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Land degradation — a threat to agriculture




  • Pakistan is facing a number of environmental threats, of which, land degradation appears to be the worst. According to a study, the severity and cost of land degradation in South Asia that includes Iran and Afghanistan is approximately two per cent of the region’s GDP and seven per cent of the value of its agricultural output. Pakistan faces a similar situation.

    The breakdown of losses, according to types of land degradation, are water erosion $5.4 billion; wind erosion $1.8 billion; fertility decline $0.6-1.2 billion; water-logging $0.5 billion and salinity $1.5 billion.

    The study found that altogether 140 million hectares, which is equal to 43 per cent of the region’s total agricultural land, suffered from one or the other form of land degradation. Of this, 31 million hectares were strongly and 63 million hectares moderately degraded.

    The worst affected was Iran, with 94 per cent of agricultural land degraded, followed by Bangladesh 75 per cent; Pakistan 61 per cent; Sri Lanka 44 per cent; Afghanistan 33 per cent; Nepal 26 per cent; India 25 per cent, and Bhutan 10 per cent.

    In Pakistan, land degradation mainly encompasses deforestation and desertification, salinity and sodicity, soil erosion, water-logging, depletion of soil fertility and negative nutrient balances.

    Deforestation and desertification: Pakistan has a total forest area of about 12 million hectares. Out of that, the total forest, scrub and planted trees are spread over 4.2 million hectares; natural and modified coniferous scrub, riverain and mangrove forests occupy a space 3.5 million hectares, tall tree forests encompass 2.4 million hectares, scrub forest exist on 1.1 million hectares, and plantations occupy 0.7 million hectares.

    The forest area of Punjab is only less than three per cent, whereas in Sindh it becomes half of that. The continuous destruction of forests is causing a substantial loss.

    The declining rate of woody biomass is the second highest in the world. It ranges between 4-6 per cent per year. Almost 7,000-9,000 hectares are deforested every year and this rate is especially severe in the north where per capita consumption for fuel-wood is 10 times higher due to harsh winters.

    Because of increase in population, the consumption of household firewood would probably go up to three per cent per year. At this rate, the country’s woody biomass may be totally consumed in the next 10-15 years.

    The lopping of trees for commercial purposes has accelerated forest depletion. Unrestricted livestock grazing is also a threat. Regional case studies also portray a dismal picture.

    A study of the Siran project area, Hazara, the NWFP, shows a 52 per cent decline in resource between 1967 and 1992. Similar is the situation in the Kaghan and Allai valleys. The mangrove forests of the Indus Delta have halved from 2,600 square kilometres in late 1970s to 1,300 in 1990s, due to the grazing by camels. Almost 50 per cent of the original riverain forests have been degenerated beyond economic viability.

    More than 60 per cent of natural grazing areas of the country have production levels lower than one third of their biological potential. More than one-third of the country area has been classified as under risk of desertification.

    Soil erosion implies loss or removal of surface soil material through the action of moving water, wind or ice. The extent of the area affected by water and wind erosion.

    About 13.05 million hectares of area is affected by water erosion and about 6.17 million hectares by wind erosion.

    Soil erosion is taking place at an alarming rate and is mainly due to deforestation in the north. Water erosion is prominent on steep slopes such as the Potohar track and surrounding areas, an area extensively used for cultivation. The highest recorded rate of erosion is estimated to be 150-165 tons/hectare/year. The Indus River carried the fifth largest load of sediment (4.49t/h) in the world in 1990.

    Wind erosion has a relatively lower impact than water erosion. However, the combination of the two is more devastating. This reduces the productivity of the land by 1.5-7.5 per cent per year. This affects almost one-fifth of the Punjab.

    The problem of waterlogged area may not be as serious now as it was in the past. Water logging has reduced due to prolonged drought and excessive mining of ground water.

    The fertility of soils is rapidly depleting. The data generated by public and private organizations reflect the general agreement about the deficiency of nitrogen in 100 per cent soils. Same is the situation with the organic matter content, which is on around average 0.5 per cent only.

    In case of phosphorus, more than 90 per cent soils are deficient. Potassium deficiency in soils, not a soil fertility problem earlier, is increasing rapidly due to discriminate use of only nitrogenous and phosphate fertilizers. Various public and private organizations are reporting a soil potassium deficiency in the range of 20-40 per cent. For that reason, the NPK formulations for various crops have also been introduced. Among micronutrients, field scale deficiencies of economic significance prevail in case of zinc, boron, and iron.

    All the provinces show negative nitrogen balance, although in Punjab the deficit is declining. Over the decade, negative phosphorus balances did not change significantly in Punjab but worsened in the other three provinces. In 1985-86, the level of deficit was highest in Punjab. However, in 1995-96 they were all fairly similar. Potash balances deteriorated over the decade.

    All the above environmental issues are creating risks for sustained agricultural growth. According to a conservative estimate, the impact of land degradation and biodiversity loss on productivity and public health add up to three per cent of the GDP per year. It could be higher if toxic waste disposal, biodiversity, river and coastal resource depletion, were taken into account.

    A high priority is needed to cope with land degradation problem whose neglect the country cannot afford.

    Courtesy: The DAWN

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