September 20, 2017

How to feed people under a regime of climate change

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Protecting the soil

Industrial agriculture’s main contribution to carbon dioxide emissions is via the loss of soil carbon to the atmosphere. [18] This is caused by intensive industrial agriculture in particular by such practices as:

  • deforestation and the drainage of peat lands and wetlands in order to make available ever more land for agriculture and livestock rearing,
  • deep ploughing which exposes the soil to the elements, and when practised on steep slopes, causes serious soil erosion,
  • the use of heavy machinery that compacts the soil reducing or eliminating open pore space for providing channels for air, water, plant roots and soil micro-organisms,
  • the use of fertilisers as a substitute for natural fertilisers which destroys soil structure killing and hence soil organisms,
  • the use of pesticides, some of which as Rachel Carson [19] showed way back in 1962, do exactly the same thing,
  • overgrazing that has led everywhere to soil degradation and desertification,
  • in general intensive large scale monoculture of wheat and maize etc. year after year which eventually turns the soil into a lifeless dust-like substrate for crops that can only mature if dosed with increasing amounts of artificial fertilisers and other inputs.

The most obvious method of preventing soil-loss and indeed of increasing the organic matter in the soil, is by the use of manures, compost, mulches and cover crops such as forest bark, straw or other organic materials which can be fed back into the soil. These serve to protect the soil from erosion, desiccation, excessive heat and to promote, in this way, the decomposition and mineralisation of organic matter. [20]

It also has other advantages such as reducing soil-born diseases and in addition it also increases productivity. As Jules Pretty notes, in the Niger Republic mulching with twigs and branches permits cultivation on hitherto abandoned soils, [21]:

“producing some 450kg of cereals per hectare. In the hot Savannah area of northern Ghana, straw mulches combined with livestock manures, produce double the maize and sorghum yields than does the equivalent amount of nitrogen added as inorganic fertiliser”. [22]

Pretty cites other impressive examples of this sort, in Guatemala, the State of Santa Katarina, Brazil and elsewhere.

It is important that the soil should be left uncovered for as short a time as possible. An undercrop, preferably leguminous such as lucerne, can be sown along with a crop of cereals so that when the latter is harvested the land remains under cover, and at the same time, enriched.

Conservation tillage, better still zero tillage appears ideal as it entirely avoids ploughing. However to get rid of the weeds requires a lot of herbicides which are undesirable on many counts. What is clearly needed is zero tillage without the use of herbicides. If the area involved is small, mulches could presumably be used to smother the weeds. A little ingenuity would, I am sure, enable us to find alternative methods for killing weeds. Significantly, Waipuna, a New Zealand Company, suppresses weeds on roadsides by spraying them with hot water. The heat is retained with the use of an organic mousse partly made from coconut milk. It is apparently very effective.

The FAO, in a report already referred to, tells us that the absorption of carbon by the soil is maximised under a system of agroforestry. It can be as high as from 2 to 9 tonnes annually. [23] Apparently, if agroforestry were practised worldwide, agriculture could absorb in a ten year period some 2010 1.3Gt of atmospheric carbon annually. [24] The IPCC, in its 2000 Third Assessment Report, [24] also concludes that agroforestry yields the best results not only by increasing soil organic matter but also above-ground, woody biomass.

The USDA National Agroforestry Centre [2000] agrees that carbon sequestration under agroforestry is particularly high. They favour short-rotation coppicing that, if the wood is burnt instead of a fossil fuel, provides a double benefit through carbon sequestration and energy substitution. The Agroforestry Centre suggests that, with coppicing, soil carbon can be increased by 6.6 tonnes C/ha/yr over a 15-year rotation and wood by 12.22 tonnes C/ha/y over the rotation. [25]

Combining agriculture with forestry is a solution multiplier: wind velocity is reduced. In summer, the temperature under trees is much lower than in open areas and also warmer in winter. Just planting individual trees in the fields provides the necessary shade for plants and for livestock. The humidity under trees is also greater than on open sites because of the reduced evaporation and increased water-retention made possible by the improved soil structure. The litter provided by the trees makes excellent fertiliser especially when composted. Forested areas also play an enormous role in preventing floods as the rainfall stored under the forest floor, rendered porous by the tree roots, is released slowly to open spaces and to rivers rather than all at once from otherwise hard deforested land. [26]

Forested areas are also a source of food and forage as well as vegetable dyes, medicinal herbs and wood for posts, to prop up vines for instance, and for fencing. Tree crops are also a valuable supplement or substitute for annual crops. The sweet chestnut has a very high food value, for instance, and was grown extensively in high altitudes in southern Europe for making flour for pasta and bread. In the tropics, perennial tree crops such as breadfruit, plantain, jackfruit etc. are still important and are made the most of in Javanese and Singhalese forest gardens.

All in all, the agricultural methods required to protect our invaluable soil resources, which is essential for coping with climate change, provide many additional benefits. They give rise to a higher biodiversity of soil micro-organisms and micro-fauna. They are much more energy efficient because of their far lower dependence on energy-intensive inputs. By adding so much biomass to the soil, they increase productivity as well as reduce costs, thereby rendering a farm less vulnerable to discontinuities. Last but not least, they provide very much healthier food.

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Another essential change to our present agricultural system involves the phasing out of modern perennial irrigation methods. Modern irrigation is one of the most energy intensive components of industrial agriculture. Pimentel considers that when it is based on the use of water extracted from a depth of more than 30 metres, pumped irrigation requires more than three times more fossil fuel energy for corn production than does the rain-fed cultivation of the same amount of corn. [27]

In addition, rice cultivation which feeds a vast proportion of the people of the tropical world gives rise as already mentioned, to very much more methane gas when rice fields are flooded and treated with artificial fertiliser rather than rain-fed and grown organically. The reason is that flooding cuts off the oxygen supply to the soil, causing the organic matter it contains to decompose into methane gas. [28]

Admittedly modern perennial irrigation is highly productive and makes three crops a year quite feasible. Indeed, about 11 percent of the world’s crop land (250 million hectares in 1994) are under perennial irrigation and supply as much as 40 percent of the world’s food. [29]

Our dependence on perennially irrigated land is largely due to the cultivation of crop varieties such as the hybrids of the Green Revolution and now the genetically modified varieties which require very much more irrigation water, just as they do more fertiliser and pesticides. This is not the case with traditional varieties some of which are also highly productive and to which, in some areas of India, farmers are beginning to return to.

It is also due to the emphasis today on highly water-intensive export crops such as sugar cane, eucalyptus and worse still beef. As Reisner notes, to produce a pound of corn (maize) requires some 100 or 200 gallons of water. But to produce a pound of beef requires up to 8,500 gallons i.e. 20 to 80 times more water. [30]

In any case, modern irrigated agriculture could not be less sustainable. The amount of water used for irrigation is doubling every 20 years and at present consumes nearly 70 percent of all the water used world-wide, something that cannot go on for much longer, with or without climate change. Almost without exception modern irrigation especially in tropical areas leads to waterlogging and salinisation. As this occurs so the land is taken out of production – more of it, so it appears, than is actually brought under irrigation every year.

In the USA alone, 50-60 million acres, 10 percent of all cultivated land has already been degraded by salinisation and many thousands of acres have been removed from cultivation. The depletion of groundwater resources has been just as dramatic. The massive Ogallala aquifer, which was at one time regarded as practically inexhaustible, is been depleted at the rate of 12 billion cubic metres per year. Over the years it has lost 325 billion cubic metres of water, the annual depletion of aquifers worldwide amounting to at least 163.6 billion cubic metres. [31] Land taken out of irrigated agricultural simple becomes second rate grazing land, that can support a mere fraction of the previous human population in the area.

If modern irrigated agriculture has had it’s day it is also because more than a billion people world-wide are now suffering from water shortages, and it is expected that the number will increase dramatically in the coming decades especially with global-warming. We must remember that much of the water that flows in many of the world’s main rivers is derived from melting glaciers in the mountains where the sources of the rivers lie. However, glaciers world-wide are in full retreat as a result of global warming, which means that the flow of many rivers will be seriously reduced – in some cases, according to Cynthia Rosensweig, by as much as 25 percent.

Also, as Bunyard notes, [32] the amount of water required for irrigation as surface temperatures rise, must increase, partly because of the increased evaporation from the soil, the reservoirs and the irrigation channels but also because of increased evapotranspiration from the vegetation and in particular the forests.

The reaction of governments and of the World Trade Organisation is as usual, to transform the problem into a business opportunity. Under the General Agreement on Trade in Services, water is being privatised and wherever this happens, of course, the price of water doubles or trebles and in the state of Orissa, according to Vandana Shiva, [33] has increased tenfold and is now way beyond the means of the small farmers.

The only answer is to abandon the cultivation of water intensive crops and the rearing of livestock for export. Instead we must return to the traditional varieties of subsistence crops most of which are rain-fed, and to traditional methods of irrigation which are seasonal as opposed to perennial and do not give rise to salinisation, water-logging or the other terrible problems caused by modern irrigation systems. [34]

Significantly, farmers in the Malwa Plateau in the State of Madhya Pradesh in Central India are returning to unirrigated wheat varieties which they had abandoned under government and corporate pressure some 30 years ago. Some of them grow a short season leguminous crop or an early ripening variety of cereal which is given a full dose of farm manure before the monsoons and is thoroughly ploughed in. No drainage is required so that as much as possible of the rainfall is absorbed as soil moisture. Neither of these crops interferes with the traditional wheat, the variety grown being very deep rooting as it searches for moisture and nutrients, and this insulates it from competition from the largely leguminous weeds.

When the monsoon waters withdraw, the field is tilled and the wheat sown, the winter dew assuring that it reaches maturity in late February. At the same time there are great savings on inputs for the Green Revolution HYVs require that the weeds be removed since, with their short roots, they are unable to utilise the moisture that lies deeper down in the ground. There are further benefits in terms of soil quality improvement of course, the reduced demand for water. [35]

Traditional irrigation has been practised throughout the Indian Subcontinent, Sri Lanka, Java and elsewhere for hundreds of years. It is based on water harvesting and is managed by local communities in a highly democratic and equitable manner and needless to say, in a totally sustainable one.

Anil Agarwal and Sunita Narain tell us that during the drought of 1987 in India, distant villages close to the Pakistan border, which had not yet ‘benefited’ from government water schemes, still provided water for people to drink for the simple reason that their traditional water harvesting systems had remained intact. In the ‘developed villages’, on the other hand, people went thirsty, wells had either no water or no electricity for powering the pumps and the villages were forced to depend on occasional government tankers.

Agarwal and Narain also tell us how Jodpur, the famous desert city, once had an astounding water-harvesting system with nearly 200 water sources – about 50 tanks, 50 step wells and 70 wells. In their houses, people used to collect the rainwater from rooftops via water collection devices called ‘tanks’. [36]

In addition, the surrounding catchment areas were once covered with thick forest abounding in wild animals. Today of course, the forest has gone and the tanks – beautiful structures as they were – are largely used as refuse dumps. When modernisation brought people a piped water supply, Agarwal and Narain note, “they came to neglect their traditional systems and to depend on the government” [37] – yet another policy that must be reversed.

The tanks must now clearly be restored and indeed extended as a matter of urgency. At the same time communities must organise themselves in order to learn how to operate and manage them as they once did. There is no alternative.

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