The Plethodon genus of salamanders in the Blue Ridge have had 200-300 million years without glaciation to adapt to local drainages and microclimates. Since salamanders don't go for long walks, several species that evolved in Virginia's Blue Ridge have never crossed a state line on their own. (Many have been carried back to out-of-state university labs in glass jars and plastic baggies by biologists, after collecting samples...)
Species that have evolved to take advantage of unique characteristics in local situations are less flexible when circumstances change. "Generalist" species like Virginia pine may be at a slight disadvantage when competing with Table Mountain pine, but the "specialist" species are at a disadvantage when the circumstances change.
For example, the Fraser fir in the southern part of the Blue Ridge may have evolved from the Balsam fir. The Balsam fir is common up into Canada, but the Fraser fir is restricted to the Appalachian highlands. Perhaps the Fraser fir is better adapted to deal with the heat and drought in the southernmost part of the Balsam fir range. However, the Fraser fir is threatened by the wooly adelgid, a tiny insect that seems to be killing the Fraser fir forest on the top of Clingmans Dome in Great Smoky Mountains National Park. Fraser fir on Mount Rogers and elsewhere are also threatened, and the species while the survival of the Balsam fir is not in question.
More specific to Virginia, the round leaf birch is a tree know to occur naturally at only one location, in Cressy Creek watershed near Chilhowee, Virginia. Other birch species occur throughout the area, especially "sweet birch," but along that one streamside a genetic mutation was favorable and a new species was better-adapted for that site. When the species was rediscovered in 1975, after being thought extinct, there were only 41 trees.
A species that is restricted in its range is usually at high risk of disappearing completely, if circumstances change. The chain link fence surrounding the small plot of land on Cressy Creek does not even keep out vandals (maintenance of the fence is intermittent) and certainly would not stop what the lawyers call an "Act of God." One flood, one fire, and the round leaf birch could be eliminated from that one natural site in Virginia.
Like the Franklinia, the round leaf birch has been planted in other locations as a precautionary measure. Human vandalism, including illegal collecting for private gardens, was determined to be the greatest threat, and 15 years after discovery only 11 of the original 41 trees were still surviving.
The state and Federal governments provided seedlings from a nursery to reduce collection pressure on the natural population. Additional sites also reduced the risk that one disaster, such as a hurricane like Camille, could eliminate the species. The round leaf birch has already been upgraded from "endangered" to "threatened." The US Fish and Wildlife Service's Virginia Round-leaf Birch Recovery Plan requires "Establishment of 10 self-sustaining populations, defined of the basis of having each produced through natural regeneration 500-1000 individuals >2 m tall" before the round leaf birch species can be "delisted"completely.
If you're taking apart a piece of equipment, you'll be careful to save all the nuts, bolts, screws, and washers as well as the large and obviously-important pieces. As humans change the landscape of Virginia, the endangered species advocates want to save all the pieces of our natural systems even though such actions may raise the cost of building new houses, roads, power plants, even docks in tidal creeks.
The main law protecting rare plants and animals is the Federal Endangered Species Act. It's not popular in many places - it's known as the "shoot, shovel, and shut up" act in a few places.
Even though there is strong public support for saving charismatic megafauna like the bald eagle, officials still get reliable reports of secret, illegal destruction of eagle nests that might interfere with projects such as Cherry Hill on the Potomac River in Prince William County. It's much harder to convince developers, or the average taxpayer and voter, that the small pieces of the web of life are just as important as the national symbol. After all, the Shiny Pigtoe mussel in the upper Tennessee River watershed may have evolved to be slightly different from other mussels since the ice ages, but it does not appear to hold the key to curing cancer. Why should we spend so much time and effort saving it? And the Lee County cave isopod - just what is an isopod, and what has that species ever done for humans?
The decision to "delist" the bald eagle will allow more development of its natural habitat, such as the forested shorelines along the Potomac/Rappahannock/York/James rivers. The proposal was controversial - the current populations of bald eagles are healthy, but look for second homes to line the shorelines in 20 more years. If the population drops again, this time because of loss of habitat instead of DDT poisoning, the eagle might be relisted in the year 2020. Biologists have really long calendars, when they talk about extinction potential...
Virginia identifies "rare" species in the state, in addition to those species officially listed as "threatened" or "endangered" by the Federal government. There's a standard set of codes for "rare" species. Code "S1" means they are rare in Virginia, while "S5" means they are common. G1 means a species is rare globally, and "G5" means it's common.
The state designation is of concern to Virginia agencies - but walk across the border into North Carolina and the classification might be different. So... if a species is at the edge of its normal range, rare in Fairfax County but common elsewhere - should we bother to protect it here?
For example, the "Common Moorhen" is S1/G5 - common elsewhere, but rare in our area. The bird is, well, inedible at best. It's also known as the "mudhen." But it's rare in this area. Does that mean we should not build a highway through a swamp, just to protect mudhens? We should route the highway through already-existing subdivisions and tear down houses instead?