Rubber trees cultivation in Xishuangbanna

Written by William le 15 september 2013





     The legend says one day, two Daihunters saw a golden deer in the forest. They followed his tracks forseveral 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 littleparadise, they sculpted the mountain with their sweat, built terraceson the steep hills and called this kingdom ''Sipsongbanna'':the landof 12000 rice fields.
   

     Originally, the entireXishuangbanna was covered by dense forests, tropical primary forests.Traditionally, the hill tribes used slash and burn agriculture toproduce food. This method consists in cutting a piece of forest,burning the vegetation to bring nutrients to the soil, and use thatrich soil to grow cereals, fruits and vegetables. On the first year,this method gives very good yield, then, as time goes on, thenutrients get depleted, and the output gradually decreases. When thesoil is too poor, the farmers find another piece of land and startthe process again: slashing, burning, cultivation and moving away. Inthe past, Xishuangbanna's tropical climate would allow the vegetationto grow back fast enough so that after ten years, the land could beused again. This very ancient technique of agriculture has workedvery well as long as the population density was low.

     Another way to grow rice is to usepaddy fields. This method is more efficient than slash and burnagriculture but it requires a very flat ground. Unlike standardfields, paddies do not need to go under a fallow period to recover,however, water must be delivered permanently with a good irrigationsystem, it is very important in order to achieve high yield.. 

     Slash and burn and paddy fieldsare the two main ways in which people grow food in Xishuangbanna,yet, the farmers of this beautiful county have many long-termplantations: mostly banana, rubber and tea plantations. This kind ofagriculture has a different purpose: it must bring a cash revenue tothe farmer, that's the main way farmers use to make money, the othercrops are only for subsistence. Hevea plantations is the mostimportant cash crop in Xishuangbanna. The farmers get a good profitout of the rubber extracted. The surface area used for Heveacultivation is expanding very fast.

     In 15 years (from 1988 to 2003),the average income per person has tripled in Xishuangbanna. Thisdevelopment has been faster than the average in China and still is(in 2010 Xishuangbanna had 12% growth while China averaged 9%). Thiseconomic success is due to the diversity of activities in the region:agriculture (rubber, tea, fruits), industry (mining, logging) andservices (tourism, retail).

     The tourists come to Xishuangbannato enjoy its preserved nature, beautiful landscapes, mysteriousforests and rich biodiversity. They are like the two Dai huntersfollowing the golden deer. Tourism accounts for 16.5% ofXishuangbanna's GDP. Meanwhile, the huge plantations of rubber treesdamage the natural landscape, usually made of jungle and paddyfields.


   
This is a satellite photo taken aroundMenglun, all those curves are rubber trees. You can imagine the sizeof those plantations. Scientists found out that such large scaleprojects had significant impacts on the environment.


    First, the soil cover is different ina hevea plantation and in a tropical forest. The tropical forest hasa thick canopy, inside the forest is dark, even by day. When arainfall occurs, part of the rainwater is captured by the canopy, thethick layer of leaves acts as a buffer and the rainwater continues tofall on the ground long after the rain has stopped. In a rubber treeplantation, the canopy is much lighter, the ground is more exposed,and when the rain falls, it strikes the ground directly and quicklyflows down the slopes. During the rainy season, water mostly falls inthe form of short and intense showers. When the soil becomessaturated, the excessive water is not held on the ground and flowsdown, it is called the surface runoff. Each kind of terrain has adifferent capacity to hold water or let it flow down and thereforecreate surface runoff. Here are a few reasons why this capacity toabsorb water it is an important point in terms of land management:
   

          -Excessive surface runoff candramatically increase the water level of a river, it increases therisk of floods during severe rainstorms.

          -Water has an important rolefor the soil: it distributes the nutrients. When the rainwater runsdown the slope, it takes some of those nutrients with it. It createstwo problems: the soil on which rain falls loses nutrients which areimportant for plant growth; and the nutrient-rich water eventuallypollutes lakes, rivers and even seas, which create a risk of algalblooms and biodiversity loss (a big issues in the Baltic sea and theGulf of Thailand). 

         -Rainwater fills up thegroundwater reserves. The change in forest cover and water retentioncapacity might put the groundwater reserves at risk by affectingtheir refill rate. This freshwater is used for irrigation anddomestic use. 

     Second, tropical forest interceptsfog (it means it ''creates'' fog), hevea plantations do not. Fog isimportant during the dry season because it brings water to theplants. As a result of the massive development of rubber plantations,there is much less foggy days in Xishuangbanna, its misty atmospherehas vanished. This is probably the most noticeable effect on thelocal climate, people are very concerned about it. It might haveimplications on tourism and biodiversity.

     Third, the tropical forest is animportant habitat for wildlife, it hosts many more species thanrubber plantations do. Xishuangbanna is at the border betweentemperate climate (like in northern Yunnan) and tropical climate(like in Thailand). As a consequence, it has a particularly richbiodiversity and is the home of many rare species, including over 150unique species. In total, 5000 plants and 1000 animal species avebeen observed in Xishuangbanna, and many of them rely on the tropicalforest to survive.

     Even though Nature is priceless,ecosystems can be given a value, which is representative of thebenefits they bring to our society, or in other words, the effort wewould have to deploy if they were not here. Each type of environmentcan be attributed a value in dollars per hectare per year. Theecosystem of one hectare of tropical forest gives a service to mankinestomated to $2007/year, while in a rubber tree plantation, theecosystem is only ''worth'' $92/year. In 1988, the total amount ofecosystem service in Xishuangbanna was worth 2474 million dollarswhile in 2003, it was estimated to 2084 million dollars (inflationadjusted), a decrease by 16%.
   
Global ecosystem services value, youcan notice that tropical forests are high priced while deserts aregiven a low value.

     Moreover, the ever expanding heveaplantations take on the land traditionnaly used for slash and burnagriculture, as a consequence, the farmers must rely mainly the paddyfields to produce their food. Slash and burn agriculture allows thefarmers to cultivate a wide range of vegetables and rice varieties.The paddy field cultivation is less diverse and is more dependent onwater and fertilizers. This is a big change for farmers because theyare leaving the traditional methods which were complex and required alot of knowledge about soil, varietials and Nature in general.Instead, they choose more simple and efficient methods which havebeen satisfying so far but might not be sustainable. Now, the farmerscultivate only a few species and earn money with rubber, and they buyvegetables at the market. This new way of living makes them moredependent on the price of rubber and on the weather. What wouldhappen in case a very poor harvest on their unique cash crops? Thetraditional agriculture involved dozens of species and having badyields due to pest on one crop had no serious consequences. In termsof agriculture, diversity provides the farmer food security.
   


     The picture on the left representsXishuangbanna as it was thousands of years ago: only tropical andmountain rain forest. The central map is a model of the land use in2003, as you can see, rubber tree plantations have taken over thesouth of Xishuangbanna, the western areas are mostly planted with teagardens. Scientists have assessed the consequences of two scenarios:the ''rubber plantation scenario'' takes the hypothesis that noregulation is made and that the price of rubber stays high. The heveaplantations would expand up to 1500m high, only the establishednatural reserves and the tea gardens are preserved. In the secondscenario, the government would take measures to control and restrainthe rubber industry, and start forest conservation projects. In thiscase, the area occupied by rubber trees would be roughly the same asit was in 2003 and many other plantations and fields would beconverted into tropical forest.
   

    The expansion of hevea plantationsin Xishuangbanna surely have a positive short term economic impactbecause the demand for natural rubber is high. On the long termthough, the trend is uncertain, what would be the impact of thelandscape change on tourism? How about the retail industry? The teaindustry? Wood carving? Jade trade and jewelery? If the touristsdon't come to Xishuangbanna because of the damaged environment, theeconomic improvement made on the rubber might well be offset by thenegative impacts on other sectors.
   

     Why is Xishuangbanna tea moreexpensive than Lincang tea? Probably because Xishuangbanna hasprestige, it is a very famous region all across China, a borderland,full of Pu Er tea, elephants, tropical forest; the land of Daipeople, a haven of South East Asia, not the land of rubber trees.Xishuangbanna is a 'place to go' in Yunnan, just like Dali andLijiang. Especially in those areas, which already enjoy a goodreputation, it is important to protect environment and culture, toinvest in natural capital and to give this gem the setting itdeserves.

     A research program assessed thatin the area around Menglun (a typical town in central Banna), theeconomic development has been achieved at the expense of ecosystemservices.



Development and land use in Menglunarea between 1988 and 2003


   
Ecosystem services value in Menglunarea in 1988 and 2003
 
   In this area, for 1$/y GDP earned,2$/y of ecosystem services have been lost. Can we consider thisdevelopment sustainable? The answer is not that easy because themodel used has its limitations. To a certain extent, the valueattributed to ecosystem services is variable, how would you value theaesthetic service given by a tropical forest? How much is worth awalk in the forest, the bird's song, butterflies flying around you,is it possible to put a price on such things? Ecosystem service valueincludes the extra spending if this forest was not here. In a poorenvironment, people fall sick more often because of pollutedair/water, poor soils makes yields lower, implies the buying ofagrochemicals to prevent pests and diseases and give extra work tothe farmers. Dozens of parameters are included in the calculation ofthis ecosystem service value, this kind of assessment is relativelynew, and like all branches of environmental science and there is roomfor improvement.
   

     Meanwhile, decisions must betaken, policies must be established, the precautionary principlesuggests that people start to act without waiting for completescientific knowledge. We might never be able to estimate what willhappen...until it happens. But what is sure is that changes in theclimate of Xishuangbanna are observed and they are faster than thoseexpected due to global warming. Scientists believe that in thisplace, at the limit of two types of climate, the forest creates andsustains its own micro-climate, if it is destroyed, the climate willbe dramatically affected. Present actions dictate the future, humansmust take the right decisions now to achieve a more developed world,this is the key of sustainable development.

references:

-Fu et al,2005, Fallow agroecosystemdynamics and Socioeconomic development in China
-Hu H.,2008,Impact of Land Use and LandCover Changes on Ecosystem Services in Southwest China
-Xu et al, 2005,Land-use and land-coverchange and farmer vulnerability in Xishuangbanna prefecture insouthwestern China
-Li et al. 2007, Past, present andfuture land-use in Xishuangbanna, China and the implications forcarbon dynamics
-Liu et al, 2002,Practice of conservingplant diversity through traditional beliefs: a case study inXishuangbanna, southwest China
-Liu et al,2009,Runoff generation insmall catchments under a native rain forest and a rubber plantationin Xishuangbanna





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