There are three factors that have magnified the human impact on the earth. For example, world population quadrupled in the 20th century consisting of massive use of fossil fuels, and enormous economic growth. There was an uneven spread of all three over the world, but economic growth came to appear possible and desirable almost everywhere. This lead to human environmental disruptions becoming a part of global proportions. Because of the doubling of cropland and corresponding contraction of forests and grasslands, numerous extinctions of plant and animal species, air pollution in many major cities and rivers, and chlorofluorocarbons (CFCs) thinned the ozone layer. By 2000, scientific consensus on the occurrence of “global warming” as the result of burning of fossil fuels and loss of trees.
Environmentalism began in the 19th century as a response to the Industrial Revolution. It only became a global phenomenon in the second half of the 20th century which began in the West with Rachel Carson’s Silent Spring. Actions came from the grass roots and citizen protests. In Germany, environmentalists entered politics as the Green Party where environmentalism took root in developing countries in 1970s–1980s. This tended to be more locally based, involving poorer people, more concerned with food security, health, and survival, and more focused on saving threatened people, rather than plants and animals. Environmentalists sometimes have sought basic changes in political and social structure of their country.