Impacts Of Conversion Of Tropical Forests To Small-Scale Agriculture - Essay Example

Impacts of conversion of tropical forests to small-scale agriculture This paper discusses various small-scale agricultural practices around tropical forests such as shifting cultivation, agroforestry, home garden and shade forming and compares it with other uses of tropical forests such as selective logging, plantation and monoculture. This paper also looks in to the impact of theses agricultural systems on the structure, diversity, floristic, and dynamics of tropical forests. With the help of literature review it points out the concerns of various researchers, scientists and environmentalists for depletion of tropical forests and its ecological impact. Introduction From a biologist perspective tropical forests are the richest and most exciting areas on earth sheltering a diverse wildlife. Tropical forests are differentiated from other type of forests due to their gigantic trees amazingly diverse fauna of colorful birds, millions of brightly hued insects, and a variety of fascinating mammals. It is widely accepted that tropical lowland forests are the most species-rich type of terrestrial ecosystem (DeVries & Walla, 2001; Bush & Lovejoy, 2007), for example, a hectare of Malaysian tropical rainforest may contain 180 kinds of trees. Tropical rainforests are generally concentrated near the equator in Asia, Africa, South America, Central America, and on many of the Pacific Islands. According to WWF’s biome classification, tropical rain forests are considered a type of tropical wet forest and may also be referred to as lowland equatorial evergreen rain forests. All five layers of tropical rainforests i.e. emergent layer, canopy layer, understory layer, shrub layer, and forest floor are enriched with different plants and animals. Tropical deforestation, desertification, decreasing biodiversity, climate change and the scarcity of fresh water are issues of recent and ongoing global conflict and debate (Matti Palo and Jussi Uusivuori, 1999; Matti Palo and Heidi Vanhanen, 2000). On the other hand, according to various studies by WWF committees, rainforests are the most endangered habitat on earth and every year approximately 140,000 sq km of tropical rainforests are destroyed because of small scale agricultural practices and timber industry. The rate at which these forests are disappearing is again fueled by the rapid population growth in the areas harboring theses forests. Small-scale agricultural practices Shifting cultivation Generally used definitions of shifting cultivation defines it as a agricultural system where plots of forests land are cultivated temporarily by clearing the land by the means of fire or logging and then abandoned when the soil looses its fertility. When the fertility level of land drops below economical viability, it is left to be reclaimed by natural vegetation. The ecological impacts of shifting cultivation are often devastating. With the development of a holistic view of agro-ecosystem approach and agriculture being considered as a part of a greater natural ecosystem, the shifting cultivation is defined from a different perspective. Whereas many earlier studies described the shifting cultivation system as inherently stable and provided a checklist of attributes, more recent work based on an agro-ecosystem approach has stressed fallow as part of an overall subsistence strategy, flexibly responding to stress as the social, economic or natural environments change (Warner, 1991; Gliessman 1985, Altieri et al 1973). Agroforestry The term agroforestry is used for a combination of agriculture and forestry technologies for creating a more integrated, diverse, productive, profitable, healthy and sustainable land-use system (National Agroforestry Center, NAC). According to the World Agroforestry Centre (ICRAF), "Agroforestry is a collective name for land use systems and practices in which woody perennials are deliberately integrated with crops and/or animals on the same land management unit. The integration can be either in a spatial mixture or in a temporal sequence. There are normally both ecological and economic interactions between woody and non-woody components in agroforestry". In agroforestry a former grow plants in their form to gain optimal economical benefit of their land. Home gardens Home garden is a term to define an agricultural practice widely employed in humid regions of India and Indonesia, where cultivation of trees and crops, and breading of livestock is done on the same land using inter-crop techniques. Home garden system is also prevalent in African countries and plays a major role in food supply security in poor areas. Home gardens are similar to kitchen garden; they only differ in terms of function, size, diversity, composition and features (Sthapit et al., 2006). Shade coffee/cacao gardens Shade garden refers to agriculture system where small forest patches are managed to grow coffee or cacao gardens. These managed gardens are habitat of great bio diversity. Analog forestry Analog forestry is a term used for agricultural system of growing trees and plants that seek to establish a tree-dominated ecosystem that is analogous in architectural structure and ecological function to the original climax and sub-climax vegetation community. Thus, Analog Forestry draws design input not only from traditional models but also from the natural forest successional dynamics. When an ecosystem is designed to be analogous to the indigenous climax state, the efficiency and dynamics of the natural processes can be replicated. These quasi-natural forests are designed to mimic the structural and functional aspects of indigenous forests and are referred to as analog forests (Senanayake, R. and John, J, Jack. 1998). Other tropical forest uses Selective logging Selective logging is practice of cutting down trees in a certain proportions based on some kind of defined criterion. The criteria, for example, may by the size or age of tree. The reason for selective logging is often cited as forest regeneration to maintain natural forest structure after and between selective harvests. Selective logging can have tremendous adverse ecological effects if healthy practices are not followed properly. Environmental Defense Fund show that areas that have been selectively logged are eight times more likely to be settled and cleared by shifting cultivators than untouched rainforests because of the access granted by logging roads. The impacts of selective logging include: Loss of deep-rooted perennial trees and shrubs Reduced canopy cover Increased invasion of environmental weeds Increased soil compaction Increased greenhouse gas emission Plantations Plantation refers to the practice of agriculture system where a particular alternative crop is planted over a large tract of land. These alternative crops usually give higher economic returns to formers or the firms involved. Plantation started as a major economic practice during 17th century. Plantations though give higher economical returns, in the tropical forest lead to large scale damage to wild flora and fauna and create ecological imbalances. Monocultures The term monoculture refers to agricultural practice where a single crop is produced over a wide area. Monoculture leads to standardization of agricultural practices which results in lesser waste and loss from inefficient harvesting and planting. This form of agriculture systems are widely used where environmental conditions favor a particular type of crops. Difference between small-scale agricultural practices and other tropical forest uses such as selective logging and larger-scale agricultures e.g. plantations, monocultures Scientist, ecologists and researchers differ in their opinion about advantage and disadvantages of small scale agricultural practices and other forms of tropical forest uses and their impacts in nature. Small scale agricultural practices such as shifting cultivation, agroforestry and home gardens are generally limited to small tract of forest lands and generally involved local people who were settled around these forests whereas other uses of tropical forests such as selective logging, plantation and monoculture involve large forest areas and involve large firms and local governments. The other differences between these agricultural and other uses of forest land depend upon the scale and the practices followed. Some researchers believe that if proper practices are followed shifting cultivation and other small scale agricultural uses of forest land do not disturb ecological system much but other researchers contend that shifting cultivation adversely affects the tropical biodiversity. Similarly economists and forest planners think that selective logging, plantation and monoculture systems do not harm ecological system, in contrast they even help in proper management of forest resources where as several studies shows that selective logging and plantation harm tropical forests more as felling of a single large tree can bring down dozens of surrounding trees which are connected to the target tree by vines and lianas. The thinning of the protective canopy exposes the forest to increased sunlight and drying winds that can kill symbiotic soil organisms essential for decomposition and nutrient-fixing, while drying leaf litter and increasing the forests vulnerability to fire. Effects of small-scale agricultural practices on the structure, diversity, floristic, and dynamics of tropical forests Many researchers believe small-scale agricultural practices such as shifting cultivation have been the main cause of tropical deforestation. The impact of small scale agricultural practices on the structure, diversity, floristic, and dynamics of tropical forests has been diverse and a matter of research for ecologists. Most of the scientists, ecologists and environmentalist perceive shifting cultivation as primitive, backward, wasteful, unproductive, and exploitative system of agriculture causing enormous environmental degradation and destroying diverse tropical flora and fauna. Shifting cultivation system has been a point of debate for land degradation, atmospheric pollution and global climatic change. Major works by various researchers states that “No matter where we go we find primitive agriculture was carried on at the expense of forest” (Thomas 1956). Studies show that excessive small scale agricultural activities such as shifting cultivation and agroforestry damage the structure and dynamics of tropical forests. The primary forest of trees with deep grip and canopies are converted in to secondary woodland of shrubs and bamboo which may result in more serious floods and serious soil erosion. Shifting cultivation and other form of agriculture practices, bare open the tropical forest land which leads to the destruction of the topography from erosion by gully (Laurent Chazee, 1993). How drastic the impact of these small-scale agricultural practices will be on the structure, diversity, floristic, and dynamics of tropical forests depends upon various ecological factors such as intensity of these practices and environmental condition of the region. For example, reclaiming the fertility of forest land depends upon the fallow time and erosion of land. The impact of small scale agricultural practices if often long lasting as destroyed trees take long times to grow and often these ecological changes to the tropical forests are persistence. Effects of small-scale agricultural practices on wildlife groups As mentioned above in introduction part of this paper, tropical forests are home to more than 50 percent of the worlds terrestrial biological diversity. The survival of this flora and fauna is endangered with depleting tropical forests. Small scale agricultural practices, for example, endangered the habitats of colorful tropical birds which were responsible for pollinations in wild flora. These agricultural practices also brought wild life closer to human habitats which resulted in extinction of many species of wild fauna of rich tropical forests. Summary Tropical forests are the richest and most exciting areas on earth sheltering a diverse wildlife. Small-scale agricultural practices, though considered safe by many scientists and ecologists, have been proved to be having detrimental effects on the health of tropical forests. 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