People in many parts of the world have relied on slash-and-burn farming for thousands of years, and some estimates suggest its used on half of all land in tropical areas [source: Virginia Tech]. Although this practice can serve as a successful method of agriculture in the short term, it also leads to significant problems on both local and global scales. Each acre of land subject to slash-and-burn deforestation releases 180 metric tons of carbon into the atmosphere [source: MIT]. This carbon eventually reaches the Earths ozone layer, where it contributes to the greenhouse effect and global warming. After this initial carbon release, slash-and-burn deforestation then packs a secondary punch to the planet, as these burned trees are no longer available to convert carbon into oxygen through photosynthesis. Forest fires and the resulting smoke also contribute to air and water pollution, and can often rage out of control, threatening the lives of people and animals. Slash-and-burn deforestation also destroys habitats and threatens ecosystems, which is particularly problematic in these tropical areas because of their unique levels of biodiversity. For local natives, this agricultural technique represents a double-edged sword. Those who practice slash-and-burn agriculture often do so out of desperation to feed themselves and their families, and yet this technique may lead to greater risk of starvation in the near future. The ashes produced by these fires provide nutrients to sustain the land for just three to five years; after that, the land must remain fallow for a decade or more to regenerate. Without the traditional vegetation and root system, however, significant erosion occurs, and the land is unable to sustain enough nutrients to ever reach its former glory. During the rainy season, erosion may contribute to dangerous flooding, while the lack of tree cover and vegetation can make existing drought conditions worse during the dry season. Some scientists believe that even the mighty Mayan empire succumbed to the effects of slash-and-burn farming. For years, the Mayans relied on this technique to survive in the tropical region now known as Guatemala. Scientists have determined that just before the Mayan empire fell -- around A.D. 900 -- widespread deforestation had resulted in a complete absence of tree pollen. The lack of trees in the area led to a temperature increase of roughly 6 degrees, which eventually brought about widespread drought. The drought signaled the end for the Mayans [source: NASA]. “Conservation agriculture is an alternative to slash and burn crop production methods that were used successfully for millennia,” says Theo Dillaha, Program Director of the SANREM CRSP and Professor of Biological Systems Engineering at Virginia Tech. “The basic principle of slash and burn agriculture is to alternate lands between crop production and native vegetation and forests. During crop production without fertiliser additions and good soil management practices, soil quality and crop yields decline over time.” “When crop yields decline to unacceptable levels, the fields are abandoned, and regrowth of native plants restores soil quality over time. Once the soil quality is restored, the native vegetation can be cut and burned to release nutrients back into the soil for crops.” Dillaha explains this system worked well when there was ample time for native vegetation regrowth, typically five or more years for each year of cropping. But population increases and food needs have decreased the forest period of the cycle so much that slash and burn is no longer effective. Alternatively then, conservation agriculture is a proven technique seeking to maintain and restore soil quality. And doing so is vital. As is so often the case, developing world farmers are often the most tempted to use short term unsustainable methods. But destroying the land’s fertility only reduces production potential, speeding migration, conflict and associated impacts. Slash and burn agriculture, and the pattern of shifting cultivation it drives, is a major threat to tropical rainforests across the world. Slashed and burnt land will produce a harvest for a couple of years after it is first cleared, but the soil rapidly loses its fertility, forcing farmers to clear fresh land every few years. This cycle of shifting cultivation is causing destruction of both primary and secondary rainforest on a massive scale. While this practice may allow farmers to get by and secure a harvest, it is widely acknowledged that it offers them no way of tackling poverty and improving their quality of life. It offers no sustainable development opportunities and the practice cannot withstand intensification in any conventional sense. Now, over vast areas of former rainforest, and for perhaps hundreds of millions of subsistence farmers, this process often fails even to provide food security and the cash crops families need to meet the costs of everyday life. A new set of techniques are urgently required which will be effective and sustainable; a set of techniques which will provide food and cash crop security without exposing the family to debt, dependence or other externalities or requiring incredibly high amounts of labor in locations far from home. And, crucially, a technique that can break the cycle of deforestation caused by slash and burn by allowing families to produce a harvest year after year from the same plot of land. After many years of scientific research the Inga Foundation has developed a technique that can deliver all this; Inga Alley Cropping. Slash and burn subsistence versus logging as destroyers of the rainforest The destructive effects of over-intensive slash and burn agriculture are exponentially greater than those of logging because the logged-over forest at least contains the seed and root of its own regeneration. By fragmenting the forest and allowing former forest to become dominated by invasive grasses, slash-and-burn agriculture not only closes the door on regeneration, but throws away the key. We are seeing today a slowly enacted environmental and human catastrophe which seldom makes television news headlines. Abstract Slash-and-burn (jhum) is one of the primary causes of deforestation in tropics. In North-East India, increasing human population density has resulted in the practice of unsustainable form of slash-and-burn that includes shortening of the fallow period as well as permanent conversion of forest to permanent agricultural expansions. This unsustainable form of slashand- burn leads to soil degradation, soil erosion, loss of forest vegetation and threatens the survival of wild flora and fauna. Garo Hills has the richest reservoir of plant diversity of India and is one of the biodiversity hotspots of the world. There are numerous sacred forest patches in the Garo Hills. The prominent pressure to native forest biodiversity in the Garo Hills is the increasing anthropogenic conversion of mature and primary forest to jhum land. The decreasing fallow period has a deep impact on the life sustainability in Garo Hills and has reduced the quality of soil and thereby reducing the possibility of vegetative restoration at the locality. There was a tremendous increase in slash-and-burn land, i.e. 5.15 percentage in the year 2010 when compared to only 0.83 percentage in the year 1991. The overall reduction in the forest, mainly due to jhumming can severely affect a viable forest habitat of the endangered fauna like the Asian elephant and Hoolock Gibbon. The need to understand the effect of slash-and-burn cycle and to differentiate between the ecological sound traditional methods of jhum from the current unsustainable forms is most important. Impacts on soil Burning forests is identified as one of the soil degrading practice that results in soil structural dilapidation. Although, shifting cultivation practices cause tremendous loss of nutrients [19] and degradation of natural vegetation [20]. The benefits of slash-and-burning in improving soil fertility by immediate release of concluded minerals nutrients for crop use seems to be short-lived due to its degenerate effective soil physical properties. In the farmer’s perception, this practice has clear benefits like: it consumes slash vegetation, increases field accessibility, provides a fertilizing layer of ash, improves soil structure and reduce weed tree composition as well as occurrence of pests and diseases [21]. After the cropping year farmers leave the crop land as fallow land and before the natural plants grow to cover the ground surface, the soil is exposed (Figure 5A and 5B) to climatic element of rainfall. Afterwards, soil aggregates are dispersed; pores are closed with particles and further result in much higher rates of runoff [22]. The level of soil alteration may be huge if the magnitude of trash is large and the resident time of burning is long or thin, dry litter is completely incinerated. Forest loss Meghalaya, including Garo Hills is one of the richest botanical regions of India [26] and one of the most diverse luxuriant tropical vegetation condition of the world [15]. Extensive cutting and burning activities during jhumming is the major biotic interferences in the Nokrek Biosphere Reserve [27]. This burning activity has directly and circuitously affected rich plant diversity and caused forest land degradation, habitat destruction and solely depleted the biodiversity of the Reserve [28]. Land use cover is an important component to understand global land status; it shows present as well as past status of the earth surface [29]. Status of land use changes of Garo hills is mentioned in Table 1 which shows dynamic degradation of forest cover. The study was conducted by Yadav in 2012 [30], as “Landscape Dynamics in Garo Hills of Meghalaya, North East India using Geospatial Technology” for master thesis (M.Sc. Biodiversity and Conservation) and submitted to Guru Gobind Singh Indraprastha University, New Delhi, India.It was found that in entire time period, a large area under open forest has been converted into non-forest area. The area of slash-and-burn land increased in whole time period continuously. Yadav in 2012 reported Jhum as one of the drivers of deforestation in Garo Hills which increased tremendously (Table 1) during 1991 to 2010. The area of dense forest decreased in between 1991 to 2001 but increased in 2001 to 2010 period. This may be due to the effort put by Government and other organizations who are working for restoration of forest in Garo Hills. The prominent pressure to native forest biodiversity in the Garo Hills is the increasing anthropogenic conversion of mature and primary forest to jhum land. From 1980 to 1990, more than 6% of worldwide tropical forests and 10% of Asian tropical forests were converted to shifting cultivation [2] (WRI, 1996). As per the 1979 report of the North Eastern Council in the Indian state of Meghalaya, a total of 4116 km2 land was practiced for jhumming, of which 760 km2 was used at one point of time every year by 68000 jhummias, i.e. families involved in jhumming [31].Vegetation and land characteristics of Garo hills are heavily influenced by jhum activities which have greatly amplified in recent decades with increase in human population, resulting in several fragmentation of previously undamaged forest tracts. Reduction of native forest cover is a major impact of slash-and-burn. During 2000, a total of 7900 families (39,500 people) used 68 km2 of land for Jhumming at annual increase of 3.67% in South Garo Hills [32]. In Garo hills, native tribal communities have same permanent agricultural land, especially in western, southern and eastern parts bordering Bangladesh and Assam. Because of the hilly landscape, settled cultivation is practiced only in small portion of the total cultivated land, mostly confined to the valleys. High labour cost and energy input involved in trace cultivation, and absence of other viable alternatives implies that the majority of population continues to depend on shifting cultivation for their livelihood. Impact on wildlife Large, wide-ranging mammals, especially herbivores such as Asian elephant, can act as useful indicators of overall landscape biodiversity because they use large, often heterogeneous landscape areas to find resources [33,34]. Elephants also provide vital ecological functions such as: creation and maintenance of forest paths and pools used in turn by many other species including ungulates; dispersal of fruits and seeds through dung deposition; alteration of vegetation composition and structure through browsing and trampling; and other functions [35-37]. Conserving elephants would also serve to conserve many other wildlife species; thus, elephants appropriately serve as an “umbrella species” [38]. In India, Asian elephants (Elephas maximus) are present in their highest densities and numbers in Garo Hills of Meghalaya [39]. Little quantitative work has been done on elephant-habitat relationships in this region where the species’ distribution is known to be highly fragmented [40]. If elephants and their habitat are to be conserved, particularly in Garo Hills, and elephant-human conflicts are to be reduced, the initial steps are to understand their spatial and temporal distributions, determine habitat conditions associated with elephant densities, identify key population stressors, and suggest conditions conducive to elephant population persistence. Much of the native forest cover used by elephants in Garo Hills has been greatly altered over recent decades, largely through accelerated short-cycle jhum activity. Such intensive land use has been previously concerned in the decline of elephant populations of the region [41]. There were total 1841, 1297, 1104 and 1285 elephant reported in the 1993, 1998, 2002 and 2008 censuses respectively and it was concluded that numbers of elephant and crude densities varied across census periods, showing constant decline from 1993 to 2002 but rebound from 2002 to 2008 when GH-XXII (Part of Khasi Hills) was included [42]. Garo Hills landscape has large patches of natural forest cover. Several forest patches in the Protected Area and the Reserve Forest were the best known for supporting large numbers of the endangered western hoolock gibbon (Hoolock hoolock), which have gradually decreased in past two decades and have locally extinct from these area mainly due to human disturbances (which may include jhum) in their habitats [43]. Because of this anthropogenic activity the natural forest ecosystem has been modified, resulting man-made and natural landscape with poor species composition. Forest fire, controlled or uncontrolled (Figure 7) have reflective impact on physical environment including land use, land cover, biodiversity, and climate change and forest ecosystem. They also have negative impact for human health and on socio-economic system of affected region. The large-scale destruction and transformation of forest into degraded formations through logging and forest fragmentation and existing biotic pressure on forest in the form of logging, grazing and collection of non-timber forest products have rendered forest vulnerable to forest fire [44]. Increasing intensity of shifting of cultivation practices leads to low rainfall due to destruction of habitat which finally reduces biological diversity and causes extinction of previously undiscovered indigenous species too. Conclusion Like other forms of agriculture, slash-and-burn can be mismanaged and lead to severe environment degradation [46]. Continuously increasing human population and their demand for food, fodder and transportation leads to natural land cover degradation, resulting into habitat degradation, biodiversity loss, and ecological instability [47]. However, carefully designed and well managed slash-and-burn can serve as a sustainable food production system and provide benefits in the form of fuel, building materials and other income source. Historically, Slash-and-burn agriculture has been among the few truly ecologically sustainable agro ecosystems in the world because crop yields can be maintained without the use of non-renewable fossil energy resources for fertilizers, pesticides and irrigation [48] but shortening of the jhum cycle primarily to meet the demands of the ever growing human population has taken its toll on the environment. The threats of soil degradation and soil erosion due to jhumming can affect the vitality of native vegetation due to loss of necessary nutrients and soil features needed for their natural survival. Ramakrishnan in 1992 [49] described a positive correlation between crop yields and length of the fallow period owing the role of the fallow in controlling soil erosion. This relationship between food productivity and soil conditions provide a means of assessing the cost to humans of degrading the soil resource, but it also provides a means to assess the natural production potential of the soil. Garo hills landscape, being a wildlife hub is being negatively affected by unsustainable jhumming. The overall reduction in the forest, mainly due to jhumming can severely affect the habitat several of the endangered fauna like the Asian elephant and hoolock gibbon. Proper strategy and management of jhum in the Garo Hills is an immediate need to safeguard pristine habitats of wild flora and fauna in the area and also for sustainable food production for humans. Although there is lack of systematic analysis of the effect of social organisations and cultural values in shifting cultivation systems, there are enough anecdotal evidences which corroborate that these are important factors. There is a need for understanding determining factors, innovations and adoption of improved fallow management practices to conserve the continously declining biodiversity of North-East Indian states. The “slash and burn” technique used to clear forests is the process of cutting down most of the vegetation in a particular area, then setting fire to the remaining foliage, and using the ashes to provide nutrients to the soil for the purpose of planting food and crops. There are many pros and cons to this method though. Some pros are that by burning mostly everything, it drives away pests. When the vegetation and foliage burns, it causes a burst of nutrients for planting, Some think it would be bad to burn all of the foliage, but plants that provide food or timber are sometimes not destroyed. After the “slash and burn” process is used, then an area is left alone of a long time in order for vegetation to grow, but then the process may be repeated again. There are also some cons to the “slash and burn” technique. Vegetation is cut down in order to prepare for the technique. Deforestation also comes along with this process because sometimes vegetation is not able to grow back if the process is repeated to quickly after the time before. Erosion can also occur during this process. Sometimes roots and water are lost during this process and they are unable to prevent nutrients from leaving the plot of land permanently. That is an example of how erosion is caused and how nutrients are lost during the process. Biodiversity can also be lost during the process. When an entire plot of land is burned, many of the plants and animals that were currently there, leave forever. The “slash and burn” technique can result in an extinction of a species if their habitat was swept away from the process. Slash and burn agriculture is the process of cutting down the vegetation in a particular plot of land, setting fire to the remaining foliage, and using the ashes to provide nutrients to the soil for use of planting food crops. Deforestation: When practiced by large populations, or when fields are not given sufficient time for vegetation to grow back, there is a temporary or permanent loss of forest cover. Erosion: When fields are slashed, burned, and cultivated next to each other in rapid succession, roots and temporary water storages are lost and unable to prevent nutrients from leaving the area permanently. Nutrient Loss: For the same reasons, fields may gradually lose the fertility they once had. The result may be desertification, a situation in which land is infertile and unable to support growth of any kind. Biodiversity Loss: When plots of land area cleared, the various plants and animals that lived there are swept away. If a particular area is the only one that holds a particular species, slashing and burning could result in extinction for that species. Because slash and burn agriculture is often practiced in tropical regions where biodiversity is extremely high, endangerment and extinction may be magnified.
Posted on: Mon, 20 Jan 2014 07:36:00 +0000