Narrator: Back on Tangier Island, Dr.

Burke discovers a troubling sign in the island's interior.

Russell Burke: Everyone notices the erosion on the outside.

But it's not just shorelines.

It's people's properties, right?

Where their houses are, where the grasses are turning from regular grass to wetland grasses.

Right now, I am standing in the marsh.

If you look around, it doesn't look like it's the marsh, it looks like it's someone's lawn.

It once was.

Now it is wetland.

And this conversion from upland to wetland is the silent killer of this island, because this is what's happening in people's backyards, even in the interior of the island.

Narrator: Dr.

Burke is using nature itself-- newly built oyster reefs-- to fight erosion.

Russell: I started with oyster restoration.

So when I see-- -All the oysters all over.

-Yeah.

I just can't help but to get excited.

-Gets you excited.

-It does.

I want to jump out.

So this definitely helps for the erosion.

I'm looking at this flat over here, and you can do extensive, reef restoration.

And that would provide a lot of protection -for what's back there.

-Yeah.

And that's really what we're hoping to do right up past that last crab house.

Oysters grow in clusters and clumps and eventually form oyster rock.

They rely on something to settle on.

So, they float around in their larval state, looking for a good place to land.

This reef, we call it an X reef.

We make sure we have nooks and crannies because when they're really small, they'll settle in there and you won't see them for a while, but eventually they're going to grow out and emerge, like a flower blooms and comes out.

So, a reef, when we first put it out there, provides a certain amount of protection.

But when it's a full living, growing reef, it does even more.