Water bird numbers are making a big comeback in the Prek Toal conservation area on the Tonle Sap lake in Battambang province, the Wildlife Conservation Society said in a report released on Saturday.

The study, covering years 2013-2014, showed a rapid increase in the number of lesser adjutant storks, spot-billed pelicans, Asian openbills and others, starting in 2014. Widespread poaching had caused bird populations to decline in the 1990s, followed by a recovery, then another decline towards the end of the previous decade, according to WCS.

WCS Cambodia said that the recovery trend persisted throughout 2015, mainly due to strong anti-poaching measures by community members. Most of the 40 rangers who patrol the area or watch from treetop platforms used to be poachers themselves.

“All of the former poachers are now employed by the project, plus some additional local people,” said Simon Mahood, one of the authors of the study. These guardians work for the Ministry of Environment and are funded by WCS, USAID and the Critical Ecosystem Partnership Fund.

According to Mahood, water birds regulate the entire aquatic community with their diet of fish, frogs and snails. “For us conservationists, they’re also a good indicator species for the health of the whole ecosystem,” he said.

Primate populations are also recovering, including the silvered langur and the long-tailed macaque. Otter sightings have increased as well.

In October, the 21,000-hectare Prek Toal area was designated as a Ramsar Site – named after the Ramsar Convention on Wetlands of International Importance. The status marks it as one of the most important wetlands in the world, due to its sheer biodiversity, according to the WCS.