Chongming Island has seen its population of wild birds recover over the last few years after the local government embarked on a 10-year program to bolster the county's ecological bona fides, officials said at a press conference Wednesday.

The program, which the Chongming county government launched in 2010, aims to transform the 1,267-square-kilometer island into an environment-friendly haven with clear water, unspoiled land and fresh air by 2020, according to a summary of the program.

To help boost the bird population, the county government re-planted a 1,000-hectare test field with plant species palatable to wild birds, said Ma Xingfa, the secretary-general of the Shanghai Science and Technology Commission. After the planting, the number of bird species on the field rose from 12 to 40 from 2010 to 2012.

In addition, the population density of local birds jumped to 1,600 birds per square kilometer in 2012, up from 20 per square kilometer in 2009, Ma said.

The county government has taken many measures to balance commercial development with ecological conservation, said Zhao Qi, the head of Chongming county, which includes Chongming, Changxing and Hengsha islands.

"We have laws that prohibit people from trapping and selling water birds. We have also banned construction in bird nature reserves without special authorization," Zhao said.

To prevent people from disturbing bird habitats, the county government also plans to limit the number of visitors to the county by charging admission at tourist destinations such as the Dongtan National Nature Reserve, Zhao said.

The county government touted other environmental achievements at the press conference. More than 99 percent of the county's rivers had Level 3 drinking water quality, up from 86 percent in 2008, according to a press release. And the number of days each year in which the Air Pollution Index (API) stayed below 50, indicating good air quality, rose from 140 days in 2008 to 192 days in 2012.