|Mineral Fertilizer Use and the Environment (IFA - UNEP, 1998, 52 p.)|
Fertilizers, especially nitrogen fertilizers, require fossil fuel energy to manufacture, and some to transport and apply. It is estimated that worldwide agriculture uses about 5% of global energy consumption. This includes nitrogen fertilizer production, which is estimated to account for less than 2% of annual world energy consumption. This estimate of 5% excludes the transport and processing of the agricultural produce which is more energy intensive, for 1 kg of bread, growing the wheat takes about 20% of the energy used, while milling, baking and distribution account for 80%. Thanks to photosynthesis, in the case of cereals and root crops the harvested energy is substantially greater than the energy input. In the case of intensive horticulture the energy input may be higher than the energy output.
In France (Commissariat General du Plan, 1997), in 1995 the manufacture of fertilizers accounted for 1% of total energy consumption. Agriculture, including the application of these fertilizers, accounted for 1.6% The food processing industry, conservation and preparation accounted for a further 8%.
The energy requirements for the manufacture of fertilizers may be met by natural gas, oil, naphtha or coal depending on the cost and availability in the region of the world where the ammonia is produced. In 1995 known coal reserves amounted to about 450 years of 1995 production, natural gas 66 years and petroleum 43 years. Additional reserves tend to become available as time passes, due to new discoveries and/or technical progress. For example, in 1978 the US natural gas reserves production ratio indicated a 12-year supply 17 years later the USA still had a reserve production ratio indicating about 9 years supply.
15.1.2. Phosphate and potash
Phosphate deposits are widespread throughout the world but their economic recovery depends on the cost. The most accessible and higher quality rocks tend to be mined first, according to IFA statistics the average P2O5 content of the 125 Mt of phosphate rock mined in 1980 was 32.7%, whereas that of the 141 Mt mined in 1996 was 29.5% At the present rate of phosphate rock production and with production costs of the same order as at present the reserves are sufficient for at least 80 years, and at somewhat higher cost for 200 years. The resources which could be economically mined at higher cost are much greater. On most soils almost all the phosphate not taken up by the crop is retained in the soil. It is possible that techniques for the recovery of this phosphate may be developed in due course. Phosphate losses by soil erosion can be minimized by following Codes of Good Agricultural Practice.
There is no concern about potash resources, the known high quality reserves being sufficient, at present rates of use, for several hundred years and resources, recoverable at higher prices for at least a thousand years. Nevertheless, prudence in the use of phosphate and potash reserves us advisable since there are no known replacements.
There is evidently a limit to the area of fertile agricultural land in the world. Even in 1975, according to an FAO survey, 54 countries could not feed their populations with traditional methods of food production, and the number has increased significantly since that date. Furthermore, substantial areas of good agricultural land are being lost each year due to urbanization and deterioration, the latter due, for example, to salinity, erosion and desertification. It is estimated that every year soil erosion and other forms of land degradation rob the world of 5 to 7 million hectares of farming land (FAO, 1995).
Apart from areas of fertile land purposely idled in the USA and West Europe, there are some reserves of land which could be cultivated, particularly in Sub-Saharan Africa and South America, but three quarters of this land suffers from soil and terrain constraints. Much is under forest. The amount of additional fertile, well-watered, non-erodable, unforested land that can be brought into agricultural production at low cost is very limited. Somewhat more land could be brought into production with significant investment in reclamation or irrigation, but the rate of increase of irrigation is slowing because water is another increasingly scarce resource.
In any case, over the last 50 years, the increase in agricultural production has been achieved mainly by increasing crop yields - the overall agricultural area has expanded relatively little. In 1960, the global area under arable and permanent crops was about 1.4 billion ha. By 1990, this had expanded by. Just 3.5% to 1.48 billion ha. But the world's farmers were able to grow about one billion tons more cereals in 1990 compared with 1960 According to FAO, four-fifths of agricultural growth in developing countries is likely to come from intensification (increased yields, multiple cropping and shorter fallows).
Agricultural irrigation uses over 70% of the world's supplies of developed water and in the drier farming regions crop production is heavily dependent on irrigation practice. Agriculture is facing increased competition for limited water resources. During the next three decades, there will be an increasing number of water-deficit countries and regions including not only West Asia and North Africa but also some of the major agricultural producing regions of the world such as the Indian Punjab and the central plain of China. The efficiency of utilization of irrigation water is often low and around 50% of the increase in demand for water could be met by increasing the effectiveness of irrigation (D. Seckler et al., 1998). It is therefore extremely important to improve the efficiency of water use and it is established that something approaching the economic maximum of plant material ensures high water use efficiency. This objective will be achieved only with a well nourished plant. Other experiments have shown that the return from nitrogen is much increased by irrigation (G. Cooke., 1966, pages 245-246, J.C. Ignazi, 1992 and J.S.P. Yadav et al., 1998). In fact any input factor that increases economic yield will improve water use efficiency (FAO, 1984).
UNDP's 1998 Report
UNDP's 1998 World Human Development Report emphasizes the fact that it is the poor which are hit hardest by environmental degradation. Past deterioration of resources worsens current poverty. This renders very difficult the important tasks of the preservation and restoration of agricultural resources, reforestation, prevention of desertification, the fight against erosion and soil nutrient replenishment. It is a vicious circle. Individuals confronted with poverty are obliged to over-exploit resources, which risks exhausting them, which in turn increases their poverty. The poor will be increasingly pushed to live on fragile land, by the end of the next decade it is possible that a billion poor people will have live on fragile land as against 500 million today.
The problem of land degradation is most serious in Africa and Asia, with two thirds of the world's poor. The problem of land degradation is worse in and areas. And this is not particular to developing countries. The continent which has the largest area of and land subject to desertification is North America (74%), just ahead of Africa (73%).
Deforestation is another problem. Almost a third of the earth's forest have disappeared and about two thirds of those which remain are subject to serious modifications. Forests retain and regulate water and their destruction can lead to floods and drought.
Today about a third if the world's population depends on renewable resources. By 2025 a substantial proportion of the population of sub-Saharan Africa and South Asia will depend largely on these resources, as will a substantial number in Latin America and the Caribbean. The area of arable land per person is likely to be half the present low level of 0.27 ha. By 2050 more than two billion people will live in regions with a land shortage, due to desertification and degradation, in particular in South Asia and sub-Saharan Africa.
In the world as a whole, the use of water is increasing rapidly. By 2025 it will have increased by 40%. By 2050 the number of people suffering from a water shortage will increase from 132 million to between 1 and 2.5 billion. Almost two thirds of the world's population will be confronted with a moderate or high shortage of water. Some believe that water will be an important cause of wars in the 21st century.