NEW DELHI (Reuters) - About a quarter of India's land is turning to desert and degradation of agricultural areas is becoming a severe problem, the environment minister said, potentially threatening food security in the world's second most populous country.

India occupies just 2 percent of the world's territory but is home to 17 percent of its population, leading to over-use of land and excessive grazing. Along with changing rainfall patterns, these are the main causes of desertification.

"Land is becoming barren, degradation is happening," said Prakash Javadekar, minister for environment, forests and climate change. "A lot of areas are on the verge of becoming deserts but it can be stopped."

Land degradation - largely defined as loss of productivity - is estimated at 105 million hectares, constituting 32 percent of the total land.

According to the Indian Space Research Organisation that prepared a report on desertification in 2007, about 69 percent of land in the country is dry, making it vulnerable to water and wind erosion, salinization and water logging.

The states of Rajasthan, Gujarat, Punjab, Haryana, Karnataka and Andhra Pradesh are the among the most arid. These are some of the cotton and rapeseed growing states of India.

(Reporting by Krishna N Das and Shyamantha Asokan; Editing by Jeremy Laurence)