Temporal Spatial Assessment of Ecosystem Services Comparing 1955 with 2008

－ Case study in Nagoya Area, Japan ―

Abstract: Global environmental problemshave becomeserious issues by the expansion of the scale and scope of human activities. The decrease of forest area has been connectingtothe deterioration of the quality and quantity of benefitsprovided from the forest, what we call, ecosystem services (ESs), which were summarized in the Millennium Ecosystem Assessment in 2005.In Japan, in recent decades, the continuous demand of development was one of bigreasons for the loss of nature, especially for urban forest in large cities, such as Tokyo, Osaka and Nagoya. It leaded to the decrease of potential ES supply. Therefore the effective conservation of forestareain urban regions is important to conservea variety of ESs provided from the forest area.In this study, digital land-use mapsin 10-m grid scale weredeveloped by classifying thesatellite imagesof 2008 and the oldland-use maps of 1955 in the northwest area of Aichi Prefecture, Japan.Then, by utilizingES unit values, the potential provisions of selected ESs were estimated.

INTRODUCTION

In recent decades, environmental problems have become serious issues by the expansion of the scale and scope of human activities. The decrease of forest area has been directly and indirectly connecting to the deterioration of the quality and quantity of benefits provided from the forest, what we call, ecosystem services (ESs), which were summarized in the Millennium Ecosystem Assessment in 2005 (MA, 2005). In Japan, the continuous demand of development caused the loss of nature, especially for urban forest in large cities.The loss and degradation of forest has recognized as one of serious issues in urban area, such as Nagoya, which has around 2.3 million populations as of April 1, 2014 (Nagoya City, 2015).For example, the green area of Nagoya City decreased from 29.8 % to 24.8 % from 1990 through 2005 (Nagoya City, 2011).The loss of forest leadedto the decrease of several ecosystem services (ESs) provided from nature. Therefore, the conservation of forest ecosystem is necessary for sustainable provisions of the ESs.

The purpose of this paper is to study the temporal change of potential provisions of ESs based on the assessment of land-use changes in Nagoya City and its surrounding area, Japan. The comparison of the potential provisions of the ESs in 1955 and 2008 was conducted.

MATERIALS & METHODS

Study area

Nagoya City is located in Aichi Prefecture, Japan (the city hall is located at 35.181°N, 136.906°E) (Figure 1(a) to (c)). The total area of the city is approximately 326 km2.The average annual temperature in 2014 was 16.1°C, and the average precipitation was 1506 mm(Japan Meteorological Agency, 2015). Nagoya is the third largest metropolitan areas in population after Tokyo and Osaka in Japan.

Materials and methods

Referring to Ooba et al (2015) and Kay Khaing Lwin(2015), in this study, digital land-use maps were developed by classifying satellite images and old land-use maps in the northwest area of Aichi Prefecture, Japan. Then, by utilizing ES unit values, the potential provisions of selected ESs were estimated.


Figure1. Maps of the study area, (a) Japan with Aichi Prefecture, (b) Aichi Prefecture outlined in black, the study area outlined in blue and Nagoya City outlined in red, and (c) the study area

The ALOS (Advanced Land Observing Satellite by JAXA) images in 2008 were used for developing a current land-use map in Nagoya region.The first step was to separate forest area from non-forest area by the NDVI (Normalized Difference Vegetation Index) analysis (Manandhar etal, 2009, Kay Khaing Lwin, 2015). After conducting the NDVI analysis, each NDVI value in each single cell was used to classify into two groups, namely, forest and non-forest areas. After making a frequency distribution graph of NDVI values, 800 samples of the NDVI values were used to determine the threshold valueof forest and non-forest areas, which was finally determined as 0.25.Second the forest area was classified into fourcategories including evergreen coniferous forest (CF), broad leaved deciduous forest (DF), broad leaved evergreen forest (EF) and bamboo forest (BF)by the supervised classification method using the results of forest field surveys in Nagoya City (Hayashi laboratory, 2015) tovalidateDF, EF and BF and Google Earth image for CF. Main tree species wereQuercus serrata andQuercus variabilis for DF,Cinnamomum camphora andCastanopsis sieboldii for EF,and Cryptomeria japonica, Chamaecyparis obtuse, Pinus densiflora and Pinus thunbergiifor CF. Then non-forest area was classifiedinto three areas; farmland, water area and urban area by the supervised classification method validated byALOS satellite images. Then the result of the accuracycheck for the supervised classification was around 81 % in total land-use categories by using 200 pointsvalidated by Google Earth.ArcGIS10.2.2 (ESRI)and ERDAS IMAGINE 2014 (Hexagon Geospatial,Intergraph)were used for GIS analysis and satellite image analysis.

As for 1955 data, land-use maps were digitized from original paper maps for GIS analysis.Then the land-use categories were classified into nine land-use types including coniferous forest (CF), broad leaved forest (BLF including DF and EF), mixed forest (CF and BLF), farmland, water area, bare-land, clear-cutting area, urban area and grassland by the supervised classification method.Then the result of the accuracy check was around 85 % in total land-use categories by using 500 points validated by original land-use maps

Finally, ES unit values were developed based on the Nagoya forest field survey data (Hayashi laboratory, 2015) and also these were collected from literatures as listed in table1. Since 2012 the field surveys have been conducted on forest in Nagoya City. According to the Nagoya green coverage GIS data (Nagoya City, 2012), there were around 240 forest areas (≧1ha) in the city. As of November 2015, nearly 190 forest sites have already been investigated through this survey. In each forest area, a 100m2 and a 400m2 investigation areaswere set up for vegetation, soil and habitat surveys (Yonekura et al, 2014, Hayashi and Ooba, 2015, Hayashi laboratory, 2015). In this study, the ES unit values were developed based on around 170 forest information (table 1.). Then the potential provisioning maps of selected ESs weredeveloped by using the resultsof land-use maps and the ES unit values. Also the differences between the potential provisions of ESs in 1995 and 2008 were examined.

Data used in this study

ALOS Satellite images by JAXA

Two ALOS images dated 20080527 and 20080225 in 10-m x 10-m resolution were used

Land-use maps in 1955 by Geospatial Information Authority of Japan(GSI)

Four old land-use maps were used, namely, Nagoya City north part, Nagoya City south part, Koromo and Seto, which were scanned and digitized for GIS analysis.

Table 1. ES unit values used in this analysis

ES / Supporting service / Regulating service / Provisioning service
Carbon sock(t-C/ha) / NO2 absorption (kg/ha/yr) / Acorn(number of trees/ha)
BF / 37 / 6.5 / 4.0
CF / 113(113) / 15.2(15.2) / 2.7(2.7)
EF / 144 / 21.7 / 7.3
DF / 104 / 5.9 / 11.1
BLF / (124) / (13.8) / (9.2)
Mix CF and BLF / (118) / (14.5) / (5.9)
Farmland / 0(0) / 6.2(6.2) / 0(0)
Water area / 0(0) / 0(0) / 0(0)
Urban area and others / 0(0) / 0(0) / 0(0)
Source / Estimated by using Tadaki et al (2004), Okuda et al (2007) and Hayashi laboratory (2015) / Estimated by using Ogawa et al (2000) and Hayashi laboratory (2015) / Developed based on Hayashi laboratory (2015)

Note: The unit values used this study were tentative version because the field surveys for all Nagoya forest have not finished yet.

The 2008 ES values are listed on the left of bracket and the 1955 ES unit values are in each bracket.

The BF and CF meant main forest types with small number of different type of trees including acorn trees.

RESULTS & DISCUSSION





Figure 2(a) showed the digitized land-use maps in 1955 and figure 2(b) was the result of classification of the 2008 land-use map from the ALOS satellite images. Figure 3 showed the location of land-use change between 1955 and 2008. Figure 4(a) to (c) showedthe potential provisioning maps of selected ESs in a 1-km grid scale.


According to the results, urban areas have been expanded greatly in this half century so that a lot of farmlands were converted to urban area. Many forest areashave been changed to urban areas, too. Also the land use changes from forest to bamboo were observed in some areas. In the course of these, a variety of ESs was deteriorated and decreased in urban area, such as carbon stock and NO2, especially, in Nagoya City and its sub-urban area.










The Nagoya forest field surveydata was used as the training sample of thesupervised classification for the 2008 satellite images. But the field survey was conducted only in Nagoya City. So, further filed survey needed for covering sub-urban forest surrounding Nagoya City. Also, the ES unit values for 1955 were estimated based on the 2008 field survey results because it was difficult to get ES unit values for 1955. However, it will need more effort to find out appropriate ES unit values for 1950s in the future.

CONCLUSION

In this study, digital land-use maps in 10-m grid scale were developed by classifying satellite images in 2008 and the old land use maps of 1955 in the northwest part of Aichi Prefecture, Japan. By utilizing the land-use maps and ES unit values, the potential provisioningmaps of selected ESs were estimated. In the future, smaller scale land-use maps were needed to develop for more detailed assessment with multiple ES estimation. Also, developing old ES unit values were needed in the future.

REFERENCES

  1. Geospatial Information Authority of Japan (GSI) (1955): Tochiriyouzu (Land-use maps), Nagoya City north, Nagoya City south, Koromo and Seto. (in Japanese)
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