By JOHN LEANING
STAFF WRITER
WELLFLEET - For Donald Lewis, a retired National Security Agency executive, working with endangered turtles on Cape Cod is a privilege.

And it's something he is eager to talk about in public, unlike his former work in the national intelligence community.

"The privilege is that the work we're doing here has meaningful, measurable results toward saving these species," he said.

Judging from a just-released report by The Nature Conservancy, Cape Cod is just about a perfect place for Lewis' type of advocacy.

The report was prepared by Natureserve, a Virginia nonprofit that collects scientific data to assist in conservation efforts for animals whose populations are dwindling.

Researchers found that across the United States, Massachusetts ranked second, behind Hawaii, in the number of reptiles at risk of extinction. All of the reptiles listed in the report for Massachusetts are turtles.

The state also ranked eighth in the number of mammals - whales and seals - that are at various levels of risk for extinction if populations are not protected and nurtured. That's where the work of people like Lewis comes in.

"From day to day, year to year, we can measure the results we're getting to help these species stay alive and healthy on Cape Cod," he said. "This is not text book academics. This is something you can feel and touch and count."

The state's high rankings for the number of at-risk reptiles and mammals should be considered an honor, said Robb Johnson, a land protection specialist with the Conservancy's office in Boston.

"In some ways, that high ranking says the Cape has done leadership work in preserving biodiversity in Massachusetts," Johnson said.

But those ratings, he warned, should also be a warning sign.

"What they mean to us is that because we have a disproportionate number of species at risk, it is incumbent on us to kick into high gear. It's a clarion call to get even busier than we've been," Johnson said.

"What's new is exactly how our state ranks with others," he said.

The Cape's unique habitats, where many of these animal and plant species survive, also require some "unique responsibilities to continue to protect those areas," Johnson said.

In the report, Massachusetts ranked mostly in the middle to lower ends of the ratings in terms of biodiversity, Johnson said.

The presence of the ocean around Cape Cod has a lot to do with the state's high rankings for at-risk mammals and reptiles.

The migration patterns of endangered whales and sea turtles bring them into state waters.

And the Cape's latitude also has much to do with some of its rare plant life, since the Cape is the remaining upland of what was once the Atlantic coastal plain some 10,000 years ago, before the sea level rose to cover it over.

"We are a real dividing line between warm and cold waters," said Dennis Murley, a naturalist with the Massachusetts Audubon Society's Wellfleet Bay Wildlife Sanctuary.

The Cape attracts dwellers from the far north such as gray seals, and creatures found in more abundance in southern climes, such as the Diamondback terrapin or the Kemp's ridley sea turtle.

At-risk land and sea turtles are the principal reasons why Massachusetts ranks so high in the reptile category.

The extremely endangered Kemp's ridley sea turtle, as well as the endangered green and leatherback sea turtles, are regular summer visitors to Cape waters.

And every fall, when the weather turns cold, scores of these turtles get stranded on Cape Cod Bay beaches, immobilized by dropping water and air temperatures.

Over the past 20 years, volunteers such as Lewis at the Wellfleet Bay Wildlife Sanctuary, have rescued more than 1,000 turtles.

On Earth Day last Monday, a green sea turtle rescued from a Cape beach in the fall was re-released into the warm Atlantic Ocean waters off Florida. It was the end result of a successful rehabilitation effort.

And Lewis, with a home near Lieutenant Island in Wellfleet, is in a prime location to observe these turtles.

"It's home, and it's also like a working lab. I live within a stone's throw of the most productive nesting site in probably all of New England for the Diamondback terrapin," he said.

Nesting sites have been found at Sandy Neck in Barnstable, Boat Meadow Creek in Eastham, in Pleasant Bay, and Namskaket Creek Marshes, forming the border between Brewster and Orleans on Cape Cod Bay.

While the turtles themselves are intriguing, what Lewis finds even more significant is that they are what he termed the "bellwether species" for the salt marshes they depend upon.

"Studying them tells us what the health of the coastal salt marsh is. The turtles are like the canaries of the salt marsh," he said.

Because they live and eat in the marsh, and nest in its uplands, the turtles "test the whole quality of that system. You watch the population trends, you know what's happening in the marsh system," he said.