was set as 30 years which was determined as long term
afforestation period by UNFCCC (2006). In addition, 30years was also set from maximum biomass data of Eucalyptus
forest in this research area (150 Mg ha-1) and from MAI data ofEucalyptus camaldulensis trees (5 Mg ha-1 y-1).
B was estimated using satellite image of LANDSAT TM
with vegetation index. Detailed method was described inSuganuma et al. (2010).
E was estimated from Life Cycle Assessment (LCA) as
shown in Tahara et al. (2009) and Kojima and Egashira (2011).
Total energy amount of producing materials and total consumed

liquid fuel by afforestation site creation was accounted, and thenE was estimated as 7.16 Mg-CO2 ha-1.
Area, represents afforestation applicable area, wasestimated using equation (1) and satellite image data.
Afforestation applicable area was calculated from selected
locations where sequestered carbon amount by afforestation
overcame baseline data plus emitted carbon amount by site
creation and clear-cut biomass of original vegetation.
However, since afforestation site named site C adopted
water-harvesting technology, the actual afforestation area was1/4 of calculated area.
Using equation (1), the estimated accountable carbon
amount inside this research area was compared with the total
emitted carbon amount inside Japan in 2008 (Ministry ofEnvironment of Japan, press release).
In addition, leakage was estimated as 0 in this researchbecause the main land use type was extensive grazing and only
25% of area was used for afforestation. Furthermore, asafforestation activities will continue with a phased approach,original grazing activities remain undisturbed. Therefore,leakage of this arid land afforestation was assumed as 0.

3. Results and Discussion
Carbon sequestration rate of site C was 2.96 Mg-CO2 ha-1
year-1 (S.E.: 0.30). Tree species with the fastest growth ratewith the highest survival ratio was Eucalyptus camaldulensis,
and its carbon sequestration rate was 8.51 Mg-CO2 ha-1 year-1.
Estimated carbon sequestration rate of natural vegetation(baseline) was 0.19 Mg-CO2 ha-1 year-1 in bareground, 1.95
Mg-CO2 ha-1 year-1 in vegetation transition area and 0.20
Mg-CO2 ha-1 y-1 in Acacia woodland. Carbon emission ofafforestation site creation was estimated by LCA as 7.16
Mg-CO2 ha-1 (Tahara et al., 2009; Kojima and Egashira, 2011).
By introducing above estimated values into equation (1)except afforestation applicable area, sequestered CO2 amountand its allocation (Total sequestered carbon amount,accountable carbon amount, baseline, carbon loss amount byclear-cut of natural vegetation, carbon emission amount byafforestation site creation) is shown on Figure 1. The X axisof Figure 1 shows the biomass amount in natural vegetation
before afforestation (Mg ha-1), and the Y axis of Figure 1
shows the total amount of sequestered carbon amount insideafforestation area in 30 years and its allocation (Mg-CO2 ha-1).
Figure 1 shows the results when afforestation sites are to becreated in bare ground, vegetation transition area and Acacia
woodland. From these results, accountable carbon amount invegetation transition area which had high baseline data wasquite low, i.e. carbon sequestration efficiency was poor. On
the other hand, the efficiency was good in bare ground andSequestrated carbon amount [Mg-CO2 ]Sequestrated carbon amount [Mg-CO2 ha-1]

Afforestation in bare ground100

Accountable carbon
Carbon loss by clear-cut
Baseline
Carbon emission by sitecreation

500

Afforestation in bare ground

500,000

Accountable carbon
Carbon loss by clear-cut
Baseline
Carbon emission by site
creation

400,000

300,000

200,000

100,000

05010152025303540450510100

Afforestation in vegetation transition area

502025303540

45

500,000

Afforestation in vegetation transition area

400,000

300,000

200,000

100,000

00051015200255Stand Biomass [Mg ha-1]

Afforestation in Acacia woodland

100

Sequestrated carbon amount [Mg-CO2]

Sequestrated carbon amount [Mg-CO2 ha-1]

15Stand Biomass [Mg ha- 1]
Sequestrated carbon amount [Mg-CO2]

Sequestrated carbon amount [Mg-CO2 ha-1]

Stand Biomass [Mg ha-1]

50101520
Stand Biomass [Mg ha -1 ]25Afforestation in Acacia woodland

500,000

400,000

300,000

200,000

100,000

00051015202530354045

Stand Biomass [Mg ha-1]

Fig. 1. Estimation results of sequestered CO2 amount per hectare
and its allocation by arid land afforestation

Acacia woodland. However, in all original vegetation type,the proportion of carbon loss by afforestation site creation wasquite high. This carbon loss means that lot’s of trees are cut
and disposed in vain for afforestation site creation. Thus, asmentioned in Tahara et al. (2009), these biomass should beefficiently utilized as another carbon mitigation activity such asfuel production and electric generation. Therefore, this typeof arid land afforestation must be carried out combined withanother carbon mitigation activity using woody biomass.
By using equation (1) including afforestation applicablearea, total sequestered carbon amount inside research area wasestimated in each original vegetation on Figure 2. From thisresult, afforestation in bare ground earned large accountablecarbon amount (964,000 Mg-CO2). Since distribution area
was not so large, total accountable carbon amount in Acacia

051015 20 25 30 35
Stand Biomass [Mg ha- 1]

4045Fig. 2. Estimation results of total sequestered CO2 amount and its
allocation by arid land afforestation.

woodland was relatively low (428,000 Mg-CO2), but not
negligible amount. That was because most of the Acacia
woodland originally had a certain amount of carbon as woody
biomass. On the other hand, the accountable carbon amountper hectare in vegetation transition area was very small but
nearly similar accountable carbon amount to that of Acacia
woodland was earned by afforestation because of its large
distribution area (481,000 Mg-CO2). Thus, even the carbon
sequestration efficiency was low in vegetation transition area,afforestation in this area was not also negligible, either. From
the results on Figures 1 and 2, afforestation in this research area
should be carried out primarily in bare ground followed by
Acacia woodland and vegetation transition area, in that order.
Assuming that all the afforestation applicable area can beused for afforestation, 44,000 ha of area in 230,000 ha researcharea will be used as afforestation site, resulted in 1.96×106
Mg-CO2 of carbon will be sequestered in 30 years. Thissequestered carbon amount corresponds to 0.16% of CO2
emission amount in Japan in 2008 (1.21×109 Mg-CO2).
Considering this sequestered CO2 amount, the contribution ofarid land afforestation in this research area is negligible to CO2
reduction of Japan. Therefore, other improvements should benecessary to maximize carbon credit earning.
One of the considered improvement methods was to create
afforestation site consisting of mono-specific trees of
Eucalyptus camaldulensis which had the fastest growth ratewith the highest survival ratio. By trial calculation, estimatedvalues of sequestered CO2 amount per hectare and total
sequestered CO2 amount of E. camaldulensis mono -specificafforestation overcame those of above mentioned data. In
particular, 54,000 ha of area in 230,000 ha research area will be
used as afforestation site, and then 1.07×107 Mg-CO2 of carbon
will be sequestered in 30 years. This sequestered carbon
amount corresponds to 0.88% of CO2 emission amount inJapan in 2008. Therefore, not so huge amount of CO2 will besequestered in restricted area. To fulfill the aim of Japan
which is 25% reduction of its CO2 emission, moreimprovement or other carbon mitigation activities should be
carried out in the future.

4. Conclusion
This study shows that the total sequestered carbon amountby arid land afforestation corresponds to 0.16% or 0.88% of CO2emission amount in Japan in 2008, depending on type ofafforestation. However, these results revealed that sequestered
CO2 amount was not enough for carbon mitigation in Japan.
To acquire enough carbon mitigation amount by afforestation,
more improvements and other methods must be developed infuture studies.
Acknowledgement
This work was conducted under the support of the Mitsui& Co., Ltd. Environment Fund, Grant-in-Aid for Scientific
Research (22254002) of Japan Society for the Promotion ofScience and the Global Environment Research Fund of The
Ministry of Environment of Japan (GHG-SSCP project).

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