Convergent adaptations: bitter manioc cultivation systems in fertile anthropogenic dark earths and floodplain soils in central Amazonia

Shifting cultivation in the humid tropics is incredibly diverse, yet research tends to focus on one type: long-fallow shifting cultivation. While it is a typical adaptation to the highly-weathered nutrient-poor soils of the Amazonian terra firme, fertile environments in the region offer opportunities for agricultural intensification. We hypothesized that Amazonian people have developed divergent bitter manioc cultivation systems as adaptations to the properties of different soils. We compared bitter manioc cultivation in two nutrient-rich and two nutrient-poor soils, along the middle Madeira River in Central Amazonia. We interviewed 249 farmers in 6 localities, sampled their manioc fields, and carried out genetic analysis of bitter manioc landraces. While cultivation in the two richer soils at different localities was characterized by fast-maturing, low-starch manioc landraces, with shorter cropping periods and shorter fallows, the predominant manioc landraces in these soils were generally not genetically similar. Rather, predominant landraces in each of these two fertile soils have emerged from separate selective trajectories which produced landraces that converged for fast-maturing low-starch traits adapted to intensified swidden systems in fertile soils. This contrasts with the more extensive cultivation systems found in the two poorer soils at different localities, characterized by the prevalence of slow-maturing high-starch landraces, longer cropping periods and longer fallows, typical of previous studies. Farmers plant different assemblages of bitter manioc landraces in different soils and the most popular landraces were shown to exhibit significantly different yields when planted in different soils. Farmers have selected different sets of landraces with different perceived agronomic characteristics, along with different fallow lengths, as adaptations to the specific properties of each agroecological micro-environment. These findings open up new avenues for research and debate concerning the origins, evolution, history and contemporary cultivation of bitter manioc in Amazonia and beyond

Fire risk and smallholders in the Brazilian Amazon: why have institutional arrangements failed so far?

In the Brazilian Amazon, uncontrolled fire is one of the main drivers of forest degradation leading to important loss of biodiversity and ecosystem services (ES). Smallholders are often considered as the main actors responsible for these damages, as they commonly depend on fire for agricultural management activities. Since the 1990's, different policies and actions have been implemented to control fire use, but with limited success and fire continues to be an important problem in the region. With the perspective of engaging a participatory policy with stakeholders and realistically bring about a transition out of fire in the Amazon, we take stock of current knowledge on fire from different science realms and understand how this knowledge has influenced policies and institutional arrangements launched in the region up to date. Building on a theory of compliance, we overview the policies developed to reduce fire in the Brazilian Amazon and identify through a review in the recent literature the reasons associated to the generalized non-compliance observed until now. Our analyses show that policies launched so far have been focusing solely on the negative impacts of fire and as such, radically ban the use of fire in a way that is at odds from the practices and motivations of local actors. This flaw explains the failure of institutional arrangements in stimulating compliance related to fire risk in the region. We sum up the different challenges that need to be addressed to build more effective institutional arrangements, which would be more adapted to the actors' motivations and able to encourage environmental services conservation. ( Résumé d'auteur

Economics of Upland Resource Depletion: Shifting Cultivation in the Philippines

This paper provides a systematic investigation of agricultural systems practiced in the uplands by starting with a formal treatment of the shifting cultivation problem. The optimum rate of use of forested land from society’s viewpoint and from the individual uplander’s viewpoint, given traditional choices between timber production and agricultural production through slash-and-burn farming is likewise investigated. The study explains swidden farming in the context of a standard resource economic model on open access exploitation, the discounting bias and zero valuation of the externalities involved.natural resources and environment, environmental issues, environmental management, resource management, uplands

Fine-scale mapping and dynamics of cyclic agroforestry agriculture using UAV remote sensing in Borneo

The swidden agriculture practice, a cyclic agroforestry system that presents high ecological heterogeneity, still represents the most used farmers' practice in the SE Asian region, experiencing rapid land-use transitions driven by the conversion of biodiversity-rich ecosystems to monoculture plantations. Increased fragmentation creates mosaic of land cover types difficult to map. Challenges persist for evaluating such matrix configuration using satellite remote sensing. The present study explores feasibility, advantage and inconvenience of UAV technology for the acquisition of geospatial data to better understand, fine-scale agroforestry landscape fragmentation, connectivity and the dynamics of the burning and cropping phase. The study site is a swidden agriculture forest landscape, north of Kapuas Hulu regency in West Kalimantan, Indonesia. The drone system consisted of a customized SkyWalker fixedwing plane equipped with RGB camera (resolution 7-12 cm). Each flight at 400 m elevation covered around 3000 ha, replicated over 3 years, in the month of October after the burning phase season. Orthophoto mosaics were created using AgiSoft software. Object based image classification (OBIA) was tested with open source software to create a reproducible and automated assessment of landscape, together with an appraisal of the landscape metrics. Ground check and vegetation sampling were performed for each mapped classes. The results showed that: (1) Up to 25 vegetation classes can be easily interpreted visually, but the low spectral resolution of RGB bands restricted the number of classes used for OBIA; (2) The area of swidden agriculture on forest increased only by 2%; (3) Over 80% of swidden fields were transformed from fern savannahs, the rest mainly taken on young fallows; (4) From 2016 to 2019, the frequency of swidden fields in the district remained constant; (5) The proportion of very short burning cycle (1 to 3 years) was around 50%, revealing that swidden cycles in this particular area were shortened; (6) Overall, connectivity of old fallows and forest patches was maintained. This particular study represents promising preliminary steps in fully mapping the agroforestry landscape for future monitoring. Local people involvement was critical in mapping their landscape. Integrating ground-based surveys with UAV remote sensing appeared as promising tool essential for achieving cost-efficient wide-scale surveys of agroforestry resources and to monitor changes and long-term sustainability of the system. The ecosystem recovery time following initial slash-and-burn practices may be longer in our study area. Soil impoverishment related to reduction in rotation length may become a serious threat likely to jeopardize the production of goods and services in the long-term. In our study site, the long-term persistence of the swidden agriculture system maybe at stake, if enhanced management of fallows and agroforestry plots (enrichment planting) is not performed

Politics and professionalism in community development: Examining intervention in the highlands of northern Thailand

It has been suggested that the practice of international development assistance is so deeply problematic that the only moral choice is to abandon the work altogether. The practice of community development in the Third World has been the subject of extensive critique for several decades. Scholars and development practitioners speak of the 'tyranny' of development and discuss the ways in which development is a means of control and domination rather than an altruistic enterprise whereby wealthier nations lend assistance to poorer nations. How are these debates relevant to highland development programs in northern Thailand? And how are development practitioners responding to the suggestion that they are making things worse rather than better? This paper explores the history of development in the hills and suggests some ways that development practitioners can - and do - take on board recent critiques of development while continuing to work for the betterment of highland lives and livelihoods

Direct seeding mulch-based cropping systems - A holistic research approach implemented in Northern Laos

Farming systems throughout the Lao PDR have changed drastically over the last 15 years due to a range of factors. In some areas where market forces are prevalent, shifting cultivation systems have given way to more conventional high-input agricultural systems. In other more remote areas, the traditional swidden system with long rotations has been put under pressure primarily due to modification of land access and increasing population pressure. In southern Xayabury in the Mekong corridor, where there is access to the Thai market, land preparation has become based on burning residues and ploughing on steep slopes. Because of the environmental and financial costs of land preparation, farmers are shifting to herbicides, which lead to chemical pollution, while crop residues and weed mulch are usually burned, thereby increasing mineral losses and erosion on bare soil. In mountainous areas such as Xieng Khouang Province, the rationale of shifting cultivation is collapsing as farmers use land for longer periods of cropping and return more frequently to each field. A holistic research approach has been implemented in Xayabury and Xieng Khouang to find direct seeding mulch-based cropping (DMC) systems that are compatible with farmers' strategies and which can be reproduced inexpensively on a large scale. The methodological framework, based on five main components, emphasises the process of adaptation and validation by farmer groups, meaning that priorities are defined by smallholders in light of the constraints of their farming systems and the overall environmental conditions.(Résumé d'auteur

Migration and forests in the Peruvian Amazon: a review

This paper reviews the literature on the links between migration and forests in the Peruvian Amazon. It highlights not only the complexity of the migrant–forest interface in Peru but also the relative lack of research on these dynamics. Historically, official narratives point to migrants as both the culprits of, and solutions to, the Amazon’s problems. At times, the government has promoted colonization of the Amazon as a means to integrate the region into the country as well as to encourage agricultural expansion and alleviate pressure on limited land in the Andes. In other periods, migrants are blamed for deforestation and environmental degradation in the region. These discourses oversimplify the complexity of the reality facing migrants to the Amazon and the factors that ‘push’ them away from their birthplaces and/or ‘pull’ them to the Amazon. They also treat migrants as a homogenous group, underestimating: the role of migration within the Amazon, the cyclical nature of migration, processes of urbanization and multi-site households, and the diversity of livelihoods migrants pursue upon arrival. A more detailed understanding of migrants, migration and the related conditions and processes driving human mobility in the Amazon should provide a more effective foundation for defining public policy in the region, for example, for the identification of strategies to mitigate the impacts of road construction or to support sustainable models of production in areas occupied by smallholder farm families. This review is intended as a step toward a fuller understanding of these processes by compiling existing information as a point of departure

A dynamic and stochastic analysis of fertilizer use in swidden agriculture

The number of times a crop can be harvested on a cleared parcel of forest land (CPFL) before this land must be fallowed is dependent on the decision to use or not to use fertilizers to enhance soil fertility. As such, we first construct a theoretical model of fertilizer use by a swidden cultivator when this cultivator can choose whether or not to enhance soil fertility by using fertilizers. Second, we analyze two different policies (fertilizer use and no fertilizer use) for overseeing the problem of soil fertility deterioration on the CPFL. Finally, we identify a particular likelihood function and we show that whether the problem of soil fertility impairment is best addressed with a fertilizer use policy or with a no fertilizer use policy depends essentially on this likelihood function.