The study of interaction among populations continues

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The study of interaction among populations continues to be one of contemporary ecol- ogy’s major emphases. Our need to control populations, including our own, grows daily. In the next chapter, after we have learned more about community ecology, we will dis- cuss the impacts of human populations and activities on other species. Suffice it now to say that the control of human populations, by methods that are equitable, humane, and ethical, is one of the major challenges facing humanity. Our need to do so will intensify in the 21st century. Human activities and interests affect nearly every other species on Earth. Increas- ingly, we spend more and more of our resources on the study and management of crit- ical species—trends that will continue. If you are looking for a career for the next 50 years, the study, control, and management of biological populations has great potential. Often, our goal is to reduce population numbers to manageable levels. Pests claim an estimated 40–50% of our crops. Periodic outbreaks of insect or fungal infestations wreak havoc on the crops of entire regions of developing countries.We are, literally, at war with our pests. Our strategy to fight this war is a complex set of principles and tech- niques called integrated pest management , which is composed of carefully thought-out combinations of pesticides, biological agents, crop rotation, pest-resistant cultivars, and anything else that works. The hope is that these will create sufficient environmental resistance to keep pest numbers in check. But it’s a war we are barely winning. Pests evolve characteristics to overcome elements of control almost as fast as we can develop them. Whenever they detect a chink in our techniques or resolve, pests respond with exponential growth. Fighting Back Discuss some examples of how integrated pest management is being used to control pests. How might IPM techniques be used by homeowners in controlling household and yard pests? Similar is our need to control alien species , those that become established in regions in which they are not native (Figure 15-27). (See also Chapter 9.) Purple loosestrife is a lovely wildflower in its native Europe. In North America it has become a scourge to wetlands. Zebra mussels are relatively unimportant in their native Caspian Sea. Soon after their appearance in the Great Lakes in 1986, they became a serious nuisance, Figure 15-27 Many of the worst pests in the United States are not native to North America. (a) Kudzu, a vine that is destroying millions of acres of native plants in the southeastern United States, is native to Japan. (b) Norway rats, which are very destructive, come from Europe. (a) (b)
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Exploration 520 C HAPTER 15 Population Ecology: How Do Organisms Interact to Form Populations? clogging water intakes of power plants, among other things. Now they are spreading south, west, and east. North America is currently hosting an estimated 5000 nonnative species, and new introductions are reported almost daily. Where do they come from?
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