One of the shared concerns of all types of environmentalism is opposing pollution, often defined to include the emission of greenhouse gases such as carbon dioxide (see global warming and climate change issues).
The term in both senses was first used in the early 20th century. They are related by the observation that if one's surroundings play a great role in individual development, and those surroundings are either green, beautiful, healthy and thriving, or gray, ugly, degraded, unhealthy and unable to sustain themselves, two different attitudes to life develop. This is reflected in the modern controversy over measuring well-being which often places importance on aesthetics and experience of a healthy natural environment, e.g. gardens.
As human population[?] and industrial activity have increased, the growth of (political, nature-promoting) environmentalism reflects considerable controversy, with those who place high importance on environmentalism (environmentalists) coming into conflict with those who accord it lesser importance or who otherwise disagree with various elements of the environmentalist's current agenda.
Environmentalists often clash with others over issues of the management of natural resources, e.g. the atmosphere as a "carbon dump", the focus of climate change and global warming controversy. They usually seek to protect commonly owned, or unowned, resources for future generations.
Those who take issue with new untested technologies are more precisely known, especially in Europe, as political ecologists. They usually seek, in contrast, to preserve the integrity of existing ecologies and ecoregions, and in general are more pessimistic about human 'management'.
Various extreme ideologies of radical environmentalism, and several ecology-based theories of anarchy (known as (small-g) green anarchism) are often cited to justify equipment sabotage, logging or fishing blockades, and even burning of houses impinging on a natural ecology. Environmentalists differ in their views of these ideologies and groups, but almost all condemn violent actions that can harm humans. They are somewhat more tolerant of the destruction of property not essential to sustaining or saving human life. The most extreme, sometimes called terrists, often claim to view themselves as part of nature, simply acting to protect itself from man.