Non-EU Switzerland is grappling with a gathering political storm over rising immigration, increasingly from the economically troubled European Union but the debate comes with a twist.

Supporters of drastic cuts in immigration to the landlocked nation say they want the inflow of foreigners stopped as the country's growing population poses a threat to Switzerland's resources, its environment and its natural beauty.

Switzerland has had right-wing campaigns against immigration in the past but it is the first time that a group committed to environmental protection has taken up a cause that is politically loaded and confounds many on the Swiss political spectrum.

Most environmentalists -- in Switzerland as elsewhere -- are left-wing or left-of-center and seldom bring immigration into their political campaigns.

Switzerland's Ecopop is different. This week the group gathered enough signatures from Swiss citizens to force a referendum on immigration, handing in its petition to the Chancellery in Bern.

The right-wing Swiss People's Party earlier announced it also has enough signatures to force a referendum on tougher immigration.

About one-fourth of Switzerland's population of 8 million is foreign. Although many foreigners earn Swiss residency on the strength of their bank accounts, more recently the eurozone's jobless have poured into the country, looking for employment.

However menial the jobs, the European unemployed can expect to find better pay in Switzerland than in their own countries or distressed job markets in the eurozone.

Ecopop campaigned and collected 120,700 certified signatures, comfortably more than the 100,000 needed under Swiss constitutional law to force a referendum on new rules for controlling the foreign arrivals.

Ecopop says Switzerland is suffering from overpopulation, threatening its natural resources and straining its public services. It wants immigration capped at 0.2 percent.

Ecopop member Philippe Roch, a former director of the Swiss environment department, told news media that Swiss quality of life was under threat because of the continuing pressure on the country's natural resources and the strain caused to its countryside.

The group denies it has a racist or xenophobic agenda and analysts say Ecopop draws inspiration from U.S. biologist Paul R. Ehrlich, co-author of a 1968 book "The Population Bomb." The Stanford University professor and his wife Anne Ehrlich argued the current pace of population growth could lead to mass starvation and called for measures to limit population.

The book's original premise predicted millions of deaths in the 1970s and 1980s due to a population explosion.

Ecopop says overcrowding is a growing challenge for Switzerland and wants new controls to stem the inflow of foreigners. Swiss rules can lead to a referendum on any issue that collects signed endorsements of a petition from more than 100,000 people.

Switzerland reintroduced in April immigration quotas for workers from central and eastern European countries but recent trends suggest many of the latest arrivals may be from troubled southern European states of Italy, Portugal and Spain.