The stratified validation sample design was chosen considering the distribution of the validation samples per occurrence class and the spatial distribution per continents. Taking into consideration the stratification criteria, one-degree cells were randomly selected to be validated.
As for the entire global level assessment of all the 2, one degree cells considered, the GEFC and available very high resolution imagery i. Bing and Google Earth were used. In addition, to the extent multi-temporal very high resolution imagery was available on Google Earth, these were used to get an even better impression of the landscape and its land-use dynamics.
According to Olofsson et al. Each of these samples was visually examined in detail at scale of , or lower for the presence or absence of the above mentioned shifting cultivation specific spatio-temporal signs of clearing and regrowth on the landscape. Fig 2 illustrates this process for one sample cell. In this specific case or Fig 2A : the global distribution of the stratified sample of the one-degree cells used in the validation data set. The red box marks the extent of Fig 2D and Fig 2E.
Geological Survey. We used a search string similar to the one used for the literature review:. The search was performed in September and generated results. After eliminating papers that were not related to recent shifting cultivation in the tropics e. The first authors of these papers were listed and their email addresses were found.
An online questionnaire was designed and sent to these authors in September using survey monkey. All answers were anonymous and cannot be traced back to the individual expert.
Thirty-eight email addresses were no longer functional and 7 authors declined to participate for various reasons. Of the remaining authors, 72 responded and 49 provided usable information see S1 File.
There was a bias towards responses from researchers who worked in Southeast Asia see Fig 3 ; but this is also the world region where most research on shifting cultivation has been done, whereas Africa has the fewest studies and is clearly under-represented in light of the considerable occurrence of shifting cultivation there [ 17 , 44 ]. This figure was elaborated by the first author using ArcGIS The respondents were asked to estimate the current spatial extent of shifting cultivation as well as past and future trends in the development of this extent in their area of interest.
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. Moreover, it is not possible to know in detail how the respondents arrived at their assessment of past and future extents of shifting cultivation. 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.
With these caveats in mind, we aggregated responses to the national scale and to three supranational regions: the tropical parts of 1 Central and South America, 2 Africa, and 3 Asia. We then made an estimate of trends in occurrence of shifting cultivation for these aggregated regions for , and also taking into account the historical trends between the Butler map and our classification.
It is important to note that these are indeed very rough possible scenarios and should be seen as expected trends rather than fixed percentages of decline. To generate a spatially explicit prediction of the temporal dynamics decline of shifting cultivation through to the s, we combined the survey results with several simple assumptions.
We initiated occurrence at a one-degree resolution in base year at the mean of the above-stated ranges for each occurrence category in the assessment of current landscape with signs of shifting cultivation based on the GFC data c.
For each grid cell, the occurrence of shifting cultivation declined linearly by the mid-point of the estimated losses in , and see Section 3. If the survey provided information about when i. The map is binary presence-absence , with no information on occurrence frequency or land-use intensity. At the regional scale, an assessment by Spencer [ 45 ] provides a slightly more differentiated picture of the presence of shifting cultivation practices in Asia.
The data sources are not entirely clear, but the assessment seems to be based on a number of studies carried out between the end of the 19th century and the late s, along with expert judgement. Spencer [ 45 ] indicates an approximate area under shifting cultivation currently cultivated fields plus all stages of fallows of around million hectares Mha for Asia.
The classic studies on shifting cultivation in Africa [ 46 — 48 ] do not provide any area data for the continent, and for Central and South America we were unable to find any regional-scale past area estimation. 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 into the s. Although the areas shown on the map also include non-shifting forms of subsistence agriculture, it is reasonable to assume that shifting cultivation predominated in the humid and sub-humid tropics, which are the main focus of the present study.
Our review of the more recent literature revealed surprisingly few studies containing regional or global estimates of areas under shifting cultivation. An area of 1, Mha was mentioned by Davidson et al. The study by Silva et al. This approach, however, suffers from the shortcoming that land cover data are of very limited use in estimating land use practices, which is acknowledged by Silva et al. For example, the large areas of tree plantations established in Vietnam and southern China in the s and s can also leave a mosaic signature at a certain point in time and might therefore be incorrectly interpreted as shifting cultivation Fig 1.
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. The number of estimates of areas under shifting cultivation at regional and national scales in the literature is also very limited.
For Southeast Asia, Schmidt-Vogt et al. However, the areas indicated for each country vary greatly depending on the source. 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 Laos—where the largest share of shifting cultivation in the country is found—are 3.
Comparison of these figures with the GLCbased area estimate for Laos of almost 11 Mha [ 1 ] underlines the problem of using the GLC to estimate areas under shifting cultivation.
For India, Goswami et al. Silva et al. As for Africa, we found only one recent national study, on the Democratic Republic of the Congo [ 36 ]. The authors estimated that these areas made up Fig 5 presents the results of our own visual approximation of the global extent of shifting cultivation around at a one-degree resolution, based on Hansen et al.
The map shows that shifting cultivation is still present across large areas of the humid tropics. However, the occurrence of shifting cultivation within most of the individual one-degree cells is very low, meaning that it is a minor component of the overall landscape. More widespread signs of shifting cultivation were found mostly in small pockets, with the exception of larger areas in Central Africa e. Based on visual inspection of annual global deforestation data [ 8 ] from to and very high-resolution satellite imagery.
Areas in which shifting cultivation can be assumed to have never existed or disappeared decades ago have been excluded from the analysis dark gray. The remaining cells 3, 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.
The very low occurrence of shifting cultivation within a majority of cells, particularly in the Americas, points towards shifting cultivation being either a form of cultivation practiced in landscapes where only a minor share of the land is used for agriculture e. The validation of the estimation of landscapes showing signs of shifting cultivation revealed that Also when considering the different levels of occurrence of shifting cultivation estimated based on the overall impression of the landscape per one-degree cell, the accuracies were high see confusion matrix in Table 2 , with an overall classification accuracy of This indicates that, despite the subjectivity involved on estimating the landscape level of occurrence of shifting cultivation in our classification, the method led to reproducible and accurate results.
While an area approximation of actual shifting cultivation landscapes based on our analysis is difficult due to the estimated and not measured shared of shifting cultivation of each one-degree cell we believe that, given the high accuracy of this estimation see Table 2 , a conservative estimate can nonetheless be derived by visually inspecting the cells and allocating reasonable shares of shifting cultivation landscape currently cultivated fields plus all stages of fallows to them as described in the methods section.
Using the mean values of the ranges specified for the different occurrence classes for all cells in all classes results in a total area of Mha.
This number certainly requires further validation before it can be claimed to be an adequate estimate of the global area under shifting cultivation. Nonetheless, it is more evidence-based than the 1, Mha of unclear origin that are repeatedly cited in the literature e. Surprisingly, our estimate is not too far from the Mha proposed in Silva et al [ 1 ], even though their estimate excludes large areas under shifting cultivation and includes areas under other forms of agriculture and natural vegetation.
At the regional scale, the only number to which we can compare our result is the Mha for Asia estimated by Spencer [ 45 ], which is considerably larger than our estimate for this region of approximately 70 Mha. 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. First, we compared the Butler [ 13 ] map Fig 4 with our own spatial estimate Fig 5 of areas that were under shifting cultivation around Second, we combined the results of this comparison with those of our expert survey.
The difference between the Butler map—which is presumably based on studies dating from the s and s [ 13 ]—and our own current investigation around is displayed in Fig 6.
Generally, the two approximations of areas under shifting cultivation are in fairly good agreement, especially when considering that the large differences in the arid areas of northern Africa, southern Angola, and Zambia and the high-mountain areas of eastern Bolivia are largely explained by the fact that Butler included other, non-shifting forms of extensive smallholder agriculture and that shifting cultivation in these areas based on the climatic condition never could have been widespread.
This is the case for Peninsular Malaysia [ 28 ], parts of Sumatra [ 60 ], Yunnan Province in southern China [ 61 ]and the southern part of the Brazilian Amazon [ 62 ], for example. For this reason, the known widespread decrease in the occurrence of shifting cultivation in Southeast Asia e.
Laos, Vietnam over the past 15 to 25 years is not reflected in this comparison. The areas newly classified as having shifting cultivation blue in Fig 6 are more likely to have been missed in the Butler map than to represent actual new areas under shifting cultivation, as many of these regions are well known to still have significant shifting cultivation landscapes.
Such areas are found in parts of Southeast Asia e. Myanmar [ 63 — 65 ] , Central America e. Yucatan Peninsula [ 66 ], northern South America e.
Venezuela [ 67 ] , and Madagascar [ 68 ]. Consequently, if further research e. After analyzing the spatially differentiated changes between the status in the s to s as shown in the Butler map and our data for Fig 6 , we combined them with data from our expert survey about changes in areas under shifting cultivation between to and to as well as with information from the literature.
On this basis, we can provide a preliminary overview of regional and national trends in the development of the extent of shifting cultivation over the past 40 to 50 years.
Regarding South and Southeast Asia, a meta-analysis by van Vliet et al. These changes are not fully reflected in the above comparison between the Butler map and our own spatial investigation for because in many areas they have resulted only in a reduced occurrence of shifting cultivation but not yet in its full disappearance.
However, the expert survey confirms that shifting cultivation has fully disappeared between the s and the s in various areas of mainland Southeast Asia, such as southern Thailand, Peninsular Malaysia, and China. In a second cluster of countries—Laos, Cambodia and Myanmar—shifting cultivation areas have decreased drastically since For large parts of insular Southeast Asia and South Asia e. India, Bangladesh , comparison of the maps Fig 6 and the survey responses point to similar trends.
Trends in humid tropical Africa vary widely. In West and Central Africa, shifting cultivation is largely continuing and has even been expanding in certain areas. This trend, which was also identified by van Vliet et al. This is reflected both in the comparison of the two spatial data sets Fig 6 and in the survey responses. However, it is important to underline that this assessment is based on very few survey responses Fig 3 due to the small number of existing studies on shifting cultivation in Africa.
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. In large parts of humid West Africa, shifting cultivation is still widespread—with the exception of Nigeria, where it has all but disappeared and remains present only in small pockets.
In Central Africa, shifting cultivation also remains very widespread, with an even higher occurrence than in West Africa; in certain areas it is still expanding, such as in the Democratic Republic of the Congo [ 36 ]. In eastern and southern Africa, shifting cultivation is still present, but not very common, with particularly low occurrences in Kenya and Tanzania.
Madagascar has seen only slight decreases; especially along its eastern escarpment the area under shifting cultivation has remained stable over the last two decades e.
In Central America, shifting cultivation is still widespread, and both Fig 6 and the survey results indicate an increase in some areas e. Panama, Guatemala well into the s. In Mexico, however, the trend has been towards decreasing areas under shifting cultivation. South America shows mixed trends: Areas under shifting cultivation have clearly decreased in the southern Brazilian Amazon, whereas survey responses indicate that they are expanding in other parts of the Brazilian Amazon and in Peru.
Despite the limited number of survey responses on Central and South America, it appears that here, unlike in Southeast Asia, areas under shifting cultivation have not seen a strong decline over the last 20 years. Predicting future trends in the development of any form of land use requires extreme caution [ 23 , 69 ]. However, future climate projections and carbon budget estimates on carbon land sinks and land use emissions based on earth system models depend on such predictions as input, so any attempt to provide an evidence base for them is certainly a worthwhile improvement compared to relying on historical trends or static futures.
Based on this we expect that shifting cultivation is likely to decrease significantly in all regions over the next 20 years, and we estimate that it will tend towards disappearance in all regions by Table 3. 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.
By contrast, we expect that shifting cultivation will persist for a longer time in Africa, especially in Central Africa. Shifting cultivation tends to persist when population density is low and when options for agricultural development or alternative livelihoods are limited [ 22 , 70 , 71 ]. Both conditions apply to considerable parts of Central Africa.
The ranges are based on the expert survey and observed trends between the Butler map and our classification Fig 5. While keeping in mind the inherent limitations of these predictions, we can identify a number of more specific patterns.
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 , and the remaining pockets are likely to be almost entirely gone by 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 results indicate that shifting cultivation is likely to persist longest in Africa. In some specific areas, especially in Central Africa, it is likely to increase over the next decade before it begins to decline.
For Central and South America, the survey shows a mixed picture, with some areas being quite stable or even likely to experience expansion in the near future, and other areas e.
Mexico and Brazil likely to see a fairly rapid decrease and disappearance. Overall, a decrease after and disappearance after is expected. Applying these largely survey-based estimates Table 3 to our map of the extent of shifting cultivation in Fig 5 , we were able to visually display our rough predictions of developments in the extents of shifting cultivation by , , and Fig 7.
We would like to emphasize that the maps in Fig 7 are indeed very coarse estimates of the future global or continental extent of shifting cultivation—and not an exact representation of where precisely it might be found in the near or far future.
We have nonetheless ventured to display our estimates in predictive maps because they are based on a spatially explicit analysis in We believe that this represents a significant improvement on the shifting cultivation predictions that have been used so far in global land use models to estimate future greenhouse gas emissions, and we hope that our estimates can be a valuable input for future comparisons between models and international synthesis studies such as the upcoming Coupled Model Intercomparison Project Phase 6 CMIP6 experiments [ 27 ] and the next Assessment Report of the Intergovernmental Panel on Climate Change IPCC.
This visualization is based on the estimation of landscapes showing signs of shifting cultivation around Fig 5 as base year and estimated decreases of shifting cultivation Table 3 based on the expert surveys and observed trend between the Butler map and our Given the unavailability of automated approaches to detect shifting cultivation at a global level and deliver data in a timely manner for ongoing earth system modeling, we have used a visual interpretation approach to detect shifting cultivation.
Based on existing data and knowledge, we have made a first attempt at estimating possible future trends in the distribution of shifting cultivation until Shifting cultivation remains widespread, despite decreases in its extent over the last four to five decades. Our cautious estimation indicates that the global extent of shifting cultivation, including currently cultivated fields and all stages of fallows, may amount to roughly Mha, with the largest share in Africa, followed by the Americas and Asia.
Our preliminary estimated for the future indicate that the area under shifting cultivation is expected to shrink considerably over the next decades. This raises issues of livelihood security and resilience among people currently depend on shifting cultivation, who may face reduced provision of ecosystem services and limited access to land due to the expansion of permanent agriculture, tree plantations, urban areas, and forest protection or restoration [ 18 , 19 , 44 , 72 ].
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 ].
According to our tentative predictions, shifting cultivation—which has been a globally important form of human crop cultivation for millennia—may be gone by the end of this century. Improvements in mapping the extent of shifting cultivation and trends in its development may be expected in the near future.
Researchers are currently developing automated approaches that are capable of processing decades of Landsat data and detecting the spatio-temporal patterns of shifting cultivation. The recently launched Sentinel-2 instruments with their augmented repeat frequency will generally help to improve remote sensing—based analyses of the humid tropics, which are complicated by frequent and persistent cloud cover. Analysis of Landsat data back to Landsat4 launched in could provide more than 30 years of pan-tropical records, covering a time of significant change in the distribution of shifting cultivation across the humid tropics and perhaps also in the length of fallow periods.
These approaches, however, are still in the making and will require substantial resources. Furthermore we wish to express our gratitude to the two reviewers as well as the editor for the very useful comments and inputs.
The research presented here contributes to the objectives of the Global Land Programme glp. Browse Subject Areas? Click through the PLOS taxonomy to find articles in your field. Introduction Recent international efforts to compare and synthesize different earth system models have come with a strong focus on quantifying the past, current, and future contributions of land use to climate change [ 1 — 4 ]. Methods 2. Download: PPT.
Fig 1. Identification of spatio-temporal pattern based on GFC global annual deforestation data [ 8 ] and very high—resolution satellite imagery.
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]: — The search was performed in September and generated results.
Results and discussion 3. Fig 4. Fig 5. Table 1. Numbers and percentages of one-degree cells studied that showed signs of shifting cultivation SC or not No SC , as well as percentages of cells showing signs of shifting cultivation in the various occurrence classes, per region. Table 2. Accuracy assessment of the global classification Fig 5. Fig 6. Comparison of the Butler map [ 13 ] showing the status in the s to s with our results showing the status around Table 3. Estimated trends in area under shifting cultivation between and the s, s, and s expressed in percentage ranges of losses compared to Fig 7.
Preliminary estimates of changes in the occurrence of shifting cultivation between today and , and Conclusions Given the unavailability of automated approaches to detect shifting cultivation at a global level and deliver data in a timely manner for ongoing earth system modeling, we have used a visual interpretation approach to detect shifting cultivation.
Supporting information. S1 File. Complied results of expert survey responses. References 1. Greenhouse gas emissions from shifting cultivation in the tropics, including uncertainty and sensitivity analysis. J Geophys Res. View Article Google Scholar 2. Harmonization of land-use scenarios for the period — years of global gridded annual land-use transitions, wood harvest, and resulting secondary lands.
It is the traditional form of agriculture in the rainforest. This case study will focus on the Amazonian Indians in South America. The land is then farmed for years before the Indians move on to another area of the rainforest. Shifting agriculture is a system of cultivation in which a plot of land is cleared and cultivated for a short period of time, then abandoned and allowed to revert to producing its normal vegetation while the cultivator moves on to another plot. The maps focus on the tropical parts of Central and South America, Africa, South and Southeast Asia, and the Southwest Pacific for two reasons: 1 These areas have the most biomass, causing land use transitions in these areas to have a particularly high impact on global carbon emissions; and 2 shifting cultivation is ….
Advantages of Shifting Cultivation: In this shifting cultivation, the growth of the crops will start fast and sometimes only it will get ready for the harvest.
In this shifting of the cultivation, there is no fear or danger for the flood and the animals which destroy the crops. Shifting cultivation is a class of primitive subsistence agriculture. In this, a plot of land is cleared by felling the trees and burning them. The ashes are then mixed with soil and crops are grown. After some time, the land is abandoned and the farmers move to a different place. After the soil loses its fertility, the land is abandoned and the cultivator moves to a new plot.
Deforestation, losing fertility of land and soil erosion are the disadvantages of shifting cultivation. Complete Answer: Shifting cultivation refers to the form of agricultural practice in which a particular land is cleared of its vegetation and is cultivated for a few years and then it is left out for the land to restore its fertility naturally, thus looking for new land to cultivate upon.
Agriculture, Sericulture, Pisciculture, Viticulture and Horticulture are the different kinds of cultivation. Farming depends upon the geographical conditions, demand of produce, labour and level of technology. Subsistence farming and commercial farming are the two types of farming. There are two main types of farming, viz.
Subsistence Farming: It is self-sufficiency farming in which the farmers focus on growing enough food to feed themselves and their families. Intensive Farming: It is characterized by a low fallow ratio, higher use of inputs such as capital, fertilizers, pesticides and labor, and higher crop yields per unit land area. Farming is practised in various ways across the world. Depending upon the geographical conditions, demand of produce, labour and level of technology, farming can be classified into two main types.
These are subsistence farming and commercial farming. The definition of agriculture is the science, art and business of farming and ranching. Commercial farms and ranches which provide vegetables and meat to the general public are examples of agriculture.
Agricultural activities means income producing activities or uses as characterized by the cultivation of crops, including but not limited to flowers, vegetables, foliage, fruits, forage, and timber; and farming or ranching activities or uses related to animal husbandry, aquaculture, or game and fish propagation. Primary sector includes agriculture, forestry, animal husbandry, fishing, poultry farming, and mining.
Quarrying and manufacturing is included in the secondary sector. Begin typing your search term above and press enter to search. Press ESC to cancel. Skip to content Home Sociology What regions is shifting cultivation most commonly found?