Application of GKSIM Model for Estimating the Changes of Land Use and Land Cover
3. Application and issues of 3 terms data
Though each data of the same moment are necessary to compare the various countries in Asian region, it is difficult to get them. Futhermore,because GKSIM model required the data at regular intervals, the data of each country in 1970,1980,and 1990 were gathered [1. Nomura (1998.5)].
The changes of land use and land cover in Korea until 2050 as an example are estimated by using land use data and land cover data, and Fig. 3.2 shows Korea in the various Asian countries about the cultivated acreage area. But compared with the data before and after 1970, the only one in 1970 is particularly the low data as the data before the correction in Fig. 3.1 shows. Because we must solve the estimated value by using the data at only 3 moment, in case the data that isn't conformed to the change tendency to the past survey data unexpectedly selected, estimated result can't be got accurately and the estimated result of Fig.3.2 seems to be uncorrected [I.Nomura (1998.10)].
Fig. 3.1 Change of cultivated acreage in Korea
Fig. 3.2 Estimated cultivated acreage in Korea (before correction)
The estimated result may not be correct by using the at regular intervals at this. There are two ways to solve this issue as follows.
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In estimating the changes of land use and land cover, the data in other year is used instead of low data to conform the change tendency of the survey data.
- A regression line is required instead of low data using in other year which is conformed to the change tendency of the survey data, and the data got the regression line is applied to estimating the changes of land use and land cover.
But if other year data in Korea is used, the way of (1) requires the samee year data in other countries because the theme of this study is to compare the various countries in Asia. As the way 0f (1) has an enormous effect on the data in other countries as this, it can't be used.
So it is better to use the way of (2). If y and x are assumed the cultivated acreage area and the year respectively, the regression line expressed by Eq.(3.1) is solved by the change tendency of the survey data.
Y=-6129.944386 x+14327401.5 (3.1)
The cultivated acreage area in 1970 can be got by Eq.(3.1), and it that is conformed to the change tendency of the survey data is shown in Fig.3.1. The estimated result of Fig.3.3 can be got using 3 terms data after correction.
Fig. 3.3 Estimated cultivated acreage in Korea (after correction)
4. Policy goal value
GKSIM model requires the maximum the minimum values that are the limit values to estimate the changes of land use and land cover. The cultivated acreage area inferred from the past survey data in Korea seems to decrease, and it is estimated that the population keeps increasing as shown in Fig.2.1. It is considered that the cultivated acreage area stops decreasing or increases as the policy. If the minimum value is set 1,950,000[ha] as the policy goal value, the policy influences to GKSIM model and Fig.3.2 and Fig.3.3 shown the estimating results are got. These results show that the estimated value is under1,950,000[ha] changes slowly. In other words, if the policy goal value that is inferred from the change tendency of the past survey data as this example is set the maximum or the minimum value, the political element is influence to the estimating result.
