Both conditions apply to considerable parts of Central Africa. This figure was elaborated by the first author using ArcGIS 10.4. https://doi.org/10.1371/journal.pone.0184479.g005. It is a form of farming practice that entails clearing a land parcel by felling and burning trees. The difference between the Butler mapwhich is presumably based on studies dating from the 1960s and 1970s [13]and our own current investigation around 2010 is displayed in Fig 6. No, PLOS is a nonprofit 501(c)(3) corporation, #C2354500, based in San Francisco, California, US, Corrections, Expressions of Concern, and Retractions, https://doi.org/10.1371/journal.pone.0184479, ftp://ftp.fao.org/docrep/fao/003/y1860e/y1860e00.pdf, https://www.cia.gov/library/publications/the-world-factbook/geos/cg.html. Shifting cultivation is an agricultural system in which plots of land are cultivated temporarily, then abandoned while post-disturbance fallow vegetation is allowed to freely grow while the cultivator moves on to another plot. This study combines existing global Landsat-based deforestation data covering the years 2000 to 2014 with very high-resolution satellite imagery to visually detect the specific spatio-temporal pattern of shifting cultivation at a one-degree cell resolution worldwide. Writing review & editing, Affiliation The accuracy levels of our classification were high with an overall accuracy above 87%. Formal analysis, As global level ground data collection is not feasible and no global data on shifting cultivation for the considered time span of 2000 to 2014 is available, we generated a validation dataset, which contains a detailed delineation of the areas under shifting cultivation for a stratified sample of one-degree cells. Shifting cultivation, a resource-based subsistence farming, is no longer relevant because of the large population and its growing demands. here. As the data we used (GFC as well as Bing and Google imagery) cover the period from 2000 to 2014 and 2015, respectively, our assessment of the current extent of shifting cultivation does not relate to any specific year. Yes Writing review & editing, Affiliation Our point of departure is a global map of the distribution of primitive subsistence agriculture produced by Butler in 1980 [13], a visual inspection of the distribution of shifting cultivation based on the 20002014 Global Forest Change (GFC) data set [8] and very highresolution satellite imagery, as well as an expert survey. of Energy, grant number DE-SC0012972, and the Global Land Project Grant from the University of Copenhagen. However, the areas indicated for each country vary greatly depending on the source. Deforestation is also a contributor to climate change and global warming. While shifting cultivations signature on the landscape may be captured as a mixture or mosaic of agriculture and forest land cover classes, this alone does not suffice to indicate with certainty the presence of shifting cultivation. We estimate the current global extent of shifting cultivation and compare it to other current global mapping endeavors as well as results of literature searches. The visualization here shows a summary of some of the main global impacts: Food production accounts for over a quarter (26%) of global greenhouse gas emissions. We estimate that shifting cultivation landscapes currently cover roughly 280 million hectares worldwide, including both cultivated fields and fallows. Solution: a. India is an agricultural country. [3037]) such approaches cannot yet be up-scaled to global level due to data availability as well as computational limitations. Fig 1A shows a one-degree square of northern Laos. We used a search string similar to the one used for the literature review: [Title]: "Shifting cultivation" or swidden or "slash-and-burn" or "slash and burn" or "shifting agriculture" AND [Year published]: 20052015. In Asia, we expect that continued rapid economic development and the related changes in agricultural practices and, more importantly, in the economic structure (from the primary to the secondary and tertiary sectors) may cause shifting cultivation to disappear faster than in Africa or the Americas. Meanwhile, the area under shifting cultivation has decreased by 71.22% from 1997 and forest cover has decreased by 4.41% during the period. For this reason, we have estimated future changes in shifting cultivation by combining observed trends between the Butler map and our own map with experts survey responses regarding future changes in shifting cultivation in different parts of the world. However, this future may also provide better opportunities for production and income generation if development efforts are sensitive to the needs of shifting cultivators [73,74]. Two steps enabled us to gain insights into larger recent (last 40 to 50 years) trends in the development of the global area under shifting cultivation. To get a first estimation of the occurrence of shifting cultivation, we classified each cell under investigation into one of five shifting-cultivation occurrence classes: none, very low, low, moderate, or high. The principle of cultivation is to turn the soil into a fine tilth to provide the ideal environment for seeds to germinate. More widespread signs of shifting cultivation were found mostly in small pockets, with the exception of larger areas in Central Africa (e.g. Nobody knows how many people today depend on shifting cultivation globally [22]. For India, Goswami et al. - Indicate how you expect the shifting cultivation occurrences to change in the future for the following periods (no change, expansion, decline, disappearance): 20152030; 20302060; 20602090. The red box marks the extent of Fig 2D and Fig 2E. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. However, more severe warming, floods, and drought may reduce yields. and the overall accuracy and the Cohens kappa coefficient were calculated. Department of Geosciences and Natural Resource Management, University of Copenhagen, Copenhagen K, Denmark, Roles Data curation, Based on the spatio-temporal pattern of the GFC data (different colours denoted different year of clearings) and the patterns of clearing and regrowth in the very high resolution imagery (here Bing), a 1/100-degree cell is being classified as showing shifting cultivation or not. Slash-and-burn agriculture is a farming method that involves the cutting and burning of plants in a forest or woodland to create a field called a swidden.The method begins by cutting down the trees and woody plants in an area. This will be useful in improving the characterization of land surface and land use dynamics for earth system models and large-scale carbon and greenhouse gas accounting. For example, data for Laos indicate between 2 and over 6 Mha, while more recent figures based on remote sensing (multi-temporal Landsat) for northern Laoswhere the largest share of shifting cultivation in the country is foundare 3.1 Mha [33] and 2.6 Mha [34]. It is a sustainable method of farming in the rainforest. For large parts of Southeast Asia, the survey results point towards that the current swift decrease in shifting cultivation continues, and that a large share of the area under shifting cultivation will have disappeared by 2030, and the remaining pockets are likely to be almost entirely gone by 2060.Moreover, the survey results indicate trends for some specific Asian countries: Humid tropical Africa is probably the region for which developments are most difficult to predict due to limited data. The five classes corresponded to the following rough ranges of area shares of shifting cultivation landscapes (currently cultivated fields plus all stages of fallows) within an entire one-degree cell: none: < 1%; very low: 19%; low: 1019%; moderate: 2039%; high: 40%. The most important questions included: The information provided by the respondents related to very different spatial scales, ranging from village to district, provincial, and, in some cases, national scales. At the regional scale, the only number to which we can compare our result is the 110 Mha for Asia estimated by Spencer [45], which is considerably larger than our estimate for this region of approximately 70 Mha. In the absence of further data to validate past estimations of the extent of shifting cultivation, the Butler map may be considered a reasonable representation of the global distribution of shifting cultivation from 1960 into the 1970s. The selection process ensured that all are experts in the field, but there may be disciplinary or personal differences in the way that especially the future of shifting cultivation was assessed. Conceptualization, [1] indicate 110 Mha for this region, but unlike FAO they did not include Mexico in their estimation. Secondly, the detection and monitoring of complex shifting cultivation mosaics using automated remote sensing approaches remains challenging [33,38,39] and the mentioned small spatio-temporal signature of vegetation clearings and regrowth is very specific to shifting cultivation and visual interpretation is therefore suitable [40]. The effects on seasons of a changing climate are already being seen across the country and vary region to region: temperatures have risen across seasons, growing seasons have become longer, precipitation patterns have changed, and extreme precipitation events have increased in frequency and severity. But information about such landscapes is urgently needed to improve the outcomes of global earth system modelling and large-scale carbon and greenhouse gas accounting. Intensive agriculture sometimes called factory farming lies at the heart of this emergency.. Maps created in QGIS 2.16. https://doi.org/10.1371/journal.pone.0184479.g001. Corrections? Nevertheless, shifting agriculture is an adaptation to tropical soil conditions in regions where long-term, continued cultivation of the same field, without advanced techniques of soil conservation and the use of fertilizers, would be extremely detrimental to the fertility of the land. The period of cultivation is usually terminated when the soil shows signs of exhaustion or, more commonly, when the field is overrun by weeds. The map shows that shifting cultivation is still present across large areas of the humid tropics. The validation of shifting cultivation mapping is generally challenging due to the lack of reference data [41,42]. Eutrophication is the process in which a water body becomes overly enriched with nutrients, leading to plentiful growth of simple plant life. [1]. broad scope, and wide readership a perfect fit for your research every time. However, there are a number of other negative effects related to irrigation. Mosaic landscapes under shifting cultivation, with their dynamic mix of managed and natural land covers, often fall through the cracks in remote sensing-based land cover and land use classifications, as these are unable to adequately capture such landscapes' dynamic nature and complex spectral and spatial signatures. Citation: Heinimann A, Mertz O, Frolking S, Egelund Christensen A, Hurni K, Sedano F, et al. PLoS ONE 12(9): The present study is a first step towards a future in which we will know more about the global distribution of shifting cultivation; we hope it opens the door to quantifying shifting cultivations importance for local as well as the global socio-ecological systems. No source is reported for the map, but most likely it builds on a number of regional studies that was carried out between the 1940s and the 1970s, as well as general knowledge of where shifting cultivation and other extensive smallholder farming systems were found. (Fig 2C): One-degree cell with a mesh of 1/100 degree cells as a basic unit for the validation data set, green cells having a shifting cultivation occurrence class of >1% in our global classification. Second, we combined the results of this comparison with those of our expert survey. However, sustainable agriculture, which uses methods that protect the environment, public . northern Zambia and in the Democratic Republic of the Congo), parts of southeastern Africa (e.g. Its authors detected changes in what they call the rural complex for the period from 2000 to 2010. Such areas are found in parts of Southeast Asia (e.g. Writing review & editing, Affiliation Updates? shifting agriculture, system of cultivation that preserves soil fertility by plot (field) rotation, as distinct from crop rotation. To assess the accuracy of our estimated occurrence levels of shifting cultivation on the landscape, this validation data was used to calculate the actual area shares of the 1/100 by 1/100 one-degree cells classified as having shifting cultivation in validation data for all 328 one degree samples cells. (Fig 2DA) and (Fig 2E): The white line grid marks the 1/100 degree cells used as basic unit for the validation data. However, the expert survey confirms that shifting cultivation has fully disappeared between the 1970s and the 2000s in various areas of mainland Southeast Asia, such as southern Thailand, Peninsular Malaysia, and China. Intensive agriculture has dominated the global food production . The area of interest ranges from 30S and 30N (6,704 one-degree cells on landmass), while the area investigated includes 2,817 cells. Any change in the climate of an area can affect the plants and animals living there, as well as the makeup of the entire ecosystem. Using recent regional and national automated classification of shifting cultivation as reference (e.g. Cultivation was also a traditional form of weed control. In addition, we used available very highresolution satellite imagery from Bing and Google (most images dating from the period between 2008 and 2015; visited between September and April 2015) in an ArcGIS Desktop 10.4 and QGIS environment to examine visually whether a given area for which the GFC data indicated a spatio-temporal pattern of small-scale clearings consistent with shifting cultivation, was indeed likely to be under shifting cultivation. Each of the 328 sample one-degree cells was subdivided in cells of 1/100 degree by 1/100 degree, resulting in 10,000 verification cells per one-degree cell. Furthermore, it should be noted that the large difference between the two spatial data sets (Fig 6) in arid and semiarid parts of Africa (Sahelian and Sudanian zones of northern Africa as well as parts of southern Africa) is partly due to the fact that Butler included other, non-shifting smallholder farming systems in his map. On the other hand, large areas with shifting cultivation in Central Africa, for example in the Democratic Republic of the Congo [36], are strongly under-represented in Silva et al. For more information about PLOS Subject Areas, click Shifting Cultivation Shifting Cultivation Agricultural Geography Agricultural Hearths Agricultural Production Regions Agricultural Revolutions Agriculture and Climate Agriculture and Pollution Agrochemicals Community Supported Agriculture Extensive Farming Feeding the World Food Desert Food Insecurity Food Movements Green Revolution The ranges are based on the expert survey and observed trends between the Butler map and our 2010 classification (Fig 5). While the literature offers good representations of the major natural land covers and human land uses [68], mosaic landscapes with a dynamic mix of managed and natural land covers often fall through the cracks in global land cover and land use classifications, as these are unable to adequately capture such landscapes dynamic nature and complex spectral signatures [912]. Table of Content Why are Forests Important? The remaining cells (3,887) were excluded from the analysis as shifting cultivation can be assumed to have never existed or disappeared decades ago (see Fig 5 and Method section). Methodology, To approximate the current extent of shifting cultivation landscapes globally we used the results of a time-series analysis of mainly Landsat images characterizing forest extent and change [8], hereafter referred to as Global Forest Change (GFC) data set. Comparison of these figures with the GLC2000-based area estimate for Laos of almost 11 Mha [1] underlines the problem of using the GLC2000 to estimate areas under shifting cultivation. While our estimates are based on non-automated methods and expert information from different parts of the world, we argue that our work nonetheless advances the state of knowledge considerably, especially with regard to earth system modeling scenarios, which have proved sensitive to the inclusion of shifting cultivation and up to now have used shifting cultivation data based on a hand drawn map from the 1980s.
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