Salinization

Introduction

Salinization will be evaluated by referring to the causes, humans as contributors, and the effect of vulnerability and consequences in order to get a better idea of what the phenomenon of salinization entails.

Salinization causes


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Salinity is a significant environmental contaminant. As Cañedo-Argüelles et al. (2013) note, both “primary (accumulation of salts originating from natural sources) and secondary salinization (which refer to anthropogenic increases in salinity and which is further amplified by climate change)” are responsible for this phenomena.

 

Extensive land-use changes in dryland regions occur, causing run-off salinities to increase as salt is mobilized from subsurface waters. Secondary salinization is caused by irrigation. Natural lakes’ salinities in drylands accelerate as water is diverted from inflows for irrigation. Deforestation leads to salinization. Mining activity is responsible for salts that enter rivers. Rising saline groundwater tables cause the salinization of some fresh waters. In the cold regions of the world stream salinization is the result of the use of salts as de-icing agents for roads (Williams et al., 2000; Löfgren, 2001; Ruth, 2003; Cañedo-Argüelles et al. 2013). Clearing of natural vegetation is another source.
 

Coal and salt mining, soda production factories, sewage and industrial effluents, and increases in river salinities may result from the construction of impoundments are also sources of salinization. (Williams 2001; Cañedo-Argüelles et al. 2013). Salinity intrusion can be caused by sea level rise (SLR) and extreme events such as cyclones. Natural salinity of rivers is complex including, “weathering of the catchment; sea spray; small amounts of salts dissolved in rainwater as a consequence of evaporation of seawater (Cañedo-Argüelles et al. 2013).
 

Salinization causes leading to other impacts

Dryland salinity causes soil erosion. The removal of indigenous plants and the clearing of forests lead to soil erosion, and amplify the occurrence of more salts present in the soil. Salinity can be ascribed to prolonged wetness and where there is limited surface cover. This will lead to soils to erode. Cyclone and storm surges induced by climate change force saline water into agricultural lands along the coast, which damages crops not only in the year the cyclone hits, but for several years afterwards (Rabbani et al. 2013). The risk of flooding occurs when shallow water tables occur as soils don’t have the capacity to adequately absorb rainfall, which ultimately leads to higher run-off rates. Terrestrial biodiversity is also negatively impacted as it’s destroyed at an unprecedented rate, causing loss of biodiversity in salt-affected areas. Food shortages will be prevalent and would then ultimately lead to famine.

Spatial and temporal scale

Spatial
Salinity and its severity is greatly felt in dryland countries, and semi-arid and arid regions. Salinization occur in arid and cold regions. In the arid and semi-arid regions of the world where crop production consumes large quantities of water, irrigation and rising of groundwater tables are the main causes of secondary salinization In the cold regions of the world stream salinization is the result of the use of salts as de-icing agents for roads. It is significant in parts of central and South America, south-western North America, the Middle East and central Asia, and parts of Australia. Coastal communities are experiencing saline intrusion caused by extreme events. The salinization of freshwater lakes is most obvious and significant in dryland regions but is not confined to them (Cañedo-Argüelles et al. 2013; Williams 2001).

Temporal

Salts can be stored in soils, sub-soils and groundwater because of aridity previously experienced and then released after a long period and occurs at different time scales. Irrigation leads to mobilising large fossil salt storage, dating from another saline geographical history in the soil. Cyclone and storm surges induced by climate change force saline water into agricultural lands along the coast, which damages crops not only in the year the cyclone hits, but for several years afterwards.

Future changes will lead to further salinization. Climate change is likely to increase river salinity in some regions e.g. a decrease in the amount of precipitation. The Australian Dryland Salinity Assessment (NLWRA, 2000)(as cited in Cañedo-Argüelles et al. 2013), predicted that 3.1 million ha of land will be affected by salt by the year 2050 and up to 20,000km of streams could be significantly salt affected over the next 20 years.
 

Humans as contributors

Salinization can be natural or human-induced. Many inland waters are becoming more saline from human activities. Change is being brought about by secondary or anthropogenic salinization. In this process, catchment changes and other anthropogenic disturbances to hydrological cycles increase salt loads to water-bodies: fresh waters become saline and saline waters become even more saline (Rabbani et al. 2013; Williams 2001).

Anthropogenic salinization is distinct from natural or primary salinization which is responsible for the development of natural salt lakes. Primary salinization involves the accumulation in closed basins of salts from rainwater and leached from terrestrial sources at rates unaffected by human activities. Natural salt lakes have been the focus of most limnologic studies of saline waters (Williams 2001).

Increasing energy demands are likely to increase mining activity, e.g. coal consumption for electricity is expected to increase 42% from 2008 to 2030 (US Department of Energy, 2008). Therefore, the future predictions clearly indicate that river salinization will globally increase (i.e. more streams will be impacted and the salt stress will increase in already degraded streams) (Cañedo-Argüelles et al. 2013).
 

Poverty, low-level resilience, and lack of alternative livelihoods, together with climate-induced hazards, are responsible for huge losses. The proportion of salinity-free farmland has gone down over the past 20 years, from more than 60% to nil. Almost all saline-free and low-salinity farmland has turned into medium- or high-salinity farmland, which has a severe impact on agricultural productivity. Salinity intrusion is the main cause of declining rice production (Rabbani et al. 2013).

Climate change, including salinity intrusion caused by extreme events (e.g., cyclone and storm surge) and slow-onset events (e.g., SLR) are leading to negative impacts on almost every economic sector, including agriculture, livelihood activities, food security and public health. A future cyclone with a higher level of storm surge could cause saline intrusion further into the landmass, thus threatening the whole coastal region and its 33 million people. Poorer households will experience significantly greater loss and damage as a result (Rabbani et al. 2013).
 

The extreme poor are disproportionately affected by salinity as a percentage of their income, by comparison to non-poor households. About one-third of people living on the coast will be badly affected. This is mainly because most of the coastal population depends on rice cultivation for their livelihoods and food security. Poor farmers are severely affected by salinity intrusion in rice fields (Rabbani et al. 2013).
 

Households are bearing the burden of loss and damage in rice farming, and the costs of repair and reconstruction of damaged infrastructure and local facilities. Loss of productivity due to illness caused by food shortages would push these poorer groups into even greater poverty. Increasingly, people are moving from the coast, mainly because of loss of livelihood opportunities. This internal migration (rural-urban, coastal-central) will intensify as sea levels continue to rise, as extreme weather events become more frequent, and if adaptation options remain inadequate (Rabbani et al. 2013).
 

By 1980, between 80 and 110 million ha of irrigated land (34–47% of all irrigated land) had been effected by salinization to some degree (FAO 1990). The impacts of anthropogenic salinization are far-reaching, increasing, deleterious, and largely irreparable. Environmental, social, and economic costs are high. In some countries, anthropogenic salinization represents the most important threat to water resources (Williams 2001). Economic losses include the loss or a diminished value of water supplies for domestic, agricultural, and other needs.
 

Conclusion

The relative importance of salt lakes is now rapidly and significantly increasing. Management responses are of several sorts. Cessation of vegetation clearance, restriction of dryland agriculture, and tree-planting will mitigate further salinization. Integrated catchment management is the key practice and needs to be emphasized more than the management of salinized waters (Williams 2001).

References:

Cañedo Argüelles, M., B.J. Kefford, C. Piscart, N. Prat, R.B. Schäfer and C.-J. Schulz (2013).

'Salinization of rivers: an urgent ecological issue'. Environmental Pollution, Volume 173, pp157–167.
 

Rabbani, G., Rahman, A., and Mainuddin, K. 2013. Salinity-induced loss and damage to farming households in coastal Bangladesh. International Journal of Global Warming, Volume 5, pp 400.
 

Middleton, N. 2008. A Global Casino: An introduction to Environmental Issues. 4th Edition. London: Hodder Education.
 

Williams, W.D. 2001. Anthropogenic salinization of inland waters. Hydrobiologia, Volume 466, pp 329-337.