|
Characteristics of Invasive Species in China
|
|
Xie Yan, Li Zhenyu
China
is the world's third largest country and one of the richest in terms
of biodiversity. Its vast territory stretches 5,200 km from east to
west. It spans 50 degrees of latitude, and covers five climatic zones:
cold-temperate, temperate, warm-temperate, subtropical, and tropical.
A wide range of habitats and environmental conditions makes China
especially vulnerable to the establishment of invasive species of
foreign origin. Potential invasive alien species from most areas of
the world may find suitable habitat somewhere in China. Criteria to define an invasive alien species:
1、has been introduced
into an area where it is not native from its natural range by either
intentional or unintentional human activity; Features
of invasive species in China 3. Have
invaded into various ecosystems. Alien species occur in almost
every watershed and ecosystem, including forests, wetlands, grasslands,
croplands, residential area in cities, etc. The aquatic ecosystem
has most severely effected. 4. Invasive
species cover most of taxonomic groups. They represent many taxonomic
groups, including mammals, birds, reptiles, amphibians, fishes; arthropods
and crustaceans; algae, ferns and seed plants; and fungi, viruses,
bacteria, and other micro-organisms. 5. Many
unintentional introductions. As travel and trade have increased,
travelers and transported goods have provided pathways for introducing
more and more species as hitch-hikers on clothing and vehicles; in
containers, packaging materials, shipping waste, and ship's ballast;
and as contaminants in shipments of agricultural seeds and other biological
materials. Some of the most invasive, damaging and widespread unintentional
introductions include the banana moth (Opogona sacchari), fall webworm
(Hyphantria cunea), brown rat (Rattus norvegicus), ragweed (Ambrosia
spp.), amaranth (Amaranthus spp.), goldenrod (Solidago spp.), crofton
weed (Eupatorium adenophorum), and spinyflower alternanthera (Alternanthera
pungens). 6.
Many intentional introductions. China has a long history of introduction
of non?native species, especially species proven to be productive
elsewhere and offering potential economic benefits to China. Early
introductions were associated with immigration and trade among different
regions. Alien species have often introduced from other countries
and from one region of China to another for economic development,
recreation uses, or environmental improvements. Many of them have
been introduced by institutions involved in agriculture, animal husbandry,
forestry, horticulture, aquaculture, and species specific centers
for farming and breeding. 7. Impact
of invasive species are obvious. Unintentionally
introduced diseases and pests have caused great economic loss in many
sectors, such as agriculture, husbandry, forestry and horticulture.
These losses have drawn the attention of government agencies responsible
for customs and quarantine. Particularly pests in agriculture include
black spot of sweet potato (Ceratocystis fimbriata), fall webworm
(Hyphantria cunea), vegetable leaf miner (Liriomyza sativae), and
ragweed (Ambrosia spp.); in animal husbandry, crofton weed (Eupatorium
adenophorum); in forestry, fall webworm and alligator weed (Alternanthera
pungens); and in horticulture, banana moth (Opogona sacchari). Intentionally
introduction has caused economic or environmental damage. The four
popular fish farming species, black carp (Mylopharyngodon piceus),
silver carp (Hypophthalmichthys molitrix), bighead (Aristichthys nobilis),
and grass carp (Ctenopharyngodon idella), were widely distributed
and bred in most rivers and lakes in China. They have been also introduced
from their native ranges to other regions of China, and bighead and
silver carp have been reported to cause serious disruption. Other
intentional vertebrate introductions include nutria (Myocastor coypus)
from South America to support the fur trade. Several introduced vascular
plants also cause significant disruption, including water hyacinth
(Eichhornia crassipes) and alligator weed (Alternanthera philoxeroides)
(both originating in South America), and common cordgrass (Spartina
anglica) from western Europe. Invasive
species have changed local ecosystems by modifying species composition,
population structure, food chains and environmental pollution. Accordingly
has largely reduced their ecological functions as circulation of soil
nutrition, erosion control, and biodiversity protection. The damages
they have caused to lands, freshwater area and offing are obvious.
For instance, Yunnan Province has 432 documented fresh water fish
species. However, the specimens of about 130 fish species or 30% of
total number in Yunnan have not been caught for the last 5 years.
About 150 fish species or 34.7% of total number, which were the common
species in 1960s, have become the uncommon species. The rest 152 species
have an evident decline in population sizes comparing with that of
1960s. According to experts, the main reason is the introductions
of alien fishes.
8. Intentional or unintentional
introductions when restoring the natural vegetation.
For many years, government departments of agriculture, forestry, and
animal husbandry, as well as customs authorities in China, have paid
great attention to the potential harm of a small number of alien species,
leading to the quarantine of alien diseases and pests. However, it
was only a few years ago that the concept of invasive species was
introduced into China and the potential threats to China's natural
heritage are not yet widely recognized. Not enough attentions are
paid to those have not caused severe economic damage but are competing
with and substituting for the endemic species and changing the local
ecosystems. Therefore, intentional or unintentional introductions
of alien species when restoring the natural vegetation on a large
scale will necessarily bring the great loss of Chinese abundant and
endemic biodiversity and beyond retrieval. At present, the introductions
of alien species on a large scale in China include: Alien
species including eucalypts, alien pines, alien larches are planted
in a wide area during large-scale reforestation and many economic
trees are planted at inappropriate altitudes or regions. Those woods
have been proved with very limited ecological functions. In
the large-scale erosion control and reforestation, China mainly depends
on importation of grass seed from other countries, especially from
United States. Nursery, study and utilization of Chinese endemic grass
seeds are very few and largely inadequate. China is devoid of the
efforts in vegetation restoring by collecting and implanting local
endemic grass seeds. This would large reduce and change local biodiversity. Alien
species are used in vegetation restoring in Nature Reserves. The main
reason is that people have no confidence in their local species. Many
people hold the view that alien species must be better than local
ones. For instance, The Dongzhaigang Nature Reserve has restored mangrove
by using Rhizophora spp. from Bengal. Moreover, many alien species,
which usually are the main sources of invasive species in these regions,
are used in developing gardens in nature reserves and scenic spots. The mass usage of alien species in vegetation restoring and greenlization surrounding urban area usually thoroughly changes local ecosystems and landscapes.
|
Rainbow
lorikeet (Trichoglossus haematotus)