Abstract
This paper discusses a method for
desertification monitoring and estimation.
Vegetation Index (VI) and Temperature Index
(TI) can be get from AVHRR data. They are
utilized for recognizing the features of
desertification in China. Estimation indicators of
desertification are abstracted from them.
Introduction
Desertification is one of the main global
environmental problems. It has resulted in
deteriorating environment and poor econemy ,
and imposed threat to the surviving environment
of the overall mankind. Its damages have been
found in one sixth of the global population and
two third of the countries/regions in the world
with an annual direct economic loss up to
US$ 42.3 billion. This fact has called for
international communities pay wide concerns
and closed attention to desertification problem.
To combat desertification and protect ecological
environment of the earth have become the
common action of mankind.
China is one of countries that are affected by
desertification with serious adverse impact. One
third of national terrestrial land is threatened
by desertification. It is important especially for
protecting natural resource and sustainable
development in China to combat desertification.
According to the definition in UN convention
to Combat Desertification, "Desertification"
means land degradation in arid, semi-arid and
dry sub-humid areas resulting from various
factors, including climatic variation and human
activities [1]. Land desertification is in macro
scale and dynamic process. It is a significant
task to monitor desertification status and
dynamic changes timely and efficiently, to
provide evidence for executives and planning
sectors to assist them in making macro-decisions
for combating desertification. This paper
examines the approaches of desertification
monitoring and estimation based on remotely
sensed data in macro-scale.
Stydy Area and Object
The arid, semi-arid and dry sub-humid areas
in China, classified by moisture index in 1981-
1990 (see following table) are the areas for this
study, they are mainly distributed in 11
provinces/autonomous regions in northern and
western China (Fig.1). Classification of
desertification patterns are divided into
following patterns according to the major
external movement forces to cause
desertification process
- Desertification caused by wind erosion
and eolian process;
- Desertification caused by water erosion
and alluvial process
- Desertification caused by frozen and
melting process at cold plateau;
- Desertification caused by soil
salinization/alkilization and waterlogging;
- Desertification caused by other interacted
factors (resultant factors).
Figure 1
Climate types of desertification
According to the severity of desertification,
each pattern above is divided into slight,
medium and severe grading classes. The wind
erosion desertification whose area is largest and
damage is most
obvious in China, is objective for this study.
Surface vegetation and temperature informations
were abstracted from NOAA/AVHRR data
(provided by EROS Data Centre of USA, helped
by Mr. Zhu Zhiliang ). The parameters of
remotely sensed data for desertification classes
were drawn, and grading indicators of the
severity of desertification were determined
based on the ground survey data.
Indicators of climate types classification[2]
| Climate Types |
Moisture Index(MI) |
|
| Extreme arid area |
MI < 0.05 |
| Arid area |
0.05 ³ MI < 0.20 |
| Semi-arid area |
0.20 ³ MI < 0.50 |
| Dry sub-humid area |
0.50 ³ MI < 0.65 |
| Humid area |
MI £ 0.65 |
