PMC

Areas examined for impacts of late-Quaternary defaunation.

Amboseli National Park, Kenya. Typical vegetation is shown where elephants roam freely (A) compared with a nearby area where elephants are excluded (B).

Percentage diagram of pollen from Lago Eberhard (Top) and Pantano Dumestre (Bottom). Pollen percentages are shown as the proportion of terrestrial pollen total sum. Only taxa most informative for inferring vegetation changes relevant to megafauna extinction are shown. For a complete presentation and analysis of these records, see refs. and . Reproduced with permission from ref. .

Comparison of Lago Eberhard (Left) and Pantano Dumestre (Right) charcoal and vegetation-change records. Traces A and B indicate percentage of organic matter through time; traces C and D indicate percentage of grass charcoal; traces E and F indicate fire frequency, measured as fire events/500 y; traces G and H indicate Charcoal Accumulation Rates analyses (CHAR); traces I and J indicate rates of change analyses (ROC) in the pollen records. Information is extracted and modified from refs. and . Black triangles show the timing of the onset in the increase of Nothofagus for each site. Reproduced with permission from ref. .

Chronology of vegetation change in northern California compared with sea surface temperature (SST) and regional extinction of megafauna. (Left) SST and pollen-percentage curves are from ODP site 1019 (). (Center) Twin Lake pollen diagram reproduced with permission from ref. . TCT, undifferentiated pollen from Taxodiaceae, Cupressaceae, and Taxaceae. Blue shading indicates Younger Dryas (YD). Megafauna dates are from ref. , except for the oldest proboscidean date from ref. . (Right) Proboscideans (Mammuthus and Mammut) (A), Bison (B); Equus (C), Paramylodon (D), and Sporormiella (E) from Mono Lake on the left and Exchequer Meadow on the right (, ). Probability distributions for extinction timing at right estimated using GRIWM method (); see for explanation. The dating of the Sporormiella decline is not amenable to estimating extinction timing with the GRIWM method because of the nature of the data, so here we simply report the 95% uncertainty in the dates used to constrain the ages of the youngest occurrences at each of two separate lake localities.

(A) General view of the Última Esperanza area. The location of the bog and lake records that provide vegetation change and fire history are shown by the blue rectangles. The megafaunal sites are shown by orange dots. The thick gray line shows the approximate maximum late glacial extent of the Última Esperanza Ice Lobe. Until about 18,000 y ago, a proglacial lake submerged the study area; thus, in this region, it is possible to obtain information about both the earliest records of occupation by megafauna and humans and extinction of the megafauna. (B) Closer view of the Cerro Benítez, Cerro Señoret, and Lago Sofía areas. This is the region that supplies the data discussed in the text and summarized in , which allows building the detailed chronology of human occupation, vegetation change, fire history, and megafaunal extinction that is used to interpret effects of defaunation. A3-DH, Alero 3 Dos Herraduras; AQ, Alero Quemado; CCh, Cueva Chica; CDM, Cueva del Medio; CLS1, Cueva Lago Sofía 1; CLS4, Cueva Lago Sofía 4; CM, Cueva del Milodón. Reproduced with permission from ref. .

Red lines delineate the area of the Pampas considered in this paper, which is the area of southeastern South America that comprised a grassland-steppe ecosystem during the Last Glacial Maximum (). Green dots show the provenance of paleoclimate proxy data that indicate a shift in vegetation and climate in various regions, which took place at somewhat different times over ∼2,000 y beginning ∼12,000 y ago, as explained in the section. Details of the environmental interpretation at each site are given in the following references: ref. (site 1, Pay Paso); ref. (site 2, Los Ajos); ref. (site 3, Arroyo Sauce Chico; site 4, Empalme Querandies; site 5, Cerro La China); and ref. (site 6, Sauce Grandé; site 7, La Horqueta II; site 8, Napostá Grande). Black dots show sites that have yielded Notiomastodon (), although very few of these specimens have been radiocarbon-dated. Abbreviations for environmental conditions in the late Pleistocene are as follows: HP, Humid Pampas; IP, Inland Pampas; SP, Southern Pampas; XW, xerophytic woodland.

Chronology of megafaunal extinctions plotted against climate change as indicated by oxygen isotope and pollen data (left colored bands, where blue is cool and red is warm); vegetation change [right colored bands, with yellow equating to cold grassland dominance, yellowish green representing mixed grasslands and Nothofagus forest, and olive green (younger than ∼11,000 ka) indicating predominance of Nothofagus forest]; and timing of increase in fire frequency (dotted-line box). See and for more details on vegetation change and fire frequency indicators. The megafaunal extinction chronology and the chronology of human arrival is based on dates listed in ref. ; all dates were vetted for robustness, with only those of rank 11 (as explained in ref. ) or higher used. The timing of local ice-free conditions is taken from ref. (light blue rectangle). Also shown is the timing of the Reclús Volcano eruption (red line), which although it distributed considerable ash in the region, had no apparent effect on the timing of the faunal or vegetation changes (). The time axis is in calibrated years before present. For the radiocarbon dates on megafauna and human occupation, the dots (or triangles for humans) show the median and the whiskers show the 2-σ probability. Distributions indicating the probability of timing of extinction for megafauna and first arrival for humans were calculated using the GRIWM best-estimate method; see ref. for explanation and R-code. Dietary preferences are indicated in brackets by C (carnivore), M (mixed feeder herbivore), G (grazer), and U (unknown) (, –). Reproduced with permission from ref. .

Chronology of megafaunal loss, vegetation, and climate change in the Pampas. The diagram shows robust calibrated radiocarbon dates on bone collagen or tooth enamel (the error bars span the 2-σ probability distribution and, for many dates, are too small to appear on the chart). A transition (darker green shading) from an ecosystem dominated by C3 (Pooid) grasses to C4 (Panicoid) grasses begins ∼12,000 y ago and is asynchronous across the Pampas (see for details). The red and blue shading on the left illustrates cool (blue) and warm (red) times. ACR, Antarctic Cold Reversal, which overlaps the northern hemisphere’s Younger Dryas to some extent but is somewhat earlier. Gray distributions indicating the probability of timing of extinction for megafauna were calculated using the GRIWM best-estimate method (); also see ref. . for R-code. GRIWM’s best estimate of the extinction time and its 95% confidence band are younger than 5,000 y ago for glyptodonts (estimated probable timing of extinction: 1,903 calibrated years BP; range: 4,126 to −256 calibrated years BP; the negative number indicates the probability extends into the future) and Notiomastodon (estimated probable time of extinction: 2,415 calibrated years BP; range: 3,001–1,838 calibrated years BP). Clearly, these anomalously young extinction estimates come from a paucity of radiocarbon dates, with those few available being widely spaced in time. Such results do not provide evidence for persistence of megafauna well into the Holocene; rather, they emphasize that more radiocarbon dates are needed. Dietary preferences of extinct megafauna are indicated by G (grazer), B (browser), M (mixed feeder), and U (unknown) (, ).