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There is a growing number of studies that use historical sources to reconstruct recent environmental change. In Mexico there are abundant sources of information that can be used to determine variations in the climate over the historical period. In this paper we draw together information from a variety of primary and secondary historical sources to reconstruct fluctuations in the climate of central Mexico over the last 600 years. The Aztecs are believed to have entered the Basin of Mexico during a period of severe drought. Wet conditions, however, characterized much of the Aztec (AD 1345-1521) and early colonial period prior to a return to drier conditions in the 1640s. Between 1640 and 1915, a series of severe droughts caused widespread devastation throughout central Mexico, particularly during the mid- to late 1700s and late 1800s. Since the early 1900s this region has experienced slightly wetter conditions. The climatic record from the Basin of Mexico is compared with proxy climatic data from two other areas in Mexico: a detailed lake-level curve from Lake Patzcuaro in central Mexico and the few tree-ring records from northern Mexico. Although the palaeoclimatic records from central Mexico are similar, there is greater divergence between the records from central and northern Mexico. In general, fluctuations in the climate over the last 600 years can be explained by changes in the relative strength of the summer 'monsoon', but it is possible that ENSO events can cause considerable differences in prevailing climate conditions in the northern and central parts of the country.

The Zacapu basin, Michoacán, Mexico, is one of a series of internally drained lake basins in the central highlands of Mexico. The basin has a history of occupation spanning at least 2000 years and before the arrival of the Spanish was a major centre for the Purépecha culture. Results are presented of diatom studies from four lacustrine sediment sequences which have Holocene radiocarbon dates: CEMCA Point 1, CEMCA Point 4, the Zacapu core and Zacapu Section 1. These lie along a transect from the former marsh floor up to the western slopes of the basin. Zacapu Section 1 indicates a deep lake in the basin at some time, but the date on this section is thought to be unreliable and the sediments are probably Pleistocene in age. The other sequences record few major changes in water level in the basin, although dry episodes occurred about 4500 BP and, more severely, about 1000 BP. A period of marked catchment disturbance about 7000 to 6000 BP is believed to be the result of volcanic activity on the western flank of the basin. Major anthropogenic disturbance is recorded over the Postclassic and Hispanic periods (since about AD 900).

The Upper Río Lerma valley, Estado de México, is a high-altitude (2575 m a.s.l.) basin floored by Quaternary alluvial, lacustrine and pyroclastic deposits. Two pits were dug in the swampy bed of the recently drained L. Chiconahuapan. Ten 14C dates have been obtained from these profiles, which consist of diatomaceous organic lake muds and peats with intercalated tephras. The oldest unit is the Upper Toluca Pumice (Tripartite Ash), dated 11 580±70 yr BP. Analyses of sediment chemistry, loss-onignition, mineral-magnetic variations and subfossil diatom assemblages provide evidence of environmental changes since this date. Alkaline ponds or freshwater lakes developed during the intervals 9000–6000, 6000–5500, 3600–1400 and 800–0 yr BP, and acidic marshes or bogs during the intervening dry episodes. An important phase of accelerated erosion, beginning around 3100 yr BP and culminating around 1400–700 yr BP, appears to have been associated with human disturbance of the basin soils.