The myth persists that in 1492 the Western Hemisphere was an untamed wilderness and that it was European settlers who harnessed and transformed its ecosystems. But scholarship shows that forests, in particular, had been altered to varying degrees well before the arrival of Europeans. Native populations had converted much of the forests to successfully cultivated stands, especially by means of burning. Nevertheless, some researchers have maintained that the extent, frequency, and impact of such burning was minimal. One geographer claims that climatic change could have accounted for some of the changes in forest composition; another argues that burning by native populations was done only sporadically, to augment the effects of natural fires.

However, a large body of evidence for the routine practice of burning exists in the geographical record. One group of researchers found, for example, that sedimentary charcoal accumulations in what is now the northeastern United States are greatest where known native American settlements were greatest. Other evidence shows that, while the characteristics and impact of fires set by native populations varied regionally according to population size, extent of resource management techniques, and environment, all such fires had markedly different effects on vegetation patterns than did natural fires. Controlled burning created grassy openings such as meadows and glades. Burning also promoted a mosaic quality to North and South American ecosystems, creating forests in many different stages of ecological development. Much of the mature forestland was characterized by open, herbaceous undergrowth, another result of the clearing brought about by burning.

In North America, controlled burning created conditions favorable to berries and other fire-tolerant and sun-loving foods. Burning also converted mixed stands of trees to homogeneous forest, for example the longleaf, slash pine, and scrub oak forests of the southeastern U.S. Natural fires do account for some of this vegetation, but regular burning clearly extended and maintained it. Burning also influenced forest composition in the tropics, where natural fires are rare. An example is the pine-dominant forests of Nicaragua, where warm temperatures and heavy rainfall naturally favor mixed tropical or rain forests. While there are extensive pine forests in Guatemala and Mexico, these primarily grow in cooler, drier, higher elevations, regions where such vegetation is in large part natural and even prehuman. Today, the Nicaraguan pines occur where there has been clearing followed by regular burning, and the same is likely to have occurred in the past: such forests were present when Europeans arrived and were found only in areas where native settlements were substantial; when these settlements were abandoned, the land returned to mixed hardwoods. This succession is also evident elsewhere in similar low tropical elevations in the Caribbean and Mexico.