Soil Erosion, Climate Change and Global Food Security: Challenges and Strategies. Part 8.

This is the eighth part of a much longer article published in the journal Science Progress, and which may be found here: http://stl.publisher.ingentaconnect.com/content/stl/sciprg/2014/00000097/00000002/art00001


19. Grain Yields Starting to Plateau?

There is evidence that the world’s grain yields are beginning to plateau73. In 1950, the average grain yield was 1.1 tonnes per hectare, but this had climbed 3.3 tonnes per hectare in 2011, while the U.S. and China were able to quadruple their grain yield over that same period. From the inherently fertile soils in the U.S. Midwest is produced 40% of the world’s corn crop and 35 % of its soybean crop. In Iowa, more grain is grown than in Canada and more soybeans than in China. The land to the west of the Alps, which extends across France to the English Channel is also very productive, meaning that Western Europe is able to export a surplus of wheat, in addition to feeding its own dense population. In the U.S., wheat is principally grown in the semiarid Great Plains, whereas in Europe it is produced on the fields of France, Germany, and the United Kingdom, which receive ample rainfall. The European wheat yields are typically in the range 6─8 tons per hectare, whereas in the U.S. 3 tonnes/hectare is good. In China, India, and other tropical/subtropical countries in Asia, it is common to employ double- or triple-cropping for rice, and so the annual yield is much greater, despite the yield per harvest being less.

The new dwarf wheats and rices that were introduced in the 1960s were selected genetically to be enhanced in their growth by both good irrigation and the application of fertilizers. More recently, farmers have worked on developing hybrid varieties of corn that can tolerate crowding, to improve yields, and whereas 50 years ago probably 25,000 corn plants were grown per hectare, when there is sufficient soil-moisture perhaps 70,000 plants per hectare can be raised. Between them, China, India, and the United States use 58% of the world’s fertilizers, as the major grain producing nations. China and the United States produce roughly 400 million tonnes of grain each, and the amount of grain produced per tonne of fertilizer in the United States is in excess of twice that of China. This is partly a consequence of the U.S. being the world’s main producer of soybeans (soya beans), since being a legume, this plant can fix nitrogen in the soil, which can in turn fertilize crops planted later on, e.g. corn, in a rotation of the two crops, thus requiring a smaller application of nitrogen fertilizer. During the period 1950─1990, the world grain yield increased by an average of 2.2% per year, but during 1990─2011, this fell to just 1.3% per year. In Japan and in South Korea, the rice yield has plateaued, having achieved the limit that can be met according to the prevailing day length, solar intensity, and ultimately that of photosynthetic efficiency.

Japan and South Korea together produce 12 million tonnes of rice annually, or 3% of the world rice harvest. Wheat yields in Europe achieved their limit more than a decade ago, with 8 tonnes per hectare as the maximum in the United Kingdom and in Germany. It appears that the yield of rice in China, the world’s most populous country, may also be about to plateau73. Since China uses twice the amount of fertilizer that the U.S. does, probably the application of it at a greater density will do little to improve yields. Chinese wheat yield too may be close to the maximum level, meaning that, along with those in Western Europe, practically 30% of the world’s wheat harvest would be grown in countries that probably cannot increase their production. Rising global temperatures are likely to place further limits on agricultural production.

20. Possible remedial actions for land degradation.

Soil erosion is most effectively prevented by covering the land with vegetation, a strategy which helps prevent erosion by both wind and water, in addition to ameliorating runoff and consequent flooding while allowing natural groundwater, and in some case aquifers, to recharge thus securing freshwater supplies. Terracing too has been practiced across the world since time immemorial, and is an extremely effective way to control erosion. Rows of trees and shrubs planted along the edges of agricultural fields provide windbreaks, which serve to protect the fields against the action of winds, and confer a number of additional positive features, e.g. providing microclimates for crops (by sheltering them from the drying and other damaging effects of wind), making a habitat for beneficial bird species, contributing to carbon sequestration, and enhancing the agricultural landscape from an aesthetic viewpoint. Traditional planting methods, such as mixed-cropping (rather than monocropping) and crop rotation are also known to reduce erosion rates appreciably. Some sustainable soil management principles have been outlined74 and are summarised in the following list:

· Soil livestock (microbes, earthworms etc.) cycle nutrients and provide many other benefits.

· Organic matter is the food for the soil livestock herd (soil food web).

· The soil should be covered to protect it from erosion.

· Tillage accelerates the decomposition of organic matter.

· Excess nitrogen urges the decomposition of organic matter.

· Moldboard ploughing speeds the decomposition of organic matter, destroys earthworm habitat, and increases erosion.

· To build soil organic matter, the production or addition of organic matter must exceed the decomposition of organic matter.

· Soil fertility levels need to be within acceptable ranges before starting a soil building programme.

The following techniques are proposed in order to build soil:

• To apply manure as a soil amendment. Typical rates for dairy manure would be 10 to 30 tonnes per acre or 4,000 to 11,000 gallons (15,000 to 42,000 litres) of liquid for corn. This provides organic matter and nutrients, and avoids the loss of SOM. Crop residues grown from manured soil would further contribute organic matter to the soil.

• Farm manure and other organic materials should be composted in order to stabilize their nutrient content.

• Cover crops and green manures: rye, buckwheat, hairy vetch, crimson clover, subterranean clover, red clover, sweet clover, cowpeas, millet, and forage sorghums can be grown as cover crops. If they are allowed to grow long enough to produce sufficient herbage, cover crops can contribute SOM to the soil.

• Reduce tillage: the effects of tillage on the soil may be adverse. Tillage reduces the natural aggregation of soil and the number of earthworm channels, while porosity and water infiltration are often decreased. Soils that have been tilled are more prone to erosion than soils left covered with crop residue.

•Minimise application of synthetic nitrogen fertilizers: ideally carbon and nitrogen sources should be added in combination: animal manure is a good source of both. If nitrogen fertilizer is used, it is best to apply it along with a heavy crop residue to the soil, e.g., a rotation of corn, beans, and wheat would thrive if nitrogen fertilizers were added after the corn residue was rolled down or just lightly tilled in.

21. Seed-saving and climate change.

In many primitive societies, to save and preserve seeds was considered as an almost sacred duty. While the practice has lapsed in the past several decades, it may prove necessary to embrace it once more. This is the message from a recent report by the Ecumenical Advocacy Alliance, The Gaia Foundation & The African Biodiversity Network, "Seeds for Life: scaling up agrobiodiversity.” http://www.gaiafoundation.org/sites/default/files/seedsforlifereport.pdf, in which it is argued that adapting agriculture to cope with climate change cannot be done without preserving seed diversity. Thus, in the absence of a wide gene pool of crops, it will not be possible for farmers to spread their risk, or breed new varieties to adapt to changing weather patterns. The blame for a profound loss of global diversity is placed on the fact that modern agricultural methods and the marketing of agribusiness corporations rely on relatively few varieties and crops.

The report proposes that to remedy this situation, farmers must be supported in a revival of their traditional seed saving practices and the accompanying knowledge, such that this diversity is maintained and made accessible both for farming today and into the future. Many farmers grow from just one or two varieties of purchased seed, but the entire crop may fail if the rains arrive too late or too early, are too heavy or there is no rain. Climate change is expected to cause irregularities of this kind, and yet it is those seed varieties that were harvested traditionally and saved, but were then abandoned decades ago, that may serve best in the future. The Green Revolution has changed the face of farming since the 1960s. Before then, it was the practice to plant dozens of different crops, from which the seeds were routinely saved, in a process of developing and adapting new varieties such that the many and various challenges of soil, pests, disease, nutrition and flavour could be coped with. Since the Green Revolution came about, there has been an enormous loss both in the diversity itself and the associated knowledge of how to tend and nurture it, particularly on farms in North America and Europe. There is currently a rising pressure on farmers to adopt corporate seed varieties at the expense of their locally-adapted versions, in Africa, Asia and Latin America.

22. Permaculture.

As a working and practical definition, permaculture2,75,76 may be described as a low impact method which uses perennial cultivation methods to produce food crops, working through principles that are in harmony with nature. This might sound slightly "new age", but since much of the energy used in mechanised agriculture is employed to forge processes that restrain the land from returning to its natural wilderness, if productive agriculture can be had at a minimum of this energy input, then we have the essence of a significantly more efficient and "natural" way forward. Certainly in developed nations, food is not grown locally but must be brought in from surrounding regions, and much of it is imported globally. The monoculture system that is typical of modern farms drains nutrients from the land, which is fed with artificial fertilizers, and many of the natural flora and fauna (soil food web) no longer exist. Such single crops are vulnerable to pests and diseases: for example, the Irish potato famine was a result of Blight disease which rapidly devastated the single species of potato which was being grown at the time, and was the staple food for the poor. Previous generations grew cereal crops but since the potato was more robust to changes in the weather and produced about four times as much food per hectare, it became the crop of choice. Production of 'biofuels' is diverting more land to the growth of monoculture crops, and along with the eradication of vast swathes of rainforest (e.g. to grow palm for palm-oil), it is far less 'green' as a fossil-fuel alternative than is frequently claimed. The necessary competition between growing crops to feed humans and animals or cars has also driven up the price of staple foods like wheat and corn.

The term Permaculture75,76 (a portmanteau word derived from permanent agriculture, or culture) was coined by Bill Mollison and David Holmgren in the mid-1970s, to describe an “integrated, evolving system of perennial or self-perpetuating plant and animal species useful to man.” According to Holmgren, “A more current definition of permaculture76, is ‘Consciously designed landscapes which mimic the patterns and relationships found in nature, while yielding an abundance of food, fibre and energy for provision of local needs.” People and their buildings, and the ways they organise themselves, are central to permaculture. Thus the permaculture vision of permanent (sustainable) agriculture has evolved to one of permanent (sustainable) culture.” Broadly, permaculture may be classified (insofar as such an holistic entity may be) as a branch of ecological design and ecological engineering which aims to develop sustainable human settlements and self-maintained agricultural systems modelled from natural ecosystems. One major change incurred by converting to permaculture is that cereals cannot be produced at the scale of industrialized agriculture, and amendments in our diet would be necessary, to consume more vegetables, fruit, nuts, berries etc., which can be produced effectively by its means.

The core tenets of permaculture are:

· Take Care of the Earth (“Earth Care”): Provision for all life systems to continue and multiply. This is the first principle, because without a healthy earth, humans cannot flourish.

· Work with nature.

· Act to oppose destruction and damage.

· Consider the choices we make.

· Aim for minimal environmental impact.

· Design healthy systems to meet our needs.



· Take Care of the People (“People Care”): Provision for people to access those resources necessary for their existence.

· Look after ourselves and others.

· Working together.

· Assist those still without access to food and clean water.

· Develop environmentally friendly lifestyles.

· Design sustainable systems.



· Share the Surplus (“Fair Shares”): Healthy natural systems use outputs from each element to nourish others. Humans can do the same; by taking control of our own needs, we can set resources aside to further the above principles.

· Resources are limited and only by curbing our consumption and population will there be enough for all, now and in the future.

· Build economic lifeboats.

· Develop a common unity.

· Modify our way of life now - don’t wait: become part of the solution not part of the problem.

· Need to become reconnected with the natural world: shift in thinking and being.

Permaculture is about making an effective design, emphasizing patterns of landscape, function, and species assembly. It asks the questions: Where does this element go? How can it be placed with other elements for the maximum benefit of the system overall? The fundamental principle of permaculture is, therefore, to maximize useful connections between components to achieve their best synergy in the final, and optimal design. Permaculture does not focus on individual elements, in isolation, but rather on the relationships created among those elements in the way they are placed together; the whole becoming greater than the sum of its parts. Therefore, permaculture design aims to minimize waste, human labour, and inputs of energy and other resources, by building systems with maximal benefits between design elements to achieve a high level of holistic integrity and resilience. Permaculture designs are “organic” and evolve over time according to the interplay of these relationships and elements and can become extremely complex systems, able to produce a high density of food and materials with minimal input.

23. Turning problems into solutions: from erosion to accumulation.

The Chikukwa project77 in Zimbabwe is an edifying example of how a thoroughly degraded landscape can be brought back to verdancy using practical permaculture. As noted earlier, when land has become badly degraded, especially in developing countries, it is often considered too expensive to recover using engineering/technological approaches and is accordingly "written off". In contrast, the Chikukwa project shows that by using low tech methods, even highly degraded land, with severely eroded soil can be brought back to life - and with very little money, but a good design. This is not a quick-fix strategy, and has taken over two decades to achieve; however, it is a sustainable landscape, which is the more important element. The fruition of this project is immediately apparent from the “before and after” photographs77 such as those shown in Figures 14 and 15. There is a 50 minute video available which describes the project in its entirety: www.thechikukwaproject.com. Chikukwa is on the edge of a mountainous region of Eastern Zimbabwe, on the border with Mozambique. The Chikukwa clan consists of 7000 members who live in 6 villages situated along a 15 km stretch of hills and valleys. Indeed, from Figure 15, it would be easy to think that they have simply continued to live a centuries-old life according to their traditions.

This is not so, and the Chikukwa project began in 1991 when the water supply that had provided for around 50 households in the village of Chitekete suddenly dried up. Attempts to dig for water were thwarted by further rains which caused the stream to become silted up again. At this time, the area was being increasingly deforested and most of the people were growing cash crops to earn their living. Along with cattle being let loose to graze, the denuding of the mountainsides of vegetation exacerbated soil erosion which further compounded the water problem. Those mountainsides, formerly lush and abundant had dried out, and soil erosion had impacted badly on the fertility of the land, which was steadily becoming desert. The lack of normal groundwater recharge as a result of deforestation had caused the springs to dry up, and when new water sources were tapped, they became blocked by silt from erosion. Beyond the practical aspects, the drying up of the springs had a spiritual dimension too, because according to traditional beliefs, water spirits live in wells and springs, who must be cared for by ensuring the health of the springs. In permaculture terminology, Chikukwa is well described as an edge, both in terms of ecology, culture and language, and the edge effect has undoubtedly yielded a rich and active vibrancy in all respects. Ironically, it is as though an interstitial industrialized phase has been bypassed, and a direct route to a sustainable community has been taken instead. The demand on external inputs is but minor, and the community can be described as being largely self sufficient. This, however, a way of life that is remote in all respects from that in the developed nations, and the majority live in mud huts and provide for themselves and their families by subsistence farming. Every family has access to running water, taken from mountain springs; communal land in the valley is used to grow wheat and maize flower, providing bread and maize meal. Along the mountainsides are grown fruit trees which everyone can help themselves to.

[Figs 14 and 15]

The Chikukwa project is built on the principles of permaculture and the testament of its success is that, in contrast to the majority of agriculture projects in Africa which fail very quickly, it remains in flourish. The “before” photos taken in the early 1990s show barren hillsides with a few trees spartanly surviving here and there, with massive erosion gullies in common sight. Around the springs the banks are bare and trampled by cattle, while the drying up of the springs made it necessary for villagers to walk five km and more to bring water from a more permanent stream further downhill. There was little feed for cattle during the dry season and wood for fuel was in short supply, while the harvest had become poor. During the wet season, there were floods as rainwater poured down the hills, inundating houses and bringing silt up to the window ledges. In the after” photos, we see households that are now small farms, surrounded by orchards and vegetable gardens. The hillsides are ringed by contour bunds (Figure 15) topped by vetiver grass, while abundant indigenous woodland is hosted by the gullies. Bunds are small barriers to runoff coming from external catchments, which slow down water sheet flow on the ground surface and encourage the build up of soil moisture and groundwater recharge (infiltration). Bunds are among the most common techniques used in agriculture to collect surface runoff, increase water infiltration and prevent soil erosion. Bunds are constructed using either stones or soil, and by building them along the contour lines of a hill or mountain, the flow of water is slowed down leading to a greater degree of infiltration and enhanced soil moisture. Bunds may be used on both even and uneven grounds (with a gentle slope of up to 5%), by adapting the exact design.

A dense woodland, planted on the slopes, provides firewood and timber. Water is harvested during the wet season by woodlots and swales which release it steadily, so that the springs run throughout the year. Accordingly, yields of cereals, vegetables, fruits and animal protein have been increased, making Chikukwa an exception in the wards of South and Eastern Africa where food shortages are typical. By establishing a fresh landscape, the Chikukwa project has established a fresh landscape, and its strategic components have been embraced in each of the region’s six villages, each of which has, as its water source, a spring about a third of the way down from the hilltops. In order to protect the indigenous woodland, deliberately planted and sown by the villagers, the gully is fenced off. One or more poly pipes leads down from the spring to a community water tank which supplies water to taps in household yards taps in household yards. Woodlots of fast growing trees are planted on the upper slopes and on some of the lower ridges, to maintain the health of the springs, and aid the storage and release of ground water, while preventing erosion and they also provide fuel and timber. While in principle, permaculture2,75,76 can be applied on all scales, it cannot be adopted as a substitute for industrialized modern monoculture crop production. It is not possible to separate our growing of food from other aspects of community, and so if we adopt the design principles of permaculture for our food production, we must adapt all other lifestyle elements as a necessary and simultaneous part of the process.