A butterfly that went extinct decades ago after the destruction of its Bay Area habitat is now the driving force behind its restoration with the help of a close relative now fluttering in its terrain.

At the Presidio in San Francisco, researchers, community scientists, and park officials gathered recently in hopes of filling a vacancy at a newly restored sand dune habitat with prospective new residents. It's taken 30 years to restore these dune habitats. Now, another historic effort is underway to restore another lost treasure. Scientists are hoping the silvery blue, a small butterfly native to North America, will take up residence and perform a critical function once done by the extinct . 

Professor , senior research fellow with the , heads up the experimental project. He recently carried a cooler bag to the dunes near Lobos Creek in the Presidio National Park, withdrew a smaller cooler pouch, and removed small plastic containers, each holding a single silvery blue butterfly. All of them sipped on a cotton ball soaked in fruit punch-flavored Gatorade, which seems to be their favorite sustenance during these exercises.

As the morning sun rose and the area warmed up, the silvery blues were released underneath a mesh fabric so they could acclimate. Later, the mesh was removed, and volunteers tracked their flight for about an hour.

"By bringing back this butterfly, we are bringing back more of what used to be here," said , associate director of natural resources at the .

"We are expecting that the silvery blue will fill the gap that was left by the Xerces extinction," explained , wildlife ecologist for the Presidio.

Before the Gold Rush, the Xerces blue thrived in sprawling coastal dunes around San Francisco that stretched from the Presidio through Ocean Beach, Fort Funston, and the Richmond and Sunset neighborhoods. The species kept the habitat healthy by pollinating plants and serving as food for other animals, such as birds and lizards.

Rapid urban development destroyed the dunes, and that destroyed the Xerces. One report indicates that the last Xerces spotted in the area occurred in 1943.

"This is an iconic species that literally was the first butterfly or invertebrate to go extinct in North America," said Kapan. "[The project is] an amazing opportunity to try to regenerate those missing connections using its closest relative. It's an opportunity to try to practice how we fix the environment."

Genetic sequencing at Cal Academy confirmed the closest living relative to the Xerces blue is the silvery blue. Like the Xerces, silvery blues also like cold foggy weather, dune habitats, and deerweed on which they lay their eggs. Scientists were allowed to gather silvery blues living near the coast of Monterey and relocate them to San Francisco's Presidio.

Parker-Shames said that adding the silvery blues to the dune habitat at the Presidio helps build resilience into a warming world.

"If one year it's too hot for a particular species and their population sort of has a dip, there's another species there that can help fill the same role," she noted.

The unprecedented effort is a four-year project that involves Cal Academy, the Presidio Trust, , the , and . The is also involved.

This effort to make San Francisco more resilient and increase biodiversity is part of a larger effort exemplified in the urban nature alliance known as "."

Last year, scientists released the first batch of silvery blues, and observations suggest success. Each released butterfly has a small mark added to their wings for identification. The scientists are now spotting unmarked butterflies. They say these unmarked silvery blues are the offspring of the first released butterflies flitting around the park.

So far this year, about 50 silvery blues have been released. Driggs and Mills have already seen a newly released female laying eggs on the deerweed.

"It's really cool, honestly," said Driggs.

• Project Earth