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Paleolimnological evidence indicates the ancient Maya transformed terrestrial ecosystems by felling forest vegetation to construct large civic-ceremonial centers and to expand agriculture. Human settlements influenced lacustrine environments but the effects of Maya activities on aquatic ecosystems remain poorly studied. Here we analyzed a sediment core from Lake Petén Itzá, Guatemala, to infer paleoenvironmental changes resulting from Maya occupation of the archaeological site of Nixtun-Ch’ich’. Increases in charcoal and fecal stanol concentrations indicate Maya occupation of the Candelaria Peninsula by the late Early Preclassic period. Geochemical proxies reveal a period of lake ecosystem alteration during construction and expansion of the city’s urban grid in the Middle and Late Preclassic periods. Depopulation of the city in the Terminal Preclassic resulted in a decline in lake trophic state. Whereas previous studies of Petén waterbodies have indicated depressed lacustrine primary production, the core collected near Nixtun-Ch’ich’ shows evidence of ancient Maya lake ecosystem deterioration.

The long-term effects of deforestation on tropical forest soil carbon reservoirs are important for estimating the consequences of land use on the global carbon cycle, but are poorly understood. The Maya Lowlands of Mexico and Guatemala provide a unique opportunity to assess this question, given the widespread deforestation by the ancient Maya that began ~4,000 years ago. Here, we compare radiocarbon ages of plant waxes and macrofossils in sediment cores from three lakes in the Maya Lowlands to record past changes in the mean soil transit time of plant waxes (MTTwax). MTTwax indicates the average age of plant waxes that are transported from soils to lake sediments, and comparison of radiocarbon data from soils and lake sediments within the same catchment indicates that MTTwax reflects the age of carbon in deep soils. All three sediment cores showed a decrease in MTTwax, ranging from 2,300 to 800 years, over the past 3,500 years. This decrease in MTTwax, indicating shorter storage times for carbon in lake catchment soils, is associated with evidence for ancient Maya deforestation. MTTwax never recovered to pre-deforestation values, despite subsequent reforestation, implying that current tropical deforestation will have long-lasting effects on soil carbon sinks.

A two-part archaeological and limnological study of the Malian Lakes Region has revealed the high research potential of the region. The exploratory reconnaissance of the Gorbi Valley, on the eastern edge of Lake Fati, identified, mapped and sampled eight new sites. The results of the survey suggest a long duration occupation of the Gorbi Valley, as well as possible connections with the populations of the Inland Niger Delta and southeastern Mauritania. The Lake Fati core represents the first lake sediment core from the western Sahel. This 5.4 m sediment core contains a continuous record of lake mud from 10.43 to 4.66 kyr BP. Analysis of the core reveals that Al and Si abundances are decoupled following a deposition of 16 cm of sand at 4.5 ka BP, with Al decreasing and Si increasing rapidly. This period of sand deposition is significantly younger than that of the transition at 5.5 ka BP recorded in marine cores from ODP site 658, taken off the Mauritanian coast, potentially extending the timeframe in which dune systems were stable and lake systems were at their highstand. While highlighting the need for more localized climate chronologies and archaeological investigations, this study may shed light on circumstances surrounding the initial colonization and further development of the Lakes Region.