Journal of Agriculture and Rural Development in the Tropics and Subtropics
Volume 110, No. 1, 2009, pages 9–22
How Do “Renewable Products” Impact Biodiversity and
Ecosystem Services – The Example of Natural Rubber in China
M. Cotter∗1, K. Martin1and J. Sauerborn1
This paper aims to present the implications brought by the expansion of “renewable
products” plantation systems in the tropics with cultivation of rubber (Hevea brasilien-
sis) as a main focus. Throughout South East Asia, natural forest is being replaced by
rubber or oil palm (Elaeis guineensis) plantations, with severe consequences for the local
flora and fauna. Main aspects of this review are: i) The provision of an overview over
renewable resources in general and rubber in particular, with eco-physiological and agro-
nomical information concerning rubber cultivation. ii) The effect of rubber plantations
on biodiversity and species composition under different rubber farming approaches. In
addition we debate the possible influences of such large scale land cover transformations
on ecosystem services. iii) The conversion of natural forests into rubber plantations
releases considerable amounts of carbon dioxide into the atmosphere. We estimated
these values for different land cover types in southern China and assessed the carbon
sequestration potential of local rubber plantations.
Keywords: biodiversity, renewable products, rubber, ecosystem services, carbon seques-
Ever since, mankind has been dependent on natural resources. From the timber used
to build houses to the materials for clothing or the construction of tools, most of these
were renewable products obtained from the direct environment. These days, with fossil
fuels and minerals to be on the decline, the large scale use of renewable resources is
given an increasing degree of importance for a fast-growing human population.
The natural forests of the humid tropics are particularly rich in flora and fauna forming
several hotspots of biodiversity. In South East Asia’s forests, deforestation rates are
highest, mainly because of an increasing agricultural expansion in order to meet the
economic and nutritional needs of a growing population. Two of the main contributors
are rubber and oil palm plantations. The bulk of rubber plantations in the Greater
∗corresponding author: Cotter@uni-hohenheim.de
1Dipl.-Biol. Marc Cotter, Dr. rer.
University of Hohenheim, Institute for Plant Production and Agroecology in the Tropics and
Subtropics, 70593 Stuttgart, Germany
nat.Konrad Martin, Prof. Dr. Joachim Sauerborn,
Mekong Subregion replace primary and secondary natural forest, threatening the unique
wildlife and disturbing ecosystem services.
In this article, we highlight the possible impacts of large scale use of renewable products
with the example of rubber cultivation in South East Asia, especially in southern China.
Of particular interest are the implications of the replacement of tropical rainforest by
rubber plantations concerning biodiversity, ecosystem services and carbon sequestration
The world demand for renewable resources is constantly growing because of an increas-
ing need by a rising human population. Renewable resources are defined as materials
produced by living organisms (plants, animals, microbes) used for purposes other than
food and feed. Such materials include timber, natural fibre, oil and grease, sugar, starch,
natural rubber, colorants, pharmaceuticals, and others containing special substances like
resin, tannin, wax and/or natural protective compounds against pests and diseases (Tab.
Table 1: Selected tropical plants for industrial and energetic use
PlantRaw materialFinal product
Tectona grandis (Teak)
Swietenia spp. (Mahogany)
Shorea laevis (Yellow Balau)
furniture, toy, veneer, paper
Agave spp. (Sisal)
Gossypium spp. (Cotton)
Corchorus spp. (Jute)
natural fibretextile, packaging material,
carpet, yarn, rope, sack,
Elaeis guineensis (Oilpalm)
Butyrospermum parkii (Shea nut)
Ricinus communis (Castor oil)
hydraulic fluid, detergent,
Saccharum officinalis (Sugarcane)
Siraitia grosvenorii (Arhat fruit)
Manihot esculenta (Cassava)
Dioscorea spp. (Yam)
starch ethanol fuel,
Hevea brasiliensis (Rubber)
Parthenium argentatum (Guayule)
Manilkara bidentata (Balata)
natural rubber tyre, condom, mattress,
rubber profile, conveyor belt
Bixa orellana (Annatto)
Lawsonia inermis (Henna)
colouringcolour, dyeing of leather,
hair, fingernails, etc.
Cinchona spp (Quinine)
Rauvolfia serpentine (Indian Snakeroot)
Zingiber zerumbet (Ginger)
bioactive chemicals pharmaceuticals
The cultivation of these renewable resources can contribute substantially to the improve-
ment of a local and regional economic situation but it can also result in biodiversity loss
and environmental degradation.
3Natural rubber as a renewable resource
Natural rubber extracted from the tree Hevea brasiliensis (Willd. Ex A. Juss.) Muell.
Arg. distinguishes itself from all other raw materials, for it is elastic and at the same
time reversible and hence inimitable. To gain rubber the bark of the rubber tree is cut
so as to collect the latex, a milky sap from the latex vessels localised in the inner bark.
Latex is an emulsion that contains e.g. water, proteins, resins, tannins, and rubber in
varying quantities. The Mayas called the tree “Caa-o-chu”, that means “weeping tree”
Table 2: Characteristics of the rubber tree
scientific name:Hevea brasiliensis (Willd. Ex A. Juss.) Muell. Arg.
habitus: tree (may reach heights of more than 20 m within a
fertilisation: mainly allogamy by small insects such as midges and
thrips, autogamy occurs to various degrees
centre of origin:Amazon basin in South America
natural range:humid tropics
first harvest:5 – 7 years after planting
economic life span:about 30 years
production unit:plantation / family farming
predominant constituent harvested: latex, timber
actual yield of dry rubber:
∼ 3 – 4.5 kg tree−1year−1
about 8.5 kg tree−1year−1(Ong et al., 1994)potential yield of dry rubber:
major disease:South American leaf blight of rubber (Microcyclus ulei
Not until industrialisation, natural rubber became a basic material. Nowadays, it pro-
vides the basis for many high-performance products which we come across in cars, trains,
airplanes and ships, in engines and industrial plants. Wherever elastic motion is required
and where it is essential to seal, convey, mount, insulate, transmit power or to damp
vibration, rubber is of importance.
4Ecophysiology of Natural Rubber
Hevea brasiliensis is a tropical tree. It grows best at temperatures of 20 – 28°C with
a well distributed annual precipitation of 180 – 200 cm. Traditionally, H. brasiliensis
has been cropped in the equatorial zone between 10°N and 10°S. Urged by a growing
world demand rubber has now spread successfully to the latitudes 23°N (China) and
21°S (Brazil) and is cultivated up to 1200 m above sea level (Tab. 3).
Table 3: Characteristics for suitable cultivation of Hevea brasiliensis
mean temperature (°c)
mean precipitation (cm)
rainy season (months)
moisture deficits (months)
sunshine (hours d−1)
rooting depth (cm)
soil carbon (%)
25 – 28
200 – 250
11 – 12
4 – 5
Today, natural rubber provides about 40% of the world rubber demand and is used in
the manufacture of over 40,000 products (Ray, 2004). Synthetic rubber, invented at
the beginning of the 20thcentury, covers about 60 % of the current consumption. The
world production of natural rubber is constantly growing from about 2 million tons in
the 1960s to more than 10 million tons in 2007 (FAOSTAT, 2008) (Fig. 1).
In its centre of origin, the Amazon basin, H. brasiliensis is consistently endangered by
the fungus Microcyclus ulei (South American leaf blight of rubber). The pathogen
so far inhibits plantation growth of rubber trees in South America (Lieberei, 2007).
Beneficiaries of this situation are located in South East Asia where the fungus has not
spread to date. Thailand, Indonesia and Malaysia are the main rubber producers followed
by Viet Nam and China (FAOSTAT, 2008) (Tab. 4).
Table 4: Major natural rubber producers of the world (data of 2007)
Country Area harvested (1000 ha)Yield (t ha−1)Production quantity (1000 t)
Figure 1: Natural Rubber – World (Source: FAOSTAT, 2008)
1998 1999 2000 20012002 2003 2004 20052006 2007
Natural Rubber - World
area harvested (ha) production quantity (t)
Microcyclus ulei remains the Achilles’ heel of natural rubber production. Not only that
its introduction to South East Asia would cause an economic loss to the producers but it
would precipitate a crisis within the many industries (medical, transportation, defence,
etc.) which are dependent on natural rubber in the manufacturing of their commodities.
Rubber production systems and the conservation of natural biodiversity Natural forest
vegetation in the humid tropics is dwindling in an alarming rate, and the loss of biodiver-
sity due to the decline of such habitats is a well-known fact. The level of deforestation
in SE-Asia is the highest among tropical areas (Sodhi et al., 2004). The major reason
for this is the increasing agricultural expansion, especially due to oil palm and rubber
The expansion of rubber plantations in SE-Asia largely takes place by the reduction
of primary and secondary natural forest areas. The loss of natural forests is especially
serious in the major rubber production areas of Asia, because they are located within
the so called Indo-Burma hotspot, one of the 34 global biodiversity hotspots identified
by Conservation International (2007). This region largely corresponds with the
Lower Mekong catchment area and also includes parts of southern and western Yunnan
as well as southern Chinese offshore islands such as Hainan.
The replacement of any type of forest by a rubber monoculture results in a reduction
of natural tree species diversity to zero, because the rubber tree is not even native
to that region. Many studies also confirm significant reductions of fauna in plantations
compared to natural forest. For example, Danielsen and Heegaard (1995) found that
conversion of primary forest to rubber and oil palm in Sumatra led to simple, species-poor
and less diverse animal communities with fewer specialized species and fewer species of
importance to conservation. In the plantations, only 5-10% of the primary-forest bird
species were recorded. Primates, squirrels and tree-shrews disappeared except for one
species. Similarly, Peh et al. (2005) found reductions in primary-forest species of more
than 70% in such habitat types in Malaysia.
There are two approaches to reduce biodiversity losses in rubber and other types of
monoculture plantations. The first is the diversification in terms of plant species rich-
ness and vegetation structure of the plantation itself, and the other is the preservation
of landscape diversity, specifically the maintenance of natural forest patches within plan-
Diversification of rubber plantations is realized in a variety of cropping systems. From
southern Yunnan (China), Wu et al. (2001) classified the existing rubber plantations
into four types. These are
(a) monoculture rubber, representing the most common type,
(b) temporarily intercropped rubber plantations, with annual crops (e.g. upland rice,
corn pineapple, passionflower) established between young rubber trees before canopy
(c) rubber plantations of multiple species and layers of shrubs and perennial herbaceous
plants such as tea, coffee, cardamom and vanilla, and
(d) mixed rubber plantations based on the principles of traditional home garden systems
with perennial plants including tea, coffee, fruit trees bamboo and bananas, which
are mainly established in aging rubber plantations.
In this sequence, there is an increase in structural as well as plant diversity, but most or
all of these plant species do not represent natural forest species. Although no studies on
faunal diversity have been conducted in these types of plantations, it can be expected
that it is still very low and do not support significant numbers in forest species. In terms
of plant species diversity and structure, such polyculture systems are probably similar to
the mixed-rural landscapes in Malaysia, consisting of agricultural land, oil palm, rubber
and fruit tree stands (Peh et al., 2005).
More complex and more diversified is the so-called “jungle rubber”, “rubber garden” or
“rubber agroforest” system of Indonesia, specifically Sumatra and Kalimantan. It can
be defined as a balanced, diversified system derived from swidden cultivation, in which
man-made forests with a high concentration of rubber trees replace fallows. Most of the
income comes from rubber, complemented with temporary food and cash crops during
the early years (Gouyon et al., 1993). In its structure, they resemble secondary forest
with wild species tolerated by the farmer.
Beukema et al. (2007) compared plant and bird diversity of the Indonesian jungle rubber
agroforestry system to that of primary forest and pure rubber plantations. They found
that species richness in jungle rubber was slightly higher (in terrestrial pteridophytes)
similar (in birds) or lower (in epiphytes, trees and vascular plants as a whole) than in
primary forest. For all groups, species richness in jungle rubber was generally higher than
in rubber plantations. The authors conclude that the jungle rubber system does support
species diversity in an impoverished landscape increasingly dominated by monoculture
plantations. From a more specific study on terrestrial pteridophytes (ferns and fern allies)
in jungle rubber and primary forest, Beukema and van Noordwijk (2004) conclude
that jungle rubber systems can play a role in conservation of part of the primary rain
forest species, especially in areas where primary forest has already disappeared.
Of economic reasons, however, the most common type of rubber cultivation is the
monoculture system. In such landscapes, natural biodiversity can only be conserved in
remaining plots of natural vegetation, which should be preserved as reservation areas.
Several aspects of this approach needed to be considered for practical implementations
(Debinski et al., 2001):
(a) The frequency and spatial distribution of habitat fragments and patches determines
species distribution patterns.
(b) Species populations may be separated on patches of their habitat within a landscape
of less suitable habitat, and
(c) Species dispersal patterns may interact with patch size and patch context to de-
termine species distributions within and among patches (“patch context” describes
the habitat type adjacent to a patch)
Derived from this, a concept for measuring landscape structure has been developed,
named “landscape connectivity” (Merriam, 1991). It describes the degree to which
the landscape facilitates or impedes movement of species populations among habitat or
resource patches. An important question related to this is whether the size and structure
of the landscape matrix acts as a corridor or barrier between patches.
All these points also apply to forest patches within monoculture rubber plantations.
However, no study dealing with matrix effects on species movements in such landscapes
has been conducted so far. Specifically, there is no information on the arthropod diversity
of rubber plantations in comparison to forests. In order to develop species conservation
concepts in rubber dominated landscapes, research needs to address this question.
5 Ecosystem Services
Ranging from the provision of clean drinking water to the pollination of fruit crops,
mankind is deriving benefits from a wide array of processes and interactions that take
place in our environment. These services are vital to the functioning of our ecosystems,
and vital to the livelihood of men, as they provide not only the basis for human life, but
also additional attendances like food and health security or cultural and spiritual values.
The total amount of these services can only be estimated, but cautious predictions state
a yearly value of 33 trillion (1012) US$ (Costanza et al., 1997; Eamus et al., 2005).
Generally, ecosystem services can be grouped into four categories. (1) Provisioning
services that include goods taken from the ecosystem like food, fiber, fuel, genetic re-
sources, fresh water and biochemicals. (2) Regulating services take place on a more
global scale; they include climate regulation, pest and disease regulation, natural haz-
ard protection, water purification. (3) Cultural services include recreation and aesthetic
values, knowledge system, spiritual and religious values. (4) Supporting services com-
prise soil formation and retention, provision of habitat, primary production, water and
nutrient cycling (Millennium Ecosystem Assessment, 2005).
Ecosystem goods and services are in danger as the human impact on the environment
is constantly increasing (IPCC, 2007). Deforestation and the increase of agricultural
areas, water pollution and rising fresh water demand, degradation and unsustainable use
have put many ecosystems on the brink of collapse.
6 Impacts of rubber cultivation on ecosystem services
In South-East Asia large areas of natural vegetation with their plentiful diversity of flora
and fauna have been put under great pressure from the establishment of plantations.
Rubber is playing a great role in this process, as the anticipated revenues are appealing
to farmers and policy makers alike. In China’s Yunnan province, more than 11% of the
total area is covered with rubber (Li et al., 2007), but there are townships where rubber
cultivation contributes to more than 45% of the land cover (Hu et al., 2007). For one of
these townships, Menglun, Hu et al. (2007) estimated the value of ecosystem services
provided. According to this report covering land use change over a period of 18 years, the
total value of ecosystem services dropped by US$ 11.4 million (28%). The services most
affected were nutrient cycling, erosion control and climate regulation. The biodiversity
service of “habitat/refugia” had not been covered, but considering the detrimental effect
of monoculture plantation systems on species richness and the corresponding ecosystem
services, the total value of ecosystem services for the research area can be expected to
be even lower than reported.
This effect seems to be alleviated by the fact that the townships gross domestic product
increased, leading to a ratio of 1:1.39 for increase in GDP to loss of ecosystem services
in US$ (Hu et al., 2007).
7 Deforestation due to rubber expansion
The increasing demand for natural rubber products has lead to a wide spread replacement
of natural forest vegetation with rubber. Li et al. (2007) states that, between 1976 and
2003, tropical seasonal rain forest in Yunnan was reduced by 67%, mainly due to the
planting of rubber.Lowland rain forests are the most affected forest types due to
the climatic needs of the rubber tree. But also mountain rainforests and other forest
communities of higher elevations are seriously under pressure, as agricultural production
shifts into these regions.
According to the recommendations given by the International Panel of Climate Change
(Houghton et al., 1997) as used by Germer and Sauerborn (2007), we assessed
the potential amounts of carbon and carbon dioxide emission that are expected when
preparing land for the conversion into rubber plantations.
Again, the data from the Yunnan Institute of Forest Inventory and Planning Li et al.
(2008) served as a basis for our biomass assumptions. As basis for the distribution of
below to above ground biomass, we used a BGB to AGB ratio of 1:1.13 as given by the
Houghton et al. (1997).
For the emission of CO2during decomposition, we assume that after 30 years under
humid subtropical conditions, all cleared biomass, above and below ground, will be
decomposed. Houghton et al. (1997) suggests a vegetation independent forest carbon
stock estimate of 50% of the biomass. Carbon (12 g/mol) will mostly be released as
carbon dioxide (44 g/mol). One ton of cut forest biomass would release 0.5 t of carbon
through decomposition, resulting in the emission of 1.8 t CO2.
As an example, the average carbon content of one hectare of undisturbed tropical sea-
sonal rainforest in Yunnan was reported to be 121.74 t, which is an estimated 243.5 t
of biomass, assuming a forest stock carbon content of 50% (Houghton et al., 1997).
The complete decomposition of this amount would lead to the emission of (243.5 t ×
1.8) = 438.3 t CO2.
Table 5: Emission of CO2 equivalents by forest clearing.
Above ground biomass
TSRF: tropical seasonal rainforest; SEBF: subtropical evergreen broadleaf forest (57% of
Yunnan forests); TSRF anth., SEBF anth. both with strong anthropogenic influences (e.g.
selective logging); Grass: grassland, Shrub: shrubland. Carbon content values from Li et al.
(2008), other values calculated following IPCC guidelines.
8Carbon sequestration potential of rubber
Properly managed rubber plantations that are supplied with sufficient amounts of fer-
tilizer have a high potential to act as a continuous sink for atmospheric carbon dioxide
(Cheng et al., 2007). This is mainly due to their high sequestration rates and the fact
that there is a constant export out of the production system by means of tapping.
Cheng et al. (2007) reported a 30 years lifetime carbon sequestration of 272 t C ha-1
in rubber plantations on the island of Hainan. Comparing this to the sequestration rates
of rain forests and secondary forests on Hainan, 234 and 150 t C ha-1over the same
period, the high productivity of a rubber plantation becomes discernable. Nevertheless,
more than 57% of the sequestrated carbon ends up in easily decomposed litter. This
decomposition process returns considerable amounts of carbon back to the atmosphere,
up to fifty percent of the total carbon content in the first year (Anderson and Swift,
Based on the equation used by Cheng et al. (2007), we were able to derive carbon
sequestration values for rubber plantations (CR) in Yunnan province, China’s second
biggest rubber producer. We can calculate CR as:
CR = CBi+ CLa+ CLi,
with the carbon content of biomass (CBi), carbon content of latex yield CLa, and the
carbon content of litter (CLi).
Data from the Yunnan Institute of Forest Inventory and Planning published by Li et al.
(2008) were used to obtain information about local forest biomass and its carbon content
(CBi = 61.48 t C ha-1for rubber plantations below 800m).
The amount of sequestrated carbon that is removed from the field during latex tapping
was estimated by multiplying average values of latex carbon content by latex yield per
hectare (FAOSTAT, 2008) by the economic lifetime of a rubber plantation in years
(CLa). Due to suboptimal climate conditions rubber tapping in Yunnan usually begins
seven years after establishment of the plantation, in comparison to an average of five
years reported for Hainan. This results in a slightly lower average economic lifetime. In
order to estimate the amount of litter produced over 30 years we proportionally adjusted
the values for Hainan litter biomass per hectare to the lower total biomass of Yunnan
rubber plantations (CLi).
Based on these calculations, the estimated carbon sequestration during a 30 years life-
time for rubber plantations below 800m elevation in Yunnan province is 192 t C ha-1,
which consists of an estimated litter mass of 107 t C ha-1and a latex output of 23 t C
Figure 2: Total carbon sequestration by rubber over 30 years per hectare. Total values
are divided into latex production, litter production and rubber biomass (non-
Rubber carbon sequestration over 30 years
These estimates do not consider the soils potential to release and sequestrate carbon
under different management regimes. In this context, the dynamics of carbon cycling
regarding the substantial amounts of litter produced by rubber plantations should be
put to further investigation, as these results could lead to a clearer picture of the overall
carbon sequestration potential of rubber.
CO2 balance in plantation establishment
During its lifetime of 30 years, a rubber plantation in Yunnan province can sequester
an estimated 192 t of carbon or 703 t CO2per hectare (based on an atomic weight
ratio of 1:3.66). Plantations in Hainan province can be expected to achieve about 272
t of C sequestration, mostly due to their higher biomass and litter production. These
values are, as stated above, comparable to the 30 years sequestration potential of Hainan
When comparing these vegetation types concerning their CO2balance, one decisive fact
has to be considered. Rubber plantations are man-made ecosystems which replace local
floral communities entirely. In most cases, this is done by clearing the forest for the
Based on our estimates, if one hectare of relatively undisturbed tropical seasonal rain-
forest in Yunnan province is cleared, this process releases about 438 t of CO2into the
atmosphere. A fully grown rubber plantation on the same spot would need around 20
years to re-sequester this amount of CO2. Although after several decades a net gain
in carbon fixation could be achieved, the loss in biodiversity and ecosystem resources
would be persistent.
Table 6: Carbon sequestration over 30 years and annually
av. Cseq a−1ha−1
av. Cseq a−1ha−1
165 t est.
5.5 t est.
106 t est.
3.3 t est.
Carbon sequestration rates per hectare over 30 years and annual average. Data for Hainan
were published by Cheng et al. (2007); values for Yunnan Rainforest and Secondary forest were
derived proportionally from Hainan sequestration rates and Yunnan biomass values.
10 Rubber and grassland rehabilitation
In order to find more sustainable locations for the establishment of rubber plantations,
disturbed ecosystems like degraded grassland and abandoned fallows from swidden agri-
culture could be used. These land uses are rather scarce in the elevation levels that
are suitable for rubber plantation in Yunnan province, but nevertheless it is a promising
concept for other regions nearby. All throughout the tropics and subtropics, the trans-
formation of agricultural areas to grassland ecosystems is a common problem. These
areas are often dominated by very competitive grass species that effectively prevent nat-
ural succession into secondary woodlands and forests. The conversion of these land use
types into rubber plantations would not only increase the farmers’ welfare but also se-
cure important ecosystem services that grassland and fallows have difficulties to provide
(Li et al., 2008). In addition, the establishment of plantations on these degraded areas
would emit decisively less carbon dioxide than the conversion of forests. CO2release
into the atmosphere during land preparation is estimated to amount to about 110 t ha-1
for shrubland in Yunnan, and 19 t ha-1for grassland, in comparison to the 438 t ha-1
for Yunnan seasonal rainforest. Compared to the values reported above, this would lead
to a faster and significantly higher net gain in CO2sequestration by rubber plantations
when used to rehabilitate grassland. Similar results have been published for oil palm
plantations (Germer and Sauerborn, 2007).
Figure 3: Carbon sequestration by rubber grown below 800 masl. over a period of 30
years in Yunnan province, compared to net carbon sequestration considering
the release of CO2 during plantation establishment. C seq. is the estimated
carbon sequestration potential of rubber (above); previous land cover: TSRF
is tropical seasonal rainforest, SEBF anth is subtropical evergreen broadleaf
forest with anthropogenic influence and Grass is grassland.
potential C seq net TSRF net SEBF anthnet Grass
net carbon sequestration over 30 years
t C/ha carbon in previous landcover t C/ha
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