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Bio-Physical, Socio-Economic and Environmental Impacts of Salt-affected Soils
Africa: Ghana, Kenya,
Effects on production
Impact on the Environment
Most studies of long-term experiments provide information only about biophysical impacts at the site of the experiment. There are also off-site environmental impacts of salinity development. These may be at least as important as those on-site. Chemical effects contribute because nutrients are leached from the soil during leaching processes of salt-affected soils and contaminate water supplies. Biological effects because of the loss of organic matter, which weaken the strength of soil aggregates, increase the loss of nutrients in run-off, and increase carbon dioxide and methane released to the atmosphere. Nutrient losses by leaching are most often observed where nitrogen fertilizers are being used injudiciously, and where organic manures are concentrated and the effluent arising is allowed to reach streams or rivers.
Where irrigation systems are established it will be important that proper attention is given to the inclusion of adequate drainage systems with methods to dispose of the saline drainage waters such that salinization does not become an environmental hazard.
The washing of nutrients and organic matter, and of nutrient rich topsoils, into streams and rivers is a serious cause of eutrophication. The nutrients and organic matter cause a proliferation of water borne organisms which use oxygen in the water and deplete it, at the expense of fish. Until now there have been few studies in which a comprehensive attempt has been made to quantify fully the off-site effects of salt-affected soil development on environment.
Impacts of Salt-Affected Soils on Production, Socio-Economic Conditions and Environment in Selected Members of the Network
Countries with FAO Collaborative Projects:
Ghana: The unfortunate situation for the communities not to generate enough agricultural produce due to the salty nature of their lands has adversely affected the people in their daily lives. The subsistence farming activities result in poor yields and the communities depend on food supply from other areas outside the communities. Most of the farms are less than one acre and are not properly maintained. The poor farm yields do not encourage the farmers to invest meaningfully, which results in land degradation and which further compound the land problems. The only meaningful vocation of the people for their household income is fishing in the sea, lagoons and the Volta River, using dugout wooden canoes.
The situation of the communities has resulted in low family income causing school drop-outs and health care problems.
The poor nature of the vegetation has resulted in its over exploitation as the communities harvest tree, shrubs and mangroves for household fuel.
The youth, due to the poor living conditions in salt-affected areas, migrate to the cities for better living conditions and work.
Kenya: Soils characterized by high salinity or sodicity in Kenya are harmful to crops through the high osmotic pressure of the soil solution which reduces the availability of water to the crops. Strongly saline soils have little vegetation cover and are subsequently susceptible to water erosion. Whereas, excess exchangeable sodium and high pH strongly influence the soil physical properties. The soil becomes more dispersed and less permeable to air and water causing dense impermeable crusts that greatly reduces seedling germination and water penetration. The reduced infiltration of water enhances erosion. When sodicity occurs in the deeper subsoil, wetting of the soil leads to structural collapse and subsequent caving in. This leads to the formation of tunnels which upon widening form deep and wide gullies. Sodicity also strongly influences the availability and transformation of essential plant nutrients restricting plant growth. Salinization in many cases has led to abandonment of the irrigated lands. The Kimorigo and Kamleza irrigation schemes in Taveta sub-district, Coast Province, for example, have been out of operation since 1996, due to salinity problems although some drainage systems have been installed. Part of the Kamleza scheme used to grow rice, now the loss in productivity has led to economic loss for the country through loss in crop production. Increase in crop production cost due to increased use of fertilizers and changing tillage methods, increases production costs and energy required for ploughing. More investment from the Government is required for soil rehabilitation.
Nigeria: The irrigated cropped lands in the semi-arid, northern Guinea and Sudan savannas (the highest concentration of irrigation projects in Nigeria) have been degraded due to salt accumulation in the soils (Hadejia, Kano and Sokoto-Rim valleys and Tungan Tudu and Kalmalo lake projects in the northwest, as well as Yau and Abadan irrigation schemes in the northeast). At the moment, these areas are experiencing rapid decline and poor management and uncontrolled environmental pollution that may threaten the agricultural potential of the country. The quality of the soils and water in those locations have been deteriorating with serious effects on crop yields. Technologies and resources available to farmers for abatement have been meagre, particularly in the old projects consequently resulting in total abandonment of the projects. The impact of the involvement of research institutes in finding solutions to the problem has not been felt. Due to the severity of salinity development in these areas and plant nutrient exhaustion, the average yield per unit land area is extremely low, less than 1.2 ton/ha for cereals. As a result, the total produce of most farmers is not even enough to cover their annual consumption. Because of these situations, the economic condition of the larger mass of the population in affected areas has been gradually affected, leading to poverty and famine.
Tanzania: Salt-affected soils are regarded as problem soils in Tanzania but very little has been done in terms of their management. This is perhaps because most of these soils have been found in close proximity to normal soils. Therefore, farmers have had some choice as to where they wished to cultivate. However, in view of the increased population and change in land tenure it is inevitable that some "unlucky" farmers will have to cultivate these soils intensively. Agricultural yields in most of the salt-affected soils have been low. For instance, in the irrigation scheme of Kileo, farmers could harvest up to 3.5 tons of maize per ha in the non-saline non-sodic soils. In the salt-affected soils, however, yields can be as low as 1.4 ton/ha. A similar trend was observed for beans. This situation is familiar in many areas affected by this problem. Farmers completely abandoned another irrigation scheme in Kirya, when levels of sodicity in the area became too high for them to harvest any appreciable yields from maize or beans. In the sugar estate called TPC in Moshi, northern Tanzania, nearly half the 6 000 ha of the estate are too sodic and saline for any sugar cane production. The estate of TPC falls in the arid zone at the foot of Mount Kilimanjaro. This zone is hot and arid with as little rain as 700 mm per annum. When irrigation water evaporates it brings with it salts which are deposited on the surface soils and hence the observed trend.
Notwithstanding the negative effects of salt-affected soils, such areas have provided many people in Tanzania with a livelihood. Salt mining is one activity directly associated with saline soils. Salt mining employs many people along the coast regions bordering the Indian Ocean, as well in many upcountry regions where such soils have sufficient amount of salts for harvesting. Livestock keepers frequently graze their livestock on the salt- affected soils where agricultural crops are not grown. The soils in Lower Moshi, under the Kilimanjaro Agricultural Development Programme, though saline and sodic are used for paddy production, hence the need to screen for salt-tolerant crops as the strategy to utilize these soils.
Bangladesh: Biophysical elements such as soil, vegetation and animals have been greatly affected by salinity. Many soils became unproductive, poultry and livestock populations in the coastal region have been reduced due to a decrease in grazing grounds. The greatest damage to the environment and socio-economic conditions of the local populace have been inflicted by unregulated shrimp enterprises. About 25 million of the total 125 million people of Bangladesh are seriously affected by soil and water salinity in the coastal belt.
The adverse effect of increasing salinity on the environment due to indiscriminate shrimp cultivation can be gauged from a case study in the coastal district of Satkhira where intensive shrimp farming is practiced by influential entrepreneurs. Shrimp farming started in Satkhira in the 1980s within areas protected by coastal embankments. Shrimp is grown in strongly saline water brought in through illegally dug channels across the embankments. Out of the 170 000 ha of agricultural land in the Satkhira district, almost 61 000 ha is already under shrimp cultivation presently. The fast expansion of shrimp ghers (gher is the local term for the shrimp pond) has severely affected the natural vegetation, human and livestock populations. The once green and lively southern part of the Satkhira district now has taken on the look of a "salt desert". The natural vegetation has almost vanished, planted fruit trees in hundreds of villages have died away. At least 2 million cattle died during the last 15 years due to a drastic shrinkage of the grazing grounds. Drinking water sources of the rural population have become polluted with saline waters causing diarrhea and other gastrointestinal diseases which affected 0.8 million human beings over the last 15 years. Thousands of hectares of agricultural land (mostly rice lands) have been abandoned due to saline seepage from the shrimp ghers rendering 0.2 million farmers jobless. Many farmers have been compelled to sell away their lands at nominal prices, the number of landless farmers having increased in the process. According to the gher owners, only 2 laborers are needed for a 10 ha gher, whereas rice cultivation in a 10 ha farm could employ at least 25 agricultural laborers. Thus, for every 100 ha of land brought under shrimp cultivation, 230 agricultural laborers became jobless. While the individual gher owner may have enjoyed windfall profits, the damage done to the environment and the human populace would run into the billions in financial terms. In addition, shrimp cultivation has resulted in undesirable social conflicts as political influence and muscle power are often used to establish and maintain the ghers.
In case of crop agriculture, soil salinity is the most important factor in farmers' decision making process. Usually 30-50 percent yield losses occur depending on the level of soil salinity. The cropped areas and production relative to the total land areas are lower in the saline region than in the non-saline region. Because of variations in the level of soil salinity and availability of water from rainfall, the cropping patterns are distinctly different in the eastern region (mild to moderate soil salinity, high rainfall) from those in the western region (relatively strong soil salinity, low rainfall); while two crops (Aus-T. Aman-Fallow) or even three crops (Aus-T. Aman-Rabi) at some places are common in the former, the dominant cropping pattern is Fallow-T. Aman-Fallow in the latter, the fallowing being due to high salinity throughout the year except in the wet season. Due to the unavailability of salt-tolerant HYV crops the farmers grow mostly local varieties for which the average rice yield in the coastal districts is much less than that in the other districts.
Salinization also causes environmental and ecological problems. Although impacts of salinization on ecological environment show differences in patterns and extent, the common character is that it leads to lower environmental quality and damage of natural resources directly or indirectly. Some impacts already exist and others show long term hazards and will appear in the future, including impacts of salinization on soil properties and land resources, impacts on vegetation and climate, on environment of water resources, on tourism resources and on living beings.
Salinization has potential hazards to sustainable agricultural development as follows: a) salinization causes reduction of reserve land resources; b) amelioration of salt-affected soils, especially solonetz and solonchak in arid zones is restricted by high investment rate required c) salinity problems influence utilization of water resources for agriculture; d) salinization reduces benefits of water conservancy projects.
Pakistan: Besides reduced crop yields, desertification and land going out of production, the impact on local population due to salinization has been observed to be poor living conditions, health problems, crumbling mud and brick houses, reduced life expectancy in females, and difficulties in transportation and communication.
Indonesia: As the lands with relatively fertile soils have mostly been utilized, agricultural activities have been extended to coastal salt-affected soils. Crop productivity in coastal saline tidal lands can only be made by appropriate management practices which need Government investments. Development of salt-affected soils have resulted in declines in yield of both cash and food crops in Indonesia. Salinity development and its attendant off-site effects of rural poverty, food insecurity, high cost of food production and rural-urban migration are now widespread socio-economic impacts felt in coastal salt-affected regions in Indonesia.
The Philippines: Farmers located in six coastal municipalities of Camarines Sur, Philippines (most salt-affected region in the Philippines) were interviewed covering the wet and dry season cropping. On average, the farmers were 45 years old and had been farming for 17 years, and were well aware of salinity intrusion into their farms. The farms averaged 2.2 ha. About 63 percent of the farms are owned, 32 percent are shared, and 5 percent are leased. All of the farms were planted to high yielding rice varieties, applied with varying rates of inorganic fertilizers. Except for very few farms, all were planted twice a year but those with moderately to severely salt-affected soils hardly produced yields. Because of limited rain water supply during dry season, farmers provide supplemental water from pumps but found to be salty due to seawater intrusion and the effect of seepage from adjacent salt-affected areas. Farmers have continued to grow rice, as they have no alternative crops. A few, however, had expressed the desire to try watermelon as water is limited during the dry season.
The farms that were not affected by salinity produced 3 ton/ha/season. On the other hand, farms affected with varying levels of salinity showed a clear decline in the rice yield. Even in slightly saline farms yields were 40 percent lower during the wet season than farms free from salinity. Yields in the dry season were dramatically lower than the wet season because of salt water intrusion. The cost and return analysis revealed that rice cultivation may be only economical in slightly salt-affected farms during the wet season as indicated by the net return. Planting during the dry season exposed the farmers to high risks.
Financial uncertainty, particularly during the dry season, has motivated farmers to seek other non- and off-farm sources of income to support their families consisting on average of 6 members. They utilized their productive time for other economic activities since rice farming in their salt- affected farms was not of economical benefit. A few farmers knew that there are specific salt-tolerant varieties but claimed that these are not readily available in their locality.
The farmers, who depend on irrigation, are fully aware of the need to prevent saltwater intrusion into the irrigation canals, but they do not have the technical programme to control. On the other hand, those depend on rainwater utilized water in the creeks but are affected by saltwater intrusion.
Thailand: Environment and socio-economic impacts of salt-affected soils are of great concern. Although inappropriate land use such as salt making and brackish water shrimp farming gives farmers high profits, they can cause serious impacts on adjacent areas and the environment. This includes reduced capacity of the land to provide long term economic production, increased investment cost and problem of soil and water management.
In the Northeast region, inland saline soils are constantly expanding. Inappropriate land use results in soil salinization from the movement of saline water, and reduction of arable land and forest areas. A socio-economic study carried out at Nakornratchasima province of the Northeast region showed that 31 percent of salt-affected areas have gone out of cultivation. A systematic sampling of 427 farmers from 31 villages was conducted to find out the farmers’ opinion on the prevention and improvement of salt-affected lands. Most of the areas are owned by large landholders (>3.2 ha). Seventy percent of these large landholders agreed to have their land reforested to prevent soil salinization while fifty percent of the small landholders (<1.6 ha) refused. The reasons were lack of expertise, excessively saline water, inadequate manpower and lack of capital.
The major problem created by expansion of shrimp farms is increased pollution of the environment. Soil salinization by shrimp culture was reported to severely affect 30 750 ha in Nakornsrithammarat and Songkla provinces . In the central plain, its impact is being scattered on adjacent shrimp ponds. Because of very strong salinity, the farmers have been forced to leave their cultivated lands. Moreover, the discharge of harmful by-products from shrimp ponds like excess feeds, fertilizers, chemicals and antibiotics have affected the environment in many ways. The effluent produced by shrimp farms has been reported to carry water discharge, total organic carbon, total nitrogen and sludge (wet weight) of 67 000, 89.6, 5.1 and 134 ton/ha/crop, respectively.
The Government reflected the deep concern of the country with regard to the conflict that has exploded between rice and shrimp farmers in arable fresh water areas, and the extent of salinity problems faced by the small farmers, with negative effect on their income and yearly agricultural production loss, and with the expected negative impact on food security of the country. Therefore, on 7 July 1999, the Prime Minister (using Section 9 of the National Environment Quality act BE 2335 introduced in 1992 by the National Environmental Board) announced the Government’s decision to ban shrimp cultivation in fresh water zones within 120 days. He also announced Section 10 of the same Act to reclaim the land after this period.
Hungary: Salinity/alkalinity are among the most significant limiting factors of soil fertility in Hungary. There are only a few countries in the world, and none in Europe, where the ratio of salt-affected soils is as high as that of Hungary. More than 95 percent of the existing salt-affected soils are situated in the valley of the Danube and the Tisza which is significantly reflected by the reduction of 30 percent of the total agricultural production of the region, with clear effects on the income and the economic conditions of local farmers. Even larger effects on the environment are observed by the deterioration of groundwater conditions: shallow or easily rapidly rising watertable, high salt concentration and unfavourable ion composition threatening larger areas as potential salt-affected soils.
b) Romania: The areas with salt-affected soils are characterized by a lower level of socio-economic sub-structure development and living standards as compared with the surrounding areas. The biophysical and socio-economic impacts of the occurrence of soil salinization is reflected by low bio-diversity of the affected areas and very low income of local farmers. As a result of the fast transition from the former socio-economically centralized system to the present free market economy, attention of the Government for the reclamation of salt-affected soils is very little. One can notice severe problems with such soils. For instance, on an area of 100 000 ha of such salt-affected soils in Arad, Buzau and Braila counties, the absence of concern for the application of adequate measures led to significant decrease in crop yields, so that, between 1989 and 1998, this was 74 percent for barley (from 5 757 kg/ha in 1989 to 1 480 kg/ha in 1998), 59 percent for winter wheat (from 5 340 kg/ha in 1989 to 2 210 kg/ha in 1998), 50 percent for sugar beet (from 30 000 kg/ha in 1989 to 15 000 kg/ha in 1998), 45 percent for alfalfa (green matter) ( from 31 697 kg/ha in 1989 to 11 000 kg/ha in 1998) and 100 per cent for soybean.
Turkey: Most of the areas under irrigation do not have enough drainage systems. Çukurova plain was one of the most productive plains in Turkey. After a couple of decades irrigation without proper drainage, salinization problems have been observed. Harran Plain (one of the most important irrigation areas in the Southeast Anatolian Project) also has potential salinity risk at the level of 30 percent because of the insufficient drainage systems. This caused reduction in food production of 30 percent in these regions with significant effects on the income of local agricultural farmers.
Half of the irrigation systems in Turkey are controlled by government agencies. The rest are controlled by the private sector. In the latter sector water use efficiency is very low.
Because of the economic problems, especially in rural areas, and also lack of education, some of the forested lands and pastures were altered to agricultural lands. These degradation processes caused more runoff from highlands to lowlands. This situation brings about change of water-salt balance in low lands causing salinity development and lower agricultural production.
The land tenure system with high profits, without taking precautions related to management practices, plays an important role in increasing salinization and gradual decline in soil productivity. The number of land holdings, smaller than 10 ha, consist of 81.8 percent of the total land holdings in Turkey. These holdings cover 42 percent of the cultivated areas. Average land holding size is around 4.38 ha. This situation is one of the indirect factors causing secondary salinization. Lack of land consolidation is one of the major problems related to possible reclamation and management of salt-affected soils in Turkey and, therefore, continuing decline in soil productivity. It is estimated that the arable land demand is currently about 2.4 persons/ha, which will increase to 5 persons/ha in the near future. Therefore, there is an urgent need to successfully manage salt-affected lands and water resources in Turkey.
Argentina: Fruit horticulture covers almost 50 percent of the irrigated crops, sugar cane occupies close to 15 percent and alfalfa and other forage crops cover 11 percent of the producing irrigated areas. Topographic irregularities and irrigation practices generate salt-affected soils in all the agro-ecological regions of the country. Irrigated soils are mainly located in the alluvial and/or colluvial river valleys of the arid and semi-arid regions of the country. Mendoza province presents the largest irrigated area with 443 500 ha (26.9 percent of the total irrigated) followed by the provinces of Buenos Aires and Santiago del Estero with 176 500 ha (10.7 percent) and 163 900 ha (9.9 percent), respectively. San Juan province shows the highest proportion (79 percent) of salt-affected soils of irrigated area. The problem is widespread in Mendoza (near 50 percent), Santiago del Estero (54 percent) and other provinces have a very high proportion of salt-affected irrigated soils. In the mentioned areas crop production decreased in the last few years from 20 to 30 percent, particularly of the mentioned fruit, sugar cane and forage crops, with severe site-effect in several cases on the living standards and incomes of local farmers.
The construction of poorly-planned irrigation works for crop production caused man-made salt-affected soils, especially as a consequence of limited and incomplete drainage networks. These problems have been detected in the Mendoza-San Juan area, the provinces of Santiago del Estero and Río Negro, and the Lower Valley of the Colorado River in the province of Buenos Aires.
The need for food requires more attention being given by the Government to proper management and rehabilitation such salt-affected soils and the careful use of poor-quality irrigation waters.
Brazil: The salinization problem has to be faced as a serious one in the country, particularly in the Northeast semi-arid part, e.g. in the Sao Francisco River Basin, because of the great risk for farmers cultivating their irrigated land without proper management practices. In these regions, the crop production has been affected with clear reflection on the agricultural production of local farmers, pushing some of them to abandon their land and looking for other sources of income to cover the needs of their families.
Mexico: A poll among local farmers was carried out in the Rio Fuerte ID (1998). It was to analyse the effect of soil salinity on local agricultural production, from the farmers' point of view. Farmers believe soil salinity is solely inherent to the soil and they do not know why shallow watertables occur. The poll registered that 94 percent of those interviewed had some problem related to soil salinity and poorly drained soils in their fields.
Egypt: Scarcity of arable land and decrease in per capita arable land area are attributed to many factors including population growth, soil contamination and development of salt-affected soils. Productivity and agricultural sustainability can be decreased by 9 percent and if the present trend in salinity development processes continue yield reduction may reach 16 percent by 2020. This will cause reduction in return from capital investment and labour inputs. Lower income of the small-scale farmers from agriculture will force them to work on land of others or migrate to cities or other countries. The potential impacts of salt-affected soil on water quality include the enrichment of water with nutrients, sediments, pesticides, salts, etc., influencing human health and creating ecological risks; lowering the suitability of water for irrigation and the navigability of rives and increasing the cost of flood control and dams. In many cases, wastewater is used after minimal treatment even untreated water is used directly, threatening public health and exposing agricultural works and crop consumers to pathogens and toxic minerals. Potential hazards caused by re-use of drainage water are the contamination of crops leading to decrease in crop production and infection to humans and animals. The toxicity of drainage water used for irrigation is higher than the allowed toxicity limit for plants (pesticides and fertilizer drained from the soil to the drainage system).
Iran: It is to be noted that farmers in salt-affected areas are usually less fortunate in terms of economical capabilities. Generally, the worst salinity situations in Iran are present where farmers are relatively poor and face economic difficulties. Therefore, they are unable, even reluctant, to employ new technologies without financial help from the government. Some of them think that nothing can improve the yield under their conditions, therefore, they do not care much about their crop. This negative attitude aggravates the impacts of salinity. It is, therefore, important that credit policies be supported by the pertinent government agencies to help farmers overcome the problems associated with the harsh environment and make greater contributions to the agricultural development of the country.
The future life of these people is at stake and highly dependent on what happens to their soil. Therefore, any sustainable development programme for the rural areas in Iran should seriously pay attention to the problems caused by the salinity of soil and water resources.
Among the major obstacles which prevent the achievements of high yields in Iran is the salinity of soil and water. It is estimated that in areas where salinity is present, average yields losses due to this problem may be as high as 50 percent. The problem of salt-affected soils poses one of the most serious threats to food production and sustainability of natural resources in the country.
Syria: The salinity problem in Syria is considered to be the major constraint to agricultural production. It has led to lowered productivity compared to world standards. A substantial portion of the irrigated lands are affected with different levels of salinization. Waterlogging is the second major problem that affects soil productivity in Syria. The Euphrates basin projects are the main agricultural projects in Syria, where salinity is affecting 30 percent of these lands. In the lower Euphrates basin in Deir Zor province, salinity has resulted in 44 000 ha going out of agricultural production with salinity reaching 16 ds/m, in addition to 30 400 ha being highly affected with too low productivity. The soils of the lower Euphrates basin (120 000 ha) are totally saline. Salinity is spread out in the Central Euphrates Basin (28.500 ha). Saline lands in the Upper Euphrates Basin (Raqqa province and Maskane plains) are estimated as 15 000 ha, out of 64 000 ha irrigated lands. Due to the problems created by shortage of water and cultivable land resources, population pressure and development of salt-affected soils, particularly in irrigated areas, self sufficiency in food remains a difficult objective in Syria. Production constraints in irrigated salt-affected soils are all faced by the farmers in using such land which resulted in lowering of their income from agriculture production and even abandoning many farms. The number of abandoned farms has been increasing rapidly with severe effect on national agriculture production.
Tunisia: Salt-affected soils are found in all the territory, but more so in the central and southern parts of the country in the arid and semi-arid regions such as in the Mejerdha valley. The immediate impact of salinity development in these areas is either a decline in crop yield or an increase in the level of the inputs needed to maintain or improve yields which cannot be afforded by local small-farmers. The resultant low income and food security in affected areas results in movement of high number of people from rural areas to urban centres seeking employment or additional sources of income.
Australia: In contrast to many other natural resource degradation problems which are important in Australia, salinity has more serious off-site costs on urban populations, infrastructure and environment. Awareness of these wider effects and the larger costs has, through public education programmes, changed the issues from a purely "farmer’s problem" to a problem shared by the whole community. Salinity problems are coming to be ranked as the very highest priority natural resource management issue in Australia.
Just as there is great variation in estimates of the areas of land affected by salinity, there is similar variation in estimates of the economic impacts. Estimates are difficult due to the wide range of off-site costs of salinity.
The true cost of damage to vegetation including highly valued environmental sites, wetlands, fauna and flora diversity is quite high. It is predicted that in the state of Victoria, in a "do nothing" scenario, there will be a significant decline in the quality of 44 000 ha of state and internationally significant wetlands, in excess of 100 species of flora and 100 species of fauna which will be seriously threatened over the next 15 to 20 years.
Off-site water quality effects are due to effects on water supply and water treatment for urban uses, effects of shallow saline watertables on telephone cables, gas pipelines, roads and bridges and any industries that use water for example for processing products or for cooling purposes. Urban effects show through damage to parks and gardens, domestic hot water services, motor vehicle radiators, damage to building foundations. In the southwest WA cropping and grazing zone, salinity of streams in agricultural areas has been rising – in 1985, 43 percent of runoff was suitable for human purposes. By 1996, 52 percent of this runoff was no longer suitable for human purposes. Capital costs of providing alternative water supplies due to this salinization of surface water has been calculated at US$143 million.
In Victoria, the impact of deterioration of surface water quality to urban and industrial users is estimated at $18 million /year.
Declining incomes in rural areas affected by salinity also have significant social and economic effects throughout rural communities.
To offset some of the costs of salinity control, better land management and reduction of soil erosion and nutrient runoff from land (with reduced eutrophication of streams) should be implemented.
Canada: Root-zone salinity causes plants to grow slowly and produce less. Studies also show effects on the final height of wheat plants at harvest as well as their yield of grain. Average height declined by increasing salinity, but more gradually than the declination in relative yield. A figure of 2.3 million ha, based on federal and provincial soil survey data, has been estimated for severely saline soils where non-irrigated crops yield would be lowered by 25 percent or more. The 1994 wheat crop was grown on 10.5 million ha across Western Canada and produced 22 million tons of grain valued on average at US$ 214/ton. As the effects of slight to moderate salinity reduced yields by an average of 12 percent, the loss of revenue, equalled about US$ 113. If Canada’s research and development cost to combat soil salinity approaches US$ 1 million annually, and with these efforts, the 12 percent is reduced even to 8 percent, the benefit-cost-ratio of this investment would equal 38 to 1 annually
Colombia: Salinity areas are located in the north coast between Panama and Venezuela borders, and in the Andean Valley, particularly in magnesium affected areas. In these areas the soil become more dispersed and less permeable to air and water causing dense impermeable crusts that greatly reduce seedling germination and water penetration. The reduced infiltration of water enhances the erosion effects in these areas. The quality of the soils and water in these locations have been deteriorating with serious effects on crop yields. Technologies and resources available to farmers for abatement have been meagre, consequently resulting in total abandonment of their lands. Due to the severity of the problem developed in these areas and plant nutrient exhaustion, the average yield per unit land area is extremely low, less than 1.2 ton/ha for cereals. As a result, the total produce of most farmers is not even enough to cover their annual consumption. Because of this situation, the economic condition of the larger mass of the population in affected areas has gradually deteriorated, leading to poverty.
Salinity in India is a major issue affecting the sustainability of irrigated as well as non-irrigated areas particularly in the states of Rajasthan, Gujarat, Haryana, Uttar Pradesh, West Bengal and Orissa. There are both on-site and off site-effects on infrastructure, environment, public health and others means of livelihood. Economic losses due to salinity in the state of Gujarat alone have been estimated at US $ 225 millions.
Italy: Irrigation with saline-sodic waters is practised in Sicily in many areas where these waters represent the only source of available water, causing the development of secondary salinization and sodication in large areas, groundwater salinization and consequent reduction in crop yield and income of local farmers.
Spain: Salt-affected soils show harsh conditions for normal plant growth due to a) plant osmotic stress caused by high ionic strength of soil solution, b) specific ion toxicity, 3) unfavourable physical conditions and combinations of these. Biota living in these soils is reduced and crops are affected in variable degrees, reducing yield with increasing salinity. Finally the production is so low that farmers abandon their lands. In many irrigated areas in Spain and in the Comunidad Valenciana in particular such as in Torreblanca, Castellon, the high productive potential of their soils is seriously threatened by salinity increasing.
The salinity occurrence, combined with severe drought in the southern part of the Comunidad in the past years, has led not only to the crop loss but even to some tree loss. The crops cultivated in salt-affected soils are melons, tomato, cotton, artichokes, asparagus, palm trees (in order of increasing salinity), and rice in flooded salt-affected soils. Decrease in yield is quite noticeable particularly under mismanagement (e.g. lack of adequate drainage system). In non-cultivated salt-affected areas that include some Natural Parks, Reeds, Typha dominguensis, Juncus and halophytes are extensive. Halophytes are used for livestock feeding.
Sudan: In salt-affected soils located in the low rainfall regions in the northern Sudan along the River Nile, south Khartoum, north Gezira, the Managil Scheme and the White Nile Schemes north of Kosti, the production potential of the soils have deteriorated with serious effects on crop yields. Technologies and resources available to farmers are very limited, consequently resulting in total abandonment of their lands. Due to the severity of the problem developed in some areas, the average yield per unit land is extremely low, about 40 percent of normal soils. As a result, the total produce of most farmers is not even enough to cover their annual consumption. Because of these situations, the economic condition of the larger mass of the population in affected areas has been gradually affected, leading to poverty, famine or migration of high numbers of people from rural areas to urban centres seeking employment or addition sources of income.
Uzbekistan: The disappearance of the Aral Sea, the fourth greatest lake on earth is well known to the world. Since the1960s, when the full-scale development of cotton production through irrigated agriculture in Central Asia was started, the irrigated area in Central Asia increased from 4.5 million ha to 7 million ha. The population in the region rose from 14 million to 50 million. The water requirements for the economy rose from 60 to 120 cubic km per year, of which 90 percent for irrigation. The excessive use of water by irrigation led to the gradually drying up of the Aral Sea and to the desertification of its deltas. Its waters changed from brackish (10g salt/l) to hyper-saline (40g salt/l), making it an unsuitable habitat for most of its often endemic species. During the last 20 years, the lake level sank gradually by 17 meters. The people in the immediate vicinity of the sea and the rivers deltas suffered catastrophic socio-economic consequences including: complete loss of the economical importance of the lake (fishing and navigation disappeared); degradation of the lake and delta ecosystems and loss of biodiversity; elimination of large agricultural areas in the deltas due to insufficient fresh water and increasing salinization of the soils; increased difficulties of producing good quality drinking water. These led to a drastic decline in employment possibilities in the vicinity of the lake and a dramatic decline in the health situation.
There is a direct relationship between yield of agricultural crops and salinization. Crop capacity losses due to soil salinity in cotton yield reaches about 18 – 26 percent to 43 percent in severe cases in about 28 percent of the 4.3 million ha irrigated lands, that is more than US$ 200 million per year. The same tendency is seen also for food crops (cereals, etc). Increasing soil and water salinity is a serious threat for the rural population. According to the World Bank estimation, up to 2 billions US$ (about 5 percent GNP of Central Asia) are lost because of soil salinity.
Basically two major bottlenecks threaten the productivity and sustainability of irrigated agriculture: constrained farmers' incentives to improve production and productivity and the deterioration of the production base. The lack of incentives and funds for proper operation and maintenance (0&M) and rehabilitation of irrigation and drainage (I&D) infrastructure has led to serious deterioration of the irrigation and drainage systems (off-farm and on-farm), weaknesses in canal operations and management at all layers within the irrigation system, huge water losses, widespread and severe water and soil salinization and declining crop yields. It is estimated that the deterioration/losses of the resource base for agricultural production is costing the country US$ 1 000 million annually.
Strengthening of geological cycle led to worsening of river water quality and pollution of agro-landscape, mainly in the low stream of the Amu-Darya and Syr-Darya rivers, particularly serious problem in the low stream of the Amu-Darya, where the river is the main source of potable water supply and irrigated agriculture. Hundreds of drainage lakes have appeared in the desert filled with salty runoff. A large volume of salt enters drainage lakes or else drainage water returned to the rivers. About 60 million tons of salt is added annually to the rivers in this way, polluting river water. For example, Yuzhny Collector brings 13 million tons of salts every year into the Amu Darya river.
The resulting consequences for biodiversity are gloomy: from the original 178 animal species that lived in the deltas, only 38 species remain. The remaining fish population has dwindled. Game, birds and other wildlife, including species of ducks, swans, pelicans, cormorants, muskrats, and deer are becoming rarer.
Through the disappearance of most of the once vast areas of soil-retaining black saxaul woods, tugay forests and reeds and the consequent desertification, many of the original habitats have disappeared.
The socio-economic consequence of the ecological crisis of the development of salt-affected areas in Uzbekistan is expressed in loss of large part of biodiversity, poor vegetations, fishery, stock breeding and pasture stock breeding formation of salt and dust storms, worsening of domestic - potable water quality, changes of climate and population health. The index for sickness prevalence for both adults and children in Karakalpakstan can be considered as very high compared to other regions. This is especially the case of Muynak, Shumanai and Karauzak districts of North Karakalpakstan, with a dramatic increase of tuberculosis, nervous system diseases, anemia, rheumatism, bronchitis, arthritis, etc.
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