Biological diversity of deserts
1 China¡¯s
desert biodiversity
2 Threats
to China¡¯s desert biodiversity
3 The
urgent rescue of China¡¯s desert biodiversity
China¡¯s
deserts are roughly distributed to the northwest of the line Lang Shan-Helan
Shan-Burhan Budai Shan and have a total area of 1,920,000km2,
accounting for 20% of the national territory. It includes three large basins
(Junggar, Tarim, Qaidam) and a high plain (Alxa). Surrounding the whole desert
area and between its basins exist high mountain ranges. The natural conditions
and biological diversity on these mountains are different from those on flat
ground. This section deals with the latter only.
Strong
continentality, little precipitation, extreme climatic variations, intense
sunshine, strong winds and sandstorms in winter and spring are typical climatic
features of deserts. According to their substrata, deserts may be divided into
sandy, gravel (Gobi), loam (loess deposits), clay (saline desert) and rocky
(inselbergs). The first two have the largest areas and biodiversities
encountered in different substrata differ from each other.
1
China¡¯s desert biodiversity
(1) Plant species diversity
a. Poorness
Compared
with other terrestrial ecosystems, the species composition of deserts is relatively
poor. The total number of seed plants encountered in the vast desert areas of
Northwest China is just a little more than 600. The Junggar Basin plain with an
area of 200,000 km2 is considered to have the richest flora, yet,
only about 500 species have been recorded. The flora of the Tarim Basin
(500,000 km2) comprises less than 200 species. The Ga Shun Gobi of
East Xinjiang has a still poorer floral composition and only 34 species of plants
have been collected from within its area of 20,000 km2.
b.
Ancientness
Although
plant species richness is low, deserts contain large numbers of ancient and
relic elements. Many plants occurring here are relics of the Tertiary, even the
Cretaceous, representing the dry and hot environment of the Tethys Sea. The
species composition of most such desert communities is dominated by them.
c.
Uniqueness
The
ancientness of its flora and fauna, combined with extremely harsh ecological
conditions, has determined the uniqueness of the biotic elements of China¡¯s
deserts. Large numbers of native endemic genera and species have been found
here. The following five genera are well-known: Tetraena, Potaninia, Tugarinovia,
Stilpnolepis and Synstemon.
They are either monotypic or oligotypic genera and characterized by their
specialized morphology, narrow distribution range and, for some, their
phylogenetic position is hard to determine.
The genus Ammopiptanthus has only two species. A.
mongolicus is distributed in the eastern part of the Alxa desert, while
another species, A. nanus, is distributed in the southwestern corner of the Tarim Basin,
occupying a small area on the northern slope of the Kunlun Mountain. These two
ammopiptanthuses are the only evergreen shrubs to be found in Northwestern
China¡¯s deserts. They are xerophytic relic species of subtropical evergreen
broadleaved forests of the Old Tertiary.
There are
more native endemic species. Large numbers (>100) of edificator and dominant
species of the desert vegetation of this region are native endemics. The 29
species identified in Table 1 may be cited as representative.
Considering
the number of species and the roles they play in such ecosystems, the
Chenopodiaceae, Zygophyllaceae, Tamaricaceae, Compositae and Polygonaceae may
be thought of as leading families in the deserts of Northwestern China. Four
other characteristic families of flora occur in the same area: Cynomoriaceae,
Frankeniaceae, Cistaceae and Gymnocarpaceae.
Table 1 Major endemic plant species of Northwest
China¡¯s deserts
|
Species |
Distribution |
|||||||
|
Junggar |
Tarim |
East Xinjiang |
Qaidam |
He Xi Corridor |
Alxa |
Eastern Alxa |
Whole area |
|
|
Ephedra przewalskii |
+ |
+ |
+ |
+ |
|
|
|
|
|
E.
pr. var.
Kaschgarica |
|
+ |
|
|
|
|
|
|
|
Calligonum
roborovskii |
|
+ |
|
|
|
|
|
|
|
Anabasis brevifolia |
+ |
+ |
+ |
|
+ |
+ |
|
|
|
Iljinia regelii |
+ |
+ |
+ |
|
|
|
|
|
|
Kalidium gracile |
+ |
|
|
+ |
+ |
+ |
|
|
|
Salsola passerina |
|
|
|
|
+ |
+ |
|
|
|
S.
laricifolia |
+ |
|
|
|
+ |
+ |
|
|
|
S.
abrotanoides |
+ |
|
|
+ |
+ |
|
|
|
|
Sympegma regelii |
|
|
+ |
+ |
+ |
+ |
|
|
|
Gymnocarpus
przewalskii |
|
|
|
|
+ |
+ |
|
|
|
Potaninia mongolica |
|
|
|
|
|
+ |
|
|
|
Amygdalus mongolicus |
|
|
|
|
|
|
+ |
|
|
Ammopiptanthus nanus |
|
+ |
|
|
|
|
|
|
|
Nitraria
sphaerocarpa |
+ |
+ |
+ |
|
+ |
+ |
|
|
|
N.
roborovskii |
|
|
|
|
|
+ |
|
|
|
N.
tangutorum |
|
|
|
|
|
+ |
|
|
|
Zygophyllum
xanthoxylon |
+ |
+ |
+ |
|
+ |
+ |
|
|
|
Z.
kaschgaricum |
|
+ |
|
|
|
|
|
|
|
Tetraena mongolica |
|
|
|
|
|
|
+ |
|
|
Myricaria pulcherima |
|
+ |
|
|
|
|
|
|
|
Reaumuria songorica |
|
|
|
|
|
|
|
+ |
|
R.
kaschgarica |
|
+ |
|
|
|
|
|
|
|
R.
trigyna |
|
|
|
|
|
|
+ |
|
|
Tamarix
toklamakanensis |
|
+ |
|
|
|
|
|
|
|
Asterothamnus centriasiaticus |
|
|
|
|
+ |
+ |
|
|
|
Brachanthemum
gobicum |
|
|
|
|
|
|
+ |
|
|
B.
pulvinatum |
|
|
|
|
+ |
+ |
|
|
|
Canovinia
maximowiczii |
|
|
|
|
|
|
+ |
|
(2) Ecosystem
diversity
At the
level of the ecosystem, desert types in Northwestern China are diversified, and
not as monotonous as generally imagined. Based on preliminary statistics, the
sandy desert has eight ecosystems, the gravel-sand and gravel desert (Gobi) has
13, the rocky-crushed stone desert has 10, while the clay desert has 7. Along
the banks of desert rivers and in other azonal habitats, there are at least 9
ecosystems.
(3) Animal species diversity
Because of
similar ecological conditions, an obviously universal convergence of species
can be detected in deserts on different continents. This is also seen in animal
species between China¡¯s deserts and elsewhere: rodents, reptiles and ungulates
are numerous while there are few amphibians.
An abundant
and unique ungulate fauna has developed in the deserts of China. Among these,
ancestors of our present livestock can be found. These include, for example, Equus przewalskii, E. hemionus, Camelus bactrianus, Cervus elaphus yarkandensis,
Saiga tatarica, Procapra przewalskii and
Gazella subguttarosa. Other species come down from the
surrounding arid mountains to the borders of such deserts, and include Capra ibex, Ovis ammon and Pseudois
nayaur.
Rodents,
especially representatives of the Dipodidae (12 species) and Gerbillinae
(Cricetidae) (7 species), are particularly conspicuous in desert ecosystens.
Compared with adjacent humid regions, the species of birds and larger mammals
differ less, but birds of prey are more numerous (12 species).
Reptiles
are widely distributed in the desert ecosystems of Northwest China. Both
species and individuals are numerous. The most commonly seen are species of Phrynocephalus. And Eremias. In the western part of the deserts of
Xinjiang lives a unique terrestrial tortoise, Testudo horsfieldi. The
genus Phrynocephalus is an endemic
Palaeo-Arctic genus containing about 30 species in the world, and China has 12.
The poorest
are desert amphibians. There are only two toads found in Xinjiang, i. e., Bufo viridis and B. raddei. The former is
distributed in Western Xinjang, the latter is more widely distributed.
China¡¯s
deserts are also relatively poor in insects. Middle-Asian elements dominate,
but certain endemic groups can be found. For example, the family Pamphagidaes
has 5 endemic genera in Xinjiang, while Sphingonotus
(Oedipadidae) has 14 endemic species, also in Xinjiang.
Table 2
lists several representative endemic desert animal species.
2
Threats to China¡¯s desert biodiversity
Though
deserts are generally considered to be territorially vast and sparsely
populated, the impact of human activities ought to be relatively low. Many
parts of the deserts of Northwest China have, however, been severely damaged.
The biological resources are being seriously deveasteated and biodiversity reduced
rapidly. Threats come from:
Table 2 Representative endemic animals of the
northwestern deserts of China
|
Ungulata |
Procapra
przewalskii |
China, endemic |
|
|
Equus
hemionus |
China, and Mongolia, endemic |
|
|
Equus
przewalskii |
China, and Mongolia, endemic |
|
|
Camelus
bactrianus |
China, and Mongolia, endemic |
|
|
Cervus
elaphus yarkandensis |
Tarim, endemic |
|
Carnivora |
Ursus
arctos pruinosus |
China, and Mongolia, endemic |
|
Lagomorpha |
Lepus
yarkandensis |
Tarim, endemic |
|
Rodentia |
Allactaga
elater |
China, and Mongolia, endemic |
|
|
A.bullata |
|
|
|
Stylodipus
andrewsi |
China, and Mongolia, endemic |
|
|
Sapingotus
kozlovi Euchoreutes
naso Meriones
chengi |
China, and Mongolia, endemi; in Tarim China, and Mongolia, endemic Only in Turpan |
|
|
Brachiones
przewalskii |
China, and Mongolia, endemic; in Tarim |
|
|
Citellus
erythrogenys |
|
|
|
Phodopus
roborowskii |
Xinjiang, Qinghai, Inner Mongolia |
|
Reptilia |
Testudo
horsfieldi |
Ili valley, Middle Asia |
|
|
Phrynocephatus
przewalskii |
|
|
|
P. versicolor |
|
|
|
Eremias
przewalskii |
|
|
|
E. vermiculata |
|
|
|
Teratosincus
przeualskii ect. |
|
(1) Gathering fuel and digging medicinal herbs
It is
estimated that in desert areas of the Junggar Basin, on the average, each
inhabitant family utilises at least 2 tonnes of Saxoul (Haloxylon ammodendron and H. persicum) each year. This means that
6~7 ha of natural Saxoul forests must be cut, and is leading to their severe
destruction on the southern fringe of the Gurbantuggut Sandy Desert. Within
this area, large quantities of sand dunes have been created. The Populus euphratica forests of South
Xinjiang, with an area of 530,000 ha ten years ago, now has only less than half
left. Most of the original 4 million ha of Tamarix shrublands in Xinjiang have
also been destroyed. In the Alxa desert of Inner Mongolia, the Saxoul forests
have been reduced by 60% within 20 years since 1958. In addition, valuable
medicinal plants, such as licorice (Glycyrrhiza
spp.), Ephedra (Ephedra przewalskii),
Cynomorium (Cynomorium songaricum)
and others have all decreased owing to severe collection and uprooting.
(2) Overhunting and habitat destruction
Equus przewalskii, Saiga tatarica,
Xinjiang tiger (Panthera tigris
lecoqi), Desert bear (Ursus arctos
pruinosus), Camelus bactrianus,
Equus hemionus and Procapra
przewalskii are all desert dwellers, and were rather numerous in the
deserts of Northwest China a few centuries ago. Equus przewalskii disappeared from the wild in the nineteen-sixties
mainly because of overhunting. Saiga
tarica, originally widely distributed in Middle Asia, Mongolia and the
Junggar basin of China, has not been seen in China since the early
nineteen-fifties. The Xinjiang tiger is a unique subspecies of Asian tiger,
with an original distribution along the lower course of the Tarim River and in
the vicinity of Nobnor. Because of hunting and habitat changes, it became
extinct at the beginning of this century.
(3) Irrational agricultural reclamation
Irrational
agricultural reclamation in some areas has directly destroyed many wild plant
resources and wildlife habitats have been greatly decreased, resulting in a
reduction in numbers and even extinctions.
(4) Recent
large scale prospecting and exploitation of petroleum and mineral ores, as well
as the construction of roads and cities, threatens wild animals and plants in
various ways (habitat destruction, blocking the migration routes of wild
animals and disturbance).
(5) Irrational use of water resources
Excessive
use of water from the upper and middle courses of rivers, has caused the
decline and withering of large tracts of both natural and artificial forests in
the lower course, depending on supply. For example, the Tarim River, because a
large amount of water in its upper course is used for agricultural irrigation,
the flow into the lower course has decreased rapidly and eventually ran out, leading
to a reduction in the area of the Populus
euphratica forests from 45,000 to 16,000 ha along the 100 km section from
Yensu to Korgan. Because of the large amounts of water intercepted in the He Xi
Corridor for agricultural irrigation in its middle course, the flow in the
lower course of the Ruo Shui River decreased from 1,200,000,000 m3
in the 1960s to less than 500,000,000 m3 in the 1980s, resulting in
a reduction of the Populus euphratica forests
which have similarly declined from 50,000 ha in the 1940s to 22,700 ha today. Tamarix ramosissima forests have
declined from 150,000 to 100,000 ha. There are few Elaeagnus angustifolia forests left. The reduction in flow of the
lower course of the Shi Yang River has caused a 2/3 deterioration in the
vegetation of artificial forests, natural Populus
euphratica forests and Tamarix forests
at the Mingin Oasis.
Desertificaion
is a complex result of climatic variation and human factors, but vegetation
destruction, the irrational utilization of water resources, blindly reclaiming
and overgrazing are also important factors. The desertified lands of China are
still expanding at a rate of over 2,000km2 each year, The southern
border of the Tarim Basin, the southern fringe of the Gurbantunggut Desert, the
He Xi Corridor, the eastern part of Qaidam and the southeastern part of Alxa
are regions of intense desertification.
In most
cases, along with the growth in desertification, species richness has been
lowered, valuable and rare species have decreased and inferior grass and weeds
have increased simultaneously. The recent, rapid, expansion of desertified
lands in arid regions constitutes a complex threat to China¡¯s desert
biodiversity.
Due to all the
various destructive agents mentioned above, some plants and animals have been
verified to be extinct in recent decades. Examples include the plants Betula halophila and Glycyrrhiza triphylla, and animals such
as the Xinjiang tiger, Equus przewalskii, Saiga tatarica (extinct in China¡¯s
territory) and Aspiorhynchus laticeps (extinct
within the last 20~30 years). There are many more endangered ones. Table 3
provides a representative list of 25 endangered plant species:
Table 3 Representative rare and endangered
desert plants
|
Ephedra
leptidosperma |
small
shrub |
endemic
on rocky hills of Alxa |
|
Calligonum
alaschanicum |
shrub |
east
Alxa, steppe-desert endemic |
|
Cornulaca
alaschanica |
annual |
sandy
massive of south Alxa, endemic |
|
Adonis bobroviana |
perennial
herb |
Qilian-longshou
Shan, endemic |
|
Corydalis
kaschgarica |
perennial
herb |
Southslope
of Tian Shan, endemic |
|
Pugionum calcaratum |
annual |
Alxa
endemic |
|
Symstemon petrovii |
annual
or biannual herb |
Hexi
corridor and Helanshan, endemic |
|
Medicago alaschanica |
perennial
herb |
East
Alxa-Helan Shan foot Hills, endemic |
|
Astragalus
dengkouensis |
perennial
herb |
East
Alxa steppe-desert, endemic |
|
Ammopiptanthus nanus |
small
shrub |
Wuqia,
Xinjiang, endimic |
|
Tetraena mongolica |
small
shrub |
foot
of Zhuozi Shan, East Alxa, endemic |
|
Tamarix
taklamakanensis |
shrub |
Tarim
desert, endemic |
|
Myricaria
pulcherrima |
shrub |
South
Tarim Basin, endemic |
|
Helianthemum
songaricum |
small
shrub |
East
Alxa, endemic |
|
Ferula sinkiangensis |
perennial
herb |
terraces
of Ili R, endemic |
|
F. fukonensis |
perennial
herb |
Fukan,
endemic |
|
Scutellaria
alaschanica |
perennial
herb |
mountain
of East Alxa, endemic |
|
Stilpnolepis
centiflora |
annual |
Tengger
desert, Endemic |
|
Hippolytia
kaschgarica |
small
semi-shrub |
Southslope
of TianShan, endemic |
|
Canovinia
maximowiczii |
small
semi-shrub |
Hexi-Qaidm,
endemic |
|
Brachanthemum
pulvinatum |
small
semi-shrub |
South
Alxa-Qaidum, endemic |
|
Jurinea
pilostemonoides |
perennial
herb |
South
border of Junsgar |
|
Saussurea
yabulaiensis |
perennial
herb |
Yablai
Shan-Long Shou Shan, endemic |
|
Saussurea popovii |
perennial
herb |
Nearby
Urmqi, gravely mountain slopes |
|
Tulipa sinkiangensis |
perennial
herb |
Rock
hillls, North Xinjang, endemic |
3
The urgent rescue of China¡¯s desert
biodiversity
As
mentioned above, the severity of the biodiversity threats suffered by China¡¯s
deserts is no less than that suffered by other ecosystems. During this century,
the number of verified extinct animal and plant species are even more here than
in other areas, and the actual number of extinct species may be far more than
we know. More attention should be paid to the rescue and protection of
biodiversity in desert regions.
The
significance of protecting desert organisms:
(1) The
animals and plants of desert regions
Living
under extreme natural conditions (drought, bitter cold in winter and extreme
heat in summer, a large range of temperature variations, intense sunshine, strong
wind erosion and sand burial, coarse and crude soil, salinization, and gypsum
accumulated in the soil profile) many desert plants have successfully developed
many adaptive mechanisms including ecological, physiological, morphological,
behavioral, and genetic. Many wild plants are important for combating
desertification with biotic measures, and some desert animals are ancestors of
our present-day livestock. The conservation of desert organisms not only,
therefore, has important scientific significance, but is absolutely necessary
for medicinal treatment and health care.
(2) Desert
animals and plants contain a large number of species with an economic value
For
example, many grasses and small semi-shrubs are nutritious forage, and many
have a medicinal value. According to a survey, there are 356 species of
medicinal plants in sandy desert (including sandy areas outside the desert),
103 of which are commonly used.
(3) Desert
ecosystems play a vital role in fixing shifting sand dunes, reducing wind erosion
and improving the environment
The
destruction of desert ecosystems will lead to environmental deterioration.
To protect
and rescue desert biodiversity, we suggest:
(1) Pay
more attention to survey and research work, the timely monitoring of population
changes, projects for protecting priority species and habitats, i. e.,
endemics, keystone species, important habitats, centres of origin, and the
reproduction of native species.
(2)
Enhancing the construction of protected areas, improving their facilities and
providing research equipment. More than 30 nature reserves have been
established within desert regions, but this is still not enough. Some important
endangered species, such as Ammopiptanthus
nanus, Tetraena mongolica and Helianthemum songoricum, are not yet
included in reserves, and supplementary ¡°protected sites¡± or ¡°protected small
areas¡± need to be established.
Several ex situ facilities have also been
established in the desert regions of China with the purpose of protecting wild
animals, e. g., at Fukan and Wuwei, and they are playing a role in
re-introducing extinct species (such as Equus
przewalskii, Saiga tatarica) and
increasing the population number of endangered species (Equus hemionus, Canelus
bactranus). These ventures should be further supported and improved.
(3)
Strengthening the construction of legal institutions, first, for controlling
the use of biological resources. Considering the special situation of desert
regions, it is necessary to create Regulations
for Biodiversity Conservation in Arid Lands. Regulations, such as strictly prohibiting digging, collecting,
seizing or killing rare and endangered plants and animals also need to be
developed. Ecological assessment should be conducted before agricultural
reclamation and mining take place. At the same time, it is useful to levy
ecological (or resource) compensation taxes.
(4) To
raise the level of public awareness, ecological education needs to be
strengthened. Improving the knowledge of decision makers, managers and native
people with regard to the value of desert biodiversity, the significance of
protecting them and the vulnerability of desert ecosystems, is also important.
(5)
Developing international exchange and co-operation. Deserts are distributed all
over the world. Various countries are located in desert regions. Many of them
have accumulated rich experiences and knowledge of how to protect desert
ecosystems and rationally use their biological resources. It is worthwhile
drawing lessons from them. Second, China¡¯s northwest is contiguous with Middle
Asia¡¯s and Mongolian deserts. Many desert animal species gather in border
regions, and some migrate between the two sides. They are shared resources of
the two countries. In order to protect them effectively, co-operation is necessary.
In addition, international co-operation is beneficial to technological
improvement and international aid.