Biosalinity Awareness Project

...understanding the impact of salinization and implications for future agriculture

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Global Perspective
Our freshwater ancestors have confronted many of the same environmental constraints that we face today.  Either they adapted, physiologically perhaps through innovation, or they relocated, invading new lands and mining fresh resources when the soil and water became too salty.  However, many species are now approaching a time when there will no longer be such a choice.  As our deserts grow and seas rise, we will ultimately be forced to cope with and adjust to growing biosalinity and freshwater scarcity.

As with global environmental changes (i.e. desertification and biodiversity loss), it is important to understand how evolutionary processes and, more importantly, human activities contribute to the earth’s diminished capacity for sustaining essential vegetative cover.  Our success or failure in coping with these changes, given that they are not immediate and catastrophic, will ultimately depend on how we manage our precious resources and shift priorities from short-term wealth creation to long-term sustainable use. 

Biosalinity is a dynamic state often described in terms of geochemical (soil and water) and biological (plants) responses to increasing salinization in our environment.  If population growth persists unabated and our natural resources continue to be depleted or degraded at an alarming rate, biosalinity will eventually become a significant constraint limiting our ability to meet the future demand for basic necessities, such as food, water, fuel, and shelter. 

Biosaline agriculture is defined as crop production on saline soils where, in most cases, seawater or brackish/saline groundwater are the only sources of irrigation water.  It is most concerned with the development and propagation of sustainable vegetative alternatives for salt-affected lands that are deemed unsuitable for conventional farming, including: (1) more effective soil/water management and improved crop salt-tolerance, and (2) the domestication of halophytes for commercial and/or environmental cultivation.  The ultimate goal of this discipline is to help provide food and water security for future generations by conserving and rehabilitating scarce resources, substituting them for more abundant saline ones in newly emerging agro-ecosystems. 

Halophytes (salt-tolerant plants) are now being considered as an attractive option for future cash crops, offering a number of distinct conservative and restorative advantages.  On the irrigated farms and pasturelands of the interior, brackish and saline water could be more effectively utilized to produce food and other renewable commodities; along the coast, the abundance of seawater could be harnessed for growing these new crop varieties.

Introduction

The loss of arable lands due to salt accumulation is estimated by some at 10 million hectares per year, with even more experiencing significant yield reductions at the margins.  According to the United States Salinity Laboratory (USSL), UN Food and Agriculture Organization (FAO), and others monitoring salinity, approximately one billion of the 13 billion hectares worldwide are now salt-affected: roughly 30% of all irrigated lands, more than 50% in some countries, are considered economically unproductive.  Biosalinity has imposed the most serious limitations on agricultural productivity in the arid and semi-arid regions, which now comprise roughly half the world’s land mass.  Salt-affected soils and water are distributed throughout the world and no continent is free from the problems and constraints associated with increased salinity. 

Current pressures on freshwater supplies are due, in large part, to poor management practices, loss of essential watersheds, and intensive large-scale irrigation.  Over 70% of the available freshwater, up to 90% in arid zones, is now being used for crop production; this represents a mere 0.01% of the earth’s total water supply (97% of which is seawater).  It is also estimated that 55% of this water is wasted in its distribution and application as a result of evaporation, seepage, and runoff; thus, approximately 35% of this most precious resource is being squandered in modern industrial agriculture.  The UNESCO World Water Assessment Program forecasts a 40% increase in global freshwater demand and a corresponding 35% decrease in per capita supply by the year 2025.  Geographic, climatic, and economic conditions tend to exacerbate the disproportionate allocation and use of freshwater: many countries now harvest and consume freshwater at a rate greater than its replenishment.

Each year, millions of people are affected by water and crop famines while millions of hectares are lost to salinity.  Robust population growth, perhaps 10 billion by 2050, and the increasing demand for basic necessities will induce scarcities on a scale which humans have never before experienced.  Biosalinity has already demonstrated its potential for reducing fertility and dramatically altering our landscape, more so as our remaining forests are cleared for cultivation and greater numbers of people are forced to rely on increasingly marginalized lands for their sustenance.  Unfortunately, the perception of urgency still remains highly eco-centric and localized as most species are unable or unwilling to look beyond the boundaries of their immediate existence.

Americas

Approximately 200 million hectares of land in the Americas are affected by salinity, primarily in the southwestern US and Mexico.  Elevated salt concentrations have affected as much as half of the irrigated lands in the San Joaquin Valley, Sonoran Desert, Colorado River and Rio Grande basins.  Saline and sodic soils are becoming increasingly problematic in the grasslands of the US, Canada, and South America while saline coastal habitats and inland deserts are expanding throughout the Americas.

Europe 

Salinity and desertification are having the largest impact on the productive farmlands of southern and eastern Europe with Spain, Portugal, Greece, and Italy experiencing prolonged drought conditions and unprecedented saltwater intrusion into freshwater aquifers; while the desert and salt are claiming vast tracts of cultivable land in the countries surrounding the Black Sea.  In Spain, more than 20% of the total land is now considered desert or seriously degraded and non-productive.  The European Union is actively involved in finding solutions to salinity problems both at home and abroad, playing a leading role in the UN Convention to Combat Desertification.

Middle East

In the Middle East, irrigation practices, high rates of evaporation, and the expansion of sabkhat (saltflats) have contributed significantly to increased groundwater and soil salinity with over 120 million hectares affected.  Irrigated lands of the Euphrates River delta (Syria and Iraq) are experiencing some of the most serious constraints.  In Egypt, along the Nile, approximately one million hectares of arable land are salt-affected while accumulations in the Jordan River basin have adversely impacted agricultural production in Syria, Jordan, and Israel.  In Iran, it is estimated that up to 25 million hectares are considered as non-productive due to excessive salinity.

Africa

Approximately 80 million hectares in Africa are deemed to be saline, sodic or saline-sodic.  Most affected are the West African lands of the Sahel being claimed by the desert as well as the semi-arid grasslands and woodlands in the sub-Saharan regions that have been grazed, stripped, and degraded for fuel and/or cash crop plantations.  Many productive coastal areas and irrigated rice farms are now subject to mounting salinity from seawater intrusions, high rates of evapotranspiration, and a lack of appropriate resource management.

Asia

A total of 7 million hectares (more than 20% of India’s arable land) is considered to be salt-affected, principally in the inland deserts of Rajasthan, the coastal areas of Gujarat, and the sprawling Indo-Gangetic plains from the Punjab to West Bengal.  Pakistan is experiencing the most acute crisis with up to 10 million hectares affected in the relatively small country; some observers estimate that between 5-10 hectares are lost to salinity and waterlogging every hour, mainly on the coasts and irrigated farms of the Indus River basin.  The destruction of important inland watersheds and subsequent erosion, coupled with climatic changes and rising sea levels, have contributed to the current vulnerability in the coastal deltas and tidal wetland of Bangladesh, where approximately 3 million hectares are affected by salt accumulations. 

Rough estimates for China indicate that over 26 million hectares of the total land area are salt-affected including the steppes and arid lands of the northwest and northeast provinces, Inner Mongolia, and the Yellow River basin.  The damming of rivers for large-scale irrigation schemes in the Aral Sea basin, a low-lying desert terrain, has resulted in a measurable loss of biodiversity and agricultural productivity in a number of Central Asian nations.

Australia

It is estimated that over 6 million hectares of Australian dryland farms are affected by varying degrees of salinity; recent projections forecast that this figure will triple by 2050, with more than 80% of these threatened lands in the western wheatbelt.  One of the major causes of recent salinization in Western Australia and the Murray-Darling River basin has been the replacement of perennial, deep-rooted vegetation with shallow-rooted, annual crops.  Currently, more than 10% of Australia’s total cultivable land is salt-affected (whereby yields are reduced by more than 50%) and studies indicate that more than 30% will be affected by 2050.  Given the magnitude of the salinity crisis and the motivation to compete in world markets, Australia will most likely be the first to adopt large-scale commercial halophyte and salt-tolerant biomass production systems.
 

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