Initiatives aimed at reining in the number of immigrants, asylum seekers and refugees to the wealthy Alpine nation have been abundant in recent years.

Most recently, voters in February narrowly approved reinstating quotas for immigration from the neighbouring European Union, throwing non-member Switzerland's relations with the bloc into turmoil.

But while saving Swiss jobs and culture are often cited as reasons to tighten the borders, Sunday's vote marks the first justifying its demand to cut immigrant numbers with their impact on the country's environment. The so-called Ecopop initiative maintains the current influx of foreigners is swelling the country's population and cities and shrinking its idyllic landscapes and green spaces. "Population growth is at historic levels in Switzerland," said Anita Messere, part of the Ecopop committee behind the initiative.

"This is really harming the environment," she told AFP, arguing that the inhabitable plains of the mountainous country were being covered in concrete at a rate of more than one metre per second. Foreign nationals already make up nearly a quarter of Switzerland's some eight million inhabitants, according to official statistics.

And immigration is adding 1.1-1.4 per cent annually to the Swiss population, according to Ecopop, which wants the country to push that percentage down to the European average of just 0.2 per cent.

Once balanced against the some 93,000 people who emigrate from Switzerland each year, immigration would at that rate add around 16,000 more people to the population annually, allowing it to grow to 8.5 million by 2050. But if nothing is done, Switzerland will count as many as 12 million people by 2050, according to the Ecopop campaign. To help rein in over-population beyond Switzerland's borders, it also calls for 10 per cent of the country's development aid budget to be dedicated to family planning initiatives abroad.

AFP