Tropical Ecology 59(4): 605–618, 2018 ISSN 0564-3295 © International Society for Tropical Ecology www.tropecol.com

Prospective of rubber-based on swidden fallow for synergizing climate change mitigation and adaptation

ANUJ KUMAR SINGH

Meghalaya Climate Change Centre, Meghalaya Basin Development Authority, Shillong-793003, India

Abstract: There are global calls to address the concerns associated with the global climate change. The world-wide efforts to mitigate and adapt climate change have a concerted focus on increasing the forest and green cover and augmenting the process for achieving the land degradation neutrality. The global scientific and policy making bodies have agreed upon a common agenda to minimise the implications of climate variability and to realise that it has become essentially vital to act on both the fronts of mitigation and adaptation synergistically and find ways to dovetail them for optimizing the efforts at all levels of efforts. Agroforestry provides with such opportunities in tremendously beneficial ways. This has potential not only to provide an alternative to the traditional but at the same time offers a package of ecological and sustainable economic benefit. Natural rubber based agroforestry on swidden fallow and degraded land may significantly contribute to strengthen the resilience of the overall ecosystem as well as of the farming community by diversifying their livelihood activities in the face of climate change. Rubber is a popular cash crop in Southeast Asia and South Asia, and has been grown mainly as . In Asia and Southeast Asia continents, natural rubber has been cultivated in slash and burn agriculture system since long back. However, with the advent of rubber-based agroforestry models it has been being recognised as an effective land management system and is seen as an alternative to swidden agriculture. Though, it needs extensive trials and testing before actually implementing the agroforestry model on a specific type of soil and climatic settings. In the present article, a review of adoption of rubber agroforestry systems on swidden landscapes and their potential in synergizing mitigation and adaptation is endeavoured estimating the multiple benefits of such systems by way of restoring the degraded land and enhancing the ecosystem’s resilience and reducing the vulnerability of communities to climate change.

Key words: Adaptation, climate change, land restoration, mitigation, rubber agroforestry, swidden landscape.

Introduction (CO2) is considered as the biggest player. Most of the GHGs emission is released from the burning of Climate change has emerged as one of the fossil fuels, but the emission is compensated by greatest challenges of the 21st century. At the core tropical ecosystems which stores around 340 of this global concern is the unprecedented billion tons of C (Gibbs et al. 2007), equivalent to increase in the atmospheric concentration of more than forty times of the total annual greenhouse gases (GHGs) wherein carbon dioxide anthropogenic emissions from fossil fuels. A large

*Corresponding Author; e-mail: [email protected] 606 PROSPECTIVE OF RUBBER AGROFORESTRY ON SWIDDEN FALLOW

A

Fig 1. Forest transition curve (Source: Barbier et al. 2010; Dewi et al. 2017).

amount of this stored terrestrial C is released into B the atmosphere when the land use change takes place and major C reservoirs i.e. forests and grasslands are converted to agricultural systems (IPCC 2007). Land-use and land cover change has been recognised as a major contributor (33%) in global C emission over the past 150 years, however, the relative contribution has significantly declined to the range of 10 to 13% annually (Houghton et al. 2012). Tropical deforestation is largely driven by agricultural expansion, which is estimated to release about 1.5 billion tons of C each year (IPCC 2007). This has led to a growing interest in lowering the emissions rate of GHGs Fig. 2. (A). Degraded secondary forest on swidden from different types of land-use in one hand and landscape in West Khasi hills district, Meghalaya, simultaneously increasing the C sink at the other. India (Photo credit: Anthony Kharkongor), and (B). A Global efforts and negotiations at different swidden land exposed to erosion (foreground) and a platforms agreed upon to focus on forestry and growing secondary forest on swidden fallow agroforestry sector with the goal to achieve a (background), (Photo credit: Batiplang Syiemlieh). significant long term reduction in atmospheric GHG levels, particularly from tropical areas (Soto- Many of the swidden fallows are deteriorated to Pinto et al. 2010; Verchot et al. 2007). The land-use the condition that they may not be able to restore and land cover change may be a gradual transition their productivity leading to loss of soil resources process or a sudden transformation. The transfor- and a number of ecological and socio-economic mation of the forests into agricultural land uses is implications. The swidden fallows may also generally characterized by transition curve develop into a secondary forest in 10–30 years but illustrating the shrinkage of forests and tree cover is generally devoid of natural attributes of a forest along a gradient of land use change and agri- and biological diversity (Fig. 2A, B). cultural intensification until a point is reached Adoption of agroforestry as a production system when tree cover is brought back into the agri- is considered as one of the most promising climate cultural land by agroforestry, reforestation or adaptation and mitigation strategies. Agroforestry other similar interventions (Fig. 1) is accepted worldwide and it has potential to Swidden agriculture which is also known as provide a broad range of socio-economic and have received global attention ecological benefits. Though, agroforestry is an due to direct linkage of tropical deforestation with ancient farming practise being exercised since the biodiversity loss, land-use change, global centuries, however; its importance has increased warming and climate change (Fujisaka & Escobar significantly in recent decades due to recognition of 1997). The land left fallow for many years its multifarious beneficial effect against climate gradually converts into degraded wasteland due vagaries which has very adverse effects on to excessive nutrients leaching and soil erosion. agricultural productivity and subsequently on ANUJ KUMAR SINGH 607 livelihoods of farmers. Agriculture being largely Agroforestry for Swidden fallow dependent upon the climatic variables has always management been one of the high priority sectors where the implications of climate change impacts have Shifting cultivation which is still in practice in potential to exceed the adaptive capacity of millions about 40–50 countries is estimated to be responsible of smallholder farmers dependent on this sector. for large scale deforestation (70 and 50%) in Africa Agroforestry interventions, because of their ability and Asia, respectively (Bandy 1994; Mertz 2009). to provide economic and environmental benefits, are The global extent of shifting cultivation may be considered to be the best “no regrets” measures in estimated by the fact that the secondary forests reducing the communities’ vulnerability and generated as a consequence of shifting cultivation enhancing their adaptive capacity and resilience to constitutes a significant portion of the 850 Mha the impacts of climate change as well as (million hectares) of secondary forest in tropical significantly contribute in enhancing the food Africa, America and Asia (FAO 2005). Shifting security (Sheikh et al. 2014). cultivation has a range of associated ecological and Due to increasing demand of supplies and socio-economic implications with a mix of short and products coupled with the accelerated development long term impacts. processes especially in developing countries of the Agroforestry is an important strategy for tropics and sub-tropics, the degradation of natural biological carbon sequestration because of its carbon resources in inevitable and it manifests in land storage potential in multiple plant species degradation, deforestation, soil erosion and combinations and soil as well as its importance in excessive cultivation (Chen et al. 2017). Climate diversifying the production system, land restoration change may act as a catalyst in the process of land and in reforestation (Montagnini & Nair 2004). degradation and un-checked degradation may lead Agroforestry may provide a feasible swidden fallow to desertification. As the ecosystem or the land management option, especially in the landscape are fundamentally single entity vulnerable regions where land and water are composed of various constituent components. already a scarce resource and sustainability of the Thereby, any disturbance or alteration in one environmental services are threatened by climate component triggers change in the other which change. The area affected by shifting cultivation affects the entire system one way or the other with must be taken into management consideration multiple implications. Unchecked deforestation through agroforestry practices. A number of combined with shifting cultivation increases the agroforestry systems have been developed over the vulnerability of the area at the events of flash decades and are being practiced in India. However, floods. The flood water from upper reaches travel any model will only be workable if it is suitable to along with muddy debris, sand and uprooted local environmental conditions and is able to suffice vegetation and deposits in agricultural fields, the requirements of the farmers. Agroforestry can human settlements and low lying water bodies be practiced in both sub-tropical and temperate causing damage to the crops, humans and climates. Commercial plantation crops like rubber, livestocks, and also severely affects water quality. areca nut and tea represent a popular profitable This also affects over all ecosystem structure and agricultural activity in sub-tropical climate regions function which may take decades to fully restore. of Meghalaya and have become a source of Sustainable land use and land management livelihood to the sizable amount of farmers. Though, practices like Agroforestry may significantly help monoculture plantation is mainly focused on the to bring the degraded land back to its productive business aspects ignoring its long term negative capacity and also enhances systems capacity to impacts on ecosystem in particular and natural withstand climate change. In view of the potential resources at large. Rubber agroforestry or rubber of agroforestry systems, this article reviews the based integrated farming systems have provided past researches carried out on rubber based with a resilient financial shield and coping capacity agroforestry systems across the globe, and against market uncertainties to the smallholders in endeavors to explore the possibility of integrating Indonesia and Thailand (Joshi et al. 2002; rubber-based agroforestry system in swidden Somboonsuke 2001). fallows to synergize climate change mitigation and Rubber has demonstrated flexibility and adaptation for long term sustainability and adaptability from a complex rubber agroforest to optimization of resource remunerations. monoculture plantation to a well-managed rubber-

608 PROSPECTIVE OF RUBBER AGROFORESTRY ON SWIDDEN FALLOW based agroforestry system. Given enough time to (Xu 1993). Natural rubber plant (Hevea brasiliensis) grow, in structure and composition agroforests is one of the most important commercial plantation mimic the natural forest to significant extent. crop grown in different parts of the world since over Fientrenie and Levang (2009) have extensively 200 years. Asia is the home of around 72% of the studied the different stages of development of a total natural rubber production in the world being complex rubber agroforest on swidden land. In the Thailand, Indonesia and Malaysia the leading development of a complex rubber agroforest, the producers. Rubber cultivation is a growing forestry primary vegetation is first cleared by slashing practice as demonstrated by the global demand followed by burning and the land is prepared for growth rate of natural rubber which is about 3.4% cultivation. This cultivated stage alters the soil annually. Agroforestry based production systems properties and a humid microclimate enabling the help the farmers to diversify their income as well as enhanced microbial activity in the soil. enable to maintain diversity of food, timber, fruit Simultaneously, the shady environment favours crops and cash crops. With the improved the development of young forest species such as management mechanisms, the productivity of the rubber, fruit trees and timber trees followed by system may be increased. post pioneer phase where fast growing crops such In India also, rubber monoculture and rubber as coffee, pepper, clove and cinnamon are agroforestry are being practiced for a variety of introduced which maintains a biophysical reasons. In state of north eastern India, environment favourable to the growth of young rubber plantation was introduced as a biological trees. Gradually, the agroforest attracts native measure to check soil erosion due to shifting herbs, shrubs and forest tree species enabling the cultivation and as a measure to rehabilitate the development of understory vegetation. In land degraded due to shifting cultivation successive 15-20 years a full-fledged complex forest (Chaudhuri et al. 2008). Despite being one of the with a dense canopy is developed and natural major causes of deforestation, soil erosion, soil regeneration process multiplies the complexity of degradation and siltation of water bodies, shifting the agro-forest. The same principle with necessary cultivation or swidden agriculture is still in modifications may be adopted in a swidden fallow practice in north eastern states in India. Also, the land for developing a rubber-based agroforestry forest survey of India has identified swidden system using modern management mechanisms agriculture as a prominent cause for forest and emerging technologies. Today, the clonal degradation and deforestation in Meghalaya (ISFR varieties of rubber are available which are fast 2015). Rubber is a broadleaf deciduous plant which growing and high yielding in terms of latex and gets mature for tapping in 5–7 years and possesses biomass production. Rubber-based agroforestry great potential to supplement farmers’ livelihoods system has one unique advantage of replacing the as well as serve as tree biomass carbon pool. rubber with timber or fruit crops when rubber tree Clonal saplings should be preferred for plantation reaches to its maturity at around 35 years or else as it maintains homogeneity, early maturity and the same can be retained for carbon finance provides quality latex produce (Wibawa et al. benefits from biomass carbon conservation and 2006). credit mechanisms. Thus, adopting rubber-based Sub-tropical climate is ideal for rubber-based agroforestry on the swidden fallows has agroforestry systems. Climatic conditions in Garo substantial potential to prove to be a solution for hills region of Meghalaya offers congenial swidden fallow degradation and associated environment for adoption and expansion of rubber- environmental implications. based agroforestry especially on abandoned lands especially on the one which has been earlier used Rubber agroforestry on swidden for swidden agriculture. Rubber cultivation in Garo fallow hills region is practised but at small scale and plantations are mainly monoculture which may not In recent decades, research into rubber be optimally contributing to soil nutrients reserves agroforestry has intensified, with priority given to and other ecosystem functions (Fig. 3A, B). Rubber- alternatives to rubber monoculture, which is at once based agroforestry provides an alternative of rubber ecologically unsustainable and a source of economic monoculture in shifting agriculture systems with instability. One very important avenue in this multifarious advantages both ecologically and direction is to explore the benefits of rubber economically. Establishing rubber-based agro- agroforestry systems over monocrop rubber systems forestry has potential to provide an effective land ANUJ KUMAR SINGH 609

and semi-arid regions (63, 50, 21 and 9 Mg C ha–1), A respectively. They also emphasised on indirect role of agroforestry on carbon sequestration and climate change mitigation by reducing pressure on natural forests. Another indirect avenue of carbon sequestration by agroforestry systems is through the soil conservation and nutrients enrichment, which could enhance carbon storage in above- ground and below-ground biomass and soils. Agroforestry also offers livelihood alternatives, promotes biodiversity and provides an alternative to swidden agriculture (Adesina et al. 2000; Brady 1996; Faminow & Klein 2001; Gordon & Bentley 1990; Kidd & Pimentel 1992; Rahman et al. 2007;

Rasul & Thapa 2003). B Rubber agroforestry: a mitigation outlook

Rubber is a fast growing perennial tree which grows well in tropical and sub-tropical climates (Charoenjit et al. 2015). Due to its fast-growing nature, it is associated with high level of biomass and possesses great potential of sequestering carbon over its lifetime (Nguyen 2013). According to Brahma et al. (2016), biomass carbon stock of rubber is equivalent or even exceeds many other tropical and sub-tropical agroforestry systems. Due

to the increasing demand of natural rubber and its C commercial consistency, rubber agroforestry have attracted the interests of cultivators as well as of policy makers in secondary and degraded forests restoration. Globally, massive expansion of rubber plantations has been recorded in the world’s sub- tropical and tropical areas over the past 50 years (Chen et al. 2016). This rapid development of rubber plantations is recorded in Southeast-Asia, the Amazon Basin and Africa with an estimated total planted area of 10 million hectares out of the estimated 4 billion hectares coverage for total world forests (FAO 2010). A typical case of rubber afforestation and reforestation is in Columbia Fig. 3. (A). A mature rubber monoculture plantation where highly degraded lands have seen rubber on swidden land in South Garo hills district of cultivation of 1,500 hectares (World Bank 2005) and Meghalaya, India, (B). A close view of latex tapping worth becoming a model for replication on similar in a Rubber monoculture plantation, and (C). A land conditions. rubber monoculture plantation on swidden slope. Biomass potential of a plant is a function of photosynthetic capacity of per unit leaf and the management solution for the land degraded due to total leaf area of the plant. In optimum sunlight age old swidden agriculture along with other conditions, the photosynthetic rate of a mature associated environmental and livelihood benefits. rubber leaf is 10–15 µmol CO2 m-2 s–1 (Nataraja & Montagnini and Nair (2004) studied carbon Jacob 1999) as compared to about 5–13 µmol CO2 storage in agroforestry systems in different m–2 s–1 in many other tree species (Sethuraj & ecoregions and estimated to be highest in Jacob 1997). This observation necessarily gives an temperate region followed by humid, sub-humid impetus to the choice of rubber tree in agroforestry 610 PROSPECTIVE OF RUBBER AGROFORESTRY ON SWIDDEN FALLOW system where fast growing trees are preferred for correlation of soil C pool with the rubber age adoption. Therefore, planting fast growing species sequence but pointed out a decrease in soil carbon like rubber is a potential means of ameliorating the pool with increase in the soil depth. Another study ever increasing concentration of atmospheric carbon reported increase in soil organic carbon (SOC) in dioxide. rubber plantation at the rate of 1.13 Mg ha–1 year–1 Rubber is primarily cultivated for latex over the period of 11 years (Maggiotto et al. 2014), extraction. It also plays a significant role in whereas forest-to-rubber transition led to a loss in biological carbon sequestration and biomass carbon SOC stock by an average of 37.4 Mg ha–1 over a sink management and that way it contributes in period of 46 years (De Blecourt et al. 2013). A climate change mitigation (Brahma et al. 2016). It transition from forest to rubber may lead to loss of also has the possibility to explore and harness the soil carbon and other soil attributes but a transition benefit of gaining carbon credits, carbon from a fallow land to rubber plantation or conservation and management mechanisms under agroforestry has potential to increase soil organic the Clean Development Mechanism (CDM) and carbon inter alia other soil nutrients. Studies on REDD+ frameworks targeted at improving the total biomass and carbon accumulation by rubber terrestrial carbon sinks and removing the emissions tree in different geographic and climatic conditions through the planted or managed forests (Watson have been summarised in Table 1. The variations in 2009). Rubber on large scale production are the carbon sequestered by the various pools may be accounted for as planted forests and contributes to attributed to the variation in the methods applied development by financial gains and carbon for the carbon computation. emissions reduction (Egbe et al. 2012). A number of As a semi-deciduous tree, the rubber tree studies (Cheng et al 2007; Feng et al. 2013; supplements organic matter to the soil upper layer Maggiotto et al. 2014; Munasinghe et al. 2014; through wintering effect (Geetha & Jacob 2003), Petsri et al. 2013) have reported the carbon stocks also the deposition of leaf litter increases with the in different carbon pools of rubber plantation in age of the rubber tree. The increase in SOC is also diverse genotypes and geographic locations. Apart observed to a great depth due to well-developed from being a very good sink of atmospheric carbon, root systems of the older plantations and changes rubber also contributes in soil fertility improvement in root microclimate due to microbial activities. In through leaf litter decomposition and nutrient the degraded lands such as swidden fallow, enrichment on the upper layers of the soil (Dijkman microbial activity may be initially low, but when 1951; Sethuraj 1996). plantation or agroforestry system is once Rubber agroforestry has potential to alter established the soil moisture level increases and physical and chemical characteristics of degraded soil microbial flora begins to act in its full soil, hence helping in restoring the soil health. functionality. However, the older plantations are Rubber monoculture plantation may not reported to have larger biomass accumulation rate substantially contribute in nutrient building and which corresponds to higher soil organic carbon soil health but can significantly contribute in stock (Maggiotto et al. 2014). biological carbon sequestration. Alternative to Cunha et al. (2000) reported a total biomass of rubber monoculture plantation is rubber-based 349.53 kg per plant in a 12 year old rubber agroforestry which brings along the possibility of monoculture plantation in Brazil. While Cotta et nutrient supplementation to soil and contribution in al. (2006) evaluated a 34 year old rubber soil rebuilding in degraded land. In India, in soil plantation in combination with cocoa trees cultivated with two cycles of rubber trees (60 years), estimated total rubber tree biomass of approxi- the organic C content was nearly that of the mately 170 Mg ha–1. The multi-crop combination in primary forests, also the available P was estimated agroforestry systems have greater potential for to be increased and was attributed to be derived atmospheric carbon sequestration than a mono- from litter fall. Though, total N and exchangeable K culture (Guo et al. 2006). Tree biomass estimation registered a minor decrease (Karthikakuttyama et in rubber plantations of diverse ages and grown in al. 1998). Nutrient dynamics is complicated in a potentially different geographic and climatic complex system like a natural or planted forest settings have reported carbon accumulation rate where interdependence of interacting variables is ranged from 1.4 Mg C ha–1 year–1 to 6.7 Mg C ha–1 high. A sizable number of studies have reported year–1. (Cotta et al. 2006; Cunha et al. 2000; Dey such interdependence of variables in rubber 2005; Wauters et al. 2008;Yang et al. 2005). Chun- plantations where Liu et al. (2017) reported no man et al. (2007) had studied carbon sequestration ANUJ KUMAR SINGH 611

Table 1. Total biomass and carbon stock in Rubber plantations in different geographical and climatic conditions (Extracted from Magiotto et al. 2014).

Source Location Age Total biomass (t ha-1) C-accumulation rate (year) Above ground Below ground Total (t C ha–1 yr–1) Maggiotto et al. (2014) Brazil (PR) 4 9.35 2.58 11.93 1.26 Brazil (PR) 6 28.00 6.33 34.33 2.43 Brazil (PR) 15 124.12 22.18 146.30 4.17 Cunha et al. (2000) Brazil (BR) 12* 114.40* 46.40* 160.80* - Brazil (MG) 12* 56.90* 13.90* 70.80* - Cotta et al. (2006) Brazil (BA) 34 136.82 32.40 169.22 2.49 Fernandes et al. (2007) Brazil (MG) 12 88.67 37.79 126.46 4.72 Wauters et al. (2008) Brazil (MT) 14 - - - 2.97 Ghana 14 - - - 5.45 Dey (2005) India 6 33.90 14.40 44.40 3.58 India 17 141.10 29.10 170.20 4.48 Yang et al. (2005) China 4 - - 9.60 1.20 China 6 - - 24.50 2.05 China 16 - - 132.70 4.15 China 38 - - 340.00 4.47

*Assuming the plant density for State of Sao Paulo, Brazil: 460 trees ha–1 (Francisco et al. 2004), Using allometric equation. in a 30 year old rubber plantation in China and floribunda) can also be intercropped with rubber reported that the plantation sequestered 272.08 t (Singh et al. 2012). Rubber tree may also be grown ha–1, averaging 9.07 t of carbon sequestration per in combination with food and beverage crops such annum, where the litter had the larger role in as maize, cassava, sweet potato, coffee, tea, sequestering the carbon amounting to 58% of the pepper, lemon grass and also with fruit crops such total carbon sequestered. Study also suggested as banana and pineapple (Zheng & He 1991). Such higher carbon sequestration potential in rubber combinations of crops grown at different stages of plantation in comparison with C sequestration by tree growth under rubber enables optimum rain forest and by secondary rain forests. The utilization of land and water resources (Zhu 1994) study gives a booster dose to the advocates of and also have higher soil organic matter content expansion of rubber plantation in the wake of (Feng et al. 2013). global warming and climate change. However, the Intercropping helps in maintaining the rubber plantation expansion should not be nutrients and moisture balance in the farm, encouraged on the primary croplands which may permanent cover to the ground and mutually helps jeopardize food security in the long run rather in increasing the production as well as helps in rubber-based agroforestry may prove to be a increasing the soil productivity and prevention sustainable adoption. from erosion. The selection of intercropping crops may be made based on the regional preferences, Rubber agroforestry: an adaptation approach climatic suitability and market mechanisms. Some of the tried and tested rubber-based Rubber can be grown in combination with agroforestry systems recommended depending different fruit and tuber crops. Intercropping upon the climatic conditions (Kropf & Hoang 2012) various crops before maturity of the plantation are highlighted below: provides an additional revenue to the farmers. Rubber-based multistrata system may be  Jackfruit, acacias or mahogany may be grown established by intercropping with Sweet potato, as windbreaks for rubber trees. Cassava, Colocasia, ginger and turmeric before  Elephant grass may be integrated with rubber canopy closure and plantation reaches to maturity. when the farm is established in marginal soils Apart from the food crops, the medicinal and to provide fodder for cattle, cow, buffalo, goat aromatic plant viz. medicinal yam (Dioscorea or rabbit. 612 PROSPECTIVE OF RUBBER AGROFORESTRY ON SWIDDEN FALLOW

 Food crops such as peanut, beans, sweet al. 2012). In case of swidden fallow land, the soil is potato, taro, maize, or cassava may be more prone to degradation and coupled with integrated with rubber during the first four drought like situation, the fallow may advance to years. desertification. Whereas, agroforestry has  The integration of cassava with rubber in the potential to arrest the soil degradation and by first three years of farm establishment may developing the carbon pool it contributes in soil produce 14–18 tons of root tubers per hectare rebuilding and enhancing the resilience of the per year. ecosystem and it becomes more relevant in the face  Coffee and pepper can be intercropped with of risks associated with the climate change rubber trees in the early years plantation. (Bhadouria et al. 2016; Singh & Bhadouriya 2013). Transition from of rubber monoculture to Crop diversification enables income rubber-based agroforestry has significant effects on diversification and acts as a protective shield soil chemical properties (Carsan et al. 2014; Chen et especially for smallholders. In the face of climate al. 2017; Liu et al. 2016). The rubber-based change, diversification of income of the farmers is agroforestry system increases biological diversity one of the priority adaptation measures and in both above and below the ground enhancing the terms of efficient and optimum utilization of scarce resilience of the ecosystem and improving the resources such as land, agroforestry appears a win- ecosystem services. The diversified agroforestry win strategy and an alternative to swidden system has potential to improve ecosystem agriculture (Noordwijk et al. 1995). Agroforestry functioning and ensuring the higher economic and also provides an opportunity to overcome the ecological incentives (Liu et al. 2016; Snoeck et al. monoculture constraints like reliance on one crop 2013). In addition, rubber-based agroforestry and one source of income and also enables to fetch systems improve the water use effciency of both the benefit from the environmental services offered by rubber and the intercropping trees and crops (Wu et the complex agroforestry systems. This becomes al. 2016). The rubber-based agroforestry systems more relevant in case of swidden fallow and retain more soil moisture than monoculture rubber degraded lands which are gradually inching plantation accelerating the microbial activity and towards desertification amidst climate uncer- mineralization process which in turn significantly tainties and land scarcity scenario. Noordwijk et al. improves the physical and hydrological properties of (1997) suggested intercropping of clonal rubber the soil (Hardanto et al. 2017). trees with upland food crops such as rice, maize and Rubber agroforestry system has greater legumes on the swidden land. Rubber-based nutrient optimization potential than rubber agroforestry has potential to provide higher monoculture. Rubber-based agroforestry systems economic returns from crop diversification provide a larger volume of tree biomass and especially when rubber is intercropped with fruits corresponding litter fall (Carsan et al. 2014). and vegetables. In addition, it also provides with a Further, rubber-based agroforestry systems flow of income that amply contributes to the house- significantly control splash erosion and reduces holds’ resilience of the smallholders (Viswanathan nutrient leaching more efficiently than monoculture 2006). rubber stand (Liu et al. 2016). Rubber-based Rubber agroforestry and ecosystem’s agroforestry systems also helps in soil aggregation, resilience soil rebuilding, nutrient enrichment (Chen et al. 2017) and contributes in strengthening and resilience of the ecosystem ensuring the sustaina- Ecosystems are always exposed to natural and bility of the ecosystem services. man-made disturbances. The diversity and complexity of ecosystem plays an important role in Synergy between mitigation and ecosystem’s resilience to various stresses. The un- adaptation vegetated fallow land is more vulnerable to drought and erosion and further threatens the The net loss rate of global forests though integrity of the ecosystem’s structure and recorded a decline by about 50% between 2010 to sustainability of the ecosystem. As far as carbon 2015 in comparison to the net loss rate during sequestration is concerned, a vegetated landscape 1990s, the forests are still being eliminated at an will naturally be capable of sequestering more unjustifiable rate, especially in tropical and carbon than a land without tree cover (Pradhan et sub-tropical countries (Keenan et al. 2015; Sloan & ANUJ KUMAR SINGH 613

Table 2. Comparison of carbon content in different Table 3. A comparison of run-off and soil erosion tree plantations (Extracted from Kongsager et al. rates under different land-use systems (Extracted 2012). from Xu 1993).

Tree crops Age Above-ground Accumulation Land- use Run-off Relative Soil Relative (Year) (t C ha–1) (t C ha–1 year–1) systems (mm amount erosion amount Cocoa 21 65.0 3.1 ha–1 (kg ha–1 –1 –1 Oil Palm 7 21.7 3.1 year ) year ) Oil Palm 16 28.0 1.8 Tropical rain 99 1 63 1 forest Oil Palm 23 45.3 2.0 Rubber + Tea 206 2 2241 33 Rubber 12 61.5 5.1 system Rubber 44 213.6 4.9 Rubber 283 3 2694 43 Orange 25 76.3 3.1 monoculture plantation Sayer 2015). Commercial agriculture (68%) Shifting 3395 35 48897 778 followed by subsistence or smallholder agriculture cultivation (33%) are the main drivers responsible for deforestation (FAO 2016; Hosonuma et al. 2012). potential of carbon sequestration as compared to There have been global efforts by researchers the land with high carbon content (Singh et al. and policy makers for enabling the transition from 2012). Considering this fact, rubber agroforestry shifting cultivation to a permanent and more can be encouraged on the lands undergoing environmentally system. degradation due to swidden agriculture practices The scientific community is in consensus on the instead of well managed fertile croplands. Rubber fact that the climate variability is mainly due to has demonstrated capability of growing on slopes increase in the concentration of greenhouse gases which makes it more adaptable in hilly (GHGs) in the atmosphere. It is also agreed that a topographic conditions (Fig. 3C). One interesting large proportion of GHGs are emitted by land use and encouraging study suggests that the rubber- change, deforestation and use of fossil fuels. The based agroforestry system supports a considerable atmospheric concentration of these greenhouse mass of earthworm which in turn helps to gases mainly CO2 can be diminished either by decompose litter and adds organic carbon in the reducing the emission or by enhancing the soil. The organic content in the soil will help the terrestrial sinks by biological measures (Segura & short rotation intercrops with the plantation. Andrade 2008). Agroforestry systems offer a Rubber wood has been traditionally used as a wood unique solution by dovetailing mitigation and fuel and for charcoal production in regions where adaptation measures together. Agroforestry rubber plantations are at large scales. Through systems demonstrate a unique capability of CO2 agroforestry, these monoculture plantation sequestration and simultaneously improve the systems can be transformed into more ecologically ecosystem productivity (Orjuela & Andrade 2011). productive, biologically diverse and economically By integrating trees with crops is seen as an beneficial production systems which may also economically viable and ecologically sustainable contribute in climate mitigation and food security. adoption (Albrecht & Kandji 2003; Andrade et al. Rubber-based agroforestry systems have been 2008; Beer et al. 2003; Swamy & Puri 2005) at the tried for land amelioration in different parts of the same time mitigation potential and ecosystem world. Two separate rubber-based agroforestry services supplied may be explored for its economic models e.g. Rubber (H. brasiliensis) + Cleroden- valuation (Ospina-Ante 2003). Kongsager et al. dranthus spicatus and Rubber (H. brasiliensis) + (2012) had extensively studies carbon seque- Amomum villosum demonstrated significant stration potential of different plantation crops in improvement in the soil condition and structure in a Ghana and found rubber to be having highest degraded landscape in China (Jiang et al. 2017). carbon sequestration potential followed by orange, Jiang et al. (2017) and Xu (1993) reported enhanced Cocoa and Palm oil (Table 2). infiltration, less runoff and reduced soil erosion in The plantation grown on waste and degraded rubber agroforestry systems in comparison land with moderate carbon content has greater to rubber monoculture plantations (Table 3). The

614 PROSPECTIVE OF RUBBER AGROFORESTRY ON SWIDDEN FALLOW

Table. 4. Comparison of contribution of rubber based agroforestry systems on income diversification of the community (Extracted from Vishwanathan 2008).

Type of rubber based Tripura (India) (India) Meghalaya (India) Songkhla agroforetry system (Thailand) Income Rank Income Rank Income Rank Income Rank Rubber monoculture 54292 7 44,427 7 45,519 7 29,027 7 Rubber + fruit + 57,057 5 47,672 5 49,837 4 44,811 1 agriculture Rubber + poultry 55,715 6 45,807 6 46,764 6 31,314 6 Rubber + livestock 60,325 1 50,288 1 21,316 2 42,948 2 Rubber + rice 58,080 4 49,412 3 49,595 5 32,775 5 Rubber + fishery 58,466 3 47,733 4 51,502 1 40,476 3 Rubber + piggery 59,398 2 50,193 2 51,030 3 37,187 4 benefit of agroforestry systems extend beyond the adopting agroforestry is perhaps the only way mitigation of soil erosion and have the potential to forward to optimize the land productivity, compensate greenhouse gas emissions associated increasing the forest cover, checking the ever with deforestation and swidden agriculture increasing desertification and enhancing resilience activities (Dixon 1995; Nair & Nair 2002). of the natural systems and community dependent Rubber-based agroforestry has potential to upon them. Such potential is seems to be diversify and enhance the income of the embedded with rubber-based agroforestry systems communities and provide them with the shield which not only provides an opportunity for against the uncertainties associated with the transition from swidden agriculture system and monoculture plantation forestry. Viswanathan and monoculture plantations to more systematic and Shivakoti (2006) reported the role of rubber-based sustainable production system. That production integrated farming system in diversifying the systems not only has economic benefits but also livelihood activities and its financial benefit to the provides with the way out to synergize climate communities in India and Thailand (Table 4). In mitigation and adaptation for long term resilience addition to providing with the potential source of and sustainability of the ecosystem services. income, rubber-based agroforestry systems sufficiently contributed in reducing the small- References holders’ vulnerability to market uncertainties and helped in enhancing their resilience to cope with Adesina, A., Mbila, D., G. Nkamleu & D. Endamana. financial emergencies (Viswanathan 2008). 2000. Econometric analysis of the determinants of adoption of alley farming by farmers in the forest Conclusion zone of Southwest Cameroon. Agriculture, Eco- systems and Environment 80: 255–265. In the wake of climatic erraticism, it is vital to Albrecht, A. & S. T. Kandji. 2003. Carbon sequestration act on both mitigation and adaptation fronts in tropical agroforestry systems. Agriculture, Eco- synergistically. Agroforestry provides with such an systems and Environment 99: 15–27. opportunity in tremendously beneficial ways. This Andrade, H. J., R. Brook & M. Ibrahim. 2008. Growth, has potential not only to provide an alternative to production and carbon sequestration of silvopastoral the traditional plantation but at the same time systems with native timber species in the dry offers a package of ecological and sustainable lowlands of Costa Rica. Plant and Soil 308: 11–22. economic benefit. Natural rubber-based agro- Bandy, D. 1994. Alternatives to lash-and-burn: a global forestry on swidden fallow land may significantly strategy. Technical Report, International Centre for contribute to strengthen the resilience of the Research in Agroforestry. overall ecosystem as well as of the farming Barbier, E. B., J. C. Burgess & A. Grainger. 2010. The community by diversifying their livelihood forest transition: towards a more comprehensive activities in the face of climate change. Also, given theoretical framework. Land Use Policy 27: 98–107. the fact that land holding size is shrinking Beer, J., C. Harvey, M. Ibrahim, J. M. Harmand, E. nationwide in case of India, in that scenario, Somarriba & F. Jiménez. 2003. Servicios ambien- ANUJ KUMAR SINGH 615

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(Received on 11.04.2018 and accepted after revisions, on 21.10.2018)