Some meteorologists and soil scientists measure the impacts and length of a drought to determine if it is an example of desertification.
Droughts can persist for months or years, but eventually subside; lands undergoing desertification never recover past productivity. In the United States, for example, 65 percent of the country was affected by drought in the s, but the Great Basin eventually recovered, and modern occurrences of drought usually affect no more than 10 percent of the land.
As social and political forces intensify the pressures on the land that lead to desertification, land degradation itself can lead to further disruption of societal and political stability. The loss of fertile soil, water, and other resources, both for subsistence and for commercial use, leaves many people in dryland areas without the means to support themselves and their children. Biomass burning also destroys an important sink for atmospheric carbon. So fire is a factor reducing woods and accelerating soil deterioration, thus increasing hazards of desertification.
Yet this heating is responsible for all of the direct changes in physical and chemical soil properties caused by forest fire. This waxy coating is water repellent, slowing infiltration. Water repellence may last from weeks to some years Baker , DeBano Overland flow from these areas can trigger rill erosion and mass erosion, thus inducing degradation and further processes which lead to desertification. After low-severity fires, recovery to pre-fire conditions may take only as long as necessary for soil biota to re-establish and surface organic matter to re-accumulate.
The changes listed above - especially the loss of organic matter from above and below ground - affect the chemical and physical nature of forest soil with consequences for post-fire regeneration as well as post fire water yield and soil loss via erosion. Following a severe fire, increased surface runoff during storms enhances the potential for surface erosion and shallow landslides, especially on sites in which roots and other organic structures that hold loose material on slopes were consumed or killed Bitterroot National Forest Large, severe fires pose greater risks of erosion until vegetation cover develops and litter begins to accumulate.
On slopes with scarce protective vegetation cover and debris after fire, soil can erode even without heavy rains, due to the sheer force of gravity. Forest productivity. Maintaining the health and productivity of forest ecosystems is an important prerequisite to sound stewardship and the sustainable development of forested lands. Slow productivity of forests means reduced amount of biomass, and consequently a forest cover less resistant and more prone to irreversible transformations.
Forests have been, and continue to be, exposed to a broad range of natural and human-caused stressors. Natural stressors include weather extremes, forest insects and pathogens and catastrophic events. Human-caused stressors include activities such as land use change; inappropriate or non-sustainable timber harvesting practices; road building, which reduces the capacity of the site to continue as productive forest land; introduction of exotic pests and air pollution.
Altered ecological conditions caused by human activities or climate change can increase the susceptibility of forests to natural stressors such as drought, changes in the water table, pest epidemics and wildfires. The interaction of human stressors and natural stressors can accelerate the deterioration of forest health.
The proximity of settlements and structures to forested land creates management challenges including those related to fire. Forest health problems that reduce the resiliency of forests or that reduce the capacity of forests to support the needs of people and society should be addressed as strategic issues in forest management. The increasing importance of forests makes forest health efforts more timely and critical than ever before.
But for forests to perform their vital environmental functions and to realize their enormous productivity potential, they have to be managed. Silvicultural measures must be taken to improve the health of forests stands, to stimulate their production and to avoid the causes of poor stand health, in order to prevent the action of secondary organisms.
The maintenance of species diversity and stand types is equally important for an efficient fight against biotic threats. Proper forest management technologies should be used more widely as the first steps in moving from merely exploitative logging to sustainable forest use. Although there are many unanswered questions about truly sustainable silvicultural systems for forests, there are many well-known practices that can be employed more extensively which could improve forest management and reduce the degradation of forests and their susceptibility to deforestation.
A recent assessment on the forest sector has provided an overview of gaps and priorities for promoting sustainable forest management and development.
The following orientations have been highlighted: promotion of multifunctional objectives; strengthening of links between short-term and long-term strategies; monitoring based on criteria and indicators; promoting and motivating forest owners, forest enterprises and forest marketing; improving public administration; support for diversification of forest enterprises activities; strengthening of research, training and communication EOFM, Sustainable forest management involves the enhancement of various aspects of forest functions such as conservation of biodiversity, conservation of soil and water resources, and contributions to the global carbon cycle, as well as wood production.
The impact of grazing. Domestic animals reduce regeneration through overgrazing, browsing, and trampling. Large vertebrate herbivores are supposed to be an important structuring agent in terrestrial food chains, through their impact on plant diversity and plant nutritional value. In low productive systems, sustained heavy grazing by large vertebrates may change interplant relationships, e.
Vertebrate grazing or browsing has, therefore, the potential to change biodiversity. In more productive systems, grazing may increase plant species richness by removing strong competitors, thus giving space for the growth of less competitive species.
In contrast, in low productive systems, such as many alpine areas and on the arctic tundra, intense grazing can reduce plant species richness and species diversity.
The ecological impact of ungulate grazing is not only determined by the productivity of the system, but also by the type of grazer, the degree of herbivory and the grazing history. Overgrazing is often blamed for worldwide desertification, which is partly true and partly false, depending on the situation. It depends certainly on overgrazing intensity such as slight, heavy, very heavy and destructive and also overgrazing duration, which can be measured in months, years, decades or even centuries.
Apart from prolonged droughts, acceptable and fixed stocking rates will cause temporary overgrazing in some years because of grazing capacity fluctuations. Damage to the vegetation, if any, is usually repaired by natural processes.
Stocking rates and managerial systems that result in continual destructive grazing are a major cause of desertification on rangelands. The desertification process is accelerated when these practices are maintained during drought and certain seasons where plants are highly vulnerable to abuse.
While it takes a long time, this will eventually result in desertified rangelands. Destructive grazing also causes poor livestock performance and many private landowners have learned this lesson.
It is, therefore, not as common on private lands as it is on public or community grazing lands, where central control is lacking. Role of forest management. The role of forest management is to maintain an appropriate enhancement of forest resources and encouragement of productive functions of forests wood and non-wood.
Forest management practices safeguard the quantity and quality of the forest resources in the medium and long term by balancing harvesting and growth rates and by promoting techniques that minimise direct or indirect damage to forest, soil or water resources. Appropriate silvicultural measures maintain the growing stock of resources at - or near to - a level that is economically, ecologically and socially desirable.
Forest management practices make the best use of natural structures and processes and use preventive biological measures wherever and as far as economically feasible to maintain and enhance the health and vitality of forests.
Forest management practices promote a diversity of both horizontal and vertical structures, such as uneven-aged stands and the diversity of species such as mixed stands. Where appropriate, the practices should also aim to maintain and restore landscape diversity.
Tending and harvesting operations should be conducted in a way that does not cause lasting damage to ecosystems. Wherever possible, practical measures should be taken to improve or maintain biological diversity. The principal aim of forest management planning is:.
Things going on in the wider world. Deforestation is the product of the interaction of the many environmental, social, economic, cultural, and political forces at work in any given region. In most cases, deforestation is a process that involves a competition amongst different land users for scarce resources, a process exacerbated by counter-productive policies and weak institutions.
It creates wealth for some, causes hardships for others, and almost always brings serious consequences for the environment. Deforestation is an important contributor to global warming, but its contribution relative to the other factors is not precisely known.
The principal cause of global warming is the excessive discharges in industrialised countries of greenhouse gases, mostly from the burning of fossil fuels. At the regional level, deforestation disrupts normal weather patterns, creating hotter and drier weather. Most of this increase in land area will come at the expense of tropical forests. The agriculture sector must be challenged to find appropriate solutions.
Any effort to combat deforestation must be based on a complete understanding of what the agents of deforestation are and what its direct and underlying causes are. While forests will continue to be lost for decades to come, it is critically important that the fight against deforestation is done in the most rational way possible. Impact of human population. It is evident that through history mankind has put added stress on the land, starting from use of fire by prehistoric man in Palaeolithic times, accidentally and intentionally burning large areas of forest for settlement and agriculture.
Pickering and Owen, Thornton, P. Kruska, R. Author s : Ruf, F. Chapter: 17 Page no: Agriculture and deforestation in tropical Asia: an analytical framework. Author s : Jayasuriya, S. Chapter: 19 Page no: Agricultural development policies and land expansion in a Southern Philippine watershed.
Author s : Coxhead, I. Shively, G. Author s : Jong, W. Chapter: 22 Page no: Policy recommendations. Angelsen, A. Chapter details. Author s Shively, G. Editor s Angelsen, A. Book Agricultural technologies and tropical deforestation. Facebook Twitter LinkedIn Email. Introduction: the role of agricultural technologies in tropical deforestation.
Technological change and deforestation: a theoretical overview. The transition from deforestation to reforestation in Europe. Did a green revolution restore the forests of the American South? A general equilibrium analysis of technology, migration and deforestation in the Brazilian Amazon. Will intensifying pasture management in Latin America protect forests - or is it the other way round? Intensified small-scale livestock systems in the Western Brazilian Amazon.
Technological progress versus economic policy as tools to control deforestation: the Atlantic zone of Costa Rica.
Deforestation not only occurs as a result of firewood extraction by the local population but also as a result of the creation of arable as well as pastoral land. As population figures rise, the extraction of firewood and thus the bias between firewood production and usage increases, therefore reinforcing deforestation and destruction of natural vegetation.
Furthermore the growing firewood deficiency is often substituted by dung or harvest surpluses, which, if used appropriately, may be used as fertilizers.
Resultant to this substitute usage of dung and harvest excesses by the local population, soil fertility may decrease.
Forests, often found in headwater regions, do not only improve the annual retention capacity of the soil and thus help to provide a stable discharge rate, which is crucial for the sustainable use of the MHP, but they also help to decrease the risk of flash floods and thus severe erosion after heavy rains. Overexploitation occurs when arable land is used beyond its fertility potential without substituting the loss of nutrients by fertilizers or appropriate fallow periods [2]. Contributing to this overexploitation might be the shift from rainfed agriculture to modern agricultural methods, cash cropping and population growth.
Overexploitation can lead to a variety of erosion features such as Gully erosion, landslides and alternation of discharge and should thus be prevented in order to provide sustainable use of the MHP. Overgrazing occurs when the number of livestock on a unit of land is too large. Resultant to this is the destruction of natural vegetation as well as soil compaction and erosion cattle step. Furthermore the photosynthesis and hence biomass production and carrying capacity is decreased. Vegetation damages occur not only due to cattle bites, but also due to cattle step and pawing.
Also the lack of a grazing plan which includes rotation of grazing ground, and, moreover, the lack of a national land use plan may contribute to overgrazing [3]. Like overexploitation, overgrazing can result in various degradation features such as alternation of discharge, change of soil moisture and gully erosion and thus might compromise the sustainable use of the MHP.
Degradation, primarily in form of salinization, occurs in this case due to a bias between water inflow and outflow or the use of salty water [3]. Various socio-economic as well as political causes can lead to land degradation. As mentioned earlier, population growth is a major cause of degradation, since it contributes to overgrazing, overexploitation and deforestation. Furthermore degradation occurs due to underdevelopment, since resources are often exploited to benefit developed countries and thus little profit is left in developing countries to manage or restore degraded areas [4].
Also rural-urban migration contributes to the occurrence of degradation, since urban populations need more firewood than rural populations. Hence the growth of urban populations in general goes hand in hand with an increase in deforestation and thus degradation. Not only human action can cause degradation to occur, but also natural causes such as the nature of rainfall amount, intensity, variability, distribution… , soil texture, structure, depth, moisture, infiltration rate… and topography play an important role in the scope and scale of occurring degradation features.
Under natural condition, soil erosion due to these causes is a natural process.
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