The Relationship Of Humans To Their Environment

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Expanding human populations and increasing intensity of human activity now threaten the earth's populations, which are critical to the ecological integrity of the biosphere. These global-scale threats include global warming, numerous forms of pollution, and widespread land clearing. Reducing or reversing these environmental challenges will require applying measures such as recycling of wastes, returning organic matter to soils, and using plants to reclaim damaged land. As we attempt to build a sustainable future, we should bear in mind that while plants can live without humans, we cannot live for long without plants.

It has been estimated that the total human population of the world was less than 20 million in 6000 B.C. During the next 7,750 years, it rose to 500 million; by 1850, it had doubled to 1 billion; and 70 years later, it had doubled again to 2 billion. The 4.48-billion mark was reached in 1980, and within 5 years, it had grown to 4.89 billion. It is presently increasing by nearly 100 million annually, and estimates for the year 2000 are 6.25 billion. The earth remains constant in size, but humans obviously have occupied a great deal more of it over the past few centuries or at least have greatly increased in density of population.

In feeding, clothing, and housing ourselves, we have had a major impact on our environment. We have drained wetlands and cleared natural vegetation from vast areas of land. California, for example, now has less than 6% of the wetland it had 100 years ago. We have dumped wastes and other pollutants into rivers, oceans, lakes; we have added pollutants to the atmosphere; and we have killed pests and plant disease organisms with poisons. These poisons have also killed natural predators and other useful organisms and, in general, have thoroughly disrupted the delicate balance of nature that existed before humans began degrading their natural surroundings.

If we are to survive on this planet beyond the 21st century, there is little question that humans have to stop increasing in numbers, and the many unwise agricultural and industrial practices that have accompanied the mushrooming of human populations must be replaced with practices more in tune with restoring some ecological balance. Agricultural practices of the future will have to include the return of organic material to the soil after each harvest, instead of adding only inorganic fertilizers. Harvesting of timber and other crops will have to be done in a manner that prevents topsoil erosion, and the practice of clearing brush with chemicals will have to be abolished. Industrial pollutants will have to be rendered harmless and recycled whenever possible.

Many products that now are still largely discarded (e.g., garbage, paper products, glass, metal cans) will also have to be recycled on a much larger scale. Biological controls (discussed in Appendix 2) will have to replace the use of poisonous controls whenever possible. Water and energy conservation will have to be universally practiced, and rare plant species, with their largely unknown gene potential for future crop plants, will need to be saved from extinction by preservation of their habitats and by other means. The general public will have to be made even more aware of the urgency for wise land management and conservation— which will be especially needed when pressures are exerted by influential forces promoting unwise measures in the name of "progress"—before additional large segments of our natural resources are irreparably damaged or lost forever. Alternatives appear to be nothing less than death from starvation, respiratory diseases, poisoning of our food and drink, and other catastrophic events that could ensure the premature demise of large segments of the world's population.

In recent years, scientists, and increasingly the general public, have become alarmed about the effects of human carelessness on our environment. It wasn't until the 1980s, however, that damage to forests and lakes caused by acid rain, the "greenhouse effect," contamination of ground water by nitrates and pesticides, reduction of ozone shield, major global climatic changes, loss of biodiversity in general, and loss of tropical rain forests in particular gained widespread publicity.

Human and Animal Dependence on Plants

Our dependence on green organisms to produce the oxygen in the air we breathe and to remove the carbon dioxide we give off doesn't stop there. Plants are also the sources of

products that are so much a part of human society that we largely take them for granted. We know, of course, that rice, corn, potatoes, and other vegetables are plants (Fig. 1.4); but all foods, including meat, fish, poultry, eggs, cheese, and milk, to mention just a few, owe their existence to plants. Condiments such as spices (Fig. 1.5) and luxuries such as perfumes are produced by plants, as are some dyes, adhe-sives, digestible surgical stitching fiber, food stabilizers, beverages (Fig. 1.6), and emulsifiers.

Our houses are constructed with lumber from trees, which also furnish the cellulose for paper, cardboard, and synthetic fibers. Some of our clothing, camping equipment, bedding, draperies, and other textile goods are made from fibers of many different plant families (Fig. 1.7). Coal is fossilized plant material, and oil probably came from microscopic green organisms or animals that either directly or indirectly were plant consumers. All medicines and drugs at one time came from plants, fungi, or bacteria, and many important ones, including most of the antibiotics, still do (Fig. 1.8).

Figure 1.4A Rice cakes being manufactured. Unprocessed rice is poured into small ovens where the kernels are expanded. The kernels are then compressed into cakes, which are conveyed by belt to a packaging area.

Recyling Plant Role Play Area
Figure 1.5 Some of the spices derived from plants.

Microscopic organisms play a vital role in recycling both plant and animal wastes and aid in the building of healthy soils. Others are responsible for human diseases and allergies.

Although gluts or shortages of oil and other fossil fuels may at present be politically or economically manipulated, there is no question that these fuels are finite and eventually will disappear. Accordingly, the development of alternative energy sources is receiving increased attention.

Methane gas, which can be used as a substitute for natural gas, has been produced from animal manures and decomposed plants in numerous villages in India and elsewhere for many years, and after several years of trial on a small scale in the United States, the production of methane on a larger scale from human sewage is being investigated. Potatoes, grains, and other sources of carbohydrates are currently used in the manufacture of alcohols, some of which are being blended with gasoline ("gasohol"), and such uses may increase in the future. In fact, electric cars, as well as buses and automobiles that can run on propane and either methanol (wood alcohol) or gasoline—or a mixture of both—are now in use in many communities in the United States and other parts of the world.

Figure 1.4A Rice cakes being manufactured. Unprocessed rice is poured into small ovens where the kernels are expanded. The kernels are then compressed into cakes, which are conveyed by belt to a packaging area.

Chapter 1

Coffee Beans Surface Area

Figure 1.6A Ripening coffee berries. They are picked by hand when they are red. The seeds are extracted for roasting after the berries have been fermented.

Humans Being Roasted

Figure 1.6B Coffee beans cooling after being roasted.

Cotton Shrub Flowers
Figure 1.7 Cotton plants. The white fibers, in which seeds are embedded, are the source of textiles and fabrics. The seeds are the source of vegetable oils used in margarine and shortening. After the oils have been extracted, the remaining "cotton cake" is used for cattle feed.
Penicillium Colony

Figure 1.8 A Penicillium colony. The tiny beads of fluid on the surface contain penicillin, widely used as an antibiotic.

Figure 1.6B Coffee beans cooling after being roasted.

Figure 1.8 A Penicillium colony. The tiny beads of fluid on the surface contain penicillin, widely used as an antibiotic.

What of plants and the future? As you read this, the population of the earth already has exceeded 6 billion persons, every one of whom needs food, clothing, and shelter in order to survive. To ensure survival, a majority of us eventually may need to learn not only how to cultivate food plants but also how to use plants in removing pollutants from water (Fig. 1.9), in making land productive again, and in renewing urban areas. In addition, many more of us may need to be involved in helping halt the destruction of plant habitats caused primarily by the huge increase in the number of earth's inhabitants. This subject and related matters are further discussed in Chapter 25.

Although at present the idea that humanity may not be able to save itself from itself may seem radical, there are a few who have suggested that it might become necessary in the future to emigrate to another planet. If so, microscopic algae could play a vital role in space exploration. Experiments with portable oxygen generators have been in progress for many years. Tanks of water teeming with tiny green algae are taken aboard a spacecraft and installed so that they are exposed to light for at least part of the time. The algae not only produce oxygen, which the spacecraft inhabitants can breathe, but they also utilize the waste carbon dioxide produced by respiration. As the algae multiply, they can be fed to a special kind of shrimp, which, in turn, multiply and become food for the space travelers. Other wastes are recycled by different microscopic organisms. When this self-supporting arrangement, called a closed system, is perfected, the range of spacecraft should greatly increase because heavy oxygen tanks will not be necessary, and the amount of food reserves needed will be reduced.

Inhabitants of undeveloped areas still use plants for food, shelter, clothing, and medicine and also in hunting and fishing. Today, small teams of botanists, anthropologists, and medical doctors are interviewing medical practitioners and herbal healers in remote tropical regions and taking

Figure 1.Q A polluted waterway in an urban area.

What Is Plant Biology? 7

notes on various uses of plants by primitive peoples. These scientists are doing so in the hope of preserving at least some plants with potential for modern civilization before disruption of their habitats results in their extinction.

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