3.1. Geographical Distribution and Characteristics of Forest Variation in China
According to global land cover data (GlobalLand30), the total forest area in 2010 in China was 2,120,100 km2
, while the forest coverage rate was 22.01%. This is a similar result to that reported by the eighth forest inventory (2009–2013): A value of 2,076,900 km2
. Indeed, in terms of spatial distribution, China’s forestry resources are approximately divided by a boundary line comprised by the Greater Hinggan, Lvliang, and Hengduan mountains. Forests are mostly distributed to the southeast of this boundary (Figure 3
a). In terms of forest area (Figure 3
b), the largest concentration is found under the jurisdiction of the Southern Forestry Division (1,161,200 km2
), followed by the Northeast Forestry Division (410,000 km2
), the Southwest Forestry Division (299,000 km2
), and the South China Forestry Division (141,400 km2
). The forest area in these four forestry divisions occupied 91% of the total forest area in China, while in the mid-latitude regions, the North China Forestry Division, the Loess Plateau Forestry Division, the Inner Mongolia-Xinjiang Forestry Division, and the Tibetan Plateau Forestry Division are responsible for only 9% of the total forest area. Regarding the rate of forest coverage, the division responsible for the highest rate is the South China Forestry Division (56.38%), followed by the Southern Forestry Division (52.56%), the Southwest Forestry Division (41.24%), and the Northeast Forestry Division (38.56%). In the mid-latitude regions, the North China Forestry Division and the Loess Plateau Forestry Division are responsible for forest coverage rates of 14.06% and 17.53%, respectively, while the Inner Mongolia-Xinjiang Forestry Division and the Tibet Plateau Forestry Division are responsible for the lowest rates of all, just 1.58% and 0.47%, respectively. In conclusion, it is clear that the overall forest resources in China are unevenly distributed and there is a clear trend in reduction from the southeast to the northwest.
Between 2000 and 2010, the forest area in China grew from 2,017,600 to 2,120,100 km2, a net increase of 102,500 km2, while the total forest area increased by 5.08%. In tandem, the forest coverage rate increased from 20.94% to 22.01%, an increase of 1.06%. Thus, when compared with other countries around the world, from an overall perspective, the forest resources in China have grown rapidly: between 2000 and 2010, forest area increased by 275,000 km2, which accounted for 13.63% of the forest area in 2000. In contrast, the reduction in forest area was 179,300 km2, which accounted for 8.89% of the forest area in 2000, and there were 1,838,300 km2 of forest area that did not change, which accounted for 91.11% of the forest area in 2000.
At the forest district level (Table 2
), the regional differences of China’s forest resources change are obvious. The net increases in the regions that fall under the jurisdiction of the Southern and Southwest Forestry Divisions are bigger than all others at 42,836.41 and 42,158.08 km2
, respectively. These changes alone account for 81.92% of the national net increase in forest area. The South China Forestry Division is the only one who has experienced a decrease in forest area in these forest districts, a net loss of 6062.96 km2
from 2000 to 2010. These data reveal an important trend: The increases and decreases in Chinese forest resources are occurring in the same regions. From the point of view of considering the change rate of forest cover, the Tibetan Plateau Forestry Division and the Inner Mongolia-Xinjiang Forestry Division had the most obvious growth of forest, with rates of 108.21% and 58.52%, respectively.
Regarding the provincial administrative regions (Table 3
), the largest increases in forest area were observed in Sichuan, Gansu, and Hunan provinces, as well as in the Tibetan autonomous region, where the net increases in forest area were all more than 14,000 km2
. Hainan province, in contrast, experienced the highest loss of forest area at 6398.02 km2
between 2000 and 2010, while the forest areas in Zhejiang, Liaoning, Jilin, Anhui, and other provinces also decreased slightly. In terms of the rate of change of forest area, which is variation divided by forest area in 2000, the growth rate in Shanghai was most striking, with an increase of 287.56% between 2000 and 2010. Rapid rates were also observed in Gansu and Qinghai provinces, which have experienced growth rates of approximately 80%. In contrast, the forest growth rate in the Xinjiang autonomous region reached 20.75%, while the forest area of Hainan province declined by 20.31%.
Again, in relation to these data, it is important to note that the quantities of increases and decreases of forest in provincial administrative forest regions are synchronous; that is, the province that has a massive increase in forest area also tends to has a massive decrease in forest area coincidentally; the Pearson correlation coefficient of forest area increase and decrease at the provincial level is 0.795, which is significant at the 0.01 level. There is a clear linear positive correlation between the increase and decrease in forest area at the provincial level.
Considering the distribution of hot and cold spots in countywide areas of forest change, there is a strong spatial correlation in forest gain regions, forest loss regions, and forest net change regions. Moreover, there are obvious hot spots and cold spots of forest gain, forest loss, and forest net change. There’s a strong spatial consistency between forest gain regions and forest loss regions on the whole. The main areas of forest gain and loss are the southwestern mountainous region and the northern region of Greater Hinggan. In contrast, cold spots in county forest change include the North China Plain, the Loess plateau, and the eastern coastal area, where there has been little change in forest coverage. In terms of net changes, hot spots of forest net change are located in the mid-latitudes of China, from the west to the east, from eastern Tibet to western Jiangxi province. Cold spots of forest net change are located in the east coast regions of China, from Liaoning province to the southern Fujian and Hainan provinces, and are particularly concentrated in Hainan, Fujian, and Zhejiang provinces (Figure 4
3.3. Transitions between Forest and Other Land Use Types
Grassland is the primary source of land being both converted to forest and being converted from forest in China in the early 21st century. Cultivated land and shrubland are in second and third place, respectively, as sources of land that are converted to forest (Figure 6
). Between 2000 and 2010, 169,200 km2
of grassland were converted to forest in China, accounting for 61.55% of the increase. In the same period, 60,100 km2
of cultivated land, and 33,400 km2
of shrubland were also transferred to forest, accounting for 21.86% and 12.15% of the total increase, respectively. The total areas of grassland, cultivated land, and shrubland converted to forest account for 95.56% of the total increase, while at the same time, grassland, cultivated land, and shrubland are also the main beneficiaries of forest decrease. These land use types increased by 95,800, 66,200, and 12,900 km2
, respectively, as a result of forest decrease, accounting for 52.44%, 36.23%, and 7.06% of the total, respectively, and adding up to 95.73% of the total decrease in forested land in China. As a result of these data, it is clear that there has been a very extensive transfer between forest and grassland in China, which is the key factor balancing forest area change. Indeed, the quantity of transfer between forest and cultivated land has enabled the maintenance of a basic balance. Nevertheless, it is important to note that 66,200 km2
of forest has been transferred to cultivated land as a result of a push to implement the Forest Conservation Policy. Thus, because of developments including the return of farmland to forest, this phenomenon deserves a deeper analysis. Indeed, when this is viewed from the perspective of the regional forestry divisions (Figure 6
), land use change in regions overseen by the Southern Forestry Division is the most acute, with the Southwest and Northeast Forestry Divisions in second and third place, respectively. In terms of transformational characteristics, eight forestry divisions exhibit the same variable trend that was observed on a nationwide scale; the main sources and directions of forest increase and decrease are grassland, cultivated land, and shrubland. Finally, it is worth noting that 42,810 km2
of forest have been transferred to cultivated land in the regions overseen by the Southern Forestry Division, and a similar situation is also observed in the regions controlled by the South China and Northeast Forestry Division (12,420 km2
and 5710 km2
, respectively). Therefore, one concern going forward should be to focus these three forestry divisions on the issues related to converting forests into cultivated land.
3.4. Relationships between Forest Area Changes and Socioeconomic Development
We developed four regression models to verify the relationship between forest area changes and socioeconomic development across China and in eastern regions, central regions, and western regions separately. The regions were divided by different economic levels. Thus, taking the variability of the administrative region and availability of the data into consideration, we only consider provinces, municipalities, and autonomous regions in mainland China in this analysis and exclude Hong Kong, Macao, and Taiwan. The estimated results of our regression models can be seen in Table 4
From the point of view of socioeconomic development, we have focused on the influence of the county economy level, forestry investment, urbanization level, and demographic change on forest area changes. From the regression results, the relationship between forest area changes, per capita GDP and its quadratic term is significant in model east (for eastern counties), model west (western counties), and model total (for all counties) The regression coefficients of per capita GDP are negative, while those of its quadratic term are positive in those three models; that is, forest area changes conform to a ‘U-shaped’ curvilinear relationship along with increasing per capita GDP. These results reveal that forest resources in China have tended to decrease initially and then perform an increasing trend with economic development. The forest transitions in the eastern, central, and western parts of China have regional differences. At the national scale (model total), the inflection point in forest transition occurs at 50,522 yuan per capita GDP, overall, and 5.51% counties have passed the inflection point in 2010, so the forest transition is not obvious yet. In the eastern counties (model east), this inflection point occurs at 47,232 yuan per capita GDP, and 17.39% counties have passed the inflection point. In western counties (model west), the inflection point is at 38,000 yuan per capita GDP, and 5.75% counties have passed the inflection point. There is no forest transition caused by economic development that occurred in the central counties.
As for the forestry investment factor, a proxy variable of policy factor, it is significant across China. In looking at different regions, it is only significant in the central part at 1% level. The central region has rich forest resources originally, but its economic growth structure is single. Ecological resources have a comparative advantage across China. Governments tend to take advantage of their ecological resources by developing ecological constructions. The forest construction projects, such as Natural Forest Protection Program and Grain for Green Project, were mainly conducted here. Therefore, the increase in forest in the central part of China has no significant correlation with economic development, but it can be attributed to policy factors. Thus, we cannot conclude that no forest transition has happened, because the “scarcity of forest” type of the forest transition theory is also driven by policy factors, which is also a type of forest transition. As for verification of the forest transition caused by policy factors in the central part of China, this can be studied in future work.
Data also show that the urbanization rate has had no significant influence on forest area changes. There is no excessive consumption of forest resources in the process of urbanization; or, alternatively we can say that the government is still the major influencer of forest area change, and that timber consumption is inadequate to influence the general trends. As for the demographic changes, in model west and model total, we can see that in a county, the more the variation in total population that it has, the more forest area that it has. There is also a negative relationship between variations in the rural population and the forest areas in a county, although demographic changes do not influence the forest area directly, or the relationship between them is an open relationship that cannot be tied to a certain range. Since the effect of population change on forest area change is not significant in eastern counties (model east) and central counties (model central), the argument that forest can be overconsumed by population increase and economic development does not appear in eastern and central regions in China. Indeed, the subsistence economy of rural China appears to be no more highly dependent on natural resources.