River Ecology and Restoration - River Dynamics and Integrated River Management - page 652

reduced to almost zero. In the large closed plot the abundance has reduced by two thirds and the species
number reduced by one third (Duan and Wang, 2008). The results indicate that habitat fragmentation is a
serious stress on the ecosystem and must be considered in ecological restoration of the river-lake
complex system.
Mining —Gold placer mining in rivers has become an extreme intensive disturbance to the stream
ecology in southwestern China. Figure 10.28(a) shows placer mining in the Bailong River, which is a
tributary of the Jialing River in Sichuan Province. People are removing bed gravel from the river for
placer mining. The benthic invertebrate community is completely disturbed. Moreover, mercury is used
in the process, which has also resulted in water pollution. Compared with gold mining, gravel mining is
much more wide-spread. Since the 1980s, gravel mining has become a serious ecological stress in many
rivers throughout China, as shown in Fig.10.28(b). Gravel and coarse sand are mined for building materials.
Gravel mining causes loss of habitat for benthic biocommunities and loss of spawning ground for many
fish species. Lacking laws for controlling river sediment mining and attracted by great economic benefit,
sediment mining has developed so quickly that almost all streams are stressed.
Surface mining also causes stresses on the river ecosystem. Exploration, extraction, processing, and
transportation of coal, minerals, and other materials have had and continue to have a profound effect on
(a)
(b)
Fig. 10.28 (a) Gold placer mining in the Bailong River, a tributary of the Jialing River in Sichuan; (b) Gravel mining
for building materials from the Qingjiang River, a tributary of the Yangtze River