The original vegetation cover of North America reflected the climatic pattern. The humid East and North were clothed in forest as were also the Pacific coastal area and the higher slopes of the mountains within the Western Highlands. A scanty covering of desert vegetation spread over the remainder of the Western Highlands. Grass reached out eastward from this to join the eastern forests somewhat east of the dry climatic boundary. And Arctic tundra clothed the northern fringe of the continent, the Canadian Archipelago, and the small, ice-free areas of Greenland.
Tropical scrub forest, with some heavier tropical rain forest in the wetter areas, covers Yucatan and adjacent Mexico, extending northward along the coast as far as Tampico. In southeastern United States, a pine forest spreads over northern Florida and the coastal lowlands of adjacent states as far north as North Carolina and as far west as Mississippi, the wetter and swampier sections supporting cypress forest. Northward, almost imperceptibly, the pine forest gives way to broadleaf and broadleaf-conifer forest, which extends to northern New England, northern Ontario, and Minnesota. On the west, this forest reaches to an irregular line from central Texas to central Illinois to western Minnesota. Still further north lies the most extensive of all North American forests, the northern coniferous forest, stretching from the Bering Sea coast of Alaska to the Atlantic and from northern United States nearly to the Arctic. The Pacific forests were a slight, scrubby forest interspersed with grass northward from southern California to San Francisco and, from there northward over the coastal lowlands and mountains alike, an evergreen forest of giant trees, like the Douglas fir and the sequoia.
Tall grass, or prairie, reached westward from the eastern forests over the Great Plains to about the 100th meridian. There it gave way to short grass, or steppe, which continued to the Rocky Mountain front.
The northern and central forests of the United States have been ruthlessly destroyed with the spread of population into the interior. Practically all of the prairie has also been destroyed to make way for cultivation, and the usefulness of a large part of the steppe has been seriously impaired by overgrazing with its subsequent evils of plant association change and soil erosion. By 1950, only the southern pine forest and the western forests were important, large scale producers of forest products in the United States. The southern margin of the great northern forest of Canada is the other major source of North American forest products. The prodigal waste of the natural vegetation cover over most of the United States is almost without parallel in the world.
The radical change which humanity's spread over North America brought about in the vegetation cover was accompanied by prominent changes in the native animal population. Certain well-known species, like the bison, elk, and beaver, have been so ruthlessly destroyed as nearly to bring about their extinction; among the birds, the passenger pigeon has actually been exterminated. However, many species, like woodchucks and rabbits, have adjusted themselves easily and are more plentiful now than before the coming of Europeans. Greater availability of food, especially from the plants humans grow, is responsible for this.
Originally, animals were an essential part of the primitive economy; they provided food, shelter, and clothing. A balance was maintained largely because the weapons of the hunters were crude and the number of hunters was relatively small. Animal life served the same functions for the early colonists. Later, hunters with superior equipment upset the balance. Then, too, furs commanded a market in Europe. The forests of the north and west were combed for prime fur-bearing animals, especially beaver. Later, as settlement spread across the Great Plains, great herds of bison were slaughtered indiscriminately. Often, only a small portion of the carcass was used. As cultivation and grazing expanded, species like the coyote, rabbit, starling, and crow increased more rapidly than ever before.
The northern forests and the mountainous west still produce furs, but under control aimed at preventing extermination. Over most of the continent, hunting has become recreational rather than exploitational. Protective laws specify the times when certain species may be killed as well as the numbers that may be killed.
Despite the great wealth of native animal life in North America, there were no representatives of the species that humans had domesticated, excepting only the dog. Wild horses roaming the Great Plains when Europeans first saw that area were descendants of the horses brought by and escaped from the earliest explorers. Cows, sheep, goats, pigs, and chickens were brought to North America; not any of them were natives of the continent.