Dozens of environmentalists set up their tents near Heathrow airport in London to protest towards the facility’s expansion and bring into the spotlight the air transport's contribution to global warming.

The protesters were warned by the British police that they will suffer harsh penalties if any air traffic disruptions are reported. Campaigners want to express their discontent regarding the construction of another runway at Heathrow and draw attention on the effects that air transport has on the environment.

About 250 activists were present on Tuesday at the camp’s formal opening, more being expected to attend the mass protest scheduled to last one week. Rumors that the campaigners are going to take their protest into the airport and try to disrupt normal activities, prompted the authorities to dispatch several hundred police officers near the ad hoc camp.

But a spokesman of the activists denied that they will resort to such practices, saying their “protests will be non-violent” and their main target is the entire industry, not a facility. Heathrow is one of the busiest airports in the world, one airplane taking off or landing every minute during the holiday season’s peak.

According to experts, aircrafts contribute much more to air pollution than vehicles due to the altitude they operate and amount of carbon dioxide produced.