Ministerial Conference on
Environment and Development
in Asia and the Pacific 2000
Kitakyushu, Japan 31 August - 5 September 2000
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The environmental impact of
agriculture Traditional Pacific island agricultural systems were highly sustainable. In Vanuatu, steep lands of Pentecoast and Ambae are cultivated for a variety of crops, including commercial kava plantations. These gardens have not contributed significantly to soil erosion and degradation because of their discontinuous nature amid natural vegetation, minimum tillage practices, and small size. Crops are grown without chemicals and farmers observe long fallow periods. Forest areas were traditionally an integral part of the food security system of the village and provided protection against cyclones and drought. In Tonga, shifting cultivation techniques with mixed cropping under the canopy of up to 100 associated tree species, allowed regeneration of soils, reduced pest problems, and prevented erosion for more than 3000 years (Thaman 1992). Modern commercial agriculture is the most pervasive and environmentally destructive human activity in the sub-Region. It's primary impacts are; (i) the direct removal of existing ecosystems; (ii) the reduction of biodiversity; (iii) destruction of soils; (iv) pollution of the surface and ground waters with agricultural chemicals; (v) pollution of wetlands and the marine environment with silt and agricultural chemicals; (vi) a major contributor to global warming through the loss of trees and generation of methane; and (vii) a contributor to landlessness. Agriculture is the leading cause of permanent deforestation, removal of wetlands, and other unique habitats in the Pacific islands. Habitat removal and replacement with imported "domestic" ecosystems caused serious and permanent loss of biodiversity. Sustainable traditional farming systems diminished as farmers entered the cash cropping system. Small productive mixed crop gardens with abundant trees were either burned or bulldozed to create large, treeless clearings. Tractors tilled the soil, chemical fertilisers and poisons were applied with subsidised abandon, fallow times were shortened, sometimes replaced with crop rotation, and mixed crop gardens were replaced with monoculture. Monoculture, growing a dense, single species crop, inevitably leads to outbreaks of pests and application of poisons to control the pests. In Fiji, widespread burning to clear land or remove sugar cane debris, continues to be a disaster for wildlife, and contributes to soil loss by altering soil characteristics making it more prone to erosion. On smaller islands, burning in combination with goat grazing, has devastated terrestrial ecosystems. Steep slope farming on the high islands has resulted in extremely serious soil erosion, making these areas more vulnerable to the impact of cyclones and drought. In Fiji, clear felling of forests for kava plantations reduced the forest habitat needed for yam and other wild foods that formerly were important staples during emergencies. In Samoa, prior to the taro blight, 2,400 ha of forest were being cleared a year for planting commercial fields of taro on steep slopes. Agricultural poisons, used to control pests or clear vegetation, are carried by rain runoff throughout the island ecosystems. Watts (1993) lists numerous discoveries of pesticides in soils, water supplies, marine sediments and organisms in the sub-region. In American Samoa, coastal fish species were contaminated with lead, mercury, PCBs and pesticides (Craig 1994). In Tonga, DDT, Lindane, Heptachlor, Aldrin and Endosulfan were found in a wide variety of foods, ground water, and in human tissues (IDEC 1990). In Guam, Paraquat, Lindane and 2,4,-D were detected in ground water (Morrison and Brodie 1985). Long term effects of pesticides on microbes, plankton, corals and other key elements of the island ecosystems are unknown and unstudied. Agricultural chemicals adhere to soil particles or are absorbed in organic compounds in the soil. During drought conditions these are blown off the island as dust and settle on the surface of the sea. The poisons are dissolved in the organic microlayer of the sea and become concentrated in slicks on the sea surface. The slicks are a critical habitat for most species of fish and invertebrates (including sea grasses and corals), and the concentrated poisons endanger the reproductive capacity of marine organisms (Liss and Duce 1997). |
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