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LAND USE LAND COVER AND SOIL SCIENCES VOL IV Land Rehabilitation Martin J Haigh. compaction and also accelerated runoff and erosion on hill slopes and in watercourses. In other contexts the interventions involve the mitigation of wind erosion and pollution. especially by salts or industrial wastes or military ordinance The success of a land. rehabilitation strategy if it is not expressed in economic terms is evaluated in the same. terms as progress in ecological succession commonly the integration efficiency and. resiliency of the geo ecological system, Rehabilitation treatments divide between those that treat the problems in the soil. usually by changes in land management and those that treat the consequences of soil. degradation usually by engineering In every case since the fundamental causes of the. land degradation are the social and economic processes that drive human societies to. abuse the land the long term success of any land rehabilitation intervention depends. upon the changes in land management,1 Introduction. This section describes the ideas strategies and methods currently employed for the. rehabilitation of land that has become damaged by human actions Many human. activities cause land to become degraded to the point where it becomes unproductive or. a negative factor in environmental quality Across large parts of the world human. action has degraded the landscape to a condition where its productive potential is much. less than in former times at least allegedly These include the eroded ravine lands of. China India and Pakistan the barrens of the Mediterranean Basin central Asia and the. There are large areas damaged by soil salinization following misconceived irrigation. soil erosion following agriculture or deforestation and tracts damaged by military. mining and construction activities especially surface mining and road construction In. some cases the environment has been transformed to such an extent that recovery is. unlikely to become a viable option In others there is a real potential for these damaged. lands to be recycled to new uses or rehabilitated for nature These processes both. natural and technological that involve variously aspects of both ecology and. engineering are the focus for the notes that follow. 2 The Problem Land Degradation, The driving force for land rehabilitation is land degradation Land degradation is a. composite term indicating the aggregate diminution of the productive potential of the. land including its major uses rain fed arable irrigated rangeland forestry its farming. systems e g smallholder subsistence and its value as an economic resource This term. which includes the subset of desertification refers to the decline of the biological. productive potential of land namely the entire geo ecological system that includes soils. waters climate vegetation topography and land use, Land degradation may be an inherent property of the natural system e g some of the. eroded ravine lands of South Asia may be due to tectonic uplift generated channel. incision In other cases climatic change may be implicated More usually land. degradation is caused by a mismatch between the land s self sustainable biological. Encyclopedia of Life Support Systems EOLSS, LAND USE LAND COVER AND SOIL SCIENCES VOL IV Land Rehabilitation Martin J Haigh.
potential its quality in human terms and the way the land is used Simply the way the. land is used causes more damage to the land than its restorative systems can. compensate This chapter deals with the physical and technical processes of land. rehabilitation but both land degradation and rehabilitation are driven by social and. economic causes Ultimately land degradation and land rehabilitation are human. processes that reflect the ways in which human societies use and value the land that. feeds them, Environmentalists occasionally protest that land degradation is irreversible However. this chapter is devoted to the belief that most degraded lands can heal and indeed will. heal themselves given sufficient time and the appropriate circumstances It includes the. belief that land degradation can be mitigated with the help of human intervention but. also that most land degradation is preventable and that prevention is much better than. any cure that rehabilitation work may aspire to provide. However the physical cause of land degradation is commonly a reduction in soil quality. that fosters runoff and erosion ahead of soil formation and which reduces the biological. productivity of affected lands Soil degradation is a process that lowers the current. and or future capacity of the soils to produce goods or services Soil degradation can be. mitigated if land is left for sufficiently long periods in fallow which enables. biological restoration of soil characteristics that have become degraded notably its. porosity and nutrient content During this recuperation phase biological processes can. return the soil to a good condition for the growth of plant roots However land. shortages are now reducing the time that land can be allowed to remain in fallow with. the result that the rate of degradation and loss of underlying productive potential during. the cropping period increases,2 1 Extent of Land Degradation. The question that arises however is how much of the land in the world is degraded and. how much suitable for land rehabilitation treatment The truth is that it is impossible to. know Produced during the late 1980s GLASOD was the first systematic attempt to. produce a global overview of soil and land degradation but since there is insufficient. data for all but a tiny fraction of the earth s surface much had to be based of guesswork. and estimation Nevertheless GLASOD s World Map of the Status of Human Induced. Land Degradation the second edition of which was published by ISRIC and UNEP in. Wageningen in 1991 by Oldeman and colleagues provides a benchmark GLASOD. suggests that the globally land degradation affects about 15 of the world s dry land. surface and 22 of its agricultural land base and 70 of the world s dry land areas. Water erosion is the primary cause The area where degradation is rated strong or. extreme where land rehabilitation is an issue sums to around 3 050 m ha Water. erosion is the main reason on 73 of this land and wind erosion on 8 5 Human. induced chemical soil degradation mainly due to salinization and pollution is thought to. affect more than 12 of the total degraded land area and 15 of that requiring. rehabilitation, Land use category Total area Area affected by land. million hectares degradation per cent,Total land area 13 000 15. Encyclopedia of Life Support Systems EOLSS, LAND USE LAND COVER AND SOIL SCIENCES VOL IV Land Rehabilitation Martin J Haigh.
Total agricultural area 8 735 22,Total area of degraded land 1 965 100 from which. Degraded by water erosion 1 094 56,Degraded by wind erosion 549 28. Degraded by soil structural 83 3 4,Degraded soil fertility 135 3 7. chemical degradation,Salinisation 76 3 4,Soil pollution inclusive of 21 8 1. industrial,Acidification 5 7 0,Table 1 Estimated extent of land degradation.
After loss of vegetative cover soil compaction is often named as the major cause for. land degradation by water erosion because small changes in the soils architecture can. result in large scale changes in a soil s ability to absorb potentially erosive rainwater. Soil physical damage is an increasingly serious problem for agriculture However soil. and subsoil compaction is difficult to estimate and official GLASOD estimates could be. a huge under estimation of the problem, Recent years have seen a 3 4 fold increase in both the size of farm machinery and the. frequency of trafficking across agricultural lands This has placed more loading and. more stress on their soils both surface and subsurface Studies undertaken in Scotland. suggest that as much as 90 of cultivated arable land can suffer trafficking by heavy. vehicles during an annual cycle of cultivation and although reworking of the soil. surface mitigates much of the compaction so caused damage to the subsoil layer. persists The consequences of soil structural damage include reduced agricultural. production and accelerated runoff and erosion from affected lands. Before GLASOD earlier estimates suggested that worldwide perhaps 12 x 106 ha of. degraded arable land is abandoned annually due to unsustainable farming practices In. 1984 Brown and Wolf wrote an influential pamphlet called Soil Erosion the Quiet. Crisis in the World Economy for Washington s World Watch Institute Here they. estimated that the world was losing around 28 bn t 25 400 million tons of soil in. excess of soil formation from its 1270 m ha of cropland Allowing each acre. approximately 180 mm of topsoil this suggested a decade loss rate of 7 which if true. would have eliminated half the world s productive topsoil before 2025 The mining. away of the world s productive topsoil was called the quiet crisis because the changes. involved may be imperceptibly tiny in the context of each annual agricultural cycle but. cumulatively disastrous measured across several decades. Today it has been suggested that on the global scale the loss of 75 bn t of topsoil to. erosion each year represents a cost to each person on the planet the equivalent of 70. each year in lost production Yield reduction in Africa due to past erosion is estimated. as 8 overall Many writers contest the link between erosion and yield reduction and. soil loss noting that biological productivity depends more on the quality of the soil that. remains in the field than that lost in erosion Nevertheless the fact remains that the. Encyclopedia of Life Support Systems EOLSS, LAND USE LAND COVER AND SOIL SCIENCES VOL IV Land Rehabilitation Martin J Haigh. topsoils which are lost to erosion or damaged by physical or soil chemical degradation. rank with the most productive and the most critical to people that depend on them for. their livelihoods Topsoil damaging processes create the lands that demand. rehabilitation treatment, 2 2 Estimates of Areas needing Rehabilitation Treatment. The term degraded land contains an implicit value judgment Some land has been in a. degraded state for so long that the condition is now considered natural and normal as. in most of Western Europe and on the shores of the Mediterranean much of which is. technically deforested Sometimes land degradation goes undetected because its. symptoms are hard to see as in the case of subsoil compaction and many forms of. chemical and biological pollution The trickiest issue is that most land that has been. used by humans is degraded from its original condition However application of the. term degraded involves a qualitative assessment that the land is sufficiently damaged. to warrant being recognized as a human concern Normally degraded land is recognized. because it is considered either wasteland or wasted land or occasionally land that is. rapidly wasting away from productive value, Of course collecting reliable information on either soil or land degradation at the. national let alone global scale is a near impossible task So the inevitable conclusion. must be that these estimates reduce either to educated guesswork or to political. propaganda on the part of their authors However arguably even these data are better. than nothing,Total Area 3 050 million hectares 100.
Water Erosion 73,Wind Erosion 9,Soil chemical degradation 14. Soil physical degradation 4, Table 2 Estimated extent of land area requiring rehabilitation treatment. 3 Sustainability Concepts in Land Rehabilitation, There are aspects of land rehabilitation that affect every project First there is the. decision concerning the nature of the after use Will the land be restored to nature or to. human utilization, If the land is to be restored to nature then the focus of the project becomes the. establishment of biological control of the environment This means the generation of an. autonomous self sustaining geo ecological system Here the key indicators of success. include the vitality productivity and resilience of the system Often measured are the. system s capacity to recycle organic and mineral components and its capacity to effect. self catalyzing environmental improvement which is often manifested through the. normal patterns of ecological succession, If however the rehabilitation is to human use then the key criteria become the.
Encyclopedia of Life Support Systems EOLSS, LAND USE LAND COVER AND SOIL SCIENCES VOL IV Land Rehabilitation Martin J Haigh. sustainability of that after use This is measured in terms of the cost and benefits of. maintaining environmental quality and the capacity of the local land management to. preserve or enhance the productive quality of the land howsoever defined. In reality this creates a huge problem A major proportion of land reclaimed or. rehabilitated for human use does not remain in a good quality condition One common. reason is that the land users do not have the will the skill or perhaps the resources to. sustain its quality This is as much a problem for the reclaimed coalmine lands of. Europe as it is for the agricultural lands in the developing world For example between. 1969 and 1990 the Government of India invested around Rs16 billion in soil and water. conservation Evaluating the result the Planning Commission s SWC Working Group. Land rehabilitation is an intervention designed to make a geo ecological improvement In most contexts this involves the mitigation or reversal of land degradation caused by poor land husbandry practices especially agricultural practices

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