Geoscience Reference
In-Depth Information
evation model (DEM) that provides a sense of the topographic
relationships in the reserve. This image reveals that the most
rugged terrain is on the western side of the reserve and is
unsuitable for pandas (Figure 20.33c), whereas the best panda
habitat is to the east.
A major effort at the Wolong Reserve is to document
changes in the distribution of panda habitat over the past few
decades and to predict future patterns. Much of this research
assesses the changes in
land cover
, such as roads and forests,
on the landscape over time. Satellite imagery from the mid-
1960s to 2001 at the Wolong Nature Reserve, for example,
reveals that a significant amount of deforestation occurred
throughout the reserve during that period of time (Figure
20.34). In 1965, about 43% of the nature reserve was forest-
ed, whereas by 2001 forests had decreased to approximately
36% of the area. This modification in vegetation was most
closely associated with the change from forest to cropland,
grassland, and shrub land, particularly along the rivers and the
main roads. Although the area is technically a nature reserve,
~5000 people live within the boundaries of the park. About
90% of them are farmers who engage in agriculture or live-
stock breeding in cleared areas. Perhaps the most important
cause of forest loss was the collection of wood fuel by peasant
farmers who lacked the income to purchase other sources of
fuel for cooking and home heating.
Aside from the extensive loss of forest cover, a major out-
come of deforestation between 1965 and 2001 was the inten-
sive fragmentation of the remaining panda habitat. In other
words, patches of healthy bamboo in the understory were
cut off from one another. You can see the nature and extent
of habitat fragmentation by examining Figure 20.35, which
again shows a time series of forest loss, this time between
1965 and 1997. This degree of fragmentation is potentially a
serious problem because it reduces the quality and quantity of
panda habitat and decreases the carrying capacity for the ani-
mals. It also limits the ability of pandas to move from one area
of suitable habitat to another, which increases the potential for
the animals to become genetically isolated from one another.
If this trend were to continue, it would dramatically increase
the probability of extinction through inbreeding. Unchecked,
this type of human impact is projected to result in the loss of
up to 16% of all existing panda habitat by 2035.
As the geography of forest loss in the Wolong Nature
Reserve and other panda habitats became more apparent in
the latter part of the 20th century, the Chinese government
responded by outlawing logging in protected panda areas in
1998. In return, farmers were offered government payments
to allow cropland to convert back to forest. At about the same
time, conservation efforts by international organizations such
as the World Wildlife Fund (WWF) began to have significant
positive impacts. In 2002, for example, an agreement between
(a) Potential
(b) 1965
(c) 1974
974
(d) 1997
10
0
10
20 km
(e) 2001
Figure 20.34 Deforestation of the Wolong Nature Reserve be-
tween 1965 and 2001.
Note the change in forest cover that oc-
curred during this interval of time. The “potential” map refers to
the expected amount of forest if no deforestation had occurred in
the area.
the WWF and the Shaanxi Forestry Department was signed to
create 13 new panda reserves and develop the first corridors
in the Qinling Mountains to connect fragmented habitats. A
further positive development was that rising wages associated
with regional economic development reduced pressure on for-
ests because more people gained access to electricity and thus
did not need wood fuel for heating. These combined factors,
among others, have the potential to stabilize the ongoing loss
of panda habitat and to slowly turn things around in the com-
ing decades. Panda habitat may begin to recover after about
40 years of forest regeneration. If the logging ban is main-
tained, previously forested tracts may regenerate entirely and
the odds for long-term survival of pandas will increase.
Land cover
The various things that cover the landscape, such
as forests, roads, and water bodies, at any point in time.
