A small round field of native grasses is criss-crossed and matted by wildlife trails, surrounded by a forest of oak and hickory. But in wetter seasons, this field is not a field. It’s a pond — a globally rare sinkhole pond at the foot of the Blue Ridge Mountains in the Shenandoah Valley.

Mount Joy Pond and the 274-acre tract surrounding it is one of 63 preserves created and managed by the Virginia Natural Heritage Program.

The Natural Heritage Program, a division of the Virginia Department of Conservation and Recreation, celebrates its 30th anniversary in 2016. To mark the occasion, free guided walks will be offered in October at nine of the natural area preserves in its system.

The Natural Heritage Program’s mission is to conserve Virginia’s biodiversity through inventory, protection and stewardship.  “Much of this we do through the preserve system,” said program director Jason Bulluck.

That process began 30 years ago, when the Commonwealth of Virginia partnered with The Nature Conservancy to launch the program. Heritage programs were a Nature Conservancy initiative, led by science director Robert Jenkins. Virginia was the 43rd state to embrace the program.

The first task was to inventory Virginia’s natural communities and species, said the program’s first director, Michael Lipford. “We started with one computer, four staff and rolls of paper topographic maps in an old Xerox copy room in a state office building in Richmond.”

In 1989, the state assumed full management of the program, officially directing the team to create and maintain a database to help conserve and manage the habitats of rare, threatened and endangered species; significant natural communities; geologic sites; and other natural features in Virginia.

During the last 30 years, the staff has documented the locations of more than 8,800 rare species and habitats, which includes 36 new species and more than 300 not previously known to exist in Virginia. They have reviewed more than 60,000 projects for their impact on important species and habitats, and a host of professionals from home and abroad have consulted the program database to learn about biodiversity in Virginia.

Conserving land for habitat protection is equally important. More than 55,600 acres are protected through the natural heritage preserve system.

To protect the biodiversity of these special places, public visitation is limited. Only 21 of the preserves have basic amenities to support hikers or paddlers.

“These are the preserves that can handle passive recreation, and where we have room to put in parking,” Bulluck said.

The visitor-friendly preserves typically have small parking lots, kiosks and sometimes a canoe and kayak launch. Visitors are warned about the lack of restrooms, garbage cans and cell phone coverage.

But the rewards on the other side of the gates that say “foot traffic only” are opportunities to experience some of the best examples of important natural communities that can be found from the shores of the Chesapeake Bay to the Appalachian and Allegheny mountains.

Visitors to the Savage Neck Dunes preserve on the Eastern Shore, for example, can walk among some of the highest sand dunes in Virginia that provide habitat for the federally threatened northeastern tiger beetle — and the path to the beach passes through a globally rare maritime woodland. (See the related article, Little-known Savage Neck Dunes has pines, ponds and privacy.)

On the Western Shore of the Chesapeake Bay in Mathews County, the bright, long strand of sand at the Bethel Beach preserve is another place to spot the tiger beetle, as well as some of the 185 bird species that have been observed there.

Some preserves have boardwalks and observation decks, like the Cumberland Marsh preserve along the tidal freshwater portion of the Pamunkey River and the Bush Mill Stream preserve along the brackish headwaters of the Great Wicomico River.

The boardwalk at New Point Comfort preserve overlooks Mobjack Bay with views of the water birds sustained by its marine resources. The forest and marsh are great locations for observing neotropical songbirds during migration.

Goshen Pass, a preserve in Rockbridge County, consists of 937 acres of steep, heavily wooded forest on the northeast side of the gorge where the Maury River cuts through the mountains. Trails traverse the steep topography above and along the river, where patches of a rare freshwater cordgrass (Spartina pectinata), a predominantly Midwestern species, have taken hold.

The challenge is to balance public access with the program’s mission of conservation. The guiding principle for all preserve guests, no matter how low-impact a visit might be, is to “leave no trace.”

Many of the program’s preserves are not promoted for public access. These sites have no parking, restrooms, trails and, in some cases, no access without trespassing on private property. They are managed first and foremost for the protection and study of biodiversity, but visits can be arranged through one of the preserve managers. Contact information is on the program’s website.

Mount Joy Pond is one of these less-traveled preserves. The unique geology and seasonal inundation at sinkhole ponds like the one at Mount Joy have provided a niche for several rare plant species that have evolved to take advantage of the unusual habitat. Mount Joy Pond boasts one of the world’s largest populations of the globally rare Virginia sneezeweed (Helenium virginicum).

Adam Christie, preserve manager at Mount Joy Pond, is puzzled as to why this sinkhole pond is dry in early fall. Historic photos show the pond full of water even in September. But recently, instead of water, Christie found a family of bears lying in the middle of the field where the pond should be.

To understand what’s happening, Christie has installed a series of test wells across the dry field.

As a forest ecologist, he knows that the surrounding forest can affect the water level in the pond. “We’ll do some selective trimming and some prescribed burns,” Christie said, trying to return the habitat and hydrology that scientists say has existed for the last 15,000 years.

Christie is among a program staff of more than 40 biologists, zoologists, ecologists, information specialists and analysts who work both in the office and in the field.

Maintaining current information is labor intensive. “When the data become historic — over 25 years old — we stop using it for decisions and sharing with our partners,” said program director Bulluck. Development and changing land use patterns have altered the landscape in Virginia, he explained, “so we have to verify that these occurrences still exist.”

With more than 8,800 records to maintain, the division uses computer modeling techniques to predict to within 90 percent certainty where a certain species might be found. Modeling has led scientists to previously unknown occurrences of the rare shale barren rockcress (Boechera serotina), as well as Virginia sneezeweed.

The Natural Heritage Program also partners with master naturalists who have been trained to look for specific species in places that program scientists have been unable to visit. These skilled amateur naturalists are combing Virginia for species like the Swainson’s warbler and helicta skipper. Their efforts have helped the program verify the locations of swamp pink, purple milkweed and Parker’s pipewort.

Over the years, the threats to Virginia’s biodiversity have changed.

“Our biggest threats have been habitat loss and invasive species. But now it’s also climate change,” said Tom Smith, deputy director of operations for the Virginia Department of Conservation and Recreation and former director of the Natural Heritage Program. “A lot of our protection is focused on making preserves bigger — to protect against encroachment by invasive species from the edges and to pick up as much elevation change as we can.”

Protection of these lands is only the start. Management of the preserves is never-ending work, important for biodiversity as well as for people. “Being able to see and experience these functioning ecosystems helps connect us to our own heritage,” Bulluck said.

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Guided preserve walks in October 2016

In honor of its 30th anniversary, the Virginia Natural Heritage Program is offering guided walks at nine of its preserves on Oct. 22-23. Walks take place on Oct. 22 at The Cedars (Lee County); Goshen Pass (Rockbridge County); Crow’s Nest (Stafford County); Dameron Marsh, Hughlett Point and Savage Neck Dunes (Northampton County); and Chub Sandhill (Sussex County). Walks on Oct. 23 are scheduled at Pinnacle (Russell County) and Bald Knob (Franklin County).

The guided walks are free, but pre-registration is required. Details and registration will be available at dcr.virginia.gov/natural-heritage/thirtyyears or by calling 804-786-7951.

For a full list of preserves with details about options for public access year-round, see dcr.virginia.gov/natural-heritage/natural-area-preserves.