Construction land carbon emissions and time differences
The carbon emissions of construction lands in all the cities and the demonstration area in Shaanxi Province show an upward trend from 2010 to 2018. They were 73.307 and 98.8604 million tons in 2010 and 2018, respectively. Compared with those in 2010, the carbon emissions from construction land in 2018 had increased by 34.86%. Compared with those in 2010, the carbon emissions from construction land in Xi’an, Tongchuan, Baoji, Xianyang, Weinan, Yan’an, Hanzhong, Yulin, Ankang, Shangluo, and Yangling Demonstration Area in 2018 had increased by 37.11%, 44.99%, 34.33%, 29.74%, 33.16%, 30.82%, 40.49%, 33.22%, 39.47%, 35.82%, and 29.72%, respectively (Table 1).
Table 1
Carbon emissions from construction lands in all cities and the demonstration area in Shaanxi Province from 2010 to 2018 (× 104 t)
Administrative District | 2010 | 2011 | 2012 | 2013 | 2014 | 2015 | 2016 | 2017 | 2018 |
Xi’an | 1594.27 | 1651.03 | 1708.98 | 1769.99 | 1874.24 | 1934.21 | 2008.30 | 2062.38 | 2185.92 |
Tongchuan | 248.88 | 257.88 | 267.22 | 281.41 | 300.04 | 319.84 | 332.38 | 340.41 | 360.84 |
Baoji | 591.53 | 612.41 | 634.71 | 657.11 | 684.05 | 708.61 | 739.86 | 759.47 | 794.63 |
Xianyang | 600.51 | 622.19 | 643.97 | 666.51 | 688.84 | 712.19 | 736.40 | 756.13 | 779.11 |
Weinan | 1139.59 | 1180.62 | 1223.24 | 1269.84 | 1324.83 | 1367.35 | 1418.36 | 1448.79 | 1517.46 |
Yan’an | 419.24 | 433.91 | 449.10 | 464.82 | 480.62 | 498.89 | 516.35 | 532.89 | 548.45 |
Hanzhong | 503.54 | 521.72 | 540.29 | 559.25 | 581.90 | 610.77 | 639.23 | 673.21 | 707.41 |
Yulin | 1810.67 | 1875.85 | 1943.39 | 2017.23 | 2093.89 | 2167.18 | 2238.69 | 2337.00 | 2412.25 |
Ankang | 221.41 | 229.16 | 237.47 | 245.38 | 256.42 | 266.68 | 278.71 | 298.51 | 308.81 |
Shangluo | 169.40 | 175.33 | 181.26 | 187.27 | 193.04 | 198.77 | 206.01 | 216.89 | 230.08 |
Yangling | 31.66 | 32.67 | 33.53 | 34.40 | 35.66 | 36.41 | 37.16 | 39.87 | 41.07 |
Total | 7330.70 | 7592.77 | 7863.14 | 8153.22 | 8513.54 | 8820.90 | 9151.43 | 9465.56 | 9886.04 |
Figure 1 presents the carbon emissions per capita and per unit GDP for Shaanxi Province from 2010 to 2018. The per capita carbon emissions show a continuous increase from 21.76 to 29.04 t/person. Compared with those in 2010, the per capita carbon emissions of construction land in 2018 had increased by 33.46%. Carbon emissions per unit GDP showed an overall downward trend from 0.072 to 0.040 kg/yuan. The carbon emissions per unit GDP for construction land had dropped by 44.44% in 2018 compared with that in 2010; before 2014, the decline was large, whereas after 2014, the decline began to slow down.
Spatial differences in carbon emissions from construction lands in all cities and the demonstration area
In 2010 and 2018, the carbon emissions from construction lands in Shaanxi Province were the largest in Yulin, at 1810.67 and 2412.25 t, respectively. In 2010, the order of carbon emissions from construction land was as follows: Yulin > Xi’an > Weinan > Xianyang > Baoji > Hanzhong > Yan’an > Tongchuan > Ankang > Shangluo > Yangling Demonstration Area. In 2018, the order was Yulin > Xi’an > Weinan > Baoji > Xianyang > Hanzhong > Yan’an > Tongchuan > Ankang > Shangluo > Yangling Demonstration Area. Carbon emissions continued to increase owing to sustained development as a result of urbanization and industrialization. Among the cities and the demonstration area in Shaanxi Province, Yulin produced the highest carbon emissions from construction land, which increased from 1810.67 t in 2010 to 2412.25 t in 2018, with an average annual increase of 4.16 t. In contrast, the lowest emissions were from Yangling Demonstration Area; they increased from 31.66 t in 2010 to 41.07 t in 2018, with an average annual increase of 4.95 t. In 2018, Yulin and Xi’an produced carbon emissions greater than 2000 t; Weinan, Baoji, Xianyang, Hanzhong, and Yan’an produced emissions greater than 500 t; and Tongchuan, Ankang, Shangluo, and Yangling Demonstration Area produced emissions less than 500 t. The Yangling Demonstration Area produced less than 50 t of carbon emissions. In 2010, Yulin, Xi’an, and Weinan produced carbon emissions greater than 1,000 t; Baoji, Xianyang, and Hanzhong produced emissions greater than 500 t; and Tongchuan, Ankang, Shangluo, and Yangling Demonstration Areas produced emissions less than 500 t. The Yangling Demonstration Area again produced less than 50 t of carbon emissions (Table 2).
Table 2
Carbon emissions from construction lands in Shaanxi Province in 2010 and 2018
Administrative District | Carbon emissions (t) | Per capita carbon emissions (t/person) | Per unit GDP carbon emissions (kg/Yuan) |
2010 | 2018 | 2010 | 2018 | 2010 | 2018 |
Xi’an | 1594.27 | 2185.92 | 1.88 | 2.19 | 0.049 | 0.026 |
Tongchuan | 248.88 | 360.84 | 2.98 | 4.49 | 0.133 | 0.110 |
Baoji | 591.53 | 794.63 | 1.59 | 2.11 | 0.061 | 0.035 |
Xianyang | 600.51 | 779.11 | 1.23 | 1.78 | 0.055 | 0.033 |
Weinan | 1139.59 | 1517.46 | 2.15 | 2.85 | 0.142 | 0.086 |
Yan’an | 419.24 | 548.45 | 1.92 | 2.43 | 0.047 | 0.035 |
Hanzhong | 503.54 | 707.41 | 1.47 | 2.06 | 0.099 | 0.048 |
Yulin | 1810.67 | 2412.25 | 5.40 | 7.06 | 0.103 | 0.063 |
Ankang | 221.41 | 308.81 | 0.84 | 1.16 | 0.068 | 0.027 |
Shangluo | 169.40 | 230.08 | 0.72 | 0.97 | 0.059 | 0.028 |
Yangling | 31.66 | 41.07 | 1.57 | 1.96 | 0.067 | 0.027 |
There were obvious regional differences in carbon emissions per capita and per unit GDP in Shaanxi Province. In 2010 and 2018, the per capita carbon emissions from Yulin, at 5.40 and 7.06 t, respectively, were significantly higher than those from other cities. In 2010, the order of per capita carbon emissions was Yulin > Tongchuan > Weinan > Yan’an > Xi’an > Baoji > Yangling Demonstration Area > Hanzhong > Xianyang > Ankang > Shangluo. In 2018, the order was basically the same as that in 2010. The per capita carbon emissions in 2010 were greater than 5 t for Yulin; greater than 2 t for Tongchuan and Weinan; greater than 1 t for Yan’an, Xi’an, Baoji, Yangling Demonstration Area, Hanzhong, and Xianyang; and less than 2 t for Ankang and Shangluo. In 2018, the per capita carbon emissions were greater than 7 t for Yulin; greater than 2 t for Tongchuan, Weinan, Yan’an, Xi’an, Baoji, and Hanzhong; greater than 1 t for Yangling Demonstration Area, Xianyang, and Ankang; and less than 1 t for Shangluo. In 2010, the largest and smallest carbon emissions per unit GDP in Shaanxi Province were exhibited by Weinan (0.142 kg/yuan) and Xi’an (0.049 kg/yuan), respectively. The order of carbon emissions per unit GDP was as follows: Weinan > Tongchuan > Yulin > Hanzhong > Ankang > Yangling > Baoji > Shangluo > Xianyang > Xi’an > Yan’an. In 2018, the order of per capita carbon emissions was Tongchuan > Weinan > Yulin > Hanzhong > Baoji = Yan’an > Shangluo > Ankang = Yangling Demonstration Area > Xi’an (Table 2).
Construction land carbon emission intensity and prediction model
Construction land area and carbon emissions increased in Shaanxi Province from 2010 to 2018. Compared with that in 2010, the construction land area in 2018 had increased by 18.46% (Fig. 2). We found that there was an exponential correlation between the construction land area and carbon emissions; the correlation coefficient was 0.9248 (Fig. 3). The fitted function can be used as a model for predicting carbon emissions in the future and can provide a scientific basis for quantitative accounting of carbon emissions from construction land.
The carbon emission intensity of construction land can be expressed as carbon emissions per unit construction land area. From 2010 to 2018, the carbon emission intensity of construction lands in Shaanxi Province showed an increasing trend. Compared with that in 2010, the carbon emission intensity of construction land in 2018 had increased by 13.85% (Fig. 4). The regional differences in carbon emission intensity of construction lands in Shaanxi Province were obvious. In 2010 and 2018, Yulin exhibited the highest carbon emission intensity, at 21.99 and 19.55 t/hm2, respectively; Yangling Demonstration Area exhibited the lowest carbon emission intensity, at 0.34 and 0.37 t/hm2, respectively. In 2010, the carbon emission intensity was greater than 15 t/hm2 in Yulin and Xi’an, greater than 10 t/hm2 in Weinan, greater than 5 t/hm2 in Xianyang, Baoji, and Hanzhong, and lesser than 5 t/hm2 in Yan’an, Tongchuan, Ankang, Shangluo, and Yangling Demonstration Area. In 2018, the carbon emission intensity was greater than 15 t/hm2 in Yulin and Xi’an, greater than 10 t/hm2 in Weinan, greater than 5 t/hm2 in Baoji, Xianyang, Hanzhong, and Yan’an, and lesser than 5 t/hm2 in Tongchuan, Ankang, Shangluo, and Yangling Demonstration Area (Fig. 5).
Ecological compensation standard for carbon emissions
The ecological compensation quotas of all the cities and the demonstration area in Shaanxi Province for 2010 and 2018 were obtained using the carbon emissions from construction lands and three types of carbon sequestration prices (Table 3).
Table 3
Ecological compensation quotas for construction lands in Shaanxi Province for 2010 and 2018
Administrative District | Total carbon emissions (× 104 t) | Lower limit (× 108 Yuan) | Moderate amount (× 108 Yuan) | Upper limit (× 108 Yuan) |
2010 | 2018 | 2010 | 2018 | 2010 | 2018 | 2010 | 2018 |
Xi’an | 1594.27 | 2185.92 | 19.45 | 26.67 | 43.47 | 59.60 | 163.57 | 224.28 |
Tongchuan | 248.88 | 360.84 | 3.04 | 4.40 | 6.79 | 9.84 | 25.53 | 37.02 |
Baoji | 591.53 | 794.63 | 7.22 | 9.69 | 16.13 | 21.67 | 60.69 | 81.53 |
Xianyang | 600.51 | 779.11 | 7.33 | 9.51 | 16.37 | 21.24 | 61.61 | 79.94 |
Weinan | 1139.59 | 1517.46 | 13.90 | 18.51 | 31.07 | 41.37 | 116.92 | 155.69 |
Yan’an | 419.24 | 548.45 | 5.11 | 6.69 | 11.43 | 14.95 | 43.01 | 56.27 |
Hanzhong | 503.54 | 707.41 | 6.14 | 8.63 | 13.73 | 19.29 | 51.66 | 72.58 |
Yulin | 1810.67 | 2412.25 | 22.09 | 29.43 | 49.37 | 65.77 | 185.77 | 247.50 |
Ankang | 221.41 | 308.81 | 2.70 | 3.77 | 6.04 | 8.42 | 22.72 | 31.68 |
Shangluo | 169.40 | 230.08 | 2.07 | 2.81 | 4.62 | 6.27 | 17.38 | 23.61 |
Yangling | 31.66 | 41.07 | 0.39 | 0.50 | 0.86 | 1.12 | 3.25 | 4.21 |
Yulin should provide the highest ecological compensation for 2018, with an amount ranging from 29.43 × 108 to 247.50 × 108 Yuan, followed by Xi’an, Weinan, and Baoji. Based on the average cost of afforestation in China, the latter three cities should provide ecological compensations of 59.6 × 108, 41.37 × 108, and 21.67 × 108 Yuan, respectively. Yangling Demonstration Area should provide the lowest ecological compensation, with an amount ranging from 0.5 × 108 to 4.21 × 108 Yuan. The order of ecological compensation standards for all the cities and the demonstration area in Shaanxi Province was basically the same for 2010 and 2018. The moderate amounts of ecological compensation that should be provided by all the cities and the demonstration area in Shaanxi Province for 2018 is 1.29 to 1.44 times that for 2010. Among the administrative districts, Yangling Demonstration Area and Tongchuan exhibit the smallest and largest growth multiples, respectively. The growth periods were the shortest and longest for Yangling Demonstration Area and Tongchuan, respectively.