Good Nature

Collectively, the impact of human beings and their activities is changing the face of Earth. The lights of cities can be seen from orbit; large areas that were once forests, wetlands, and grasslands have been transformed into agricultural land, housing tracts, and cities; and the gases produced by vehicles and other machines are altering the planet’s atmosphere, by adding chemicals that strengthen the atmosphere’s ability to trap heat energy. By the end of the 20th century, greenhouse gas emissions from human activities had become so great that they had begun to influence the world’s temperature and precipitation patterns, and scientists and other experts began to worry how these changes would affect natural ecosystems, the reliability of crop production, and our future way of life.