Resource-Use Patterns in Swidden Farming Communities: Implications for the Resilience of Cassava Diversity

Resource-use patterns, especially through exchanges among farmers, may ultimately confer resilience to the local agrobiodiversity. We investigated the use of cassava ethnovarieties by swidden farming communities in Brazil, exploring the structure of networks depicting farmers and the varieties they cultivate. The emergent nested resource-use pattern indicated that all farmers shared a core of top-ranked ethnovarieties (most common/abundant) while some farmers also cultivate rarer varieties. This pattern may result of individual preferences. Due to the current loss of interest and cultivation area for traditional agriculture, we simulated the extinction of crop fields to evaluate whether nestedness conferred robustness to cassava diversity. The diversity of ethnovarieties of cassava tended to be conserved when farmers were randomly removed from the network than when we preferentially removed farmers with more diverse crop fields. Stem cuttings of ethnovarieties are commonly exchanged among farmers, thus the extinction of ethnovarieties within crop fields could be restored. Therefore, we suggest that the interplay between the farmer’s resource-use patterns and exchange system strengthens the resilience of cassava diversity, which is an important staple resource for such communities.     

Slashed and burned: war, environment, and resource insecurity in West Borneo during the late nineteenth and early twentieth centuries

European colonial efforts to pacify 'rebellious' Iban in western Borneo during the late nineteenth and early twentieth centuries produced chronic resource insecurity and may have contributed to the recorded destructiveness of Iban swidden cultivation. Negative European opinions towards swiddening may have thus been reinforced by a context that the Europeans themselves created. Drawing on anthropological theories linking swidden cultivation and Iban warfare, this article presents a historical case for the relationship between pacification, resource insecurity, and swidden destructiveness. It also re-evaluates Derek Freeman's original diagnosis of Iban as 'prodigal' farmers, suggesting that there may have been more to Iban pioneering destruction than the wide availability of 'virgin' forest.     

Agricultural intensification in a Philippine frontier community: Impact on labor efficiency and farm diversity

There continues to be much debate in anthropology concerning the mechanism by which agricultural intensification takes place and its impact on labor efficiency, farm diversity, and quality of diet. A major reason for this lack of consensus is the paucity of data from case studies that focus on specific agricultural systems at the point of transition from extensive to intensive methods of cultivation. Research in a frontier community in the Philippines, where farmers are making the shift from swidden cultivation to small-scale irrigated rice production, indicates that intensification does not necessarily result in lower efficiency or a decline in dietary standards. Rather, farmers faced with growing population pressure and an unproductive short fallow swidden system have been motivated to adopt irrigation because it increases the efficiency of their labor while maintaining a reliable and diverse farming system.     

Germination ecology of Cassava (Manihot esculenta Crantz, Euphorbiaceae) in traditional agroecosystems: Seed and seedling biology of a vegetatively propagated domesticated plant

Cassava is clonally propagated, but Amerindian farmers also use plants from volunteer seedlings to prepare stem cuttings. Although sexual reproduction plays a role in cassava’s evolution it is poorly studied. We examined one aspect of cassava reproductive ecology, seed dormancy and germination. Volunteer seedlings emerge from a soil bank of seeds produced during the previous cycle of cultivation that remain ungerminated through the fallow period, then germinate synchronously after vegetation is slashed and burned. Laboratory experiments showed that germination can be enhanced by mechanical scarification and also by dry heat treatment, suggesting that burning after field clearing could help break dormancy. Germination was also stimulated by high temperatures (35°C) that in nature indicate bare soils, and inhibited by temperatures (25°C) close to those in soil shaded by vegetation and by light. Seeds of both wild and domesticated cassava exhibit physiological dormancy, an adaptation for germination in periodically disturbed habitats. In addition to these preadaptations, preliminary results also suggest specific adaptations of domesticated cassava to the distinctive disturbance regimes of swidden agriculture.     

Who Counts? Demography of Swidden Cultivators in Southeast Asia

Swidden cultivators are often found as a distinct category of farmers in the literature, but rarely appear in population censuses or other national and regional classifications. This has led to a worldwide confusion on how many people are dependent on this form of agriculture. The most often cited number of 200–300 million dates back to the early 1970s, but the source is obscure. We assess available, published data from nine countries in Southeast Asia and conclude that on this basis it is not possible to provide a firm estimate of the number of swidden cultivators in the region. A conservative range of 14–34 million people engaged in swidden cultivation in the region is suggested, however. We argue that along with improved knowledge of swidden livelihoods, there is an urgent need to develop techniques that will allow for better estimates of swidden populations in order to secure appropriate rural development and poverty reduction in swidden areas.     

Agricultural practices and household organization in a Japanese pioneer community of lowland Bolivia

This article describes the colonization process of the Japanese pioneer farmers in the Bolivian subtropical lowlands. Quantitative data for each of the farm households that can be matched for comparison between the initial phase of colonization and a later phase provide the basis for an examination of a reciprocal relationship between household organization and successively introduced agricultural practices. Two hypotheses are tested: (a) pioneer agriculture stimulates the formation of large family households to cope with an assumed labor shortage; and (b) existing variation in household organization produces variation in agricultural practices. The analysis reveals that the size of swidden farming in the initial phase and the size of permanent field cultivation in the latter phase both relate positively to the size of the male labor force. Despite the significant advantage of a large family household for providing free labor during rapid agricultural growth, a diachronic analysis does not support the hypothesis that the pioneer condition stimulates adaptive social change toward the formation of large families. Rather, the data indicate that changes in household composition have major effects on the size of cropland and the transformation from swidden farming to mechanized cultivation. Underlying mechanisms of agricultural change are further explored, and the implications for a colonization project are discussed.     

Farmers’ Perspectives on Vital Soil-related Ecosystem Services in Intensive Swidden Farming Systems in the Peruvian Amazon

A growing dilemma is how to conserve Amazonian forest while allowing local people to secure their livelihoods. Small-scale swidden farming in Amazonia is entirely dependent on the continued provision of ecosystem services (ES) that generate the conditions for agriculture. This study identified soil-related ES needed for, and enhanced by, productive swidden systems from the farmer’s perspective. Workshops in six farming communities in northeastern Peru discussed various land uses, swidden systems that continue to be productive, and swidden systems on degraded land. The participating farmers noted changes in their production systems and described the ES (or lack thereof) in terms of soil quality, crop production quantity and quality, burning practices, forest regeneration, and farming skill. The central elements described in farmers’ own strategies for managing soil-related ES were fallow management for biomass production and crop diversity, factors identified as central to future ES management work in established agricultural areas in Amazonia.     

Microsatellite Polymorphisms in Cassava Landraces from the Cerrado Biome, Mato Grosso do Sul, Brazil

Using nine microsatellite loci, we investigated genetic structure and diversity in 83 Brazilian cassava accessions, including several landraces, in the Cerrado biome in Mato Grosso do Sul, Brazil. All nine loci were polymorphic, averaging 6.00 alleles per locus. Treating each of seven municipalities as a cassava group or population, they averaged 3.5 alleles per locus, with 97% polymorphic loci, high values for observed heterozygosity (0.32) and gene diversity (0.56). Total genetic variability was high (0.668), and most of this genetic variability was concentrated within municipalities (0.577). Cluster and structure analyses divided accessions into two major clusters or populations (K = 2). Also, a significant genetic versus geographic correlation was found (r = 0.4567; P < 0.0260). Migratory routes in the Cerrado are considered main contributors to the region’s high cassava diversity and spatial genetic structure, amplifying interactions between traditional farmers and the evolutionary dynamics of this crop.     

The unmanaged reproductive ecology of domesticated plants in traditional agroecosystems: An example involving cassavaand a call for data

Although cassava is a strictly vegetatively propagated crop, in many traditional Amazonian agroecosystems, Amerindian farmers recognise volunteer seedlings of cassava and allow them to grow. If their properties are deemed desirable, plants originating from seedlings are included in the harvest of tuberous roots, and their stems are used to prepare cuttings for propagation. Incorporation of these products of spontaneous sexual reproduction appears to be important in origin and maintenance of genetic diversity in this clonally propagated plant. Our observations conducted in an Amerindian village in Guyana suggest that volunteer seedlings arise from a bank of viable seeds stored in soil, and that dispersal and burial of seeds by ants may be important in its constitution. Future investigations of the dynamics of genetic diversity in this crop in traditional agroecosystems must consider the role of the ‘wild’ sexual reproduction that occurs in parallel with vegetative propagation. We suggest that unmanaged processes of sexual reproduction play important but neglected roles in the evolutionary ecology of many domesticated plants in traditional agroecosystems.     

A weed-crop complex in sorghum: The dynamics of genetic diversity in a traditional farming system

Despite the major ecological and economic impacts of gene flow between domesticated plants and their wild relatives, many aspects of the process, particularly the relative roles of natural and human selection in facilitating or constraining gene flow, are still poorly understood. We developed a multidisciplinary approach, involving both biologists and social scientists, to investigate the dynamics of genetic diversity of a sorghum weed-crop complex in a village of Duupa farmers in northern Cameroon. Farmers distinguish a gradient from weedy morphotypes (naa baa see, haariya, and genkiya) to domesticated morphotypes; haariya and genkiya have intermediate morphological traits. We investigated the pattern of diversity in this complex using both morphological and genetic data. Our biological results are interpreted in the light of data on farmers' taxonomy and practices such as spatial pattern of planting and plant selection. Both morphological and genetic data are congruent with farmers' taxonomy and confirm the introgressed status of intermediate weedy morphotypes. Farmers actively select against weedy morphotypes, but several practices unconsciously favor gene flow. Furthermore, haariya and genkiya may facilitate introgression between naa baa see and domesticated morphotypes by virtue of their intermediate flowering period and their mode of management by farmers.     

Genetic variation of cassava (Manihot esculenta Crantz) cultivated by Chibchan Amerindians of Costa Rica

This study focuses on the genetic diversity of the cassava (Manihot esculenta Crantz) grown by the Chibchan Amerindians of Costa Rica. The authors collected cassava in various locations within two Amerindian Reserves: Talamanca, inhabited by Cabecares and Bribris, and Coto Brus, inhabited by Guaymi. Through the use of isozyme electrophoretic techniques we found variation for six out of nine systems analyzed, namely DIA, EST, IDH, MDH, PGI, and SKD. No variation was found in ADH, PGD, and PGM systems. We analyzed the distribution of variation within and between the reserves, and found most of the variation occurred within reserves (Gst = 0.1084). Only low levels of genetic differentiation were found between reserves (Nei’s genetic distance = 0.0088). The high levels of genetic variation within reserves that we found concur with results of previous studies on cassava grown by South American Amerindians and farmers. The role of the breeding system of cassava and the agricultural practices of Amerindians in the maintenance of high levels of genetic diversity are discussed.     

Persistence of Swidden Cultivation in the Face of Globalization: A Case Study from Communities in Calakmul, Mexico

Over the last decades, political, economic and environmental pressures have encouraged changes from swidden to more intensive agricultural practices, resulting in the hypothesis that swidden cultivation systems are disappearing. In Calakmul, southeastern Mexico, communities decreased the area under milpa, the traditional maize swidden system, but a collapse did not occur. To document and explain the persistence of swidden we employ a variety of data: (1) 59 standardized household surveys from 2003 and 2010 in five villages, (2) in-depth interviews in one village, and (3) coupled human–environmental timelines in this same village. Droughts, hurricanes, and remittances were important drivers of decreases in milpa cultivation. Market crop profitability and conservation programs were also reported to affect the area under milpa. Off-farm employment and governmental transfers have tended to stabilize household economies and decrease dependency on agricultural production, but have also allowed households to maintain their milpas for subsistence and cultural reproduction. Findings in Calakmul point to the need to consider swidden as an evolving and active response to changing policy, economic, and environmental conditions.     

The Last Swiddens of Sarawak, Malaysia

Swidden cultivation was observed to be under pressure but still persisting in many areas in Sarawak, Malaysia around 2000–2003. Since then rapid development of smallholder oil palm and rubber, continuing urbanization and rural to urban migration appear to have considerably reduced the area under swidden cultivation. With the aim of understanding the extent and impacts of this development, 55 households in three communities that were interviewed in 2002–2003 were re-interviewed in 2011. In an area with rapid oil palm development, the households engaged in smallholder oil palm production have experienced considerable improvements in income and wealth whereas the other households have experienced more limited wealth increases or even a decline in income. Many households have decreased or abandoned cultivation of upland rice, which used to be the core of the swidden cultivation system, and the upland soils in the area are now dominated by oil palm. In another area, where no oil palm development has taken place because of a hydroelectric dam, upland rice fields under swidden cultivation have also decreased and new high yielding rubber is now being planted because of the favorable rubber prices. Moreover, tourism has in this area gained further economic importance and overtaken agriculture as the main economic activity of households. The demise of swidden has not yet occurred in Sarawak, but a continued decline has been observed. However, there is a possibility that the new smallholder oil palm and rubber may provide an opportunity for a new type of ‘productive fallow’ that will allow continued cultivation of upland rice on a small scale.     

Environmental Consequences of the Demise in Swidden Cultivation in Southeast Asia: Carbon Storage and Soil Quality

The effects of swidden cultivation on carbon storage and soil quality are outlined and compared to the effects of the intensified production systems that swidden systems of Southeast Asia transform into. Time-averaged aboveground carbon stocks decline by about 90% if the long fallow periods of traditional swidden cultivation are reduced to 4 years and by about 60% if swidden cultivation is converted to oil palm plantations. Stocks of soil organic carbon (SOC) in tree plantations are 0–40% lower than stocks in swidden cultivation, with the largest losses found in mechanically established oil palm plantations. Impacts of tree plantations on soil quality are to a large extent determined by management. Conversion of swiddening to continuous annual cropping systems brings about substantial losses of time-averaged aboveground carbon stocks, reductions of SOC stocks and generally leads to declining soil quality. Knowledge of carbon storage in belowground biomass of tree based systems of the tropics is sparse but failure to include this pool in carbon inventories may significantly underestimate the total biomass of the systems. Moreover, studies that consider the ecological reasons behind farmers’ land use decisions as well as spatial variability in biogeophysical and edaphological parameters are needed to evaluate the effects of the ongoing land use transitions in Southeast Asia.     

高黎贡山地区民族植物学的研究Ⅰ.勒墨人

应用民族植物学的方法,对生活在云南西部高黎贡山东坡的勒墨人进行了调查。主要研究结果如下勒墨人对野生植物及环境有较大的依赖性;从 事刀耕火种轮歇栽培,并种植漆树(Toxicodendron vernicifiuum)和桤木(Alnus nepalensis)以促进轮歇地的休闲管理;栽培和管理漆树、收割生漆交换或出售,是勒墨人轮歇农业的一大特色;他们采集利用60余种野生食用植物和100余种药用植物,云黄连(Coptis teeta)和贝母(Fritillaria cirrhosa)等重要药材用于同外界进行物资交换;在对自然界的崇拜过程中,勒墨人对当地生物多样性的保护起到了积极的作用。     

高黎贡山五加科的植物地理学研究

本文从属、种及地史文献资料三方面对高黎贡山五加科植物进行了植物地理学研究。结果表明：1．高黎贡山五加科植物包括15属56种及13变种。2．从起源来看,高黎贡山五加科植物以热带起源为主,热带属占66.7％(10属）,温带属占33.3％（5属）,而与地中海地区和中亚地区的联系十分微弱。3．从种的分布区式样来看：高黎贡山五加科植物以温带分布型为主,温带分布型的物种占全科种数的88.4％（61种）,这一统计结果与属的统计结果（66.7％)的属系热带属）形成很大的反差,其原因在于掸邦一马来亚板块上的高黎贡山植物区系源于赤道热带,在板块位移过程中,随着高黎贡山的北移,喜马拉雅山脉的强烈隆升,五加科这一起源于热带的古老木本植物,因不适于比赤道带冷得多的气候环境而先后被淘汰,部分属种则在新的环境中经过适应、演化和重新分化,除个别热带属的北缘种在高黎贡山北端独龙江河谷中幸存下来（如树参属Dendropanax)以外,其余新分化出来的植物则是温带性的（如常春木属Merrilliopanax),因此,现在高黎贡山五加科植物区系中,热带起源的属多于温带属,但温带种大大多于热带种。所有这些成分中,中国一喜马拉雅分布的成分(15种）和中国特有的成分（43种）构成了高黎贡山五加科植物区系的基本骨架,这些成分标志着高黎贡山五加科植物区系的东亚温带性质。4．高黎贡山五加科植物特有现象突出。一方面表现在种类丰富,计有中国特有类群22种和变种,云南特有类群12种和变种,高黎贡山特有类群9种,另一方面表现在特有类群的丰富度与纬度成正比,就高黎贡山特有种来说,北段（贡山）的特有类群（8种和变种）远远多于南段的腾冲（仅1种）。5．由于掸邦一马来亚板块位移对高黎贡山生物区系的影响,部分高黎贡山五加科植物从滇东南或滇南至高黎贡山的一些连续分布区被间断为滇西北与滇东南的对角分布式样（如少毛云南 木Aralia thomosonii var. glaerescens,单枝五叶参Pentapanax leschenaultii var.simplex,拟白背叶鹅掌柴Schefflerahy poleucoides),而与此同时,在云南形成了一条从滇西北一滇东南走向的生态地理对角线,由于该对角线的形成,导致部分五加科植物仅能在对角线以西及以南生存和繁衍（如大叶鹅掌柴Schefflera macrophylla)。     

基诺族传统食用植物的民族植物学研究

基诺族是国务院１９７９年确认的我国第５６个民族,至今仍依赖于歇农业即刀耕火种为生,自给自足的自然经济是他们主要经济形式。除在轮歇地内栽培少数几种作物外,基诺族的菜肴绝大部分采自其周围的林地、山野。本文记述了基诺族的传统食用植物１７９种,其中野菜类８６种、野生水果类３７种,栽培植物５４种。