Geographic characteristics of drylands u Dryland areas are generally very windy as there is less dense vegetation to reduce wind speeds. There are a number of geographic features that u Strong winds and bare soils produce frequent dust distinguish drylands from other environments. storms; soil fertility tends to be poor, with little The main features are described below. organic matter and low soil moisture. u The predominant feature of drylands is water u It can take 5–10 times longer for the natural scarcity, with low, irregular and unpredictable regeneration of vegetation and soils in drylands precipitation, seasonally, annually and spatially. compared to other places that receive greater and Figure 9.5 illustrates the climate patterns for more reliable rainfall. Zinder, a semiarid location in Niger. u Dryland ecosystems are prone to desertification u Precipitation can often be in the form of short, as they are vulnerable to over-exploitation and heavy falls which are not readily absorbed by the inappropriate land use by people. soil; this means that up to 90 per cent of rain is evaporated. In arid and semiarid zones more water Economically, drylands support 44 per cent of the is evaporated than falls over the average year. world’s food production systems and 50 per cent of the world’s livestock. They are home to one-third of global population. However, indicators of wellbeing, such as Figure 9.5 Climograph for Zinder, Niger Gross National Income per capita (GNI) and education Te e at e C levels, are all lower in dryland regions compared ain all illi et e to other environments where rainfall is higher and 3 more reliable. Rainfall (millimetres) Typical land uses in drylands can be seen in the following graph, figure 9.6. 3
Temperature (°C) Temperature N Month e age te e at e C e age e i itati n
Figure 9.6 Land uses in drylands and hyperarid areas
a ing C land U an the h id e ia id
id e a id
3 er e ge re r e e r er ri re
ACTIVITIES 1. Why is desertification considered a global-scale issue? 8. Refer to the climograph for Zinder, figure 9.5, and use data 2. Why are drylands important? from the graph in your answers. 3. Refer to figure 9.1. List the possible difficulties people a. Using an atlas or Google Earth describe the location would have farming in this environment. of Zinder. 4. Use figure 9.2 to describe the distribution of those regions b. Which months receive the most/least rainfall? of the world with a high risk of desertification. c. Given that 92 per cent of the precipitation that falls in 5. Use figure 9.2 to describe the spatial association between Zinder each year is in the form of thunderstorms, what the distribution of regions with a high risk of desertification impacts might this have on the environment? and the different types of drylands. d. Describe the seasonal variation in temperatures for Zinder. Changing the land 6. Identify the characteristics of drylands that make them 9. How might the climate pattern of Zinder influence the type u vulnerable to desertification (see figure 9.4). of agriculture that takes place in this region?
UNIT 3 7. List three differences between drylands and hyperarid or 10. Refer to figures 9.3 and 9.6. What is the relationship desert regions. between the types of dryland, the length of the growing season and land use? 122