MANILA: Armed with brushes, watercolours and a palette, artist Leo Meneses strolled along the banks of the polluted Pasig River for a painting session with his friends at Manila's last surviving forest park.

But the soft morning light could not hide the gloom on his face when he arrived to find the Aroceros Forest Park placed under lock and key amid a legal battle between Manila's powerful mayor, Lito Atienza, and a group of conservationists.

"This is a special public park. Why does the mayor of Manila want it shut?" Meneses said.

Environmentalists are asking the same question.

The 2.1-hectare park is home to more than 3,000 9-metre trees, some of them more than a century old. It also is a sanctuary to about a dozen bird species and has been cited by the National Museum as a treasure trove of botanical wonders.

A short distance from City Hall, the patch of green is a rare source of clean air in the city of 12 million where thick fumes from factories and buses cover nearly everything with soot.

Students go there to relax, and families enjoy weekend picnics. It has also become a favourite inspiration for nature artists such as Meneses.

The park is now in danger of being lost after Atienza's office reclaimed it as city property. Plans are under way to construct a school administration building that would take up about half the park's space.

Sources who did not want to be named say Atienza also plans to put up residential high-rises that would take up the whole site. The mayor denies that allegation.

Early this month, construction materials were dumped in the park, ditches were dug and city workers armed with chainsaws cut down some of the trees.

Environmentalists led by the park's caretakers, the Winner Foundation, questioned the legality of the plan and have taken their case to court. They cite an agreement the Foundation signed with the previous mayor that gave them control of the forest and said it was to be untouched.

The park was developed 12 years ago by the foundation, a non-government organization headed by Amelita Ramos, who, as first lady in the 1990s, embarked on a programme to rehabilitate communities near the Pasig River.

Aroceros sits on a piece of land steeped in history.

Old maps suggest Aroceros was a bustling Chinese trading hub called Parian from the late 16th to 19th centuries during Spanish colonization.

Ditches dug by workers to lay the groundwork for Atienza's project yielded surprise artefacts including shards of ceramic, coins, iron objects and a granite floor.

Conservationists now argue that Atienza should preserve the park, citing its historical value. They say that controlled archaeological diggings should be carried out.

"The Winner Foundation and all concerned Filipinos who respect their history insist that a thorough study be made that would consist of going deeper, studying the stratigraphy and looking for artefacts made of material such as charcoal and porcelain that could, through analysis, furnish the dates of the occupation here," said local archaeologist and historian Maria Isabel Ongpin.

"Destruction of a heritage site is considered a heinous crime in history, and no self-respecting government allows it," Ongpin said.

Maria Luisa Quinones, Manila's education department chief, said Manila would only construct an office building on the site and said they had approval to cut or relocate the trees.

"We just would like to tell everyone that we secured the necessary permits and clearances before we start the building's construction," Quinones said.

"The construction will continue."

Chiqui Mabanta, a spokeswoman for Winner Foundation, accused City Hall of harassing them and of felling trees without the necessary environmental department permit.

"It is heartbreaking to see the extent of the damage," she said. "Help us save the remaining trees. We will not give up this fight."

Residents such as Meneses hope they succeed.

"I am only a painter, but I know that this place is special," he said. "When I first discovered it two years ago, I was happily surprised that in Manila's underbelly there is a forest. But now it is padlocked, and trees are being murdered. I am outraged."