In 1607, Captain Newport led 108 English colonists to a Virginia that was covered by oak-hickory forests. The forests were recognized as a valuable resource for wildlife habitat and food (deer and turkey were the most-hunted species), for fuel, and for building materials.
Virginia looked very different at the last glacial maximum 18,000 years ago. The ice sheets stopped in Pennsylvania, roughly along the line of the Ohio River and the northern half of Pennsylvania - Virginia was not glaciated. However, the colder climate dramatically reshaped the vegetation and shoreline of Virginia.
During the Ice Age, Virginia remained heavily forested. Study of sediments in old ponds shows lots of tree pollen; we had very little bare tundra comparable to the current Arctic National Wildlife Refuge. We did have a very different mix of tree species than what you see in Virginia today, because the Ice Age climate was so dramatically different.
In the Ice Age, the forests of Virginia had a high percentage of spruce (Picea) trees. These evergreen conifers are common in Canada today. There's a belt of spruce and fir trees south of the tundra, and those cold-adapted species also can be found along the high crest of the Appalachians south into Tennessee. But when the glaciers reached into Pennsylvania 18,000 years ago, was there an equivalent belt of spruce and fir on the southern edge of the ice, with broad-leaved trees like oaks and maples pushed much further to the south into the Carolinas? What were the forests of Virginia?
treeless plain, now at Arctic National Wildlife Refuge... but once common in Virginia?
Source: US Fish and Wildlife Service
spruce-fir forest, which largely disappeared from Virginia
after ice age ended
Arguments are still raging regarding what the Virginia forest looked like then. Pollen grains have been collected from sediments that accumulated in various lakes and bogs during the ice ages. As far south as Louisiana, we find spruce pollen - but in Virginia, we also find high percentages of warm-species trees, such as oak and hickory. There's other evidence, such as indications of sand "blowouts" on the Coastal Plain, suggesting that Virginia's vegetation was an open pine woodland about 15,000 years ago. We had some spruce and fir, but not in a thick band that excluded broad-leaved trees. It was a diverse forest.
The first Virginians arrived in the state about 15,000 years ago. Especially east of the Appalachians, they probably found a mixture of pines and prairie - not a thick, closed-canopy conifer forest such as you see in Ontario or the temperate forest that covers Virginia today. The earliest Virginians probably found bison, mastodons, and elk grazing in Virginia grasslands, and has only scattered trees for screening their approach during a hunt.
As the climate changed and the temperate forest cover developed across Virginia, the Native Americans adapted to the change. In the Shenandoah Valley and Dismal Swamp areas, they may have limited the forest growth on purpose by setting fires often. This increased the acres of grassland, which increased the number of deer and elk.
The prehistoric fire ecology of the Shenandoah Valley is not completely understood - but it is likely that Native Americans were well aware of the environmental impacts of natural fires. Native Americans used fire to create their desired habitat, by increasing the number of natural fires that reduced the brush and "opened up the woods" for hunting.
When three English ships sailed up a river they named the James in 1607, they found a substantially different Virginia from what greeted the first arrivals 15,000 years earlier. The climate had changed in those millennia. The Europeans arrived during the worst drought in the last 400 years - but they still arrived in a wetter, warmer Virginia than the first set of discoverers.
The vegetation of Virginia reflects the climate of the state. As the climate has changed over time, so has the vegetation. The climate got warmer and wetter after the Ice Age, and broad-leaved trees (oaks, chestnuts, hickories, maples, etc.) replaced spruce and fir. The Eastern Deciduous Forest became the dominant forest type in most of Virginia during a global warming period that has lasted until today.
Some spruce and fir forests have survived on the cooler ridgetops, in the Blue Ridge and Appalachian highlands. Pines became a major component of the forests on the Coastal Plain, outcompeting the broad-leaved trees. Rainwater rapidly drained from the surface and below the root zone in the sandy Coastal Plain, so drought-adapted pine species had a competitive advantage east of the Fall Line.
Soils and the availability of water (along with other factors, such as the slope of the land) will determine what species we see in different locations within Virginia. We see bald cypress trees in swamps vs.oak and hickory trees on dry ridgetops, because the plants have evolved to live in different conditions.
Because Virginia has about 40 inches of rain annually, it has many creek valleys and swamps where the moisture-loving trees thrive. For example, cypress trees have two obvious adaptations to growing in swampy areas - trunks that swell at the base for stability, and "knees" that presumably provide greater oxygen. Absent the genes for those adaptations, the roots of mockernut hickory trees would literally drown if growing in an area covered by standing water for long periods of time. (When humans or beavers dam a creek, nearly all trees in the flooded reservoir will drown. If the dam remains long enough, then a different sort of forest will grow on that site.)
The climate shaped the forests, and the forests adapted to drought and fire. Before the Europeans arrived, it was common for small fires to travel through Virginia forests within every 35 years or so. Native Americans and the early European explorers would commonly travel through recently-burned forests, where the undergrowth had been removed but the bark of the trees only lightly scorched. West of the Allegheny Front, the fires were more intense but rarer, burning the forests of what is now West Virginia with mixed severity every 35-100 years.
Today, we have cleared much of the original forest. Originally the colonists cleared the forests for agriculture because tobacco plants, just like corn/beans/squash, require full sun in order to grow. Later crops, such as wheat, soybeans, and tomatoes - and grass for grazing cattle - have a similar requirement for bright sun. (If people ate ferns for every meal, farmers in Virginia might have developed shade-grown agriculture in Virginia...)
Virginia households also cleared the forests for firewood, the primary fuel source for houses and industry until after the Civil War. In the last century, roads and housing developments have reshaped the patterns of fields and forests dramatically. The great expanses of unbroken woods have been replaced with small woodlots separated by wide pastures and housing developments.
Changing the pattern of fields and forests has a major impact on wildlife. When we build a road through a forest, we not only replace trees with pavement and grass medians - we fragment the remaining forest into two smaller sections. That changes the habitat, the environment that provides food and "housing" for various species.
Birds such as the wood thrush require deep woods for successful nesting. Brownheaded cowbirds won't penetrate far from the edge of the forest to lay their eggs in a nest. When a wood thrush lays its eggs in a nest constructed deep in the woods, no cowbird will fly in there and add its egg to the nest. If we cut a road through the woods, however, a cowbird is much more likely to lay its egg in the wood thrush nest. The early-hatching cowbird will then push the thrush eggs out of the nest, and the thrush parents will end up feeding a nestling of another species.
female brown-headed cowbird
Source: US Fish and Wildlife Service
The climate of Virginia could change again. If global warming does actually occur, altering the current pattern of biomes across the world,then the remaining pockets of spruce and fir could disappear from Virginia's mountains. Grasslands could replace the temperate forests in Virginia. In a few centuries, the state's vegetation patterns could resemble the sand hills of Nebraska or the oak forests of the Sacramento Valley.