John Roberts peered into several small holes in the earth and said they likely were entrances to the winter dens of giant garter snakes.
“This is what we like to see,” said Roberts, director of the Natomas Basin Conservancy. He stood near one of the group’s man-made marshes in sight of Sacramento’s downtown skyline. “They’re probably in there sleeping.”
For the past 15 years, the conservancy has been buying and preserving acreage for wildlife as part of a plan that allows large swaths of farmland in Sacramento and Sutter counties to be covered in suburban homes, shopping centers and industrial parks.
The conservancy’s main tools are its engineered marshes and flooded rice fields. Its central mission is to provide habitat for giant garter snakes and Swainson’s hawks, both threatened with extinction, and 20 other covered species.
The recent excitement over a mink that popped up on conservancy land sparked public interest in the wildlife that appears to be flourishing close to the capital’s urban spread. The mink’s appearance underscored how efforts to protect snakes and hawks have created habitat for a broad range of creatures, including red foxes, northwestern pond turtles and tricolored blackbirds, Roberts said.
“It’s a matter of maturity,” Roberts said. “Some of these marsh complexes are a decade and a half old now, and they’re starting to get established.”
With planned development in the city of Sacramento and southern Sutter County moving forward, the conservancy is set to transform additional lands for struggling species, he said.
Last week, Roberts and field services assistant Jeremy Lor paddled around one of the conservancy’s marshes in kayaks. They noted the presence of rare tricolored blackbirds, along with the damage that beavers had done to the stands of cottonwood trees used by foraging Swainson’s hawks.
Dozens of nesting black-crowned night herons perched on tules and took flight at the sound of paddles and human voices. A beaver skimmed the surface of the marsh. No turtles or snakes showed their heads above ground. The reptiles brumate in winter – their version of mammalian hibernation – Roberts explained.
Lor took the popular photo of the basin’s resident mink this winter. He said he was working in a conservancy marsh not far from suburban homes when the mink stood up long enough for him to snap its picture.
“He was looking for something to eat,” Lor said. “I gave him a little excitement. He wanted to see what was going on.”
Minks are rare but not unheard of in the southern Sacramento Valley. Lor, who spends much of his time in the field, said he last saw a mink several years ago, when he watched a pair of the creatures at work.
“It took me three years to see another one,” Lor said.
Muskrats, foxes and river otters roam the preserves, he said. Red-tailed hawks, barn owls and kites soar overhead and nest in trees. As Lor spoke from his kayak, a jumbo jet glided in for a landing behind him a few miles away at Sacramento International Airport.
The conservancy buys land and manages it as part of the Natomas Basin Habitat Conservation Plan. The plan lays out ways to mitigate the impact of development in the 54,000-acre basin, about 17,500 acres of which is developed or slated for construction.
North Natomas, once a sea of farmland and floodplains, sits just minutes from downtown Sacramento. Developers eyed the area for decades and finally won approval for large-scale residential and commercial construction that began in the early 2000s, along with the conservation efforts.
During the housing boom, thousands of homes were built, and North Natomas became Sacramento’s fastest-growing region. The housing crisis and federal building restrictions imposed in response to concerns about the adequacy of the levees brought development to a standstill by 2008. Natomas is surrounded by 43 miles of levees that protect it from the Sacramento River, the American River and several creeks.
Federal approval of levee upgrades last year will let construction proceed again in Sacramento’s 8,000-acre share of the basin. Sutter County has long-term plans for 7,500 acres of residential, industrial and commercial development near the Sacramento County line. And a 1,900-acre industrial park is planned near the airport.
The conservancy uses developer fees, ranging from about $20,000 to $30,000 an acre, and land swaps from construction projects to build its inventory of lands for habitat conservation.
The conservancy has about 4,200 acres grouped in three main areas around the basin. One cluster of properties starts a football field’s length away from the residential cul-de-sacs of North Natomas. Others are surrounded by farmland in Sutter and Sacramento counties on both sides of Highway 99.
Half the conservancy’s holdings are rice fields, which require periodic flooding. A quarter of its properties are marshlands. Both landscapes provide habitat for giant garter snakes and other species that live in or near water.
The Natomas Habitat Conservation Plan requires a half-acre of land to be set aside for every acre developed. The plan originated decades ago under what were then new federal regulations. Environmental critics say the half-acre-for-an-acre standard is too low to adequately compensate for such large-scale development.
The Natomas Basin Conservancy “is land poor and depends on intensive habitat management on its preserves, which is expensive and risky,” Jim Pachl, a Sacramento attorney and co-founder of Friends of the Swainson’s Hawk, wrote in an email. The conservancy also relies too much on surrounding agricultural lands that could eventually be developed, he said.
Eric Hansen, a Sacramento-based garter snake expert who worked for the conservancy in the past, said the group’s efforts require a difficult balancing act. Developers, farmers, water users, government officials and environmentalists all have interests at stake, he noted.
“There are a lot of moving parts,” he said.
Hansen noted that the Natomas habitat plan was one of the first of its kind and remains a work in progress.
“This restoration science is still in its infancy,” Hansen said. “So far they’ve done a good job of acquiring a spectrum of land for multiple threatened species.”
The giant garter snake used to range up and down the Central Valley, but it lost up to 95 percent of its habitat as lands were drained for farming and development, Hansen said. The snakes grow up to 5 feet long and are semi-aquatic. They eat tadpoles, frogs, small fish and worms. Population estimates vary, but experts say the relatively small number of remaining snakes live in the flooded rice fields and agricultural ditches of the Sacramento Valley.
In an old dairy barn on conservancy land, where great horned owls nest in the rafters, piles of snake traps used to count and microchip giant garter snakes are stacked on the floor. At one of the conservancy’s man-made marshes in northern Sacramento County, Roberts said there were about four dozen giant garter snakes living among the tules and cattails at last count. The snakes like the warm rocks that have been laid in south- and west-facing strips along the marshes and the plentiful vegetation that lets them stay out of sight of raptors.
From the marsh, visitors can see the skyline of downtown Sacramento, the bulky outline of Sleep Train Arena and much of the sprawl of North Natomas. Roberts said the idea behind the man-made swamps was to create a haven for snakes displaced by urbanization.
“Our thought,” he said, “was let’s give them a place to go.”