A grassroots movement, focused on sustainable management of resources and stewardship of the Earth, through changes in public policy and individual behavior.

In its recognition of humanity as a participant in (not enemy of) ecosystems, the movement is centered on ecology, health, and human rights.

The environmental movement is represented by a range of organizations, from large to grassroots entities. Due to its large membership, varying and strong beliefs, and occasionally speculative nature, the environmental movement is not always united in its goals. At its broadest, the movement includes private citizens, professionals, religious devotees, politicians, and extremists. Environmentalists are also often linked with other social movements, such as human and animal rights and pacifism.

The environmental movement in the United States can be traced back to the early conservation movement and the establishment of Hot Springs National Park in 1832. Two early conservationists stood out as leaders; Henry David Thoreau and George Perkins Marsh. Thoreau was concerned about the wildlife in Massachusetts. He wrote Walden; or, Life in the Woods as he studied the wildlife from a cabin. Marsh was influential with regards to the need for resource conservation.

The roots of the modern environmental movement can be traced to attempts in nineteenth-century Europe and North America to expose the costs of environmental negligence, notably disease, as well as widespread air and water pollution, but only after the Second World War did a wider awareness begin to emerge.

During the 1950s, 1960s, and 1970s, several world events illustrated the magnitude of environmental damage caused by humans. In 1954, the 23 man crew of the Japanese fishing vessel Lucky Dragon was exposed to radioactive fallout from a hydrogen bomb test at Bikini Atoll. In 1962, the publication of the book Silent Spring by Rachel Carson drew attention to the impact of chemicals on the natural environment. In 1967, the Torrey Canyon oil tanker went aground off the southwest coast of England, and in 1969 oil spilled from an offshore well in California's Santa Barbara Channel. In 1971, the conclusion of a law suit in Japan drew international attention to the effects of decades of mercury poisoning on the people of Minamata.

At the same time, emerging scientific research drew new attention to existing and hypothetical threats to the environment and humanity. Among them were Paul R. Ehrlich, whose book The Population Bomb, published 1968, revived concerns about the impact of exponential population growth. Biologist Barry Commoner generated a debate about growth, affluence and "flawed technology." Additionally, an association of scientists and political leaders known as the Club of Rome published their report The Limits to Growth in 1972, and drew attention to the growing pressure on natural resources from human activities.

Meanwhile, nuclear proliferation and photos of Earth from outer space emphasized the consequences of technological accomplishments, as well as Earth's truly small place in the universe.

In 1972, the United Nations Conference on the Human Environment was held in Stockholm, and for the first time united the representatives of multiple governments in discussion relating to the state of the global environment. This conference led directly the creation of government environment agencies and the UN Environment Program. Soon after, the United States also passed new legislation such as the Clean Water Act, the Clean Air Act, the Endangered Species Act, and the National Environmental Policy Act- the foundations for current environmental standards.

One of the earliest lawsuits to establish that citizens may sue for environmental and aesthetic harms was Scenic Hudson Preservation Conference v. Federal Power Commission, decided in 1965 by the Second Circuit Court of Appeals. The case helped halt the construction of a power plant on Storm King Mountain in New York State.

Since the 1970s, public awareness, environmental sciences, ecology, and technology have advanced to include modern focus points like: ozone depletion, global climate change, acid rain, nuclear power and weaponry, with its accompanying radioactive leaks and accumulating waste, lacking a method for safe, long-term disposal options, and lastly the harmful potential and threats to biodiversity presented by genetically modified organisms (GMOs).

In recent years, the environmental movement has increasingly focused on global warming as a top issue. The world's primary international agreement on combating global warming is the Kyoto Protocol, an amendment to the UNFCCC negotiated in 1997. The Protocol now covers more than 160 countries globally and over 55% of global greenhouse gas emissions. Only the United States and Kazakhstan have not ratified the Kyoto treaty, with the United States historically being the world's largest emitter of greenhouse gas.

As concerns about climate change moved more into the mainstream, from the connections drawn between global warming and Hurricane Katrina to Al Gore's film An Inconvenient Truth, many environmental groups refocused their efforts. In the United States, 2007 witnessed the largest grassroots environmental demonstration in years, Step It Up 2007, with rallies in over 1,400 communities and all 50 states for real global warming solutions. The Kyoto treaty expires in 2012, and international talks began in May 2007 on a future treaty to succeed the current one.

During its 8 years in office, the Bush administration refused to participate in international efforts to address global warming, and made ongoing efforts to undermine scientific evidence on the subject. Speaking at the G8 Summit in August, 2008 Dr. James Hansen, Head of NASA's Goddard Institute for Space Studies pointed out the urgency to act, stating that "we have used up all slack in the schedule for actions needed to defuse the global warming time bomb."

In 2008, Barack Obama was elected President, promising during his campaign to take swift action to effectively address global warming. 

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