River Ecology and Restoration - River Dynamics and Integrated River Management - page 661

sunlight, and space and can adversely influence establishment rates for new plantings, foods, and habitat.
In some cases, exotic plant species can even detract from the recreational value of streams by creating a
dense, impenetrable thicket along the streambank.
Many exotic species have been introduced as consequences of human activities. For instance, at least
708 floral species and about 40 faunal species have been successfully introduced into China in the past
century, among them several tens of species have caused ecological problems. A lot of money has been
spent to remove these species. The most harmful species are Eupatorium adenophorum , Eichoimia crassips ,
Ambrosia artemisia L., and Spartina alterniflora .
Spartina alterniflora was introduced from the U.S. in 1980 to control coastal erosion and accelerate
land creation in estuaries. The species may grow in salt marsh, because they tolerate periodical tidal
inundation and resist wave erosion. The species colonize silt coasts very quickly and stabilize the coast
with its dense roots. Nevertheless, the species dominate silt coasts and estuaries, resulting in a great
reduction in biodiversity. Many invertebrates and fish cannot live in the shallow waters with Spartina
alterniflor . The species has over to spread the neighboring coastal areas. Coastal areas and estuaries
dominated by reed ( Phragmites communis trirn ) have been colonized and occupied by Spartina
alterniflor . The fishery harvest has been significantly reduced. Figure. 10.39(a) shows Spartina alterniflor
in the Yangtze River estuary.
(a) (b)
(c) (d)
Fig. 10.39 (a) Spartina alterniflor in the Yangtze River estuary; (b) Eupatorium adenophorum in southwestern
China; (c) Eichoimia crassip in polluted waters; (d) Ambrosia artemisia L. in northeastern China. (See color figure at
the end of this topic)