After a decades-long ecological battle against invasive species and poachers, bird populations at the Chongming Dongtan Nature Reserve in Shanghai have surged from 40,000 at its lowest to nearly 500,000 last year. Led by Niu Dongliang, the reserve has transformed from a "ravaged" wetland into a high-tech sanctuary where AI surveillance and innovative flooding techniques have restored a vital link in the East Asian-Australasian Flyway.

When Niu, who now serves as the director of the reserve's management affairs center, arrived at the eastern tip of Chongming Island in 2004, it was a lawless frontier.

"When I first arrived at the reserve, some people hunted wild ducks — a single small packet of pesticide could poison hundreds of them. However, with no monitoring equipment back then, we had to walk through reeds and wade across tidal creeks for patrol, stopping them once found," Niu said.

He emphasized the difficulty of enforcement, noting that even if poachers were caught, they could claim to have merely "picked up" the dead birds rather than poisoned them, which prevented the police from taking action.

The tide turned in 2011. When Niu spotted a suspicious vessel through surveillance footage, he immediately organized an interception operation. Under stricter wildlife protection laws, eight individuals were prosecuted, and their convictions sent a strong deterrent message to other potential poachers.

"Now, more than 200 surveillance cameras are spread across the reserve, and infrared cameras set in key areas can capture people's movements even in the dark. Every access point is guarded, giving the wetland back to the wild plants and animals," he said, adding that the staff all wear camouflage or light-colored clothes to minimize human disturbance.

Beyond human activities, the rapid spread of invasive smooth cordgrass posed an even greater threat. Originating from the Atlantic coast of North America, this plant quickly encroached upon native vegetation, endangering wildlife food sources, habitats and the overall ecological function of the wetland. From the first discovery of a few scattered plants in 1995, by 2011 the reserve had more than 20 square kilometers of smooth cordgrass, accounting for one-tenth of the reserve's total area.

To address this, the reserve launched a large-scale ecological restoration project in 2013. Niu and his colleagues consulted experts, conducted experiments and finally developed a plan, involving building cofferdams to enclose the influenced area, cutting the smooth cordgrass above the water surface, and then flooding the area to submerge and rot the roots. Meanwhile, they also restored the damaged habitats and built ecological islands tailored to the living habits of different species, making these once-disappeared birds "frequent visitors".

"Birds are a very important indicator species for the health of an ecosystem," Niu said. "If they stop coming to an area, or if the variety of species declines, it means the environment has deteriorated. Everything we have done is to protect the biodiversity here."

With waterbird numbers gradually increasing, and State second-class protected tundra swans rising from just a few dozen to a record 5,216 this March, the birds themselves have delivered a clear verdict.

limenghan@chinadaily.com.cn