If you thought tourists carving their names into the Colosseum walls was as bad as it gets, think again.

One of Iceland's famous moss-covered hills has this week been ‘graffitied’ with the immortal line, “Send nudes”.

The words have been formed on the hill near near Nesjavellir on the south of the island by tearing clumps of moss from the ground. It is expected that the slogan will remain there for decades while the moss grows back.

The damage was spotted by tour guide Gunnar Birgisson. "I think someone was trying to be funny," he told The Independent. "But they don't realise they are vandalising nature and possibly causing this to spread."

Birgisson told Iceland Monitor that something has to give. The hill has many words ‘written’ on it, he says; and while some are in Icelandic, the increase in English – specifically “LIFE” and now “SEND NUDES” – suggests they’re the work of tourists.

Birgisson, who’s seen ugly tourist behaviour including people defecating in the countryside and “spray-painting a deserted farm” in the name of art, says “They believe everything is allowed in Iceland.”

"People come from such different places from Iceland that they don't know what's right and wrong," he told The Independent. "And it's a herd mentality. Some guy went up there many years ago and wrote his name. He was an Icelander, and by doing so he started it. One pair of footprints can motivate thousands to follow. It's the same with offroading - an area will be untouched for decades until one person drives on it and then everyone thinks it's allowed, so the whole area gets covered with tyre tracks. Everyone I know has caught someone offroading. They always say the same thing - that they didn't know it wasn't allowed - even though they all have a big yellow sticker on the dashboard of their rental car telling them not to do it. People need to know the law and respect it."​

Tourism has exploded in Iceland in recent years. 2016 saw more American tourists on the island than the entire Icelandic population, and 2 million visitors are expected to descend on Iceland this year – a ten-fold increase from the 200,000 who visited in 1996. The growth is seen by many locals as toxic, with Airbnbs pushing out residents, Reykjavik heaving with travellers and the main sites swamped by camera-wielding visitors.

Tour guide Árni Tryggvason, who has written a book about how tourists should behave in his country called What, Where and How, fears that mindless tourism is causing environmental problems that will be here for decades. He told The Independent:

Iceland is famous for its moss-covered landscape (Vifilsfell Moss shown here) is famous - but damage to it can take decades to repair (Hafsteinn Robertsson/Flickr (cc by 2.0))

“Today, with a rapidly growing tourism we can see endless new bad footprints all over the country. People are writing in moss, driving off-road, stacking stones, writing with stones and spilling vegetation. I’ll say that the damage is not made by bad intention, only by people who don't know how vulnerable nature and especially the vegetation is in this country where the summer only lasts for two or three months.

“The “graffiti” we see there will last for at least 70 years. It’s a horrible view and is a challenge for other shallow people who see it to do the same. Someone wrote the first words and others followed.”

However, he added that defacing the landscape is not something only foreigners have done.

“Writing in moss was something too many Icelanders thought was OK until around 1960,” he told The Independent. “Not so far from Reykjavík we can see big mossy mountain slopes where some Scout groups wrote their names in about 1950 and the words are still clearly visible.”

However, he added, “Since then, we think differently about nature.