Pict. 10.11. Eutrophization of a dead channel od the Danube (www.rdhsz.hu)

10.3.3. 10.3.3. Irrigation

Irrigated lands contribute significantly to the world agriculture output and food supply. Estimates in 1986 indicated that about half of the increase in agricultural production in the previous 35 years had come from irrigated land, about one-third of the world’s crops were grown on the one-sixth of the cropped area which was irrigated, and the irrigated land was, on average, more than twice as productive as rain-fed land (Picts. 10.12.).

Pict. 10.12. Motorized irrigation (www.idokep.hu)

The benefits of irrigation have resulted in lower food prices, higher employment and more rapid agricultural and economic development. The spread of irrigation has been a key factor behind the near tripling of global grain production since 1950. But irrigation and water resource development can also cause social and environmental problems.

Irrigated agriculture depends on supplies from surface or ground water. The environmental impact of irrigation systems depends on the nature of the water source, the quality of the water, and how water is delivered to the irrigated land. Withdrawing ground-water may cause the land to subside, aquifers to become saline, or may accelerate other types of ground-water pollution.  Withdrawing surface water implies changes to the natural hydrology of rivers and water streams, changes to water temperature, and other alterations to the natural conditions, sometimes deeply affecting the aquatic ecosystems associated with these water bodies. The operation of irrigation water supply systems can affect the environmental performance of irrigated agriculture.  Systems that deliver water continuously or in a fixed schedule are less efficient and/or limit management options available for irrigators compared to on-demand water delivery operations.  The operation and management of irrigation water delivery systems must include proper monitoring and reduction of seepage and other water losses in the system, particularly if they are a significant component of recharge of raising water tables.  The combination of low water quality supply and raising water tables will eventually lead to waterlogging and salinization, threatening the sustainability of existing irrigation systems.  Proper attention to the quality and amount of irrigation return flows is also important to identifying and mitigating possible impacts on receiving waters.

10.3.4. 10.3.4. Pesticides

Pesticides are organic and inorganic chemicals originally invented and first used effectively to better the human environment by controlling undesirable life forms such as bacteria, pests, and foraging insects. Their effectiveness, however, has caused considerable pollution. The persistent, or hard, pesticides, which are relatively inert and nondegradable by chemical or biologic activity, are also bioaccumulative; that is, they are retained within the body of the consuming organism and are concentrated with each ensuing level of the biologic food chain. Pesticide use has increased since 1950 to 2.5 million tons annually worldwide, yet crop loss from pests has remained relatively constant. The World Health Organization estimated in 1992 that 3 million pesticide poisonings occur annually, causing 220,000 deaths. Pesticides select for pesticide resistance in the pest population, leading to a condition termed the 'pesticide treadmill' in which pest resistance warrants the development of a new pesticide.

An alternative argument is that the way to 'save the environment' and prevent famine is by using pesticides and intensive high yield farming, a view exemplified by a quote heading the Center for Global Food Issues website: 'Growing more per acre leaves more land for nature'. However, critics argue that a trade-off between the environment and a need for food is not inevitable, and that pesticides simply replace good agronomic practices such as crop rotation.

10.3.5. 10.3.5. Herbicides and insecticides

Herbicides are used to kill weeds, especially on pavements and railways. They are similar to auxins and most are biodegrale by soil bacteria. However, one group derived from trinitrotoluene (2:4 D and 2:4:5 T) have the impurity dioxin, which is very toxic and causes fatality even in low concentrations. Another herbicide is Paraquat. It is highly toxic but it rapidly degrades in soil due to the action of bacteria and does not kill soil fauna.

Insecticides are used to rid farms of pests which damage crops. The insects damage not only standing crops but also stored ones and in the tropics it is reckoned that one third of the total production is lost during food storage. As with fungicides, the first insecticides used in the nineteenth century were inorganic e.g.Paris Green and other compounds of arsenic. Nicotine has also been used since the late eighteenth century.

There are now two main groups of synthetic insecticides:

1. Organochlorines include DDT, Aldrin, Dieldrin and BHC. They are cheap to produce, potent and persistent. DDT was used on a massive scale from the 1930s, with a peak of 72,000 tonnes used 1970. Then usage fell as the harmful environmental effects were realized. It was found worldwide in fish and birds and was even discovered in the snow in the Antarctic. It is only slightly soluble in water but is very soluble in the bloodstream. It affects the nervous and endocrine systems and causes the eggshells of birds to lack calcium causing them to be easily breakable. It is thought to be responsible for the decline of the numbers of birds of prey like ospreys and peregrine falcons in the 1950s - they are now recovering.

10.3.6. 10.3.6. Monocultures

The technologies allowing the shift toward monoculture were mechanization, the improvement of crop varieties, and the development of agrochemicals to fertilize crops and control weeds and pests. Government commodity policies these past several decades encouraged the acceptance and utilization of these technologies. As a result, farms today are fewer, larger, more specialized and more capital intensive. At the regional level, increases in monoculture farming meant that the whole agricultural support infrastructure (i.e. research, extension, suppliers, storage, transport, markets, etc.) has become more specialized.

10.4. Presentation

For more information on this chapter see the presentation below

Presentation

10.5. Self-checking tests

1 Explain the environmental effects of traditional farming! 2 Describe the environmental effects of factory farming!

11. 11. Environmental effects of waste production

Waste is an unavoidable by-product of most human activity.  Economic development and rising living standards in the Asian and Pacific Region have led to increases in the quantity and complexity of generated waste, whilst industrial diversification and the provision of expanded health-care facilities have added substantial quantities of industrial hazardous waste and biomedical waste into the waste stream with potentially severe environmental and human health consequences.

11.1. 11.1. Definition

Wastes are materials that are not prime products (that is products produced for the market) for which the generator has no further use in terms of his/her own purposes of production, transformation or consumption, and of which he/she wants to dispose. Wastes may be generated during the extraction of raw materials, the processing of raw materials into intermediate and final products, the consumption of final products, and other human activities. Residuals recycled or reused at the place of generation are excluded.

11.2. 11.2. Types of wastes

A clear appreciation of the quantities and characteristics of the waste being generated is a key component in the development of robust and cost-effective solid waste management strategies. Although amongst some of the more developed countries within the region the quantification and characterization of waste forms the basis for management and intervention, elsewhere little priority is given to the systematic surveying of waste arisings and the quantities, characteristics, seasonal variations and future trends of waste generation are poorly understood. Although there is a lack of comprehensive or consistent information, at the country level, some broad trends and common elements are discernible. In general, the developed countries generate much higher quantities of waste per capita compared to the developing countries of the region. However, in certain circumstances the management of even small quantities of waste is a significant challenge.

11.2.1. 11.2.1. Classification on the base of the origin

Throughout the region, the principal sources of solid waste are residential households and the agricultural, commercial, construction, industrial and institutional sectors. For the purposes of this review these sources are defined as giving rise to four major categories of waste: municipal solid waste, industrial waste, agricultural waste and hazardous waste. Each of these waste types is examined separately below.

11.2.1.1. 11.2.1.1. Municipal Solid Waste

Municipal solid waste (MSW) is generated from households, offices, hotels, shops, schools and other institutions. The major components are food waste, paper, plastic, rags, metal and glass, although demolition and construction debris is often included in collected waste, as are small quantities of hazardous waste, such as electric light bulbs, batteries, automotive parts and discarded medicines and chemicals.

Generation rates for MSW vary from city to city and from season to season and have a strong correlation with levels of economic development and activity. In countries which have a developed recycling culture, the waste stream consists mainly of intractable wastes such as plastic film, and un-recyclable packaging. At the start of the 20th century, the majority of domestic waste (53%) in the UK consisted of coal ash from open fires. In developed countries without significant recycling it predominantly includes food wastes, yard wastes, containers and product packaging, and other miscellaneousness wastes from residential, commercial, institutional, and industrial sources.

There are big differences in mounts of organic waste among cities according to the number of trees and shrubs in public places. Large and bulky waste items such as abandoned motorcars, furniture and packaging are found in the higherincome economies.

The amount of human faeces in the MSW is significant in squatter areas of many Asian and Pacific cities where “wrap and throw” sanitation is practised or bucket latrines are emptied into waste containers. The latter is common in many cities (such as Calcutta, Dhaka and Hanoi) of the region where sewerage systems are minimal.