Geoscience Reference
In-Depth Information
98.6
×
10
8
kg, and with total industry losses of
26.8 billion RMB (Wang and Zhu, 2002). This
flow break also resulted in negative environmental
impacts, such as soil salinity rises in the riverine
zone, desertification of soil, landward movement of
saline and brackish delta ecosystems and damage
to some estuary ecosystems with less sand being
transmitted and deposited.
While data are scarce on ecological changes to
the more inland stretches of the river resulting
from changes to ecological flows, for the lower
reaches and estuarine region several reviews have
been published. Estuarine primary productivity
was affected dramatically by the decrease in
nutrient input, and associated rises in salinity and
surface temperature of sea water (Tian and Wang,
1997; Fan and Huang, 2008); all associated with
decreasing flows of fresh water in the 1990s. Lack
of freshwater outflow from April to June (He
et al.
,
2000) affected the spatio-temporal hydro-dynamics
with impacts on the spawning and hatching of fish
and shrimp. The effects combined to contribute
to fish and crustacean resources declining in the
estuary and adjacent open bay. The number of fish
species declined from 146 in the 1950s to 119 in
the 1980s, and 73 in the 1990s. The fish catch in
Laizhou Bay in 1998 was only 3.3% of that in 1959
(Jin and Deng, 2000).
During the period of decreased freshwater flows,
the vegetation of the lower reaches of river shores
changed from meadows dominated by Lalang Grass
(
Imperata cylindrical
var.
major
) to a brackish/saline
vegetation type, especially an increase in reed beds
dominated by
Phragmites australis
(Wang, 2000).
The combined evidence of human and ecological
dysfunction persuaded the Chinese government In
1987 to set the total annual flow of the river at 58
billion m
3
(Yu, 2006) and the annual flow needed
for flushing 1.6 billion tons of sand into the sea is
21 billion m
3
. By 1999, the Chinese government
adopted a provincial water quota management that
maintains 21 billion m
3
for ecological flows by
limiting the maximum water use along the river to
37 billion m
3
. Thus while some problems remain,
there are now management strategies in place to
ensure the continued ecological flows of the river,
and since 1999 it has not failed to reach the sea,
thus ensuring the continued provision of services
from all its component ecosystems.
The Yangtze River
Poyang Lake, the largest freshwater lake in China,
is located on the southern bank of the middle
reaches of the Yangtze River, and is fed by five
major rivers: the Gan, Fu, Xing, Rao and Xiu.
Because of its natural links with the Yangtze
River the system is a typical flood-fed lake, with
significant water level fluctuation throughout the
year. With the flooding in summer, the lake
extends to more than 3000 km
2
, while in winter
it is less than 1000 km
2
. Water level fluctuation
is the main driver for landscape dynamics between
different wetland types in summer and winter.
The lake is a major centre for avian diversity,
with 99% of the world's critically endangered
Siberian crane (
Grus leucogeranus
)(Wu
et al.
,
2009), over 95% of the world's endangered
oriental stork (
Ciconia boyciana
), and over half
of the world's threatened swan geese (
Anser
cygnoides
) and white-naped cranes (
Grus vipio
)
wintering there (Barter
et al.,
2004; Cao
et al.,
2008). Poyang Lake also supports numerous
other aquatic animals dependent on its wetlands,
including the globally threatened finless porpoise
(
Neophocaena phocaenoides
) (Xiao and Zhang,
2002), the endangered Chinese sturgeon (
Acipenser
sinensis
)
and
the
critically
endangered
Chinese
paddlefish (
Psephurus gladius
).
Table 24.2 shows the range of provisioning,
regulating, cultural and support ecosystem services
recorded for the lake, the main drivers and their
scale effects. The key conclusions are:
1)
Ecosystem services have been declining over the
past 50 years, with major drivers being wetland
reclamation, water pollution and over-exploitation
of natural resources.
2)
Supporting services are by far the most
important, with success in managing migratory
waterbird populations.
3)
Cultural services may become more important
with the socio-economic development of China and
enhanced environmental awareness.
The CBD's ecosystem approach and its 12 guiding
principles (CBD, 2010b) offer a useful framework
