Friday, August 01, 2014

Soil Erosion, Climate Change and Global Food Security: Challenges and Strategies. Part 7.

This is the seventh part of a much longer article published in the journal Science Progress, and which may be found here:

17. “Peak Water”.

Water is a resource that will begin to run short within a few decades, as is espoused in the book65 entitled "Mirage", written by Cynthia Barnett, which focuses on water-use in the United States and in Florida particularly. It is well known that to the east of the longitudinal line along the 100th meridian, rainfall is plentiful, while to the west of it the climate is relatively arid. Indeed it was once believed that farmers in the "east" would never have to worry about watering their crops, but in recent years demand for water has surged with calamitous environmental consequences. She refers to a house falling into a "sinkhole", which is a collapse in the limestone rock that underlies Florida as a consequence of its natural dissolution by underground water. These can be opened-up as a result of human activities including well-drilling and moreover the excessive pumping of groundwater. She discusses the complex politics involved in "development", and the overpopulation of that southern tip of the Florida peninsular particularly by retirees ("seniors"), thus requiring an infrastructure - including very green and hence heavily watered lawns and golf-courses etc., – to a degree that surpasses even what can be provided by the greatly abundant rainfall there. Meeting the shortfall necessitates the extraction of groundwater on a huge scale with environmental, economic, political and social consequences, including at least one death as she describes in the chapter "Water Wars". Indeed the history of water supply in the United States is wryly inscribed in the quotation (attributed to Mark Twain), "whiskey's for drinkin' and water's for fightin'.”

A central theme in the book is that water is a commodity. Often the real costs of water provision are borne by states or municipalities rather than by corporations, who cash-in on a cheap resource for which no regard is consequently imbued, nor for environmental actions such as damming rivers as mighty as the Colorado for various "aquatic" projects. Bottled "spring" water is an immensely overpriced designer toy, costing around 10,000 times as much as tap water and often with much the same analytical composition. Indeed, not all spring-water does in fact come from a spring, and is to a large degree, pumped groundwater.

While the competition over the use of arable land to grow either food or fuel crops is a well established and critical factor in making biofuels at scale, there is less awareness about the water required to irrigate the land on which the crops are to be grown. It is unequivocal that China is the new industrial nation, in an unparalleled phase of its economic and social development. This might be expected to continue for as long as the West can afford to buy its cheap goods, but in the current recession, that duration is debatable. Underpinning Chinese industrial growth, as for all industrial growth, is energy, and in recognition of peak oil, emphasis is on biofuel (and all other kinds of energy resources in China, including coal-to-liquids, CTL conversion) as products need to be transported for sale. It is aimed that by 2020, 12 million metric tons of biofuels will be produced in China. To put this into context, this is equivalent to around one fifth of the petroleum-derived fuel used in the United Kingdom annually. The fuel is to be bioethanol, fermented from corn (maize) which is a relatively water-efficient starch crop.

According to one analysis66 in order to irrigate sufficient corn to produce 12 million tonnes of bioethanol, a quantity of water equivalent of the annual discharge of the Yellow River would be required. 64% of China's arable (crop-growing) land is in the northern part of the country, and is already under pressure since the existing use of water exceeds its reserves and water-tables are falling67. We have neither sufficient land nor water to maintain the illusion that we can continue as we are, certainly not in terms of liquid transportation fuel and thus transport itself, merely by substituting declining oil and natural gas supplies by biofuels. Massive water demand should be anticipated in consequence of expanding biofuel production in other countries too. For example, in India and in the western United States, water tables are falling. As already noted, agriculture in the U.S. Midwest is maintained by draining "fossil water" from the Ogallala aquifer, which underlies eight U.S. states. Once it is used up, this supply of water cannot be replenished. It is likely that climate change and the shifting of the temperate regions to the north may impact further on the American West. In Australia, another major producer of starch crops, water supplies are also under stress. It has been reckoned19 that some 5,000─6000 km3 of water would be needed to irrigate sufficient crop to supplant the world's petroleum based fuel by ethanol generated from corn. We may compare this number with the entire supply of fresh water available on Earth of 13,500 km3 - i.e. the crop would require about half of it. Other potential fuel crops, e.g. wheat, soybeans and rapeseed, have an even greater demand for water than does corn. This is a clear warning and additional expression of the limitations of crop-based biofuels.

The quantity of water that we use in our daily lives is deceptive. For example, an average Briton is said to use 150 litres of water a day, and yet the true total rises nearer 3,400 litres per day68, once the amount of “embedded (embodied) water” (hidden water) is included, which is the water used to grow and produce various products. 65% of the water we use is for our food, and the quantities of embedded water that are used to provide some very commonplace items are staggering. For example, it takes 3,000 litres of water to produce a beefburger, and in Britain some 10 billion burgers are consumed per year, therefore necessitating the consumption of 30 trillion litres, or 30 cubic kilometers (km3) of water. A tomato has about 13 litres of water embedded in it; an apple has about 70 litres; a pint of beer about 170 litres; a glass of milk about 200 litres.

It takes 27,000 litres of water to produce one bar of chocolate, 100 litres of water are used to make one cup of coffee. It takes 4 litres of water to make one one-litre plastic bottle of water… that’s before the water is put into it. To make a cotton T-shirt needs 2,000 litres of water, 15,000 litres for either a pair of jeans, or one kilogram of steak. To make a car takes 400,000 litres68. The amount of water used to produce food and goods imported by developed countries is worsening water shortages in the developing world, and this raises moral questions, e.g. whether it is appropriate for developed (legacy) nations to import beans and flowers from water-stressed countries such as Kenya. If the world's population increases to 8 billion by 2030, 50% more food and energy will be needed, and the demand on fresh water will rise by 30%. This not only reflects the rise in population per se, but that more affluent people eat more food – particularly meat - and the consumer society is expected to expand within its number.

As a result of overpumping (extracting water faster than the natural rate of rainwater recharge) to meet food production demands, some nations have reached a state69 that has been described as “peak water”. To place our demand for water in perspective, although on average we drink around 4 litres of water daily, in various forms, to produce the food we eat requires more like 2,000 litres, and it is the latter which is struggling against available supplies. Almost half the calories we eat is provided by grain, 40% of world supply being grown on irrigated land. The world’s irrigated land area increased from around 250 million acres in 1950 to nearly 700 million acres by the year 2000. However, in the past decade, despite an increasing global population and demand for food, the area of irrigated land has increased by merely 10%, which may mean that we are approaching a maximum in the amount of water that can be provided. The process of irrigation began with the Sumerians some 6,000 years ago, who garnered river water by means of dams and reservoirs.

Gravity-fed tunnels allowed the water to flow onto fields where crops were grown. Once it was no longer possible to expand surface irrigation by this means, water was accessed by drilling boreholes into aquifers, the majority of which were refilled from rainwater. Some aquifers are not refilled, since they contain water that was laid down millions of years ago, sometimes termed “fossil water”. Thus a fossil aquifer is something like an oil well, in that once the water it contains has been withdrawn, it is not replaced, and can similarly be counted as a finite resource. Two of the most important of the latter kind, in terms of global agriculture, are the deep aquifer which lies under the North China Plain, and the Ogallala aquifer which lies under the Great Plains of the United States.

[Fig 13]

The Ogallala aquifer (Figure 13) flows for 174,000 square miles from South Dakota to the Texas panhandle65, and it is the main source of water for the collective national breadbasket, supplying as it does one third of all the groundwater used for irrigation in the entire U.S. Ogallala contains "fossil water", set in the ground from the melt of the last ice-age 10,000 years ago, and once it is used-up there is no more. Access to cheap electric pumps in the 1950's permitted farmers to draw this legacy upward at increasing rates with the result that the Ogallala has fallen by 100 feet in parts of New Mexico, Kansas, Oklahoma and Texas. It is inevitable and merely a matter of time that all wells sunk into this huge aquifer will run dry, with impacts on agriculture overall, including the vast corn crop grown to produce corn ethanol, as a replacement for those fuels currently refined from crude oil. The Aquifer Storage and Recovery (ASR) technology is given especial mention. The idea is that during wet-periods, when water is plentiful, water is pumped into gigantic underground aquifers set deep into Florida's limestone, and which can be pumped-up again during dry months. Some 36 million gallons a day are drawn from Peace River, which starts in Central Florida's Green Swamp and ends 105 miles further south in the Charlotte Harbour Estuary.

There are almost 1,700 ASR wells in the US altogether, most of them in the states of California, Nevada, Texas and Florida, and all of them particularly short of water. However, caution is urged, as the first well sunk at Peace River became seriously contaminated with arsenic, present naturally in the aquifer. Desalination is another technology often invoked as a solution to water shortages especially in near-coastal regions, even though it is very costly to set up a desalination plant in the first place, and running one requires considerable amounts of energy. Nor is the technology guaranteed: e.g. a plant at Tampa Bay built at a cost of $110 million suffered all kinds of difficulties and finally the high-tech membranes required to separate water from salt by reverse-osmosis clogged up. Groundwater pumping was actually reduced by one third in the region, without the need for desalinated water, purely through more conventional means of reservoir and surface water treatment combined with aggressive water-conservation measures65. The tapping of aquifers permitted a greater volume of water to be extracted than was possible from rivers, resulting in an artificial expansion of agriculture and the amount of food that could be grown. Rather as the situation for oil and gas, which fuel agriculture on a scale that would be impossible without them, so water from aquifers has contributed to an artificially maintained food bubble. The UN prediction70 that the global human population will reach nearly 11 billion by 2100, is tacitly underpinned by the assumption that supplies of oil and natural gas, and indeed water, will continue to grow to meet the according demand.

The three major grain producing nations, India, China and the U.S., are overpumping their aquifers, along with several other nations with large populations, e.g. Pakistan, Iran and Mexico. Saudi Arabia, Syria, Iraq and Yemen have each passed their peak in water production, with peak grain following closely behind. 1973 was the year of the first “oil shock”, in which as a show of strength to the West over its support of Israel in the Yom Kippur War, the OPEC countries in the Middle East reduced oil exports by 5%, causing the price of a barrel of oil to increase by 400%14. However, in the realisation that a counter-embargo on grain might be imposed, Saudi Arabia introduced a liberally subsidized agricultural programme underpinned by water pumped from fossil aquifers, becoming self sufficient in wheat. This situation prevailed until 2008 when the Saudis announced that they would cut their planting of wheat by 12.5%/year meaning that in 2016 production would cease.

It is planned that in 2016, food demand in this Kingdom of 30 million people will be met by importing 15 million tonnes of wheat, rice, corn and barley. Currently in the grip of civil war, Syria is becoming dependent on imported grain, since its own production has fallen by a third since the peak production year of 2001, while in Iraq production has plateaued during the past decade. Both Syria and Iraq are experiencing a diminished flow from the rivers Tigris and Euphrates, as more of the water is being taken upstream by Turkey. Thus the restrictive effect of aquifer decline on water supplies is further compounded. The water table in Yemen is falling by around 6 feet each year, meaning that one of the most rapidly growing populations in the world will be dependent on imported grain in only a few years.

Iran has 77 million people (growing by one million per year), but suffered a 10% fall in home grain production during 2007-2012, in correlation with the fall in water production, and since a quarter of its grain depended on aquifer pumping, irrigation wells started to go dry. Thus the Middle East is a singular example where the antagonistic forces of rising populations, inadequate water supplies and policies and falling grain yields are in interplay. Pakistan (182 million) and Mexico are suffering severely from water shortages and aquifer decline. Between them, China, India and the U.S. produce around half the world’s grain, although the relative reliance on irrigation as opposed to other water supplies is quite disparate. China uses irrigation to grow around 80% of its grain, using surface water mostly from the Yellow and Yangtze river systems, while India irrigates some 60% of its grain crop, mostly using groundwater. The figure is nearer 20% in the U.S., since the majority of the grain crop is rain-fed, e.g. in the Midwestern corn belt.

Overpumping has largely depleted the shallow aquifer under the North China Plain, forcing well-drillers to turn to the region's deep aquifer, which is not recharged and is thus a one-off bestowal, which is falling by 10 feet per year. In India, over 21 million irrigation wells have been drilled from which enormous volumes of underground water are being extracted. The Indian population of 1.23 billion is growing by 15% annually, and there are no restrictions on drilling for water. In North Gujarat the water table is falling by 20 feet per year. Given that three fifths of its grain is produced on irrigated land, and a relatively small proportion of the water used for this purpose comes from rivers, it is India that is the most vulnerable to overpumping, since only a minor share of its irrigation water comes from rivers69. We are witnessing a duality, where water is in many regions the principal limiting factor in how much food can be grown, not land area per se. However, soil erosion is the limiting factor in other regions, such as Mongolia and Lesotho, where it has caused a reduction in the area of productive land.

In northwest China and in the Sahelian region of Africa, two enormous dust bowls are being formed, far greater in size that that of the 1930s U.S. Midwest. These conjoined twin forces, of constraining water supplies and soil erosion, are not only militating against an expansion in global food production, but may mean that current food levels will prove non-maintainable. The reliance of modern agriculture upon a cheap and plentiful supply of crude oil - to provide fuel for farm machinery, to transport food from farms and around nations and the world, to make herbicides and pesticides – may prove the weak link, however, should that supply fail for either economic or geo-technical reasons.

18. The relentless soil-water nexus.

In a recent United Nations report71it was stressed that an increasing demand for land and water, from both urban and industrial consumers, and by the farming industry to produce livestock, crops (both for food and other purposes) and also biofuels, is likely to prove unsustainable. It is developing nations that are likely to fare worst, since typically this is where land, soil nutrients and water are most under threat. The world’s cropland grew by only 12% during the period 1961─2009, and yet 150% more food was produced on it, as a result of markedly improved crop yields. However, in many regions, the rates of growth in agricultural production have been in decline and are now just about half of the amount at the zenith of the ‘Green Revolution’, which occurred during the Second World War and on through to the late 1970s. The latter was a consequence of the application of synthetic fertilizers on the large scale, irrigation and the selection of particular strains, e.g. of rice and wheat, that could thus be brought to high yields. The report concludes that of the Earth’s land surface, one quarter is highly degraded, 8% is “moderately” degraded, 36% is “stable” while 10% is “improving”. 18% of the Earth’s land surface is bare and 2% is covered by bodies of water. Worst affected regions are along the west coast of the Americas, across the Mediterranean region of Southern Europe and North Africa, the Sahel and the Horn of Africa, and throughout Asia. Loss of soil quality, loss of biodiversity and the depletion of water resources are all highlighted, hence a quite comprehensive problem needs to be addressed.

The impact on water resources is worsened by practices of continuous cropping72, and the amount of soil-water sets a maximum to crop productivity in rain-fed, semi-arid regions. To cope with limitations in the supply of water requires that particular management practices are employed during those stages of development that are crucial determinants of the eventual yield, e.g. floral and grain development. For example, in western Kansas following a fallow time of almost one year, even though drought conditions had prevailed, a sustained output of winter wheat was obtained, in contrast to wheat that had been grown in water-depleted soil, rather than leaving it fallow. The fallow period is often used to grow oilseed crops like canola (rapeseed). In a study by workers at Kansas State University, wheat was grown in sequences of three years, including: a wheat phase; corn or grain sorghum after wheat; then either a fallow period or a replacement crop of spring canola, soybean or sunflower. It was found that, relative to water use, continuous cropping resulted in a smaller crop yield by 18%, reduced the grain productivity by 31%; and reduced the net economic returns for the wheat crop by 56%. Reductions in these parameters were also observed when an oilseed crop was grown rather than having a fallow period.

Thus it is clear that deficits in soil-water deficits, when extreme, can have an adverse influence on grain yield formation, and more severely than on the overall biomass productivity. When such processes as floral development are impaired, the yield may be reduced by “sink strength” (the number of developing grains), in addition to “source strength” (canopy productivity). It is thought that these conclusions are general and should also pertain for crop productivity in those areas that are normally water-sufficient when they are subject to drought. It is further predicted that drought conditions will prevail more frequently and more severely, under the influence of climate change, which will amplify the oscillations of weather patterns. Research continues to identify crops, including wild varieties of the major species grown, that can maintain their yields under conditions of low water and higher temperatures, and that by introducing stress tolerance traits into productive crop cultivars, cropping systems may remain resilient to future climatic and environmental impacts.

1 comment:

steve said...

The agents of Soil erosion are the same as the agents of all types of erosion: water, wind, ice, or gravity. Running water is the leading cause of soil erosion, because water is abundant and has a lot of power. Wind is also a leading cause of soil erosion because wind can pick up soil and blow it far away.

Activities that remove vegetation, disturb the ground, or allow the ground to dry are activities that increase erosion.