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Agricultural Systems and Food Production Issues involved in attempts to intensify production e.g. – replace slash and burn in Indonesia – the Green Revolution – small-scale self-help schemes Issues involved in extending cultivation in LEDCs e.g. – irrigating oases – draining swamplands – fish farming Issues involved in the intensification and extension of agriculture Increases in agricultural production can be achieved in two ways, by: ◦ increasing the land under cultivation through, for example, irrigation, or extending farming onto marginal land, or ◦ increasing the yield per hectare when scientific advance allows such changes to occur. Issues involved in the intensification and extension of agriculture Since the end of World War 2, there have been huge advances in agricultural production. This was mainly due to: ◦ Increases in the use of mechanisation, ◦ Increased use of agro-chemicals - fertilisers, pesticides and herbicides, ◦ Greater and more effective use of irrigation methods, and ◦ The introduction of high-yielding varieties of seeds (HYVs). Issues involved in the intensification and extension of agriculture The result has been a substantial increase in global food production over the last 60 years. However, intensification can alter ecosystems to such an extent that serious local, regional and global consequences result: ◦ local – increased soil erosion, lower soil fertility, reduced biodiversity (removal of hedgerows and monoculture) ◦ regional – pollution of groundwater, eutrophication of rivers and lakes ◦ global – impacts on global atmospheric conditions (climate change) Soil Degradation ISSUES INVOLVED IN THE INTENSIFICATION AND EXTENSION OF AGRICULTURE Soil Degradation Land degradation is the temporary or permanent lowering of the productive capacity of land. It thus covers the various forms of soil degradation, adverse human impacts on water resources, deforestation, and lowering of the productive capacity of rangelands. Soil degradation is a global process. It involves both the physical loss (erosion) and the reduction in quality of topsoil associated with nutrient decline and contamination. It has a significant impact on agriculture and also has implications for the urban environment, pollution and flooding. The loss of the upper soil horizons containing organic matter and nutrients as well as the thinning of soil profiles reduces crop yields on degraded soils. Soil degradation can cancel out gains from improved crop yields. Degradation of soil and land in already marginally productive land is a significant issue for many LICs, particularly in northern Africa, the Sahara region and parts of Asia, including China. Many of these regions have fragile ecosystems where any human interventions can lead to serious degradation. Effects of Land Degradation Land degradation has both on-site and offsite effects: ◦ On-site effects are the lowering of the productive capacity of the land, causing either reduced outputs (crop yields, livestock yields) or the need for increased inputs. ◦ Off-site effects of water erosion occur through changes in the water regime, including decline in river water quality, and sedimentation of river beds and reservoirs. The main off-site effect of wind erosion is over-blowing, or sand deposition. Types of Soil Degradation This includes: ◦ soil erosion by water and wind, ◦ deterioration in soil physical, chemical and biological properties, ◦ waterlogging, and ◦ the build-up of toxicities, particularly salts, in the soil. ◦ Since soil productivity is intimately connected with water availability, lowering of the groundwater table is also noted. Definitions Desertification is land degradation in arid, semi-arid and dry sub-humid areas resulting from adverse human impact. Water erosion covers all forms of soil erosion by water, including sheet and rill erosion and gullying. Wind erosion refers to loss of soil by wind, occurring primarily in dry regions. Waterlogging is the lowering in land productivity through the rise in groundwater close to the soil surface. Also included under this heading is the severe form, termed ponding, where the water table rises above the surface. ◦ Waterlogging is linked with salinisation, both being brought about by incorrect irrigation management. Lowering of the water table is brought about through tubewell pumping of groundwater for irrigation exceeding the natural recharge capacity. ◦ This occurs in areas of non-saline ('sweet') groundwater. Definitions Soil fertility decline is used as short term to refer to what is more precisely described as deterioration in soil physical, chemical and biological properties. Whilst decline in fertility is indeed a major effect of erosion, the term is used here of cover effects of processes other than erosion. The main processes involved are: ◦ lowering of soil organic master, with associated decline in soil biological activity; ◦ degradation of soil physical properties (structure, aeration, water holding capacity), as brought about by reduced organic master; ◦ adverse changes in soil nutrient resources, including reduction in availability of the major nutrients (nitrogen, phosphorus, potassium), onset of micronutrient deficiencies, and development of nutrient imbalances. ◦ buildup of toxicities, primarily acidification through incorrect fertilizer use. Statistics on Soil Degradation Globally, it is estimated that 2 billion hectares of soil resources have been degraded. This is equivalent to about 15% of the Earth’s land area. Such a scale of soil degradation has resulted in the loss of 15% of world agricultural supply in the last 50 years. For three centuries ending in 2000, topsoil had been lost at the rate of 300 million tonnes a year. Between 1950 and 2000, topsoil was lost at the much higher rate of 760 million tonnes a year. During the last 40 years, nearly one-third of the world’s cropland has been abandoned because of soil erosion and degradation. Statistics on Soil Degradation In Sub-Saharan Africa, nearly 2.6 million km² of cropland has shown a ‘consistent significant decline’ according to a March 2008 report by a consortium of agricultural institutions. ◦ Some scientists consider this to be a ‘slow-motion disaster’. In the UK, 2.2 million tonnes of topsoil is eroded annually and over 17% of arable land shows signs of erosion. It takes natural processes about 500 years to replace 25 mm of topsoil lost to erosion. The minimum soil depth for agricultural production is 150 mm. From this perspective, therefore, productive fertile soil can be considered a nonrenewable, endangered ecosystem. GLOBAL ASSESSMENT OF HUMAN-INDUCED SOIL DEGRADATION (GLASOD) The Global Assessment of Human-induced Soil Degradation (GLASOD) is the only global survey of soil degradation to have been undertaken. The generalised map of the findings of this survey shows that substantial parts of all continents have been affected by various types of soil degradation. The GLASOD calculation is that damage has occurred on 15% of the world’s total land area – 13% light and moderate, with 2% severe and very severe Degradation results from erosion, nutrient decline, salinization and physical compaction. These frequently lead to reductions in yields. Land conservation and rehabilitation are essential parts of sustainable agricultural development. While severely degraded soil is found in most regions of the world, the negative economic impact of degraded soil may be most severe in the countries most dependent on agriculture for their incomes. Causes of Soil Degradation A major cause of soil degradation is heavy fertiliser use Research has shown that the heavy and sustained use of artificial fertiliser can result in serious soil degradation. In this profile of an artificially fertilised soil, the ability of the soil to infiltrate water has been compromised by the breakdown of soil aggregates to fine particles that have sealed the surface. Pore spaces have been filled up by the fine soil material from the broken crumbs. This can result in ponding in surface depressions, followed by soil erosion. This profile shows a much healthier soil treated with organic fertiliser. Effects of Soil Degradation A major effect of soil degradation is climate change. The International Forum of Soils, Society and Global Change in September 2007 referred to ‘the massive degradation of land and soil around the world which is contributing to climate change and threatening food security’. The Forum noted that: ◦ At least a quarter of the excess carbon dioxide in the atmosphere has come from changes in land use, such as deforestation, in the last century. ◦ Without the cover of vegetation, land becomes more reflective. It also loses fertility and the capacity to support vegetation and agricultural crops. ◦ The Intergovernmental Panel on Climate Change should develop a special report on the link between land degradation and climate change. By addressing soils and protecting the land cover and vegetation, it is possible to obtain high value in terms of mitigating climate change. ◦ A better understanding of the capacity for carbon sequestration in soil is needed. Increased Greenhouse Gas Emissions ISSUES INVOLVED IN THE INTENSIFICATION AND EXTENSION OF AGRICULTURE Increased Greenhouse Gas Emissions It has been estimated that food production and consumption accounts for up to twice as many greenhouse emissions as driving vehicles. The graph on the following slide shows US data published in the New Scientist: ◦ The average US household’s footprint for food consumption is 8.1 tonnes of carbon dioxide equivalent, compared with 4.4 tonnes from driving. A comparison of greenhouse gas emissions from food and vehicle use in the USA Household greenhouse gas emissions from food account for almost twice those produced by vehicle use. Most of this comes from the food production process itself, rather than from food miles, as is often believed. Loss of Biodiversity ISSUES INVOLVED IN THE INTENSIFICATION AND EXTENSION OF AGRICULTURE Loss of Biodiversity Mechanisation has resulted in farmers in the UK having a strong incentive to remove centuries-old hedgerows. By 1990 over half of UK hedgerows had been removed and with them the habitats and biodiversity that contributed to the make-up of the traditional countryside. Agro-industrialisation led to the increased use of monoculture. This also contributed to hedgerow removal as well as the loss of biodiversity, increased pests and habitat loss. Deforestation and Soil Erosion ISSUES INVOLVED IN THE INTENSIFICATION AND EXTENSION OF AGRICULTURE Deforestation and Soil Erosion This is a major cause of land degradation, especially soil erosion, as well as climate change. Soil erosion usually occurs as a result of the removal of the protective vegetation cover. In tropical forest areas removal (extension of agriculture in LEDCs) can exacerbate erosion when the surface is exposed to torrential tropical rain. In marginal areas (intensification of agriculture) overgrazing can result in the scant vegetation being stripped off, followed by the soil drying out and being removed by wind erosion and surface runoff. Deforestation and Soil Erosion Friable soil types are likely to be more at risk. ◦ For example, in China, the loess soils in the Yellow River Basin are lost at the rate of 100 tonnes per hectare per year. ◦ Soil erosion is a major problem in China. The Yangtze River Basin loses 2.24 billion tonnes of soil per year, which damages 67,000 ha of farmland. The effects of soil erosion mean that almost 100 million will lose the land they live on within 35 years if erosion continues at the current rate. Salinisation ISSUES INVOLVED IN THE INTENSIFICATION AND EXTENSION OF AGRICULTURE Salinisation - Definition This refers to all types of soil degradation brought about by the increase of salts in the soil. This covers both salinisation in its strict sense, the buildup of free salts; and codification (also called alkalization), the development of dominance of the exchange complex by sodium. As human-induced processes, these occur mainly through incorrect planning and management of irrigation schemes. Also covered is saline intrusion, the incursion of sea water into coastal soils arising from overabstraction of groundwater. Salinisation - Causes This is a serious problem in arid and semi-arid areas and affects 7% of the world’s land area. It occurs when transpiration from plants and evaporation exceed the amount of incoming precipitation in regions where the water-table is close to the surface. The presence of salts is harmful to many plants and, although the cause is natural, it can be made worse by man’s intensification of agriculture – irrigation without proper drainage can raise the water table locally and by capillary action salty water is drawn to the surface. Salinisation - Effects Salinisation is a problem in dry areas like South Australia with 3700km² affected. This is expected to increase by 60% by 2050 at currents rates. It is expected to cost the state around US$37.3 million per year in lost agricultural profit, and is expected to taint more than 20% of groundwater to levels above those safe for human consumption. Desertification ISSUES INVOLVED IN THE INTENSIFICATION AND EXTENSION OF AGRICULTURE Desertification - Causes Desertification is land degradation in arid, semi-arid and sub-humid areas. It refers to the effects human activity and climatic processes may have on a landscape reducing it to desert-like conditions. This often results from overgrazing of semi-arid pastures (intensification) and its results are often irreversible. Desertification - Effects The process takes place in drylands and some 15% of these (about 9 million km²) may already be degraded. Over 250 million people in more than 100 countries are directly affected and are more at risk. In Africa 66% of the total land area is classified as arid or semi arid and therefore, at risk. The Green Revolution ISSUES INVOLVED IN THE INTENSIFICATION AND EXTENSION OF AGRICULTURE What was the Green Revolution? This refers to a series of research and development and technology transfer initiatives occurring between the 1940s and 1960s that increased agricultural production, especially in the developing world. Much of the global increase in food production in the last 50 years can be attributed to the Green Revolution, which took agro-industrialisation to LICs on a large scale. The process involved: ◦ ◦ ◦ ◦ the development of high-yielding varieties of cereal grains, supported by an expansion of irrigation infrastructure, modernisation of management techniques, and the distribution of hybridised seeds, synthetic fertilisers and pesticides to farmers. History of the Green Revolution It was first trialled in Mexico and in 1961, with India on the brink of famine, the International Rice Research Institute (IRRI) selected the Punjab region for trials of a new variety of rice called IR8. This HYV produced more grains of rice per plant when grown with certain fertilisers and irrigation. ◦ 5 tonnes per ha without fertiliser and 10 tonnes under optimal conditions. Positive Effects of the Green Revolution In the 1960s rice yields in India were about 2 tonnes per ha. By the mid-1990s they had risen to 6 tonnes per ha. India became one of the world’s most successful rice producers and a major rice exporter, shipping nearly 5.4 million tonnes in 2013. Today, India is the world’s largest exporter of rice – shipping 10.23 million tonnes in 2015, 30% of the world’s total. In terms of production, the Green Revolution was a turning point for Indian agriculture, which had virtually reached stagnation. The high-yielding variety seed programme (HVP) introduced new hybrid varieties of five cereals: wheat, rice, maize, sorghum and millet. ◦ All were drought-resistant with the exception of rice, ◦ were very responsive to the application of fertilisers and ◦ had a shorter growing season than the traditional varieties they replaced. Negative Effects of the Green Revolution Serious criticisms have been made, many linked to the impact on the environment: ◦ High inputs of fertiliser and pesticide have been required to optimise production – this is costly in both economic and environmental terms. ◦ The problems of salinisation and waterlogged soils have increased, along with the expansion of the irrigated area, leading to the abandonment of significant areas of land. ◦ High chemical inputs have had a considerable negative effect on biodiversity. ◦ People have suffered ill-health due to contaminated water and other forms of agricultural pollution. Negative Effects of the Green Revolution Areas like Punjab are now witnessing the serious health consequences of intensive farming using chemicals and pesticides. A study has underlined that there is a direct relationship between the indiscriminate use of agro-chemicals and increased incidence of cancer in this region. In 2009, a study indicated that 50 Punjabi villages had widespread incidences of chemical, radiation and biological toxicity. An environmental activist, Vandana Shiva has written about these impacts in Punjab, claiming that the heavy use of and reliance on agro-chemical inputs and monocultures has also resulted in: ◦ water scarcity ◦ vulnerability to pests, ◦ incidents of violent conflict and social marginalisation. Negative Effects of the Green Revolution There have also environmental issues: been numerous ◦ In India’s Punjab, yield growth has flattened since the mid-1990s. ◦ Over-irrigation has resulted in a steep fall in the water table, now tapped by 1.3 million tube wells. ◦ Since the beginning of the Green Revolution in Asia, the amount of land under irrigation has tripled. Negative Effects of the Green Revolution In the early 1990s, nutritionists noticed that even in countries where average food intake had risen, incapacitating diseases associated with mineral and vitamin deficiencies remained commonplace and in some instances had actually increased. The problem is that the HYVs introduced during the Green Revolution are usually low in minerals and vitamins. Because the monocultures of new crops have displaced the local fruits, vegetables and legumes that traditionally supplied important vitamins and minerals, the diet of many people in LICs is now extremely low in zinc, iron, vitamin A and some other micronutrients. Evaluation The Green Revolution has been a major factor in enabling global food supply to keep pace with population growth (as per Esther Boserup). However, with growing concerns about a new food crisis, new technological advances may well be required to improve the global food-security situation.