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Each person in the United States generates five or more pounds (2.3 kilograms) of waste a day: about the weight of a medium bag of sugar. More than half of that garbage is buried and stored in landfills. Increasingly, however, cities are promoting recycling programs, often getting schools involved so students can learn about recycling and follow these practices at home. A person in a Scandinavian country (such as Sweden, Denmark, or Norway) generates about the same amount of waste as an American. People in developing countries generate less waste than Americans or Europeans; for example, a person in India generates about three-fourths of a pound (0.34 kilograms) per day. Still, every country must find a way to process the garbage that each of its residents generates every day, month, and year.

For at least 10,000 years, humans have been cultivating plants and selectively breeding them for fast growth, pest resistance, long-term survival in storage, and bigger and better fruit. We've been domesticating animals for just as long, selecting for traits that suited our needs, such as size, appearance, or even personality. For a few decades, we've also had genetic engineering methods for getting the characteristics we want in plants, animals, and microorganisms.

Climate change and the human contribution to this change is sometimes denied or depicted as an uncertainty. However, according to the American Association for the Advancement of Science (see References and Further Reading), climate change is not controversial: 97 percent of climate scientists are certain that human-caused climate change is occurring. Climate research is continuing, with scientists and engineers working to predict the consequences of climate change and finding ways to overcome its negative impact.