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Land and food
At the turn of the century, most countries (except Australia and New Zealand) were agriculturally-based, practising traditional subsistence farming, including shifting cultivation and nomadic livestock grazing. As the region's population increased, the need for greater food production put increasing pressure on land resources. The area of cropland, which stood at about 210 million ha in 1900, expanded during 1980-95 from 426 to 453 million ha, largely at the expense of forest cover which decreased by 42.6 million ha (8.3 per cent) over the same period.
Agricultural activities have often suffered from and caused environmental degradation. Bringing marginal land into production is a case in point. In Japan and the Republic of Korea, for example, urban and industrial developments on flat coastal areas have encroached on arable land and led to increasing cultivation of forested hill slopes. In Southeast Asia the introduction of the cash economy has induced some hill tribes to convert unsuitable upland areas to intensive commercial cropping. Elsewhere, particularly in Malaysia and Indonesia, rural people who relied on traditional shifting cultivation have been forced to move to marginal lands and, as a result of declining productivity, are having to adopt shorter fallow periods. By comparison, in the 1970s and early 1980s, New Zealand sheep farmers facing declining export returns responded to government subsidies by clearing patches of steep marginal forest land to boost production (Roper 1993, New Zealand Ministry for the Environment 1997). The results of these actions included degradation of watersheds through accelerated erosion, and increased sedimentation and flooding downstream.
In Southeast Asia, land conversion was intensified by increased commercial logging and the introduction of commercial crops (Kummer 1993, Uhlig 1984). For instance, arable land increased five-fold in Malaysia during 1900-50 to accommodate rubber and oil palm plantations (ADB 1994). Agricultural land use in Southeast Asia has expanded only slightly from 16.8 per cent of total land area in 1975 to 19.6 per cent in 1992 (ADB 1995).
About 50 per cent of land cover in Australia has been changed by complete clearing, thinning of vegetation, overgrazing, changed fire regimes and other habitat modifications. In New Zealand, large areas of forest had been cleared and virtually all grazeable land converted to pasture by 1920 to provide wool, meat and dairy exports. Today, around 50 per cent of land in both countries is used for grazing (Commonwealth of Australia 1996, New Zealand Ministry for the Environment 1997).
In East Asia, recent trends have been different. Rapid economic growth after World War II caused a dramatic increase in the conversion of natural and agricultural areas to urban and industrial infrastructures, particularly in Japan and the Republic of Korea. In China, the extent of arable land also decreased - between 1957 and 1990 by an area equal to all the cropland in France, Germany, Denmark and the Netherlands combined (UNESCAP/ADB 1995) - but this was largely due to land degradation. Mongolia is unique in the sub-region with 75 per cent of its total land area occupied by nomadic livestock herds and an overgrazing problem.
Overall there is less land per person in the Asia-Pacific region today than in other parts of the world, and population density is highest in South Asia. In 1995, whilst Australia had most cropland per capita (2.66 ha) in the world, much of the region, particularly in South and East Asia, had well below the world average of 0.24 ha. At least 10 major countries in the region have less than 0.10 ha and, as the graph above shows, so do two sub-regions: Southeast Asia (0.09 ha) and Northwest Pacific and East Asia (0.07 ha).
Maintaining, let alone improving, the situation is becoming increasingly difficult as populations continue to expand and agricultural land is lost to urban, industrial and transport infrastructure, particularly in coastal areas. Attempts to compensate by expanding agricultural production into other areas, as in previous decades, are constrained by the decreasing availability of suitable land and widespread land degradation.
The increasing scarcity of agricultural land has been moderated by dramatic improvements in agricultural yields with the development of high-yielding crop varieties, irrigation systems and increased agrochemical inputs. For example, grain yield in China nearly quadrupled between 1952 (1 300 kg/ha) and 1996 (4 600 kg/ha). Similarly grain production per capita increased from 300 kg per year in 1952 to around 400 kg per year in 1996 (State Statistical Bureau, various years) and the country is currently self-sufficient in this commodity. Between 1980 and 1990, food production in Southeast Asia grew faster than anywhere in the world (UNCTAD 1994). Over the past decade, food production continued to increase throughout the region but has not matched the growth rate of the previous decades. The limiting factor to producing more food in the future will be freshwater supplies, especially in populous and arid areas. In Southeast Asia, there is already little potential for additional large-scale water development schemes.
Southeast Asia, Australia and New Zealand are all net exporters of agricultural commodities. Australia feeds the equivalent of about an extra 50 million people with cereals (WRI, UNEP and UNDP 1994). However, the region as a whole is a net food importer, and food security is a high priority in most countries, particularly in East and South Asia (UNESCAP/ADB 1995).
The region will rely increasingly on imported food. By 2010, Asia's share of world cereal imports is estimated to rise to about 42 per cent from its current level of 33 per cent (ADB 1997), and this may put pressure on world food balances and affect world food prices. In South Asia, structural adjustment programmes, including trade liberalization and the removal of subsidies from forest products and some food and cash crops, will encourage intensive production and increased exports (Dutta and Rao 1996). This pattern of growth in agribusiness is likely to place an increasing strain on rural production resources.
The combination of rapid urban and industrial growth, extensive deforestation and unsustainable agriculture, including inadequate soil conservation, cultivation of steep slopes and overgrazing, has had a devastating impact on land resources. According to GLASOD, of the world's 1 900 million ha of land affected by soil degradation during the past 45 years, the largest area (around 550 million ha) is in the Asia-Pacific region (UNEP/ISRIC 1991). For Asia this constitutes about 20 per cent of total vegetated land. Dry parts of the region are particularly vulnerable, and it is estimated that 1 320 million people (39 per cent of the region's population) live in areas prone to drought and desertification (UNEP 1997). The more recent Assessment of Soil Degradation in South and South-East Asia (ASSOD 1997, see map) found that agricultural production is substantially reduced by degradation in dry areas. Nearly 180 million ha in China, including 90 per cent of China's extensive grasslands (SEPA 1998), 110 million ha in India and 62 million ha in Pakistan are degraded, representing 56, 57 and 86 per cent respectively of susceptible drylands (UNEP 1997).
Soil erosion has reduced agricultural potential in many countries. In India, for instance, as much as 27 per cent of the soil has been affected by severe erosion (ADB 1997), water being one of the principal causes of the removal of nutrient-rich topsoil, particularly in the Himalayas. In the Islamic Republic of Iran, 45 per cent of agricultural land is affected by light to moderate water erosion (FAO, UNDP and UNEP 1994). Wind erosion is also extensive and severe, affecting about 25 million ha in India and Pakistan, particularly the drybelt stretching from Central Iran to the Thar desert, and another 75 million ha in China (UNEP 1997). Woods (1983), in assessing the extent and severity of Australia's land degradation in 1977, estimated that about 38 per cent of agricultural lands required treatment for wind and/or water erosion. More recent national-scale information on erosion is currently being prepared.
Irrigated agriculture has degraded existing arable lands and resulted in vast expanses of salinized and waterlogged soils. The Asia-Pacific region is responsible for around 75 per cent of all human-induced salinization in arid, semi-arid and dry sub-humid areas - the susceptible drylands - of the world (UNEP 1997). In the mid-1980s, Pakistan, India and China could alone account for about 50 per cent (30 million ha) of the world's irrigated land damaged by salinization (Postel 1989). In Pakistan, salt build-up in the soil is known to reduce crop yields by 30 per cent (Worldwatch Institute 1997). Estimates of secondary salinity (dryland and irrigated) in Australia vary from three to nine million hectares (SCARM 1998). This has reduced productivity and sometimes increased erosion in these areas (Commonwealth of Australia 1996). Not all water-related problems are associated with irrigation, though. In the Mekong Basin, natural leaching of rock salt into soils and saltwater intrusion in the delta area have degraded some of the most productive agricultural areas (MRC/UNEP 1997a).
Excessive agrochemical inputs in parts of the region are causing further degradation and soil pollution. In Australia, for example, some 30 million ha of soils within the higher rainfall, improved pasture and cropping areas have been acidified, and have a pHwater of less than 5.5 (SCARM 1998). Acidification can lead to toxic soils, poorer water and nutrient uptake by plants, and thus reduced yields (SCARM 1998). Japan and the Republic of Korea are now cutting back on the use of agrochemicals. At the same time, maintenance of soil fertility is a crucial issue. In the Mekong Basin, soil productivity is expected to continue its decline with the use of increasingly intensive agricultural practices (MRC/UNEP 1997).
Urbanization and industrial development, including the construction of dams and mining, have continued to contribute to land degradation in the region. For example, mineral exploitation has already degraded some 2 million ha of land in China and continues to affect 40 000 ha more each year. The long-term impacts of nuclear weapons' testing and the hazardous and toxic materials left behind after military activities have been particular concerns for the South Pacific nations. In addition, some of these countries are regularly exposed to tropical cyclones which inflict damage on infrastructure and crops as well as hindering crop growth due to residual salt and the loss of topsoil (SPREP 1993).
With roughly 60 per cent of the world's population depending upon only one-third of the world's land area, the region is hard put to provide the basic needs of its expanding population. The major challenge is to optimize land use for competing needs.
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