3) MATTAWOMAN CREEK in Charles County.

This Southern Maryland tributary to the Potomac River is one of the most productive breeding grounds for fish in the Chesapeake Bay watershed.  Its wetlands support Maryland's largest population of nesting wood ducks, as well as bald eagles, great blue herons, great egrets, osprey, beavers, mink, otter and a rare lotus plant, Nelumbo lutea.

But the amount of pollution flowing into the Mattawoman Creek is rising as fast-growing Charles County becomes an exurb of Washington.  County officials have targeted much of the creek's watershed as a high growth zone, which means an extra 50,000 people could pour into the delicate ecosystem by 2020.  The state temporarily slowed some of this growth in 1998, when former Gov. Parris Glendening helped approve the $25.3 million purchase of 2,225 acres to stop a giant riverfront development called Chapman's Landing.  But now other parts of the watershed are threatened by a highway project and roads bringing strip malls, subdivisions and litter. 

4) BLACKWATER NATIONAL WILDLIFE REFUGE on the Eastern Shore. 

This spectacular, primordial landscape of marshes, islands and sunken forests is slowly being swallowed by rising sea levels.  It could soon look like a vast open sea, instead of a winding maze of streams fringed by forests and grasslands.

The bald eagles and other animals that live here dodged a bullet last year, when former Gov. Robert Ehrlich announced the day before his re-election loss that the state would spend $10 million preserving 728 acres north of the refuge.  That meant a proposed $1 billion subdivision, called the Blackwater Resort, had be scaled back, shrinking to about 600 homes from the 3,200 originally proposed by developer Duane Zentgraf.  But that still means hundreds of homes will soon be built around the refuge's bucolic entrance.  And hundreds of more homes are popping up in cookie-cutter subdivisions just east of Zentgraf's land.

5) CHINCOTEAGUE BAY, off the Atlantic Ocean 

Just west of narrow, sandy Assateague Island -- fabled land of the pony Misty of Chincoteague -- is a long stretch of sheltered water called Chincoteague Bay.  Kayakers love its wild, untouched edges and its expanses of marsh grass.  Watermen still dredge for oysters here, and vacationers feel their stresses melt away just looking across the bay to the forested national seashore, dotted with wild horses.

But recently, macroalgae blooms have been tangling boat propellers and suffocating seagrass, depriving a home for young crabs and fish.  A suspected source is nitrogen fertilizer running off of poultry operations and grain farms in neighboring Worcester County.  And just across the state line, in Virginia, developer Robert E. Warfield is proposing to expand a waterfront subdivision called Captain's Cove by adding 4,800 homes and a sewage treatement plant that would dump 900,000 gallons of effluent a day into a tributary to Chincoteague Bay.

6) HOOPERS ISLAND, on the Eastern Shore. 

This toothpick of land dangling off the bottom lip of Dorchester County is an island of time as much as a peninsula in the Chesapeake Bay.  Driving down its one dead end road, you travel back decades to a time when watermen still made their living by hauling pots of crabs onto docks, and folks lived on the water because they needed a place to tie their workboat.  The long bridges provide spectacular views at sunset -- but be careful of the waves crashing across the roadways.

Talking to residents here, you'll hear stories about vanishing islands just off shore.  And then you'll understand why those waves nearly swept your car off the road.  Hoopers Island is rapidly being submerged by rising sea levels, caused by global warming and the melting of polar ice caused by greenhouse gases.  So in a sense, Hoopers Island is being destroyed by pollution -- carbon dioxide from our SUV's and power plants.  Development isn't a threat here.  Amazingly, there isn't a McDonalds or chain-owned business on the whole island.  That alone makes Hoopers Island an endangered species on the order of the Right Whale.  But that isolation could change if a rumored second span to the Bay Bridge is built from the Western Shore to Dorchester County just north of Hoopers Island.

7) ANTIETAM NATIONAL BATTLEFIELD, Washington County 

These 3,200 acres of preserved land northwest of Washington are haunted by the ghosts of the bloodiest battle in U.S. history.  The Antietam National Battlefield is considered an almost sacred site, because about 23,000 men were killed or wounded there during cataclysmic fighting between Union and Confederate forces in 1862.  Visitors can expore the rolling hills, walk down Bloody Lane and cross Burnside Bridge (pictured above).

But the northward march of stripmalls and cul-de-sacs from the DC suburbs is threatening a new assault on the area around Antietam.  A group called the Save Historic Antietam Foundation warns: "Rapid growth and development threatens the history and charm of the Antietam Valley."  Two years ago, the National Trust for Historic Preservation put the battlefields and other major Civil War sites along Route 15 from Pennsylvania to Virginia on the group's list of most endangered historic places.  Nearby, South Mountain Battlefield State Park, where 6,000 soldiers died, has little protection against development and almost no budget for maintenance.

8) THE CHESAPEAKE AND OHIO NATIONAL HISTORICAL PARK, along the Potomac River

This 184 mile, scenic biking and hiking path trails an old canal that winds along beside the Potomac River from Washington to Cumberland, Md.  The C & O Canal park is a beautiful place to exercise, learn about the history of our nation's pre-railroad transportation system or photograph wildlife.

But The National Parks Conservation Association  calls it "An American Treasure in Peril."  The group warns that "this historic place faces many modern threats. Flooding..., invasive exotic species, rapid development of adjacent lands, utility rights of way, lack of funding, and staffing shortfalls all contribute to the decline in park resources." Moreover, the U.S. Park Service has approved plans by Georgetown and George Washington universities to build large boathouses on parkland within sight of the canal towpath. The association warns: "These plans threaten the integrity of the resources."

9) DOUGHOREGAN MANOR, Howard County

This National Historic Landmark was built in 1725 by the grandfather of Charles Carroll III, one of four patriots from Maryland who signed the Declaration of Independence. He was the only Roman Catholic signer of the document, and the wealthiest man in America at the time. His home -- and its hundreds of acres of surrounding grounds -- were frequently visted by John Hancock, George Washington, Samuel Adams and other founding fathers.

Earlier this year, an agreement that prohibited development on 892 acres of the estate expired.  To help pay for maintenance and taxes on the manor, Carroll's descendants are considering a proposal to build hundreds of homes, perhaps as a retirement community, on the eastern edge of the property.  A 1,200 acre section right around the mansion would remain in permanent preservation.  But an activist group called Preservation Howard County earlier this year named the property as the No. 1 "most endangered" historic property in the area because of the potential for large-scale construction, traffic and discruption.  It's the largest undeveloped tract of land in a county that's rapidly malling and sprawling. 

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Readers, what should I add to this list?  Give me your thoughts.