BEIJING -- China has sent one of the biggest delegations to the current UN Earth Summit in Johannesburg, and experts warn its own environmental problems -- notably land degradation, water contamination and air pollution -- are similarly vast.

The country's environmental crisis has been highlighted this summer by flood surges along the Yangtze River which have placed millions under threat throughout the center and east of the country, AFP reported.

At the heart of the flooding -- which has already killed about 1,300 people this year -- is perhaps china's biggest environmental issue, the devastation of land through farming, deforestation and overgrazing.

A quarter of all china's land is already desert, and more is succumbing at an increasing rate, UN figures show, with 2,500 square kilometers (960 squares miles) lost to desert every year.

Despite launching the world's largest tree-planting program, government efforts to tackle the problem are having a limited effect, experts say, as highlighted by the floods.

Although the re-forestation has been supplemented by logging bans, new growth is nowhere near as effective as virgin forest in soaking up water and preventing erosion of river beds, said Dai Qing, an spoken environmental activist in Beijing.

"You can't undo the damage overnight," she added.

Some blame poor coordination and the lack of a nationwide approach for the lack of progress.

"What you need is good cooperation between government ministries, and that's one of the biggest challenges here," said Maria Suokko, an expert on environment and energy for the United Nations Development Program (undp) in Beijing.

The country also suffers from extremely uneven rainfall, with north China often parched while provinces further south are inundated, as highlighted by a devastating drought in east China's Shandong Province, directly adjoining the flood-hit Yangtze basin.

However, China is not overall a water-scarce country, Suokko said, just one where supplies are distributed unevenly between north and south as well as used and delivered inefficiently.

"It's estimated that about half of all the water used (in China) in irrigation is lost because it's evaporated on the way," Suokko said.

Additionally, despite pledges to control water pollution, less than 10 percent of all municipal wastewater is treated in any way, Suokko said, meaning the vast majority of urban rivers remain filthy.

Weaknesses in regulation and enforcement add to the problem.

"They collect pollution fees from industries that pollute and any fees collected is revenue for the local government, so from the local government's perspective it might be profitable to have polluting industries," said an environmental source in Beijing who asked not to be identified.

China's rapid development and the pressures it faces providing for a 1.3 billion-strong population also pose challenges in controlling environmental damage.

The problem is a deeply serious one, with China possessing 16 of the world's 20 most polluted cities, according to a World Bank report published last year.

"China stands at the crossroads. It can now choose. It could be a model country. By making the right decision, choosing the right technology, choosing the middle way rather than rapid economic development, it could develop the country in a sustainable way," Suokko said.

"In China, environmental protection work is still being done in a narrow way, mostly by NGOs (Non-Governmental Organisations)," said Zhu Jie, a spokesman for the privately run institute of environment and development in Beijing. "This needs to be spread to companies and the average people."