iii. Changing one of the factors, such as land use, has potential impacts on other factors, such as flora and fauna, etc.
5.0 Conclusion
Land encompasses such features as underlying superficial deposits, climate and water resources, and also the plant and animal communities which have developed as a result of the interaction of these physical conditions. Land is a store of wealth for individuals, groups, or a community.
6.0 Tutor Marked Assignments
1. State five functions of land.
2. Define land resources.
7.0 References and other Resources
Di Gregorio, A. and Jansen, L.J.M. (1998). Land Cover Classification System (LCCS):
Classification Concepts and User Manual. For software version 1.0.
GCP/RAF/287/ITA Africover - East Africa Project in cooperation with AGLS and SDRN. Nairobi, Rome.
Food and Agriculture Organization/United Nations Environment Programme. (1997).
Negotiating a Sustainable Future for Land. Structural and Institutional Guidelines for Land Resources Management in the 21st Century. FAO/UNEP, Rome.
The Approach - Facing the Challenge. http://www.fao.org/3/x3810e/x3810e04.htm. Accessed 14.07.2020.
UNIT 2: STATUS OF LAND
The world‘s net cultivated area has grown by 12 percent over the last 50 years, mostly at the expense of forest, wetland and grassland habitats (Food and Agriculture Organization 2011). At the same time, the global irrigated area has doubled. The distribution of these land and water assets is unequal among countries. Although only a small proportion of the
world‘s land and
water is used for crop production, most of the easily accessible and (thus economic) resources are under cultivation or have other ecologically and economically valuable uses. Thus the scope for further expansion of cultivated land is limited. Only parts of South America and sub-Saharan Africa still offer scope for some expansion.
2.0 Objectives
By the end of this unit, student should be able to understand:
i. land distribution and suitability around the world;
ii. land resources in rainfed agriculture and iii. rainfed productivity and production gaps.
3.0 Main Content
3.1 Land Distribution, Use and Suitability around the World
The global land area is 13.2 billion ha. Of this, 12 percent (1.6 billion ha) is currently in use for cultivation of agricultural crops, 28 percent (3.7 billion ha) is under forest, and 35 percent (4.6 billion ha) comprises grasslands and woodland ecosystems (FAO 2011). Low-income countries cover about 22 percent of the land area. Land use varies with climatic and soil conditions and human influences.
Deserts prevail across much of the lower northern latitudes of Africa and Asia. Dense forests predominate in the heartlands of South America, along the seaboards of North America, and across Canada, Northern Europe and much of Russia, as well as in the tropical belts of Central Africa and Southeast Asia.
Cultivated land is a leading land use (a fifth or more of the land area) in South and Southeast Asia, Western and Central Europe, and Central America and the Caribbean, but is less important in sub-Saharan and Northern Africa, where cultivation covers less than a tenth of the area
FAO defines land suitability for agriculture in terms of capacity to reach potentially attainable yields for a basket of crops. Assuming well-adapted production systems are used, currently cultivated land is mostly of prime (28 percent of the total) or good quality (53 percent). The highest regional proportion of prime land currently cultivated is found in Central America and the Caribbean (42 percent), followed by Western and Central Europe (38 percent) and Northern America (37 percent). For high-income countries as a whole, the share of prime land in currently cultivated land is 32 percent. In low-income countries, soils are often poorer and only 28 percent of total cultivated land is classed as prime.
3.2 Land Resources in Rainfed Agriculture
Rainfed agriculture is the predominant agricultural production system worldwide. As practiced in highland areas and in the dry and humid tropics, it is the system in which poorer smallholder farmers predominate and where the risks of resource degradation are highest. Soil nutrient availability in many rainfed lands tends to below, and sloping terrain and patterns of rainfall and runoff contribute to erosion. High temperatures and low and erratic precipitation often make soil moisture availability inadequate, and techniques to improve water availability (such as water harvesting) are expensive. Higher levels of input and management can increase productivity, but many farmers cannot afford the costs or risks. All these factors affecting land and water for rainfed agriculture as practiced by the poor contribute to their vulnerability and to their food insecurity.
3.3 Rainfed Productivity and Production Gaps
The productivity of rainfed cropping is measured by yields (production per unit of area).
Productivity varies enormously, and is highly sensitive to factors other than soil and water – for example, the availability and affordability of technologies and inputs, access to market, and the local financial returns.
In sub-Saharan Africa, yields have changed little since the 1960s, and increases in production have come almost entirely from land expansion. Rainfed maize yields, for example, have remained constant at around 1t/ha. In Latin America and the Caribbean, by contrast, yields for rainfed maize tripled over the same period, from little more than 1t/ha to over 3t/ha. Average wheat yields across Europe more than doubled (2t/ha to over 5t/ha).
3.4 Land and Water Resources in Irrigated Agriculture
Irrigated systems have expanded in recent years to bring water control, which, together with rapid increases in water productivity, has greatly boosted agricultural production and incomes.
However, most irrigated farming systems are performing well below their potential, and there is considerable scope for improving land and water productivity. Groundwater abstraction has provided an invaluable source of ready irrigation water, but has proved almost impossible to regulate. As a result, agriculture withdrawals of groundwater are intensifying and some key aquifers are being depleted. Water quality is deteriorating, with impacts from irrigation on both surface and groundwater, and the salinization of irrigated lands is a growing problem.
4.0 Summary
In this unit we have leant that:
i. In low-income countries, soils are often poorer and only 28 percent of total cultivated land is classed as prime.
ii. Groundwater abstraction has provided an invaluable source of ready irrigation water.
iii. FAO defines land suitability for agriculture in terms of capacity to reach potentially attainable yields for a basket of crops.
5.0 Conclusion
Land use varies with climatic and soil conditions and human influences. Soil nutrient availability in many rainfed lands tends to below, and sloping terrain and patterns of rainfall and runoff contribute to erosion.
.
6.0 Tutor Marked Assignments
1. Explain the significance of land resources in rainfed agriculture.
2. Discuss how land expansion is contributing to increase agricultural production in sub Saharan Africa.
7.0 References and other Resources
Food and Agriculture Organization (2011). The state of the world‘s land and water resources for food and agriculture (SOLAW) – Managing systems at risk. Food and Agriculture Organization of the United Nations, Rome and Earthscan, London.
UNIT 3: FORESTS AND RANGELANDS