Environmentalists are questioning why the City of Charleston is paying more than $500,000 in conservation money for 6.5 acres of land that a developer has already agreed to protect. Charleston Mayor Joe Riley wants the city to buy the land that surrounds a two-acre city park on Johns Island that houses the Angel Oak, a tree that is thought to be more than 1,000 years old.

The proposed purchase would add an additional 150-foot buffer around the tree on three sides. (The dirt road accessing the park is on the fourth side.) It would also provide space for an expanded parking area farther away from the tree — the current lot is only accessible by driving over the historic tree’s roots. But for years, the property’s owner, Sea Island Planned Unit Development, has promised to conserve this area as part of a larger 42-acre development that fronts Maybank Highway and Bohicket Road.

Angel Oak activist Samantha Siegel is suspicious. “Taxpayers are going to pay for land that was already being conserved,” says Siegel, who has opposed the development for the past few years and launched the website savetheangeloak.org.

The mayor argues that the city needs more than just a promise from the landowner, particularly during difficult economic times when developers might be tempted to toss their current preservation plans in the trash can in order to make a buck. “If that development doesn’t go forward, that land isn’t subject to any protection for the tree,” Riley says.

Riley wants to spend the last of the city’s share of urban park money, which is funded by the county’s transportation sales tax. The City Council’s Real Estate Committee will consider whether to sign off on the application today, followed by the full City Council on Tuesday. If approved, the plan would then go before the Greenbelt Advisory Board. As soon as the sale is complete, the city could begin making improvements, including laying gravel and clearing space for parking. “The greatest danger to the tree is that parking area,” Riley says.

Last year, the Coastal Conservation League, a nonprofit environmental watchdog, offered to help Sea Island Planned Unit Development developer Robert DeMoura redesign the proposed development. The group had hoped to protect the wetlands on another portion of the 42-acre site by moving part of the development to the 6.5 acres the city wants to purchase.

Katie Zimmerman, a project manager with CCL, says the city’s offer to buy the 6.5 acres would essentially force the developer to fill the wetlands. Zimmerman is also skeptical of the city’s appraisal.

When CCL appraised the property in September 2009, the value was estimated at $172,000 per acre. However, the September 2010 numbers used in the city’s application put the value at $550,000 per acre, a substantial increase from the previous appraisal.

The city argues that by paying $500,000 for the 6.5-acre plot, it is getting the property at 20 percent of its appraised value. The mayor says the city will do its own appraisal as the Greenbelt application moves forward.