RESULTS
3.1 Deforestation in Zhejiang
Province
Figure 2. Temporal changes and
spatial patterns of deforestation in Zhejiang Province from 2000 to
2020. (a) Cumulative forest loss (line) and annual loss (bar) from 2001
to 2019. (b) Scale of forest change.
The bar charts are estimates based on satellite-based land-cover change
products and statistical yearbook data (GlobeLand30, 2000–2020;
ESA-CCI, 2000–2018; Statistical yearbook, 2000-2018). (c) Spatial
distribution of net forest loss converted to other land classifications
from 2000 to 2020. (d) Spatial distribution of net forest gain derives
from other land classifications from 2000 to 2020
Our estimation based on the Hansen’s datasets shows that the total net
loss of forest cover in Zhejiang Province from 2001-2019 is 279,501 ha
(Figure 2a), a 4.7% decline in forest from the 2000 baseline. Annually,
the rate of forest loss is about 12,549 ha per year during 2001-2008,
representing an six-fold increase from about 4,245 ha in 2001 to nearly
26,993 ha in 2008. After 2008, the forest loss appeared to be stable
during 2009-2019, but at a high rate of 16,282 ha each year. The
cumulative forest loss monotonically increased during the entire study
period.
In
addition to the Hansen’s dataset, other data products including
Globeland30 and ESA-CCI also show forest loss in Zhejiang Province after
2020 (Figure 2b). The Globeland30
dataset shows that forest cover decreased by 22,823 ha in Zhejiang
during 2000-2020 and ESA-CCI 186,014 ha during 2000-2018, but Zhejiang’s
statistical yearbook data show an increase in forest at the magnitude of
80,400 ha in Zhejiang from 2000-2018 (Figure 2b). We believe that remote
sensing based land change results do not rely on government statistics
and have higher spatial resolutions, are thus more likely to be less
biased.
At
the same time, we analyzed the spatial distribution of forest loss and
gain in Zhejiang Province using GlobeLand30 high-resolution satellite
images (Figure 2c and d). Over the space of Zhejiang Province, forest
loss was found to be a prevalent phenomenon in many parts across the
whole province. The landscape in terms of forest loss was shown to be
scattered and rarely interconnected in general, but forest loss mainly
dominated the mountainous regions within the province (Figure 2c).
Overall, forest loss happened mainly in western and southern parts of
Zhejiang, while the lost area was relatively small in the northeastern
part. Forest loss exhibited heterogenous patterns at the municipality
level (Figure 2c). Among all the municipalities in Zhejiang Province,
the greatest loss in forest cover was observed in Lishui municipality in
South Zhejiang, which is followed by Hangzhou municipality in West
Zhejiang (the most economically developed city and the capital city of
the province). Jiaxing municipality in proximity to Shanghai (the
economic center in eastern China) possessed the least loss of forest.
Forest loss was mainly due to conversion to cropland, with the largest
amount occurring in Lishui.
Forest gain also occurred in almost
all areas of Zhejiang Province. But the increase in forestland in most
of those regions was less than the loss of forests. Among all the
municipalities, Hangzhou has the largest increase and Jiaxing the
smallest increase. The main source of forest gain is through converting
cultivated land to forest, which is observed most in Wenzhou, followed
by Lishui and Hangzhou (Figure 2d).
3.2 Urban expansion in Zhejiang Province
Figure 3. Temporal changes and
spatial patterns of urban land in Zhejiang Province. Data of temporal
change of land use are from (a) Statistical Yearbook between 2000-2018
and (b) GlobeLand30 between 2000-2020. (c) Spatial distribution of net
forest loss converted to other land classifications from 2000-2020. (d)
Spatial distribution of net forest gain derives from other land
classifications over the same time span
According to a statistical yearbook
(2001-2018) (Figure 3a), the proportion of urban area in Zhejiang
Province increased steadily between 2001 and 2018. During the same
period, the proportions of urban land area and forest land area
increased by 70.29% and 1.45%, respectively, while the arable land
area decreased by 5.26%. The rest of land types had a gradual decrease
(Figure 3a). Using the Globeland30 data, we found that during 2000-2020,
the area of urban land use increased
by 169.45% while the area of
forest and arable land decreased by 0.40% and 19.20%, respectively
(Figure 3b).
Meanwhile, we used GlobeLand30 to
analyze the spatial distribution of urban land changes in Zhejiang
Province (Figure 3c and d). Spatially, urban area loss and gain occurred
in almost all over the province, but the lost patches were dispersed and
much smaller compared to the gained areas although the amount of net
loss is only around 6% of the net gain. Of these, Ningbo and Hangzhou
had the largest urban area gains, while Lishui and Zhoushan had the
smallest gains (Figure 3c and d).
Figure 4. Sankey Map of Land use
Transformation in Zhejiang Province from 2000 to 2020
The largest land use changes from
2000 to 2020 took place in the form of land use conversions between
urban construction land, arable land, and forest in Zhejiang Province
(Figure 4). The conversion from arable land to urban area is the largest
(562,399 ha), followed by conversions from arable land to forest land
(260,322 ha) and from forest land to arable land (210,474 ha). The
changes in other land uses are relatively small. It seems that urban
land expansion primarily comes from losses of arable land, while arable
land increases as a result of deforestation.
3.3 Linkages of deforestation and urbanization: Lishui and
Hangzhou
Figure 5. Land use change in
Hangzhou and Lishui from 2000 to 2020
By comparing the land use change patterns of Hangzhou and Lishui, we
found that the largest conversion from cultivated land to urban area in
Hangzhou was 77,288 ha, followed by 37,036 ha from cultivated land to
forest land and 26,551 ha from forest land to cultivated land. In
Lishui, the maximum conversion was 37,198 ha of cultivated land to
forest land, 36,787 ha of forest land to cropland, and only 16,910 ha of
cultivated land to urban area. These
results show that the biggest land change in Hangzhou is from cultivated
land to urban land. The change in Lishui municipality is mainly due to
conversion between cropland and forest land, and its area of forestland
loss is larger than that of Hangzhou municipality (Figure 5).
Figure 6. Socioeconomic change in Hangzhou and Lishui municipality of
Zhejiang Province from 2000 to 2019
Hangzhou’s GDP continued to increase from 138.256 to 1537.305 billion
yuan during 2000-2019, representing an 11-fold increase. The resident
population of Hangzhou municipality increased by 148% from 7.02 to
10.36 million. Lishui’s GDP, on the other hand, only increased from
13.676 to 147.661 billion yuan during 2000-2019 with a slow resident
population growthfrom 2.16 to 2.21 million (Figure 6).
Figure 7. Telecoupling of deforestation and urbanization in Hangzhou and
Lishui
Considering the representative land use change in Hangzhou and Lishui
municipalities, they illustrate an ideal case for demonstrating the
telecoupling concept (Jianguo Liu, 2017; Sun Jing et al., 2020). In
Zhejiang Province, Hangzhou is the most urbanized municipality while
Lishui is comparatively less urbanized. As Hangzhou’s urban population
increased, its limited land resources can no longer meet the needs of
the region’s urbanization. Therefore, urban expansion inevitably took
arable land resources from surrounding areas, leading to a reduction in
arable land area. The governments could enact policies to find back-up
land resources through the role of an intermediate agent (such as a
higher-level government). The municipality of Lishui, however, has
sufficient back-up land resources due to its lower level of economic
development, massive out-migration of rural population, and slower urban
development. Through the role of an agent, a local government can supply
its reserved land resources to meet the need of other areas in need of
land supply. Land and money may be exchanged between two such regions in
the form of flows to get what each need. For instance, Hangzhou may buy
back-up land resources from Lishui for urbanization, whereas Lishui
could receive a corresponding compensation. Meanwhile, Lishui may also
suffer from land degradation and loss of ecosystems in the region as a
result (Figure
7).