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Issues of sustainable land management
Challenges for the future
Objectives of the report
Perceived wisdom in the approach to evaluation, use and management of land resources is changing rapidly and dramatically. Past emphasis on land 'development', focused on maximizing production and return from land use investment and planned against a background belief that suitable lands for expansion could always be found somewhere, is forced to give way to a more cautious approach-one that recognizes the finite extent of fertile land and the seemingly insatiable demands of a growing human population.
Globally, and in many individual countries, there is clear evidence of impending land shortage. Areas in which the combination of land and freshwater resources is moderately or well suited to agriculture are, for the most part, already in use. Efficient use of these lands is becoming a matter of life or death for increasing millions of mankind. Future generations in still larger numbers are more seriously at risk-their livelihood endangered by present production choices that degrade the very resources on which future agriculture depends. Global production must increase dramatically to meet foreseen demand but the levels and means of production targeted locally must be those that can be maintained on a sustained basis. Global, and even local agriculture must be sustainable.
"We need a value system which enshrines the principle of sustainability over generations. Sustainable development may mean different things to different people, but the idea itself is simple. We must work out models for a relatively steady state society, with population in broad balance with resources and the environment." (Tickell, 1993).
The concept of sustainability includes notions of limits to resource availability, environmental impact, economic viability, biodiversity and social justice (Dumanski et al., 1991; Harmsen and Kelly, 1992). The concept of sustainability is dynamic in that what is sustainable in one area, may not be in another, and what was sustainable at one time may no longer be sustainable. Although sustainability cannot be measured directly, assessments of sustainability can be made on the performance and direction of the processes that control the functions of a given system at a specific location (Dumanski and Smyth, 1993).
The concept of sustainability is pertinent only against a background of limits to resource availability and use. If no such limits exist, or they are not perceived to exist, then it is common that resources are overexploited; under restraints, however, the concept of sustainability becomes increasingly important, rising as the scarcity of the resource increases. Our perception of scarcity and our knowledge of alternate resource possibilities for the same applications, determine the important factors to be considered in the supply-demand equation of sustainability and sustainable land management.
The first of these factors is the fixed supply of land suitable for agriculture and food production. The World's total ice-free land area is approximately 13.4 thousand million hectares, but of this only 24 percent or 3.2 thousand million hectares are potentially arable, i.e. land that can be cultivated and/or maintained in productive pasture. Of this, about 40 percent (1.3 thousand million hectares) is highly to moderately productive and 60 percent is of low productivity. Currently the best of these lands, about 1.5 thousand million hectares, are used for cropland, and the remainder are in permanent pasture, forest and woodland (Buringh and Dudal, 1987).
The second factor is the impact of competition between increasing numbers of people for the same land area. Each year global populations increase by about 90 million people. Since the best lands are almost all in use, necessary further expansion of agriculture will come increasingly at the expense of pasture lands and forests; lands usually of marginal quality where the risks of crop production are higher and the returns lower. Over the last three hundred years, human-induced land use change has resulted in a net gain of approximately 12 m kmē of cropland but net losses of 6 m kmē of forests and 1.6 m kmē of wetlands. Even over the past two decades the global extent of cropland has increased by 9.1 percent, whereas pasture and forest lands have decreased considerably. Currently, the rate of tropical deforestation, primarily for agricultural purposes, is estimated at 17 million hectares (0.9 per cent) per year, sharply increased from the rate of 11.3 million hectares (0.6 percent) per year estimated in the early 1980s (WRI, 1992). Temperate and boreal forests suffered in the past, but they are no longer subject to acute deforestation; in fact, forest in these areas may have increased by about 5 percent since the early 1980s.
Since the middle of this century human-induced land use change has become so drastic, so rapid and so global that its impacts are affecting processes that sustain the interacting systems of the geosphere-biosphere (IGBP, 1992). The direct effects of these changes on global systems remains poorly understood but there is general agreement on the potential impacts. For example, expansion of agro-ecosystems over the last 150 years has resulted in a net flux of CO2 equal to that released by burning fossil fuel during the same period; current release of CO2 from land conversions is between 10 and 30 percent of that from fossil fuel combustion; land conversion is also the largest human-induced source of N2O, which contributes to greenhouse gas accumulation and ozone depletion.
With or without climate change, the conversion of natural habitats for agriculture and other uses is recognized as a major cause of loss of genetic stock and of genetic diversity. At current rates of conversion, it is estimated that 25 percent of the World's plant species will disappear in the next 50 years (IDRC, 1992). Modern agriculture, with its trends towards monoculture is particularly vulnerable; already only 20 crops provide 90 percent of the World's food; and wheat, rice, maize and potato contribute more than all other crops combined (IDRC, 1992). Only four varieties produce 75 percent of all wheat grown on the Canadian prairies whilst, in India, where as many as 30 000 varieties of rice were planted 50 years ago, it is estimated that by the turn of the century three quarters of the rice fields will be planted to only 10 varieties.
The pending onset of climate change, the narrowing genetic stock and the disturbance of global biogeochemical cycles all add considerable uncertainty to the evaluation of sustainability.
The third major factor in the
sustainability equation is the depletion of biological production potential by the
insidious processes of soil and land degradation, often accelerated by human activities.
Although the extent of global soil degradation is not known with certainty, current best
estimates are that approximately 1.2 thousand million hectares of agricultural, forestry
and range lands have been affected by moderate to extreme soil degradation (75 percent of
this is moderate degradation and 25 percent is severe to extreme). A further 750 million
hectares have been affected by slight degradation. This degradation is caused by human
related activities, namely: overgrazing (35 percent of degraded land); improper
agricultural practices (28 percent); deforestation and overexploitation for fuelwood (37
percent); and industrial pollution (about 2 percent). A secondary effect of land
degradation, often at least as serious in its local consequence as the loss of soil
material, is the pollution of surface and groundwater. Transposed and dissolved materials
may cause salinization, alkalinization, and other forms of toxification and
eutrophication. The impact of these effects may be felt far from the site of initial
degradation. Within this century the impact of land degradation on production has been
masked by greatly increased fertilizer use and other inputs, but it is obvious that
productivity increases would have been much higher in the absence of degradation.
The evidence is mounting that global agriculture is at a watershed. Soon, for the first time in history, we will have run out of good land for agricultural expansion. For the first time we are faced with the imperative of increasing production on lands already cultivated in a manner which does not degrade productive resources. The magnitude of the task is illustrated by a calculation that shows that if we are to meet the needs of the anticipated global population, the amount of food we must produce in the next 50 years equals the total production of the past 8000 years of agricultural history (IDRC, 1992).
If the forms of agriculture used to achieve this increased production are to be sustainable they must be based on sound agronomic principles, but they must also embrace understanding of the constraints and interactions of all other dimensions of sustainable land management. Yields will have to increase but, at the same time, production risks will have to be controlled to ensure more reliable cash flow and permit confident planning. Soil resources will need to be controlled and water pollution cannot be tolerated. Production systems will have to be flexible, diversified and developed on a broad genetic base to ensure the possibility of rapid response to changing conditions. Land management practices, in large measure, control processes of land degradation and their efficiency in this respect will largely govern the sustainability of a given land use. However, institutional, political, social and economic pressures and structures can cause or exacerbate environmental problems and control of their influence must form part of the solution.
This immense challenge for global agriculture will require that the principles and concepts of sustainable land management become entrenched in the policy arena no less than amongst rural populations. Some major changes in economic theory and in systems of national accounting are required to ensure that the loss of options for the future consequent upon depreciation of natural resources-loss of a nation's true 'wealth'-are properly recognized. Procedures of national accounting, for example, that mistakenly assume that natural resources are so abundant that they have no marginal value must be seen to be unacceptable.
Technical and scientific advances will be instrumental in the transition to sustainable agriculture, but they will need to be tailored to local environmental conditions-much more site-specific than has been the case in the past. The 'Green Revolution' continues to achieve considerable success with the use of high yielding crop varieties, highly responsive to fertilization, irrigation and other inputs. Such successes, however, are usually achieved on sites that enjoy a narrow range of highly suitable soils and climates, are not without environmental costs. Also, they incur a margin of risk which often is higher than with more traditional means. Attempts to transfer intensive forms of agriculture to the marginal and submarginal areas in which a large majority of the world's poorest farmers live has led, all too often, only to disaster and degradation. These regions have yet to receive the research effort necessary to devise sustainable systems of agriculture capable of sustaining foreseeable levels of population.
Clearly, no 'technological fix' will
prove effectively sustainable unless it is acceptable and beneficial to the people on the
land and to society in general - but an improved technological and knowledge base will
surely be a required part of the solution. It is the responsibility of the scientific
community to develop criteria and indicators for evaluating whether land management
practices will lead towards sustainability or away from it. They must, however, work with
the farm community to ensure that recommendations that arise are realistic, efficient and
This report proposes a strategic framework approach for evaluating sustainable land management. This approach is advocated because the concept of what constitutes sustainability cannot be rigid, it needs to be capable of change from area to area and over time. As solutions become mare precise they will have to be increasingly location and time specific. A strategic framework approach offers the possibility of providing preliminary estimates' of acceptable reliability, without waiting for all of the final data. The approach is intended to be generic and universal and it assists in organizing the concepts and principles to be used in deriving a solution. It is intended as an aid to guide decisions towards sustainable management, to increase the probability of success and/or identify potential failures. It should certainly assist in interpreting the results of the very many research initiatives that are now in progress in the search for sustainability.
The evaluation of sustainable land
management is an integral part of the process of harmonizing agriculture and food
production with the, often conflicting, interests of economics and the environment.
Agriculture is expected to continue to be the engine of economic development in most
developing countries but, for this to be realistic, agriculture in the future will have to
be increasingly more productive, more economically efficient and more environmentally
friendly-in a phrase, more sustainable. Although sustainability will continue to be
elusive, learning to evaluate sustainability must begin now. The task is too important to
wait until we have all the answers.
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