Land management in Xishuangbanna
The legend says one day, two Dai
hunters saw a golden deer in the forest. They followed his tracks for
several days, and finally, they discovered a beautiful place.
Everything was green , the landscape was made of small mountains,
rivers and waterfalls. The Dai people settled in this little
paradise, they sculpted the mountain with their sweat, built terraces
on the steep hills and called this kingdom ''Sipsongbanna'':the land
of 12000 rice fields.
Originally, the entire
Xishuangbanna was covered by dense forests, tropical primary forests.
Traditionally, the hill tribes used slash and burn agriculture to
produce food. This method consists in cutting a piece of forest,
burning the vegetation to bring nutrients to the soil, and use that
rich soil to grow cereals, fruits and vegetables. On the first year,
this method gives very good yield, then, as time goes on, the
nutrients get depleted, and the output gradually decreases. When the
soil is too poor, the farmers find another piece of land and start
the process again: slashing, burning, cultivation and moving away. In
the past, Xishuangbanna's tropical climate would allow the vegetation
to grow back fast enough so that after ten years, the land could be
used again. This very ancient technique of agriculture has worked
very well as long as the population density was low.
Another way to grow rice is to use
paddy fields. This method is more efficient than slash and burn
agriculture but it requires a very flat ground. Unlike standard
fields, paddies do not need to go under a fallow period to recover,
however, water must be delivered permanently with a good irrigation
system, it is very important in order to achieve high yield..
Slash and burn and paddy fields
are the two main ways in which people grow food in Xishuangbanna,
yet, the farmers of this beautiful county have many long-term
plantations: mostly banana, rubber and tea plantations. This kind of
agriculture has a different purpose: it must bring a cash revenue to
the farmer, that's the main way farmers use to make money, the other
crops are only for subsistence. Hevea plantations is the most
important cash crop in Xishuangbanna. The farmers get a good profit
out of the rubber extracted. The surface area used for Hevea
cultivation is expanding very fast.
In 15 years (from 1988 to 2003),
the average income per person has tripled in Xishuangbanna. This
development has been faster than the average in China and still is
(in 2010 Xishuangbanna had 12% growth while China averaged 9%). This
economic success is due to the diversity of activities in the region:
agriculture (rubber, tea, fruits), industry (mining, logging) and
services (tourism, retail).
The tourists come to Xishuangbanna
to enjoy its preserved nature, beautiful landscapes, mysterious
forests and rich biodiversity. They are like the two Dai hunters
following the golden deer. Tourism accounts for 16.5% of
Xishuangbanna's GDP. Meanwhile, the huge plantations of rubber trees
damage the natural landscape, usually made of jungle and paddy
fields.
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This is a satellite photo taken around
Menglun, all those curves are rubber trees. You can imagine the size
of those plantations. Scientists found out that such large scale
projects had significant impacts on the environment.
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First, the soil cover is different in
a hevea plantation and in a tropical forest. The tropical forest has
a thick canopy, inside the forest is dark, even by day. When a
rainfall occurs, part of the rainwater is captured by the canopy, the
thick layer of leaves acts as a buffer and the rainwater continues to
fall on the ground long after the rain has stopped. In a rubber tree
plantation, the canopy is much lighter, the ground is more exposed,
and when the rain falls, it strikes the ground directly and quickly
flows down the slopes. During the rainy season, water mostly falls in
the form of short and intense showers. When the soil becomes
saturated, the excessive water is not held on the ground and flows
down, it is called the surface runoff. Each kind of terrain has a
different capacity to hold water or let it flow down and therefore
create surface runoff. Here are a few reasons why this capacity to
absorb water it is an important point in terms of land management:
-Excessive surface runoff can
dramatically increase the water level of a river, it increases the
risk of floods during severe rainstorms.
-Water has an important role
for the soil: it distributes the nutrients. When the rainwater runs
down the slope, it takes some of those nutrients with it. It creates
two problems: the soil on which rain falls loses nutrients which are
important for plant growth; and the nutrient-rich water eventually
pollutes lakes, rivers and even seas, which create a risk of algal
blooms and biodiversity loss (a big issues in the Baltic sea and the
Gulf of Thailand).
-Rainwater fills up the
groundwater reserves. The change in forest cover and water retention
capacity might put the groundwater reserves at risk by affecting
their refill rate. This freshwater is used for irrigation and
domestic use.
Second, tropical forest intercepts
fog (it means it ''creates'' fog), hevea plantations do not. Fog is
important during the dry season because it brings water to the
plants. As a result of the massive development of rubber plantations,
there is much less foggy days in Xishuangbanna, its misty atmosphere
has vanished. This is probably the most noticeable effect on the
local climate, people are very concerned about it. It might have
implications on tourism and biodiversity.
Third, the tropical forest is an
important habitat for wildlife, it hosts many more species than
rubber plantations do. Xishuangbanna is at the border between
temperate climate (like in northern Yunnan) and tropical climate
(like in Thailand). As a consequence, it has a particularly rich
biodiversity and is the home of many rare species, including over 150
unique species. In total, 5000 plants and 1000 animal species ave
been observed in Xishuangbanna, and many of them rely on the tropical
forest to survive.
Even though Nature is priceless,
ecosystems can be given a value, which is representative of the
benefits they bring to our society, or in other words, the effort we
would have to deploy if they were not here. Each type of environment
can be attributed a value in dollars per hectare per year. The
ecosystem of one hectare of tropical forest gives a service to mankin
estomated to $2007/year, while in a rubber tree plantation, the
ecosystem is only ''worth'' $92/year. In 1988, the total amount of
ecosystem service in Xishuangbanna was worth 2474 million dollars
while in 2003, it was estimated to 2084 million dollars (inflation
adjusted), a decrease by 16%.
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Global ecosystem services value, you
can notice that tropical forests are high priced while deserts are
given a low value.
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Moreover, the ever expanding hevea
plantations take on the land traditionnaly used for slash and burn
agriculture, as a consequence, the farmers must rely mainly the paddy
fields to produce their food. Slash and burn agriculture allows the
farmers to cultivate a wide range of vegetables and rice varieties.
The paddy field cultivation is less diverse and is more dependent on
water and fertilizers. This is a big change for farmers because they
are leaving the traditional methods which were complex and required a
lot of knowledge about soil, varietials and Nature in general.
Instead, they choose more simple and efficient methods which have
been satisfying so far but might not be sustainable. Now, the farmers
cultivate only a few species and earn money with rubber, and they buy
vegetables at the market. This new way of living makes them more
dependent on the price of rubber and on the weather. What would
happen in case a very poor harvest on their unique cash crops? The
traditional agriculture involved dozens of species and having bad
yields due to pest on one crop had no serious consequences. In terms
of agriculture, diversity provides the farmer food security.
The picture on the left represents
Xishuangbanna as it was thousands of years ago: only tropical and
mountain rain forest. The central map is a model of the land use in
2003, as you can see, rubber tree plantations have taken over the
south of Xishuangbanna, the western areas are mostly planted with tea
gardens. Scientists have assessed the consequences of two scenarios:
the ''rubber plantation scenario'' takes the hypothesis that no
regulation is made and that the price of rubber stays high. The hevea
plantations would expand up to 1500m high, only the established
natural reserves and the tea gardens are preserved. In the second
scenario, the government would take measures to control and restrain
the rubber industry, and start forest conservation projects. In this
case, the area occupied by rubber trees would be roughly the same as
it was in 2003 and many other plantations and fields would be
converted into tropical forest.
The expansion of hevea plantations
in Xishuangbanna surely have a positive short term economic impact
because the demand for natural rubber is high. On the long term
though, the trend is uncertain, what would be the impact of the
landscape change on tourism? How about the retail industry? The tea
industry? Wood carving? Jade trade and jewelery? If the tourists
don't come to Xishuangbanna because of the damaged environment, the
economic improvement made on the rubber might well be offset by the
negative impacts on other sectors.
Why is Xishuangbanna tea more
expensive than Lincang tea? Probably because Xishuangbanna has
prestige, it is a very famous region all across China, a borderland,
full of Pu Er tea, elephants, tropical forest; the land of Dai
people, a haven of South East Asia, not the land of rubber trees.
Xishuangbanna is a 'place to go' in Yunnan, just like Dali and
Lijiang. Especially in those areas, which already enjoy a good
reputation, it is important to protect environment and culture, to
invest in natural capital and to give this gem the setting it
deserves.
A research program assessed that
in the area around Menglun (a typical town in central Banna), the
economic development has been achieved at the expense of ecosystem
services.
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Development and land use in Menglun
area between 1988 and 2003
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Ecosystem services value in Menglun
area in 1988 and 2003
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In this area, for 1$/y GDP earned,
2$/y of ecosystem services have been lost. Can we consider this
development sustainable? The answer is not that easy because the
model used has its limitations. To a certain extent, the value
attributed to ecosystem services is variable, how would you value the
aesthetic service given by a tropical forest? How much is worth a
walk in the forest, the bird's song, butterflies flying around you,
is it possible to put a price on such things? Ecosystem service value
includes the extra spending if this forest was not here. In a poor
environment, people fall sick more often because of polluted
air/water, poor soils makes yields lower, implies the buying of
agrochemicals to prevent pests and diseases and give extra work to
the farmers. Dozens of parameters are included in the calculation of
this ecosystem service value, this kind of assessment is relatively
new, and like all branches of environmental science and there is room
for improvement.
Meanwhile, decisions must be
taken, policies must be established, the precautionary principle
suggests that people start to act without waiting for complete
scientific knowledge. We might never be able to estimate what will
happen...until it happens. But what is sure is that changes in the
climate of Xishuangbanna are observed and they are faster than those
expected due to global warming. Scientists believe that in this
place, at the limit of two types of climate, the forest creates and
sustains its own micro-climate, if it is destroyed, the climate will
be dramatically affected. Present actions dictate the future, humans
must take the right decisions now to achieve a more developed world,
this is the key of sustainable development.
references:
-Fu et al,2005, Fallow agroecosystem
dynamics and Socioeconomic development in China
-Hu H.,2008,Impact of Land Use and Land
Cover Changes on Ecosystem Services in Southwest China
-Xu et al, 2005,Land-use and land-cover
change and farmer vulnerability in Xishuangbanna prefecture in
southwestern China
-Li et al. 2007, Past, present and
future land-use in Xishuangbanna, China and the implications for
carbon dynamics
-Liu et al, 2002,Practice of conserving
plant diversity through traditional beliefs: a case study in
Xishuangbanna, southwest China
-Liu et al,2009,Runoff generation in
small catchments under a native rain forest and a rubber plantation
in Xishuangbanna
