forests and forestry: The Americas 469 in the American and Canadian Northwest and parts of the Rocky Mountain regions The presence—or absence—of forests in many ways shaped the cultures of the people who inhabited these regions Forest dwellers were able to feed themselves with game animals that lived in forests and fish from the rivers that watered the forests The forests were a source not only of lumber and firewood but also of such food items as nuts and fruits In contrast, people who lived in more barren areas, such as the American Southwest, had to rely more on agriculture aided by extensive irrigation systems to grow most of their food Those who lived on the plains led a more nomadic existence as they followed herds of game animals, such as buffalo Historians disagree about the nature of forestry management practices among pre-Columbian Native Americans Some argue that the impact of Native American communities on forests was minimal This view is based in part on low population estimates, perhaps to 15 million for North, Central, and South America According to this view, much of pre-Columbian North America was covered by vast expanses of forests that were in many places cut down only after the arrival of European settlers Other historians, though, believe that this view is romantic, driven more by the politics of modern environmentalism than by hard science These historians refer to this belief as the “myth of the pristine wilderness,” the idea that forests remained virgin and in their natural state, undisturbed by humans They note recent evidence that shows that the population of the Americas was probably at least 43 to 63 million and possibly up to double that number, making it inevitable that human populations affected the forests They point to evidence that this much larger population engaged in practices that resulted in extensive modification of forests, creating some 30 to 40 newly treeless acres per person during the centuries before the arrival of Europeans One of these practices was the use of fire to create open areas for two purposes One purpose was to clear fields, making it easier to hunt game, especially larger animals, such as deer, antelope, and elk This practice was especially widespread at the margins of the Great Plains Native Americans set large fires to prevent forests from spreading and even to push them back Some historians even believe that the open grasslands of the plains were essentially a creation of Native Americans, who deforested parts of the region to form what in effect were “buffalo farms,” or large, open game preserves In many places fires also were used to open up living spaces In particular, fire eliminated the low brush that provided habitat for snakes, rodents, and other undesirable species Fire was used to clear agricultural land as well Many Native American communities relied on slash-and-burn farm- ing techniques They cut down trees in forested areas to clear fields of 20 to perhaps 200 acres After they cut the trees, they burned off the rubble and stumps and planted such crops as maize (corn), squash, and beans Often conditions for a community deteriorated because of deforestation Demand for firewood was constant, so land was deforested in an everwidening radius around a village Further, maize consumes a large amount of essential nitrogen in the soil, so soil conditions in maize fields quickly degraded When these conditions arose, the people simply picked up and moved, engaging in the same forest-clearing practices elsewhere Some Native American communities consumed large tracts of forestland for building purposes For instance, the Cahokian culture, which occupied land at the confluence of the Mississippi, Missouri, and Illinois rivers, built an extensive defensive stockade around the community’s central hub This stockade consumed up to 20,000 trees, and it frequently had to be rebuilt as the wood deteriorated Progressive deforestation in the area led to extensive soil erosion, reducing the amount of tillable land in the fertile river bottoms and driving forest-dwelling game animals farther and farther away Interestingly, after such cultures as the Cahokia collapsed in the centuries before the arrival of the Europeans, forests began to rejuvenate and creep back into the grasslands in such places as Nebraska, Kansas, Wisconsin, and parts of Texas This phenomenon has led some historians to assert, controversially, that Native Americans may have had a greater impact on forests than European settlers later had These kinds of problems were by no means restricted to North America Mesoamerica—the region encompassing central and southern Mexico, the Yucatán peninsula, and such modern nations as Belize, Guatemala, parts of Honduras, and El Salvador—faced similar problems, particularly in the more arid regions Mesoamerica encompassed a number of zones with marked differences in terrain and flora These areas included dense tropical rain forests, sparser highland forests, savannas (grasslands), and arid regions Forestry management, of course, was not an issue where there were no forests or in the rain forests, where the sheer immensity of the forests muted the impact of human activities But forestry management was a particular concern in nontropical forest areas and the regions at their margins, not only in Mesoamerica but in South America as well In these regions, too, slash-and-burn farming was often the norm Many historians believe that the decline of the Mayan civilization beginning in about the ninth century is attributable to deforestation and soil erosion, at least in part The Maya had the same problem that North Americans had They cleared more and more land for agricultural purposes, and maize cultivation depleted the soil There are no domes-