"We live in a rapidly changing society, but parks are that island of security," Loza, whose association is based in Harrisburg, said Thursday. "They're a source of stability."
That could change, he said, if last year's decision by Chester County Court Judge Katherine Platt allowing part of the park to be sold stands. The decision is being appealed, the latest twist in a case both sides say could land in the state's highest court.
The land trust, which represents 75 conservancies across the state, filed a brief against the development in March, the third time in 20 years it has weighed in on a court case.
Downingtown has for decades considered developing Kardon Park, a stretch of ponds, fields, and forests with a paved walking path that many residents cherish for its tranquillity.
Borough officials say the land is also flush with arsenic, iron, and mercury from when it was used it as a landfill in the 1960s.
The contamination would be mitigated under a 2007 sale agreement with developers Jack Lowe and Sarah Peck, who would also maintain about 20 acres as parkland and improve trails, according to the borough. The pair plan to build 300 town houses and 20,000 square feet of retail, with apartments above those shops.
Borough officials have said the project would bring in millions of dollars in tax revenue, plus residents who would enrich the business district just south of the park.
The sale has been tied up in court since 2009, when a group of residents filed a lawsuit. In a November ruling, Platt focused on how the land was acquired - not how it is used - in deciding if it could be sold.
The two sides, which are both appealing, read the judge's ruling differently but agree Platt cleared at least half the park for sale.
That land was acquired through a state land conservation bill known as Project 70. At the request of the borough, the legislature in 2011 lifted the restriction that the land remain open, clearing the way for development, Platt ruled.
Project 70 has provided funds for the purchase of more than 500 parks across the state, according to the Department of Conservation and Natural Resources.
Loza said it was unclear if all that land became or remains public parks. But he said if Downingtown is able to do away with its Project 70 restrictions, it sets the precedent that other municipalities could try to do the same in the future, a stark shift from what he called a societal understanding that parks are protected.
"It's always been understood that you move in next door to a park, that park is going to be there the day you move in, and 10 years later, and 20 years later, and it's going to be there for everyone forever," he said.
Patrick McKenna, the borough's attorney, said in this case, where a sale would also clean up contamination, there needs to be flexibility.
"Comprehensive plans and municipal plans change over time," he said.
Lou Colagreco, the developers' attorney, added that the plan maintains parkland - one of the land trust's goals.
Oral arguments in the case are set for September, and a decision would likely be issued afterward.