Geography Reference
In-Depth Information
Therefore, the land cover conversion maybe has no great impact on climate in
the coming 40 years. However, the spatial disparity of energy flux is extre-
mely significant. The Green for Grain project makes the latent heat increase
to some extent, while the grassland degradation could lead to the decrease of
latent heat due to the conversion from grassland to barren or sparsely vege-
tated land. As for the downward shortwave radiation, it can be seen that it is
higher under the REG scenario than that of under the CES scenario in the
study period. Urbanization and the decrease in forestry area will offset the
energy flux reduction brought by grassland expansion to some extent.
Although we have carried out an estimation for the effects of land cover change
on energy balance by the WRF model, there are certain limitations in our analysis.
First, there is uncertainty on the prediction of socialeconomic developments,
moreover, the accuracy of the prediction for the socialeconomic development
determines the prediction for the land cover change, which further impacts the
simulation of regional climate. Therefore, there is uncertainty on all of the sim-
ulations. Second, there are various factors that influence the regional energy flux,
but in this study, only the land cover change is taken into account to analyze its
impacts on the regional energy flux.
5.3 Numerical Simulation of the Effects of Grassland
Degradation on the Surface Climate in Overgrazing
Area of Northwest China
As one of the most widespread land use type, grassland covers about 40 % of the
total area of China. It can not only provide amount of food and materials such as
milk, meat, forage, etc., but also can regulate the regional climate, e.g., the mit-
igation of greenhouse gas (GHG) emissions through soil organic carbon (C) and
nitrogen (N) sequestration (Fan et al.
2008
; Barthold et al.
2013
). In the past
decades, the grassland degradation and desertification in Northwest China have
greatly intensified due to the livestock overgrazing, rapid population growth,
irrational exploitation of the natural resources, and the expansion of road network
in recent years (Xu et al.
2012
; Deng et al.
2011a
,
b
). Furthermore, the grassland
degradation has led to the decline of grassland productivity and increased the
frequency of extreme climate events such as droughts and fierce freeze-up, which
have seriously influenced the sustainable development of animal husbandry (Deng
et al.
2011a
,
b
). Therefore, it is of great importance to study the influence of
grassland degradation on the climate in the overgrazing area of Northwest China
(Bounoua et al.
2002
).
Some studies have found that the grassland degradation in overgrazing areas of
Northwest China has brought about obvious effects on the regional climate (Nobre
et al.
1991
; Foley et al.
1996
; Gibbard et al.
2005
). However, those researches
mainly focused on the effects of grassland degradation in the historical period,
