As a result of ambitious tree-planting programmes in China as well as intensive agriculture in both China and India, the two countries led the way in greening on land, data from US National Aeronautics and Space Agency's (Nasa) satellites shows.

The study, which was published in the latest edition of Nature Sustainability on Monday, showed that at least 25 per cent of the foliage expansion globally since the early 2000s came in China.

The researchers from Boston University found that global green leaf area has increased by 5pc in the new century, an area equivalent to all of the Amazon rainforest.

"China and India account for one-third of the greening, but contain only 9pc of the planet's land area covered in vegetation," said lead author Chen Chi of Boston University.

"That is a surprising finding, considering the general notion of land degradation in populous countries from over-exploitation," said Chen.

"When the greening of the Earth was first observed, we thought it was due to a warmer, wetter climate and fertilisation from the added carbon dioxide in the atmosphere," said a research scientist at Nasa's Ames Research Centre and co-author of the study, Rama Nemani.

But with the data from Nasa's Terra and Aqua satellites, scientists realised that humans are also contributing.

"Humans are incredibly resilient. That's what we see in the satellite data," said Nemani.

As per the study, China's contribution to the global greening trend comes in large part from its programmes to conserve and expand forests, accounting for about 42pc of the greening contribution.

Another 32pc of the greening change in China, and 82pc in India, resulted from intensive cultivation of food crops, since the farmland in China and India has not changed much since the early 2000s, while both increased their food production to feed large populations.

However, the researchers rang alarm bells as well.

They said the gain in global greenness did not necessarily offset the loss of natural vegetation in tropical regions like Brazil and Indonesia. According to the study, the loss of sustainability and biodiversity in those ecosystems cannot be offset by the simple greenness of the landscape.