The rapid growth of China's environmental industry shows the country's willingness to upgrade its development pattern, an expert at the United Nations Environment Assembly in Nairobi said on Thursday.

"China's environmental industry, in the last five years, has been growing on average by 15 percent to 20 percent annually," said Sheng Fulai, head of the Economic Research Unit of the UN Environment Programme. "Now it accounts for 6.5 percent of the country's GDP, which is quite significant."

This shows China's willingness to shift its development model toward a more sustainable path, he said.

China has also been promoting green technology overseas, he added. "Now there is investment from China in green energy in Africa. China and African countries are joining hands ... in deployment of green technologies and in local production of green equipment."

China can also contribute to sustainable development with its railway technology, Sheng said.

"China's rail system is probably the most significant internationally in terms of the length of the railway connection. This technology is now actually applied overseas. More and more countries are becoming interested in the way that China has been promoting the railway system as a major model of transportation, which is much more environmentally friendly than road transportation," Sheng said.

Chen Jining, minister of environmental protection, said the coexistence of humans and nature is one of the biggest challenges that China is facing.

Chen added that "UNEP and China have had a remarkably mutual relationship over the years and have shared a lot of knowledge and experiences".

Environmental ministers and representatives from more than 170 countries, as well as scientists and industry executives, are attending this year's assembly, which began on Monday and ends on Friday.

Lucie Morangi contributed to this story.