Three subregions in north China appear to be especially sensitive to climate
change because of potential increases in the soil moisture deficit:
- Areas along the Great Wall-This area lies southeast of the transition
belt between agriculture and animal husbandry. Warming and increased evapotranspiration,
along with possible declines in precipitation, would make it difficult to
maintain current crop patterns. The northern rangeland would gradually intrude
into this area, creating a transition zone dominated by livestock. The northWestern
part of this area would become an arid grassland.
- The Huang-Hai plains-Climatic warming may increase the moisture deficit
(i.e., the difference between precipitation and evapotranspiration) by more
than 70 mm and result in more frequent and severe spring droughts with hot,
dry winds, damaging wheat production and limiting the present practice of
double-cropping in succession. Dryland crops will suffer from drought.
- The area north of the Huaihe River, including eastern Shandong-This
area lies along the southern edge of the temperate crop zone. Climate warming
may cause the northward shift of subtropical crop areas. However, projected
frequent waterlogging in the south and spring droughts in the north would
inhibit the growth of subtropical crops.
The state and farmers can take steps to adapt agricultural production to the
unfavorable impacts of possible climate change. Such strategies include allowing
the sown acreage of grain to stabilize at a level of 0.8-0.9 ha per capita to
attain the production target; strengthening irrigation capacity as one of the
most beneficial means of maintaining agricultural production in the face of
unfavorable climate change; and transforming medium- or low-yield farmland into
high-yield farmland. To maintain the productivity of cultivated land, it is
necessary to popularize a more optimal fertilizer mix and adopt the technique
of subsoil application according to actual changes in soil conditions. It also
is necessary to use and extend technology for agricultural adaptability-such
as using superior species of crops, improving standardized cultural techniques
under climatic variation, using dryland farming techniques, and developing feed
crops instead of grain crops.
Forests in northern China have been seriously depleted over the past few centuries.
Despite recent reforestation efforts, the forested area in the region is only
11.8% of the total land cover, which is lower than the mean value for China.
Under the influence of projected climate change, the distribution pattern of
many important tree species would be affected. For example, the present forests
of Pinus tabulaeformis, a key temperate species widely distributed in northern
China, will be reduced an additional 9.4% under a 2xCO2 equilibrium climate
10.3.1.4. Coastal Zones
For the southern coast of Shangdong, estimated sea-level rise by the years
2030, 2050, and 2100 would be 1.1, 5.7, and 40.2 cm, respectively and, for the
coast of Liaoning-Tianjin, 13.1, 22.5, and 69.0 cm, respectively (Du et al.,
1996). Construction of dikes and seawalls is likely to be the most common adaptation
strategy in these areas; this practice has been used there throughout history
to combat sea encroachment (ESD-CAS, 1994).
Box 10-2. Sea-Level Rise at Major Deltas of China (ESD-CAS,
|The Old Huanghe (Yellow River) delta, the Changjiang (Yangtze River) delta,
and the Zhujiang (Pearl River) delta are major areas of economic activity
in China. The metropolises of Tianjin, Shanghai, and Guangzhou (Canton)
are located within these three deltas, respectively. The three deltas are
located in regions with tectonic subsidence rates of about 2-3 mm/yr, 1-2
mm/yr, and 1-2 mm/yr, respectively (although hilly lands in the Zhujiang
delta have a tectonic uplifting rate of 1 mm/yr). The Old Huanghe delta
and the Changjiang delta have experienced severe land subsidence problems
in the past as a result of groundwater extraction. Recent efforts to mitigate
this problem have been successful in reducing the subsidence rate. It is
estimated that these rates can be controlled within the range of 6-10 mm/yr
for the Old Huanghe delta and 3-5 mm/yr for the Changjiang delta. In the
Zhujiang delta, natural progradation of the coast and active land reclamation
activities have resulted in a 0.5-1 mm/yr sea-level rise in the distributaries
in the estuarine area-the same order of magnitude as the projected value
due to climate change. This rate is expected to continue for some time.
In the next 50 years, therefore, the expected eustatic sea-level rise due
to climate change will not be a major factor in relative sea-level rise
for the Old Huanghe and Changjiang deltas, although it may be for the Zhujiang
Integrated vulnerability to climate change for northern China, including the
vulnerability of forests, is summarized in Table 10-10.
|Table 10-10: Integrated vulnerability
to climate change in northern China.
Most Vulnerable Region
Summary of Results
|Water Resources (W)
|Climatic, hydrological, and socioeconomic indices
||Hai-Luan River Basin, followed by the Huaihe River Basin
||Runoff change of -16 to +17%
||Decreased supply to (A) and reduction with (F)
|CERES and other crop models; moisture deficit and socioeconomic indices
||Hebei, Shanxi, inner Mongolia, and along the Great Wall
||Yield change of wheat (-6 to +42%), maize (-9 to +5%), rice (-21 to -7%),
cotton (+21 to +53%)
||Increased risk for (F) and increased demand for (W)
|Aridity and fuelwood supply indices
||Productivity increase of +1 to 10%; area change of -57 to +12% (varying
||Increased risk from (A) and effect on (W)
|Coast Zone (CZ)
||Sea-level rise of 30-65 cm
||IPCC 7-step method
||Jing-Jin-Tang and Yellow River Delta
||Likely and viable strategy of dike sand seawalls
||Increased risk to (A) and (W)
(1)L. Gates, pers. comm.
Source: Lin et al., 1994.