Giri Kadurugamuwa, director of Alliance for Sustainable Landscape Management.[Photo provided by Vishwamithra Kadurugamuwa]

Saman Kumara, a smallholder tea farmer, knows all about that. He gladly notes that the animals, rabbits for example, are back after his farm drastically cut its use of chemicals over the past two years.

"The rabbits can help us with the weeds. And even the millipedes are back. And when you have millipedes, you can tell for sure that the soil isn't that bad since the insects cannot live in hardened soil."

These days on Kumara's farm the weeds are removed by hand. "We convert the grass and other reducible farm junk into fertilizers - a practice that helps us to keep costs down."

Better soil means higher-quality tea leaves and higher income. But a farmer must have the determination to weather the first one or two years, when the reduced use of chemicals causes an initial fall in tea production.

"I felt I had no choice because the tea garden, by the time I decided to turn to sustainable management, was already experiencing a production downturn due to land degradation," Kumara says.

Sri Lanka produces 338 million kilograms of tea a year, bringing in foreign exchange of $1.6 billion. Ratnapura, the biggest tea-producing region, has nearly 98,000 tea smallholders who together own about 30,000 hectares of land.

About 30,000 smallholder farmers are being trained in sustainable land management practices which will then be applied to at least 60,000 hectares of team farms and plantations, the UN says.

The project is being replicated in other tea-producing countries, including India, Vietnam and China.

Hu Xinyan, coordinator of the program in China, said this emphasis on smallholder farmers is of profound significance for her country, where farm land has been divided up and rented to individual growers for decades.