PURPOSE Photographs are probably the best tool to illustrate effects of soil characteristics on land use, especially for laypersons. The purpose of this exercise is to assign students to take photos to illustrate soil conditions in their study areas or project areas, and to show examples of some photo­graphs that illustrate principles of soils perspec­tives. Each student should take at least 50 35-mm black-and-white or more than 20 color photos of contrasting soil properties within his or her area of interest. These photos should be taken over a period of at least several days or weeks so that differences in weather and lighting and angle of sun can be illustrated. Take several photos of the same scene under different weather conditions (calm versus windy; cloudy versus sunny; midday versus morning and evening; etc.). Experiment with close­up photos and wide-angle and telephoto lenses at different shutter speeds. Make notes on camera settings and weather conditions when each photo is taken. A lecture period should be devoted to discussion of the results, with examples exhibited of work of the various students. This exercise is an excellent method of learning by doing.

EXAMPLES The following photographs illus­trate some of the principles involved. Figure 30 is a close-up of roots of eucalypts that have been exposed by wind erosion. By getting close to the subject and carefully selecting the right angle, the photographer was able to emphasize the aesthetics of the weird and unusual formations made by the exposed roots. The shady dark side of the roots emphasizes the shape in shadows against the bright sky. The strange shapes force the viewer to th ink about the subject, which is an extensive area where more than 1 meter of soil has been removed by land abuse which caused the soil loss. Overgrazing is probably the cause, and the viewer must surely ponder about what can be done to reclaim the devastated landscape. Not even an impoverished sheep or goat is visible in the distance. If the photographer had taken a more distant view, the impact of the erosion process would probably have been much less.

Aerial photographs at an oblique angle often can be used to show landscape processes and landform

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Photographs

shapes. Figure 31 illustrates excellently the erosion and deposition on bare erosive soils. Notice that the aircraft from which the photo was taken is at a low altitude, and that the sun angle is low (morn­ing or evening). The long shadows accentuate the shapes of the shallow rills and small gullys. The plume of smoke in the distance adds to the viewer's feeling of devastation of the landscape. The photograph gives a feeling of desolation and desperation to the viewer, and anyone who has lived on such a farm knows the mental and physical anguish of such an experience of crops and soils washed away. This photograph presents a powerful argument for soil erosion control on farms.

Perspective is important, and the photographer must become a part of the landscape and compose the scene from his or her experience to create the desired effect. Figure 32 shows a village road in Honduras, with terrible ruts in the road (street) in the foreground. As a matter of fact, the photog­rapher's vehicle was stuck in the mud when the photo was taken. This photo conveys all of the implications of the horrifying effects of poor transportation systems due to poor soil conditions and lack of proper road construction and mainten­ance. Sick and injured people in the village cannot be transported quickly to a hospital, crops and produce cannot be effectively moved to market, village shops cannot be efficiently stocked, people cannot conveniently take a bus to the city to visit relatives, and the whole feeling of isolation and poverty is conveyed to the viewer. This photo helps the reader to realize that soil surveys and their interpretations should be of top priority toward regional economic development in a coun­try. The human condition is closely correlated to the soil conditions; this scene is near refugee camps and areas of revolutionary activities.

Photographers of soil conditions must be ever­perceptive and intensely seeking for scenes that express even the subtle expression of characteris­tics of soils. Figure 33 illustrates a modern scene at a shopping center in Manila. Most observers would see nothing wrong with the soils in the photo. On examining the photo closely, however, a definite warping can be seen in the surface of the

G. W. Olson, Field Guide to Soils and the Environment Applications of Soil Surveys© Dowden & Culver, Inc. 1984

parking lot pavement. This warping is due to the Vertisol characteristics of the soils, which are prone to shrinking and swelling. The unique lighting characteristics, the thin film of water on the pavement surface, and the accumulation of moisture in shallow puddles in depressions all contribute to accentuate the microrelief. The unique expression of surface warping in this photo­graph was not noticed until several weeks after the photo was taken, not until after the film had been developed and printed.

Figure 34 is another scene from the Philippines where very poorly drained soils have been de­veloped for human habitation without adequate drainage. Many disease and health problems are caused or aggravated by the wet soil conditions. Also, the political and economic conditions here are closely correlated to the soils. Often, swamps are developed because the land is cheap and can be sold after construction for quick profit. Or exploi­tive landlords capitalize on the population pressures with high rental charges. Commonly, areas such as this are the scenes of guerilla anti­govern ment activities. I ncreasi ngl y, progressive governments are recognizing that the human condition in such places must be improved to achieve a stable society, and programs are insti­tuted to improve conditions by providing drainage and improving the soils.

Some problems of soil management are truly overwhelming, and must be publicized by photo­graphs and other methods so that government action can be encouraged to take place as soon as possible. In Bangkok, for example, rapid spread of urbanization and industrialization is causing ex­cessive pumping of the groundwater from unstable geologic substrata. With the removal of the ground­water, the soil surface subsides-as much as 4 inches per year in some areas. The problem is increased because Bangkok is located on a low­lying delta at an elevation close to sea level, the area has a pronounced rainy monsoon season, and the sea level is rising because of the melting and recession of the polar ice caps. Scenes such as that in Figure 35 illustrate the problem, but flooding and subsidence is not apparent to most people during much of the year. Thus, most people are unaware

of the problem and the need for immediate action, and only a few scientists know the exact measure­ments of the subsidence (Figure 36). Control of the problem would involve legislation to regulate groundwater pumping, increasing supply of water from other sources, construction of dikes and pumping stations, building dams and flood control structures at the upper reaches of the watershed, and reducing runoff and soil erosion throughout the vast drainage basin. Soil surveys should provide an important base in planning and development of all these land-use improvements. Photographs such as those in Figures 35 and 36 can play an impor­tant role in informing the public and stimulating government action. Such soil subsidence problems are common to many low-lying coastal cities, including London, New Orleans, and Venice.

Contrast photographs can be especially valuable to show good and poor soil conditions, and the resultant economic consequences. In New York State 100 years ago, most of the land was occupied by small farms, regardless of the soil conditions. Steep slopes and wet soils were plowed with teams of horses, and even stony and shallow-to-bedrock places were cleared and cultivated. Soil surveys were not available, and land settlement was by trial and error. After 100 years, however, the results of the trial-and-error experiment of land development can be seen scattered over the landscape. Soils with steep slopes, poorly drained conditions, shallow­ness to bedrock, infertility, and other severe problems are generally related to abandoned or failing farms-and the good soils are companions with prosperous farms and productive agriculture. Statistically, the better farms are located on the better soils, and the poorer farms are located on the poorer soils (with only a few exceptions). Figures 37 and 38 are paired contrast photographs that illustrate the corresponding soil and land-use correlations. Both photos were taken within the same area near Lowville in northern New York State. Such contrast photographs present a power­ful argument that soils are important in determin­ing land use, and that we should be more aware of soil differences in the future than we have been in the past.

Photographs / 65

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FIGURE 30/Roots of mallee (eucalypt) thicket or brush vegetation which have been exposed by wind erosion of the surrounding soil in northwestern Victoria, A ustralia (photo from Soil Conservation Authority).

FIGURE 32/Ruts in road in Honduras in soils with a critical plasticity index (photo by David Olson).

66 / Field Guide to Soils and the Environment

FIGURE 31/0blique aerial photograph of eroded farm near Walla Walla, Washington, after a heavy rain (photo by Soil Conservation Service).

FIGURE 33/Warping of pavement in Manila according to the expansion and contraction of the soils.

FIGURE 34/Urban development on very poorly drained soils. This area could be much improved for human habitation through drainage.

FIGURE 35/Flooding in Bangkok due to subsidence of the soils. Excessive groundwater pumping is lowering the geologic substrata, and the sinking soil surface increases the flood hazards with each passing year.

Photographs / 67

FIGURE 36jMonitor we/! installed to a depth of several hundred feet a few months before this photo was taken. The elevation of the tube casing is stable, but the concrete floor in the shelter for the well has broken away as the ground surface settles. This photo provides a definite record that the soil surface has sub­sided several inches within just a few months time.

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FIGURE 37/Abandoned farm on soils with problems for agriculture, near Lowville in northern New York State.

FIGURE 38/Productive farm on soils with good characteristics for farming, near Lowville in northern New York State.