Ecotage is a portmanteau of the "eco-" prefix and "sabotage". It is used to describe (usually) illegal acts of vandalism and violence, committed in the name of environmental protection. As a term it goes back to 1972 and predates the more recent neologism eco-terrorism. Ecotage is also referred to as ecodefense or monkeywrenching.
The Earth Liberation Front (ELF), Animal Liberation Front (ALF) and Earth Liberation Army (ELA) claims that ecotage requires neither aggression nor any direct confrontation with police, politicians, or other authority, as the actions are carried out in secret and at times of day where the risk to life is nil. However, certain types of ecotage (e.g., tree spiking) can cause injury or death after the act has been committed.
According to its detractors, the reverence for life professed by those who perform ecotage is not reflected in their disregard for property rights or willingness to risk the lives and safety of humans to make a political point. Supporters believe this type of criticism puts more value on property than on life. Furthermore, most groups and individuals who engage in ecotage say they take all necessary precautions to avoid causing injury or death to any humans.
- Main article: Timeline of Earth Liberation Front actions
Some of the more well known cases of ecotage are:
- 1998 – Arson of buildings at Vail Mountain in the United States by the Earth Liberation Front (ELF).
- 1999 – On December 25 in Monmouth, Oregon, fire destroys the main office of the Boise Cascade logging company costing over $1 million. ELF claim responsibility.
- 1999 – Genetically engineered potatoes uprooted at Crop and Food research centre in New Zealand. 
- 2003 – On August 1, a 206-unit condominium being built in San Diego, California was burnt down causing damage in excess of $20 million. A 12-foot banner at the scene read "If you build it, we will burn it," signed, "The E.L.F.s are mad."
- 2003 – On August 22, arsonists associated with the Earth Liberation Front attacked several car dealerships in east suburban Los Angeles, burning down a warehouse and vandalizing several cars. All told, more than 100 cars were damaged or destroyed causing an excess of a million dollars in damages, most of them SUVs or Hummers which were targeted due to their low fuel efficiency.
- 2005 – Three counties and 20,000 customers lost electrical power on November 21 when activists shot out a transformer on at a power substation in South Middleton, Pennsylvania. Damage estimate: $300,000 
Ecotage was popularized in 1975 by Edward Abbey's book The Monkey Wrench Gang. It has also been treated in novels by T. Coraghessan Boyle (A Friend of the Earth), Carl Hiaasen (Tourist Season, Sick Puppy, Hoot), Neal Stephenson (Zodiac: The Eco-Thriller), and Richard Melo (Jokerman 8), and movies such as Choke Canyon (1986) and On Deadly Ground (1994).
Ecotage! is also the title of a 1972 humor book by Sam Love, which is the likely origin of the word.
- Radical environmentalist
- Environmental movement
- Operation Backfire (FBI)
- Green Scare
- The Green Anarchist Infoshop
- Ecodefense: A Field Guide To Monkeywrenching
- If An Agent Knocks: Federal Investigators and Your Rights
- Hit Where It Hurts
- Insurgent Desire
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