Biodiversity in urban and suburban areas
1 The
current condition of biodiversity in urban areas
2 Biodiversity
characteristics of China¡¯s cities
The urban
environment has been greatly changed owing to intensive human activities and
the original ecosystem no longer exists. Because of the special position and
role it plays, biodiversity preservation in urban areas is, however, still an
important link in the biodiversity conservation of the whole country which can
not be neglected.
The
urbanization process in China was fairly slow for a long period, After the
establishment of the PRC, especially after 1979, this process has been speeded
up. There were only 136 cities and 2000 registered towns in 1949. By the end of
1995, the number of cities and registered towns had reached 640 and 16,922,
respectively, with a total population of 377,899,000, making up 31.28% of the
state¡¯s total, It is expected that this will increase by 35% in 2000 and more
than 40% in 2010.
1
The current condition of
biodiversity in urban areas
Animal and
plant species in urban areas of China have similar characteristics to
elsewhere. For plants: (1) there are more species of herbs than woody plants in
urban areas, e. g., among 287 species of wild plants in Yuanmingyuan (the
ruined Summer Palace in Beijing,), there are 44 woody species making up 15% of
the total, while herbs, with 243 species, make up 85%. The corresponding
figures for Yingtaogou Park in Beijing are 23% and 77%; (23) weeds and
anthropophilic species make up a big proportion of wild plants in urban area,
e. g., also in Yingtaogou Park, Beijing, weeds comprise 16% of the total wild
species, and include certain naturalized plants, such as Canabis sativa, Amaranthus
retroflexus, Pharbitis nil, P.
purpurea, Datura stramonium and Ageratum conyzoides. In Hangzhou, it has been ascertained that there are 36 naturalized
species, mostly terrestrial weeds; (3) the abundance of wild plants increases
gradually from the city centre to suburban areas, e. g., there are less than 10
species in the densely built up city centre of Beijing while there are more
than 50 species in Zizhuyuan (Purple bamboo) Park in the urban edge, 287 in
Yuanmingyuan (the ruined Summer Palace) in the suburbs, 433 in Yingtaogou, and
511 on the Jinshan Mountain in the outskirts; (4) pollution-resistant specis
increase, e. g., the highly pollution-resistant species Broussonetia papyrifera often dominates highly polluted industrial
areas. Domestic sewage discharges result in eutrophication of urban waters
which, in turn, results in changes to the species composition and abundance of
algae. For example, on the east coast of the West Lake, Hangzhou, adjoining the
urban area, the dominant algal population of diatom and green algae has changed
to Cyanophyceae owing to water pollution. Dominant species are Aphanizomenon flos-aquae, following by Lungbya circumcreta and Merismopedia
punctata. On the other hand, air
pollution, especially by SO2, has caused vulnerable lichen species
extinction in urban areas, e. g., there are basically no lichens in the
built-up areas of Beijng.
For animals
influenced by intensive human activity, wildlife habitats in urban areas have
drastically deteriorated. Those which can survive are only anthrophilous
species, some species inhabiting residential areas, and other species in
suburban farmlands and abandoned lands, Urban animals are generally
characterized by either a few species or large numbers of single species.
Abundance increases from urban to suburban areas. Urban greenlots have been
increasing during recent years. According to statistics, revegetated areas
occupy an average of 23.9% of the built-up areas in the whole country. These
revegetated areas serve as habitats for wild animals in urban areas, resulting
in an increase in some species. Birds in residential areas are dominated by
sparrows, magpies, swifts (Apodidae), esculent swifts (Hirundo daurica) and swallows. The sparrow is the dominant species
of urban bird. The number of birds increases in parks and suburban areas, e.
g., the sparrow is the only species which can still be seen in the central
district of Shanghai, a few seagulls can be seen in winter around the urban
reaches of the Huangpujiang River in the city, while in the suburban Jinshan
area, owing to extensive greenlots, bird species increase to about 350, making
up 82.54% of the total for the city, Asio
otus otus, Cyanopica cyana
interposita, Hirundo rustica
gutturalis, Motacilla alba leucopsis, Pycnonotus sinensis, Copsychus saularis prosthopellus, Garrulax canorus canorus, Cuculus canorus canorus, Oriolus chinensis diffusus, Streptopelia chinensis chinensis are
common species. Owing to their diverse habitats, city parks used to attract
many birds. For example, Yuanmingyuan (the ruined Summer Palace) situated in
the suburbs of Beijing has 159 species of birds, accounting for 46.6% of the
total in the area. Dominant species are Parus
major, Lanius crustatus, Cyanopica cyana interposita, Oriolus chinensis diffusus, Parus palustris hellmayri, Sturnus cineraceus, Pica pica sericea, and Dendriopus major. During the last 30 years, owing to the increase in population, the
development of traffic and the increased use of vehicles, bird species in urban
areas and parks have decreased rapidly. For example, Egretta alba modesta and 3 other species of egrets, which could be
seen in the Imperial Ancestral Temple and were netted in trees in the 1950s,
have disappeared. Others such as species of Corvus, Pica pica, Oriolus, and Dicrurus microcercus are also
decreasing, as are Streptopelia, birds of prey, Upupa epops saturata, and
Eurystomus orientalis. In recent years, migrating wading birds
and waterfowl have frequently visited aquatic areas in city parks, e. g., swans
were seen several times on the Jishuitan and Yuyuantan Lakes in the urban areas
of Beijing, and large numbers of Red-beaked gull over winter every year in
Cuihu Park, Kunming. Nevertheless, the destruction of aquatic habitats due to
human activity in urban areas has resulted in a rapid decrease in waterfowl and
other species of birds relying on urban areas has resulted in a rapid decrease
in waterfowl and other species of birds activity in urban areas has resulted in
a rapid decrease in waterfowl and other species of birds relying on such areas.
Accordingly, birds of prey and insectivorous birds have also decreased rapidly.
There are
not many species of mammals in urban areas, large and medium sized such animals
having long since disappeared owing to human activity. Small species of
Rodentia and Chiroptera, e. g., Vespertilios
superans, Mustela sibirica, Rattus norvegicus and Mus musculus, are commonly found in residential areas. Mu. musculus, is widespread, in large numbers, in Beijing, while Rattus norvegicus is concentrated in wet
environments such as sewers and cellars. There are more mammals in city parks
than in residential areas. Species numbers increase in suburban areas. For
example, Xiangshan (Fragrant hill) Park in Beijing has the most abundant
mammals with about 16 species. Next is the Summer Palace and the ruined Summer
Palace with 12 species, and 4 species. Occur in urban zoos.
Butterflies
and moths (Lepidoptera) are abundant in terms of species and numbers, and are
mostly injurious insects of artificial forests and other arbors and shrubs. In
addition, the Coleoptera, Homoptera, and Hemiptera are also common. Various
kinds of flies and mosquitoes are abundant in residential areas. Accompanying
improvements in central heating for winter and the increased contact between
people, cockroaches have been increasing rapidly in residential areas,
hospitals, and schools in Beijing.
2
Biodiversity characteristics
of China¡¯s cities
(1)
Abundance of woody plants for urban
revegetation
Because it
is a vast country, Chinese cities are distributed in various thermal zones,
from cold temperate to temperate, to subtropical and to tropical zones, and in
which temperature regimes are quite different. On the other hand, Chinese
cities are mainly concentrated in eastern humid and semi-humid areas.
Metropolitan and large cities are mainly situated in eastern coastal regions.
Only two (Lanzhou and Urumqi) of 31 metropolitan cities are situated to the
west of the line from Da Hinggan Ling-Luliang Shan-Liupan Shan-the eastern edge
of the Qingzang Plateau. The other 29 are situated to the east of this line.
This geographical feature enables Chinese cities to provide favorable moisture
condition for plants and the possibility for survival of those with different
temperature requirements. Not only can many and varied native plants grow here,
but other exotic species can also survive. Consequently, the vegetation of
woody plants in Chinese cities is rich and varied (Table 1). From Harbin to the
south, via Hohhot, Beijing, Zhengzhou to Changsha (data not available for
Guangzhou), the species of evergreen plants and deciduous plants are all
increasing, while the difference between east and west are becoming less
significant, e. g., there is only small decrease in species at Chengdu, Sichuan
Province, in comparison to Hangzhou, at a similar latitude, in coastal Zhejiang
Province in the east.
Table
1 Planted species of trees, shrubs and lianas in some of China¡¯s cities
(according to the data of
1979-1980)
|
City |
LTD |
MAT |
AP |
ENT |
EBT |
DNT |
DBT |
EBS |
ENS |
DS |
EL |
DL |
BM |
Total |
|
Harbin |
45o41/ |
3.6 |
553.5 |
11 |
74 |
4 |
46 |
8 |
¡ª |
143 |
||||
|
Hohhot |
40o49/ |
5.6 |
426.1 |
16 |
¡ª |
2 |
133 |
¡ª |
12 |
5 |
¡ª |
168 |
||
|
Beijing |
39o50/ |
11.6 |
600 |
50 |
9 |
108 |
9 |
16 |
83 |
2 |
15 |
9 |
618 |
|
|
Zhengzhou |
34o43/ |
14.3 |
640.5 |
35 |
25 |
5 |
140 |
25 |
78 |
10 |
¡ª |
318 |
||
|
Changsha |
28o5¡ä |
17.2 |
1,411.4 |
55 |
90 |
6 |
163 |
110 |
100 |
36(Tree) |
21 |
581 |
||
|
Guangzhou |
23o7¡ä |
21.8 |
1,622.5 |
|
|
|
|
|
|
|
|
796 |
||
|
Chengdu |
30o23/ |
16.0 |
976 |
39 |
109 |
2 |
123 |
58 |
51 |
32 |
|
414 |
||
|
Hangzhou |
30o15/ |
16.1 |
1,400.7 |
64 |
64 |
6 |
172 |
79 |
13 |
128 |
36 |
19 |
581 |
|
Abbrevs: (LTD)
Latitude, (MAT) Mean annual temperature, (AP) Annual precipitation, (ENT)
Evergreen needle leaf trees, (EBT)
Evergreen broad leaf trees, (DNT) Deciduous needle leaf trees, (DBT) Deciduous
broad leaf trees,
(EBS) Evergreen broad leaf shrubs, (ENS) Evergreen needle leaf shrubs, (DS)
Deciduous shrubs, (EL) Evergreen
lianas, (DL) Deciduous lianas, (BM) Bamboo.
(2) Rare and old trees in China¡¯s cities
A few rare and
old trees have been preserved in the ancient cultural cities of China, urban
gardens, temples and residential courtyards. For example, according to the 1988
census in Beijing, there are 3,804 trees more than 300 years old and 19,723
trees more than 100 years of age in urban and suburban areas. The latter figure
can be increased to more than 50,000 if the city outskirts are taken into
account. Similarly, There are more than 10,000 old trees over 100 years old in
Jinan.
(3) City zoos and botanical gardens have made
important contributions to the ex situ preservation of rare, valuable and endangered species
An
important role of zoos and botanical gardens is that they provide not only
places for sightseeing and popular science education but, also, if not more
important, provide a means to teach people to love nature, to care for and to
study other organisms, and are important bases for the ex situ preservation of endangered species. Much work has been done
in the last 40 years to rescue endangered wildlife. An eminent example is the
Giant panda which has been raised in zoos since 1955 and successfully
artificially propagated since 1963. Many other animals have also been
successfully artificially propagated and a few of them have been returned to
nature experimentally. There are more than 100 botanical gardens throughout the
country, distributed in large and middle-sized cities and their suburban areas.
They have become domestication centers and bases for rare, valuable and
endangered species. During the recent 10 years, many of these botanical gardens
have successfully introduced and propagated some rare, valuable and endangered
species. This has enabled the ex situ preservation
of most species listed in the first group of the ¡°List of rare, precious and
endangered plants in China¡±. These activities have made great contributions to
biodiversity preservation in China.
In its
entirety, the city and its suburban area influence each other. Suffering from
the expansion of urban areas, suburban areas are experiencing vegetation
regression, species reduction, soil compaction, organic matter reduction, and
soil erosion. Quarrying and gravelling in some suburban areas has destroyed
natural ecosystems and landscapes, causing further deterioration to the
suburban environment, which, in turn, has deteriorated the urban environment.
Attention must, therefore, be paid to the protection of the suburban ecosystem
and its biodiversity.
Secondly,
funding is very important. A lack of money has already placed many zoos and
botanical gardens in a dilemma. This is detrimental to the ex situ preservation of endangered species. In order to effectively
preserve and to rescue extremely endangered species of animals and plants,
appropriate funding is an urgent requirement.