Correction: Earlier versions of the headline of this article incorrectly referred to an effort to save Dumbarton Oaks instead of Dumbarton Oaks Park. This version has been corrected.

The eminent biologist Edward O. Wilson found his passion for nature as a 10-year-old boy, he recalls, “exploring with a net, searching the ground for different kinds of ants. I was born as a naturalist in Rock Creek Park.”

Wilson, the Harvard professor emeritus and father of the study of ant and other animal societies, returned to Washington this week in a sort of payback to the park. A 27-acre offshoot of it, named Dumbarton Oaks Park, pales in comparative size to the main stem of Rock Creek Park, all 1,700 acres of it. But to landscape historians, it is hallowed ground. It is also on the edge of survival. With Wilson’s help, a group of preservationists have launched a new effort to save the park, which has been mugged by time, stormwater runoff, and rampant vines and other weeds.

The park adjoins the mansion and gardens of Dumbarton Oaks and was designed by the same venerated landscape architect, Beatrix Farrand, as an integral part of the Georgetown estate, indeed the pastoral counterpoint to the formal gardens above. When the owners — Robert and Mildred Bliss — gave the mansion and garden to Harvard University in 1940, they donated the rustic section to the National Park Service. It was about then that young Ed Wilson was rooting around with a net. It may have also been the last time anyone could see the purity of Farrand’s vision — an idyll of streamside woods and meadows rising from a brook with 18 decorative waterfalls and dams.

After decades of underfunding and inadequate maintenance, the park remains popular for joggers, dog walkers and even commuters on foot, but it is in ecological and aesthetic distress: Fields and woods are consumed by acres of invasive vines, trails have become overgrown, masonry features are crumbling, and the stream is plagued by siltation and erosion from torrential upstream stormwater.

Tara Morrison, the new superintendent of Rock Creek Park, said visitors can “still witness the beauty of the original design.” Others may find that a charitable assessment — five years ago a preservation group, the Cultural Landscape Foundation, said Farrand’s landscape was in danger of being lost.

Wilson arrived at the Washington National Cathedral late Tuesday afternoon to assist in the public launch of the private group formed to save the park, the Dumbarton Oaks Park Conservancy. The event was moved from the park because of heavy rain.

Strolling the cathedral grounds afterward, Wilson said that it sounds as if the park needs to be “reengineered” to fix the flooding problems , before its biological health can be restored. The degradation inevitably damages the biodiversity, he said, as colonies of native species are overtaken by erosion or overgrowth. “When you get down to a small size, the extinction rate goes up. You can take a species to extinction in that type of place very fast.”

Earlier, he told more than 100 park supporters that Rock Creek was known to have had, uniquely, two species of shrimplike creatures. In 1890, a lone specimen of a new species of ant was discovered in the park. Wilson spoke wistfully of wanting to search “for this lost species.”

The conservancy is headed by Rebecca Trafton, a garden designer and documentary maker, who said the group will host a session in October to map the park’s restoration, maintenance, funding and use before launching a fundraising campaign.

“Dumbarton Oaks is one of the greatest gardens in America, and Dumbarton Oaks Park is an inextricable piece of the whole. It is perilously close to losing its design and ecological integrity, but I think we are right at the point we can bring it back to life,” said Trafton.

Wilson was joined by Elizabeth Barlow Rogers, a garden historian and writer who led the charge to bring New York’s Central Park up from its nadir by establishing the Central Park Conservancy in 1980. You bring a park back, she said, by having a vision “and a visionary,” by having a community that values it, and by forging a partnership with the public entity that owns it. As a young mother in Washington, she would stroll with her baby daughter from Foggy Bottom to Georgetown. “And brought her to where? Dumbarton Oaks Park.”

Local volunteers and environmentalists have been trying to clean up the park for years.

Trafton is determined to bring it back. Like Wilson’s beloved ants, “we are small, but we are tough.”