Feeding the future – sustainable agricultureWith the population exceeding 6.7 billion and growing by over 6 million a month, the need to protect agricultural land and to increase food production has become critical. Does sustainable agriculture have the answers?
Key text
Key textAbout 5000 years ago, large cities were flourishing in the flat plains of what is now southern Iraq. The cities were surrounded by thousands of hectares of crop land irrigated from the rivers. Farmers grew barley, wheat, flax, dates, apples, plums and grapes, and herded sheep and goats for meat and milk.This early example of intensive agriculture proved unsustainable. By around 4000 years ago, desert had replace the fields and the cities had been abandoned. History records many such examples of agricultural communities flourishing and then failing, often because farming eroded the soil, exhausted the soil’s nutrients or caused a build-up of salt. There were many fewer mouths to feed in those days; the global population was probably no more than a couple of hundred million. So if agriculture failed in one area, plenty of arable land remained available for development. The world no longer has that luxury. The need to protect agricultural land and to increase food production has become critical. Around the world the concept of sustainable agriculture has been embraced to try to ensure that food supplies will continue to match demand. What is meant by sustainability? Meeting the needs of the present without compromising the ability of future generations to meet their own needs is the key principle behind the concept of sustainability. If natural resources such as soil, nutrients and water are used up at a rate faster than they are replenished, then the farming system is unsustainable. Sustainability is also dependent on maintaining a high level of biodiversity, especially in the soil and the surrounding environment. But moving from broad definitions to practical prescriptions is, of course, far from easy. Farmers will adopt systems that maintain or enhance the natural resource base only if these also provide a living for themselves and their families. Therefore, economic and social issues, as well as the productivity of the land and the broader health of the environment, have to be considered when working towards sustainable agriculture. Following extensive consultations with farmers and other expert groups, Australian government authorities have identified a set of key indicators of agricultural sustainability. Each indicator is accompanied by a set of measurable attributes that provide the basis for sustainability assessments.
From Sustainable Agriculture: Assessing Australia's Recent Performance (1998). A report to the Standing Committee on Agriculture and Resource Management of the National Collaborative Project on Indicators for Sustainable Agriculture The Australian scene As a major agricultural exporter, Australia feeds not only its own population but also some 50 million people in other countries. The exports are vital to our economy and make an important contribution to the world’s food supply. Farmers and scientists are working together to lift production and improve product quality, and also to overcome major threats to sustainability that have emerged over the years. A number of farmer-focused agricultural organisations have already been set up in Australia (eg, Birchip Cropping Group, Conservation Farmers Inc, Kondinin Group, and Mallee Sustainable Farming Project). These organisations collaborate with scientists who are involved in ongoing projects, conduct their own research, and keep farmers informed about research results. AusAID and the Australian Centre for International Agricultural Research also find that a collaborative approach to agricultural research is very effective in their overseas projects. Some of the biggest threats to sustainable agriculture, and approaches to deal with them, are outlined below. Loss of biodiversity Australian farmers, like their colleagues in Asia and the Pacific, have come to realise the importance of a diversity of organisms in agricultural ecosystems. A productive soil is called a 'living' soil because of the enormous number and diversity of organisms that cycle nutrients through the soil, maintain its structure, and prevent outbreaks of pests and diseases. Above ground, natural enemies and pollinators are essential for profitable and sustainable agriculture. Many modern agricultural practices (eg, monocultures, poor crop rotation, pesticides and heavy machinery) reduce biodiversity to low levels and trigger even greater adverse responses (eg, pesticide treadmills). One sustainable approach to suppressing soil-borne pests and diseases in crops is biofumigation. This utilises toxic compounds produced by brassicas (eg, cabbages, turnips and mustard) to kill soil pathogens. Farmers can alternately plant a brassica crop with another crop (eg, wheat) to break the life cycle of soil pests and diseases, instead of using synthetic pesticides. Groups are also attempting to restore biodiversity that has been lost. One Landcare group in New South Wales is using information from the Australian National Herbarium to determine what plants originally grew in the area as part of their native plant revegetation project. Dryland salinity Around 2.5 million hectares of Australia's agricultural lands are currently affected by dryland salinity. According to reports compiled by the National Land and Water Resources Audit in 2000, the annual costs associated with dryland salinity are estimated at about $600 million in Western Australia and $250 million in the Murray-Darling Basin. Dryland salinity has always existed, but it became more obvious when native grassland and mallee vegetation were replaced with crop and pasture plants. These annual crops take up less rainwater, so more water is added to the underlying water table. The water table then rises, bringing salt to the surface. What is needed for sustainability in these regions are farming systems that match the previous water use, thus halting the rise in the water table. A common answer is to plant trees in large numbers, but this is often incompatible with the key goals of maintaining food production and farm income, and trees on their own would not overcome dryland salinity. Scientists in many organisations are investigating approaches that meet the sustainability criteria. One approach is to implement ‘agroforestry’ systems that combine tree growing with cropping and grazing. Another approach is to use perennial pasture plants such as lucerne, which use more water and extract it from deeper in the soil than annual pasture plants, in rotation with high value crop plants. Along with these approaches to sustainable management, sophisticated technology to monitor saline areas and computer packages to interpret the results will be vital to tailoring options to individual regions and farms. As with many environmental problems, there is not a single 'solution'. Answers will require a mix of options that will vary from farm to farm and from year to year. Acid soils Soil acidity also costs the rural economy hundreds of millions of dollars a year, and the area affected is much greater than that plagued by salinity (Box 1: Acid eats into farm incomes). Australia has more than 7 million hectares of acid soils, which cost the nation around a billion dollars in lost income every three years. Estimates suggest that up to 90 million hectares of land in Australia have the potential to be affected by acidity (ie, have a pH of less than 6). The biggest losses in agricultural production come when acidity increases to the point where toxic elements in the soil, particularly aluminium, are dissolved. Adding lime neutralises the acid, but farmers usually cannot afford to do this on large areas of land, unless they are growing a valuable, acid-sensitive crops such as canola; as the value of a farmer's produce is increased, lime becomes more affordable. To promote sustainable management of affected areas, people are investigating land use approaches that can slow or reverse the acid build-up. These approaches will reduce the need for liming. Research groups are also working towards breeding crop and pasture varieties that grow well in acid soils. Pests and weeds The threat that pests can pose to sustainable agriculture was illustrated vividly in Western Australia’s Ord River irrigation area thirty years ago. Cotton growing began there in the early 1960s and at first showed considerable promise. About ten years later the industry collapsed, beaten by caterpillar pests that had quickly become resistant to insecticides. The development of effective integrated pest management (IPM) strategies prevented the same thing happening in cotton growing areas in the eastern States. An easy-to-use software package is now helping growers implement these strategies, which minimise insecticide spraying while maintaining yields. In recent years cotton varieties, genetically engineered for pest resistance, have also helped to reduce insecticide spraying. Another IPM approach to controlling of pests is the use of petroleum oil sprays. These sprays act as pesticides by blocking the breathing tubes of insects and also reduce egg-laying on leaves. The sprays are used in low concentrations and are biodegradable. Integrated pest and weed management, based on a detailed understanding of the ecology and biology of the target organisms, is now seen as the key to sustainable control. It can involve, for example, biological control, crop rotations, planting resistant or tolerant varieties, or using insect traps as well as sprays. Key goals include keeping pesticide and herbicide use to a minimum and only using chemicals that are environmentally benign. The broad view Sustainable agriculture is a simple concept that embraces a complex web of issues. Some of these are the state of the soil; water availability; choice of crop; stocking rates; needs for pesticides, herbicides and fertiliser; climate variability and protection of biodiversity. Then there is a range of economic issues (eg, markets and production costs). Developments in information technology will play a key role in managing the complexity. For example, CSIRO researchers have developed a farm management program, GrazPlan, that simulates interactions between factors such as pasture growth, climate, nutrient cycling and farm costs and income. Users can explore future impacts of different farm management decisions to identify sustainable approaches. To achieve sustainable agriculture we must deal both with issues involving environmental impacts and productivity of the land. Any program to successfully develop a system of sustainable agriculture must have farmer involvement at all stages of its development, and must look at a farming system as a whole, not just at individual elements. The farmer-focused agricultural organisations in Australia are working with researchers to develop farming systems that are both sustainable and profitable. Related Nova topics:
Acid soils are now recognised around the world as one of the key threats to sustainable agriculture. In Australia costs are estimated at more than $600 million a year. Of the approximately 90 million hectares of land that have the potential to be affected, 33 million hectares are highly acidic (pH less than 4.8) and 58 million hectares are moderately to slightly acidic (pH 4.9-6). Farming inevitably tends to make soil more acid. On undisturbed land, nutrient take-up by plants increases soil acidity, but when plants die the extracted alkalinity returns to the soil. Farming disrupts this cycle because the plant matter is removed, either as crops or eaten by livestock. In the nitrogen cycle, the conversion of organic nitrogen from plant residues (or dung and urine) to nitrate in the soil is an acidifying step, but the acid is neutralised when nitrate is taken up by the plant. In agriculture, sometimes these processes are out of phase (eg, nitrate accumulates when there are no plants to take it up). Nitrate is soluble and easily leached. If leaching occurs, the nitrogen cycle is disrupted and valuable nitrate is lost to the production system, leaving behind the acidity generated when the nitrate was formed. Fertilising crops or pastures hastens the acid build-up. Even fertilisers such as superphosphate that do not directly affect acid levels may indirectly increase the rate of acid addition to the soil if they increase plant growth and hence agricultural production. Growing legumes to boost soil nitrogen increases production but also increases the risk of soil acidification if the supply of soil nitrate exceeds the capacity of the crop or pasture to absorb nitrate. Leaching of nitrates from the soil is one reason why acidity tends to build up faster in high-rainfall farmland than in drier regions. Topdressing with lime remains the most effective remedy for soil acidity, but researchers calculate that more than 2 million tonnes of lime would have to be applied just to treat the worst 1.5 million hectares. This is many times the amount used each year in agriculture in Australia. Researchers can help address the problem by producing more acid tolerant crop and pasture plants. Australian scientists have found that the roots of tolerant wheats excrete a compound that makes soil aluminium harmless, and that a single gene is largely responsible for this process. This opens up the prospect of increasing the tolerance of other crop and pasture plants via genetic engineering. In another development, scientists have found that tree planting can slow, or even reverse, the acid build-up in some farm soils. Trees help in a number of ways. For example, they extract nutrients from deep layers in the soil – away from the roots of crop and pasture plants – and return them to the surface in fallen leaves and twigs. And they take up nitrates that would otherwise be leached from the soil. Changes to farming practices – such as reducing hay cutting and retaining crop stubble – can also assist. Related sites
ATSE Focus January/February 2004 Technology and ancient wisdom in sustainable agriculture (by Lindsay Falvey) Asks what is to be sustained in agriculture and the environment.
Australasian Science August 2008, pages 31-34 Farming without harming (by John Williams and Fiona McKenzie) Discusses the need for new approaches to sustainable agriculture.
March 2001, pages 22-23 Balancing biodiversity with land clearing (by Greg Siepen and Clive McAlpine) Explains ways in which farmers can contribute to the conservation of Australia's biodiversity.
Ecos No. 134, 2007, pages 22-27 Saving the life of farmland soils (by James Porteous and Steve Davidson) Looks at efforts to reverse the trend of decreasing organic matter of Australian farmland soils.
No. 129, 2006, pages 8-11 Reclaiming the Golden Triangle (by Richard Mogg) Discusses the substitution of sustainable agriculture for growing opium poppies.
No. 123, 2005, pages 29-30 Connecting sustainable agriculture to consumers (by Steve Davidson) Discusses approaches taken to market products of sustainable agricultural practices.
No. 117, 2003, pages 13-15 Rural remote control Describes on-site computers that are being developed to remotely report and manage complex agricultural processes.
No. 115, 2003, page 23 A blueprint for change (by Wendy Pyper) Lists the reforms suggested by the Wentworth Group of scientists.
No. 109, 2001, pages 20-23 Space-age farming (by Wendy Pyper) Describes the use of satellite imagery to help farmers manage pastures.
No. 108, 2001, pages 30-31 The vision of Hume (by Steve Davidson) Describes how the Australian National Herbarium helped a Landcare group choose the right species for landscape restoration.
No. 106, 2001, pages 28-33 Bubble bubble... (by Wendy Pyper and Steve Davidson) Covers acid sulfate soils and soil acidification.
New Scientist 14 June 2008, pages 28-33 What price more food? (by Debora MacKenzie) Examines the causes and consequences of increasing global food prices.
5 April 2008, pages 8-9 How to kickstart an agricultural revolution (by Andy Coghlan) Reports on an International project to help poor farmers and improve agriculture sustainability.
21 April 2007, page 18 Pastures new may destroy the planet (by Chris Pollock and Jules Pretty) Examines what is considered to be ‘sustainable’.
18 May 2002, pages 32-47 Time to rethink everything: The smart farming revolution Describes an approach to growing food that works towards increased production while preserving soils and wild environments.
12 May 2001, page 12 The people versus nature (by Fred Pearce) Describes 'eco-agriculture' as a way of saving biodiversity without starving the poor.
3 February 2001, pages 16-17 An ordinary miracle (by Fred Pearce) Describes techniques of sustainable agriculture that have been adopted on a small scale around the world.
RTD info November 2004, pages 36-39 A growing concern Comments on recent re-evaluation of the role of trees in agricultural productivity.
Scientific American August 2007, pages 66-73 Future farming: A return to roots? (by Jerry Glover, Cindy Cox and John Reganold) Explores the future of large-scale farming.
Can Australia save the world? (by Julian Cribb, The Slab, Australian Broadcasting Corporation) Summarises the problems of overpopulation and resource depletion, and discusses how Australia could become a world leader in sustainable food, land, water and ecological systems.
Chapter 2: Food and agriculture (Institute of Land and Food Resources, University of Melbourne, Australia) From the book Agricultural Education in Natural Resource Management by Lindsay J. Falvey, this chapter covers modern agriculture – its history, the need for increased food production, the impacts of agriculture on the environment, and considerations for natural resource management. The subsections are listed at the beginning of the page and you can go directly to the topic of interest.
The development of ecological performance indicators for sustainable systems (Proceedings of the 10th Australian Agronomy Conference, 2001) Discusses an approach to determining ecological performance indicators that can be used to manage farming systems more sustainably.
Chapter 24: Environmental indicators and sustainable agriculture (Australian Centre for International Agricultural Research)
From a book on managing sustainable agriculture. This chapter looks at how indicators can be used to assess agricultural sustainability.
Sustainable agriculture: A question of ecology, equity, economic efficiency or expedience? (University of Western Australia) Suggests that the core elements of sustainability fall within three categories:
value of the environment, intergenerational equity, and economic efficiency.
Also discusses the need for suitable sustainability indicators.
What is sustainable agriculture? (University of California Sustainable Agriculture Research and Education Program, USA) Covers the goals of sustainable agriculture, and presents strategies for them based on the situation in California.
Farmers and scientists working together to achieve more sustainable land management (Manaaki Whenua Landcare Research, New Zealand) Describes how farmers and scientists can work together to achieve more sustainable land management.
Cooperative Research Centre for Australian Weed Management An interesting example of a program that is working to develop weed management systems that will increase the sustainability of agriculture. This program works through community involvement and implements training and education strategies.
Australian Broadcasting Corporation (transcripts)
Agricultural organisations These are examples of organisations that promote collaboration with scientists and provide practical advice to farmers.
biodiversity. A measure of the variety of life. It is usually calculated from the number of species of organisms – although genera, families, classes and phyla can all be counted too. biofumigation. The suppression of soil-borne pests and pathogens by the use of plants that contain inhibitory chemicals. The plants can be harvested as rotation crops or ploughed back into the soil as green manure. biological control. A strategy for the control of pests or disease-causing organisms that relies on the use of other living organisms rather than chemical pesticides. 'living' soil. A healthy soil that contains living organisms. These organisms (biota) are important to the health of soil, and a gram of healthy agricultural soil can contain several million micro-organisms. Productive soil is made up of mineral particles; organic matter in the form of decaying parts of plants and animals and the waste products of living things; and hundreds of millions of micro-organisms and other living things (eg, nematodes, arthropods, worms). For more information see The living soil (Sun Prairie Organic, Canada). monoculture. The cultivation of a single crop, usually on a large area of land and on a commercial trading basis. nitrogen cycle. The continuous natural cycle by which nitrogen passes from the atmosphere to soil to organisms and back to the atmosphere. nitrogen fixation. The process of producing nitrogen compounds by combining nitrogen from the air with other substances. The only organisms that can use nitrogen gas to make organic molecules are a few kinds of bacteria. Most nitrogen-fixing bacteria live in the soil or water, but some species live in nodules on the roots of legumes such as lucerne, peas, beans and clovers. pesticide treadmill. A situation in which farmers apply a pesticide to control a pest, which then develops resistance. Pest numbers increase, so more frequent applications of pesticide are needed for control. Finally the pesticide performs so poorly that farmers introduce a new pesticide. Over time the cycle (treadmill) is repeated with the new pesticide. pH. The pH scale is used to measure the strength of acids and bases (or alkalis). The acid strength in the human stomach is about pH 2. Alkalis such as caustic soda and basic household cleaners have a pH of about 12 to 14. Neutral is pH 7, (ie, neither acidic or alkaline). The scale is logarithmic, so pH 4 is ten times as acidic as pH 5 and pH 2 is ten times as acidic as pH 3, and so on. For more information see About soil pH (National Aeronautics and Space Administration, USA). water table. The top level of water in the ground that occupies spaces in rock or soil and lies above a layer of impermeable (non-porous) rock. When the water table rises above ground level a spring, lake or wetland is formed.
External sites are not endorsed by the Australian Academy of Science. Posted September 2001. The Australian Foundation for Science is also a supporter of Nova.
This topic is sponsored by CSIRO Plant Industry and the bequest of J S Anderson, FAA.
|