Whilst the greatest effort has been made to ensure the quality of this text, due to the historical nature of this content, in some rare cases there may be minor issues with legibility. Southeast Asia offers many examples of problems arising from manipulation of ecosystems. Intensified shifting cultivation and excessive rates of timber extraction are denuding upland slopes, accelerating soil erosion, weakening natural controls of water flow, and exacerbating floods and siltation in lowland areas. The absence of suitable management jeopardizes future forest yields and water control throughout the region. Water-resource projects can destroy fisheries, cause salinization of agricultural soils, and spread dis ease. The usefulness of river impoundments has been impaired by ecological reactions that, without better knowledge and planning, may recur on a grander scale in the more ambitious projects of the future. Modern agricultural techniques increase ecosystem vulnerability to pests and diseases by weakening natural capacities for control.
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