Maps made by non-Native Americans to depict Native American land tenure, resources andpopulation distributions appeared almost as early as Europeans' first encounters with NativeAmericans and took many form: missionaries' field sketches, explorers' drawings, and surveyors'maps, as well as maps rendered in connection with treaties involving land transfers. Most existingmaps of Native American lands are reconstructions that are based largely on archaeology, oralreports, and evidence gathered from observers' accounts in letter, diaries, and official reports;accordingly, the accuracy of these maps is especially dependent on the mapmakers' owninterpretive abilities.

Many existing maps also reflect the 150-year role of the Bureau of Indian Affairs (BIA) in administering tribal lands. Though these maps incorporate some information gleaned directly from Native Americans, rarely has Native American cartography contributed to this official record, which has been compiled, surveyed, and authenticated by non-Native American tribes and their migrations and cultural features, as well as territoriality and contemporary trust lands, reflects the origins of the data, the mixed purposes for which the maps have been prepared, and changes both I United States government policy and in non-Native Americans’ attitudes toward an understanding of Native Americans.

More selective than most chemical pesticides in that they ordinarily destroy only unwanted species, biocontrol. agents (such as insects, fungi, and viruses) eat, infect, or parasitize targeted plant or animal pests. However, biocontrol agents can negatively affect nontarget species by, for example, competing with them for resources: a biocontrol agent might reduce the benefits conferred by a desirable animal species by consuming a plant on which the animal prefers to lay its eggs.

Another example of indirect negative consequcnces occurred in England when a virus introduced to control rabbits reduced the amount of open ground (because large rabbit populations reduce the ground cover), in turn reducing underground ant nests and triggering the extinction of a blue butterfly that had depended on the nests to shelter its offspring. The paucity of known extinctions or disruptions resulting from indirect interactions may reflect not the infrequency of such mishaps but rather the failure to look for or to detect them: most organisms likely to be adversely affected by indirect interactions are of little or no known commercial value and the events linking a biocontrol agent with an adverse effect are often unclear. Moreover, determining the potential risks of biocontrol agents before they are used is difficult, especially when a nonnative agent is introduced, because, unlike a chemical pesticide, a biocontrol agent may adapt in unpredictable ways. so that it can feed on or otherwise harm new hosts.