But a rise in pilgrimages to these once pristine areas have made the region a dumping ground for hundreds of tonnes of garbage and human waste which is contaminating nearby rivers, environmentalists say.

"Increased pilgrims to these areas is definitely taking its toll on these once beautiful and clean areas," said Shruti Shukla from WWF India.

"Plastic rubbish is found littered everywhere, nearby rivers are filled with human waste and roads have been built bringing in daily buses packed with pilgrims which is contaminating the air."

The Himalayan mountain range stretches across India, Bhutan, China, Nepal, Pakistan and Afghanistan and is often referred to as the "Roof of the World".

There are several popular Himalayan pilgrimage sites -- including Amarnath in India's Kashmir region, Gangotri, Kedernath and Badrinath in the northern state of Uttarakhand, as well as Mount Kailash and Lake Mansarovar in western Tibet.

Cashing in on India's economic boom and a rapidly growing middle class, many tour operators are now offering package tours to holy Himalayan sites.

The commercialisation of pilgrimages, some of which offer helicopter rides, has brought in hotels, guest houses, restaurants and roads.

Efforts have been made to clean up sites like the Amarnath shrine, where devotees flock to worship an ice stalagmite which forms every year and is believed to be a form of Shiva, but local volunteers say more needs to be done.

"Last year we tried to clean a portion of the track, but our efforts can only be termed as a drop in the ocean," said Mohammed Ashraf, president of Jammu and Kashmir Mountaineering Club.

Environmentalists say Gangotri, the origin of the Ganges river which Hindus believe to be sacred, has become a shanty town filled with filth left by around 800,000 pilgrims a year.

Experts say trees are being chopped down for firewood and to make way for hotels and roads, and human interference is even speeding up the melting of glaciers.

"It is not just greenhouse gases which are leading to melting glaciers, but it is also increased human activity and development in the Himalayas," said Syed Iqbal Hasnain, a glaciologist from New Delhi's Centre for Policy Research.