The functional extinction of Andean megafauna

Rozas‐Davila, Angela; Valencia, Bryan G.; Bush, Mark B.

doi:10.1002/ecy.1531

Cited by 36 publications

(53 citation statements)

References 35 publications

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“…The loss of Polylepis from the lower edge of its Pleistocene range would be expected as Andean forest moved upslope, probably out‐competing Polylepis below tree line. Again, we caveat this observation and note that Polylepis would undoubtedly have been responding to warming, but other factors such as the interaction between fire and topography (Valencia et al., ), the loss of megafauna (Rozas‐Dávila, Valencia, & Bush, ) and changes in precipitation (Gosling et al., ) could have contributed to the observed pattern.…”

Section: Discussionmentioning

confidence: 90%

Polylepiswoodland dynamics during the last 20,000 years

Valencia

Bush

Coe

et al. 2018

Journal of Biogeography

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Aim To determine the palaeoecological influences of climate change and human land use on the spatial distribution patterns of Polylepis woodlands in the Andes. Location Tropical Andes above 2,900 m between 2°S and 18°S of latitude. Methods Pollen and charcoal data were gathered from 13 Andean lake sediment records and were rescaled by the maximum value in each site. The rescaled pollen data were used to estimate a mean abundance and coefficient of variation to show woodland expansions/contractions and woodland fragmentation over the last 20,000 years. The rescaled charcoal was displayed as a 200‐year moving median using 500‐year bins to infer the influence of fire on woodland dynamics at landscape scale. Pollen and charcoal were compared with speleothem, clastic flux and archaeological data to assess the influence of moisture balance, glacial activity and human impact on the spatial distribution of Polylepis woodlands. Results Woodland expansion and fire were correlated with precipitation changes and glacier dynamics from c. 20 to 6 kcal bp (thousands of calibrated years before present). Charcoal abundances between 20 and 12 kcal bp were less common than from 12 kcal bp to modern. However, human‐induced fires were unlikely to be the main cause of a woodland decline centred at 11 kcal bp, as woodlands recovered from 10.5 to 9.5 kcal bp (about twofold increase). Charcoal peaks analogous to those that induced the woodland decline at 11 kcal bp were commonplace post‐9.5 kcal bp but did not trigger an equivalent woodland contraction. An increase in the coefficient of variation after c. 5.5 kcal bp suggests enhanced fragmentation and coincided with the shift from logistic to exponential growth of human populations. Over the last 1,000 years, Polylepis became hyper‐fragmented with over half of sites losing Polylepis from the record and with coefficients of variation paralleling those of glacial times. Main conclusions Polylepis woodlands formed naturally patchy woodlands, rather than a continuous vegetation belt, prior to human occupation in the Andes. The main factors controlling pre‐human woodland dynamics were precipitation and landscape heterogeneity. Human activity led to hyper‐fragmentation during the last c. 1,000 years.

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Section: Discussionmentioning

confidence: 90%

Polylepiswoodland dynamics during the last 20,000 years

Valencia

Bush

Coe

et al. 2018

Journal of Biogeography

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“…The extinction that took place at the end of the Pleistocene (Young et al, 2016) affected species composition and probably vegetation structure, but the effects of the megafauna extinction may have been more heterogeneous than the previously thought. Although some plant species probably benefited from reduced grazing and trampling (Rozas-Dávila et al, 2016), others might have suffered negative effects from increased competition or reduced seed dispersal. With the loss of dispersers, more clumped distributions of large-seeded species might be expected (Janzen and Martin, 1982).…”

Section: Did Climate Change Cause the Megafaunal Extinction?mentioning

confidence: 99%

The collapse of megafaunal populations in southeastern Brazil

Raczka¹,

Bush²,

Oliveira

2017

Quat. res.

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Whether humans or climate change caused the extinction of megafaunal populations is actively debated. Caves in the Lagoa Santa provide mixed assemblages of megafauna and human remains; however, it remains uncertain the extent to which humans and megafauna interacted or overlapped temporally. Here we present the first paleoecological record from lowland South America that tracks the decline of megafauna and its ecological implications. We provide a data set for pollen, charcoal, and Sporormiella, from two lakes in southeastern Brazil that span the last 23,000 yr. The data showed reduced abundances of Sporormiella and an inferred megafaunal population decline that began 18,000 yr ago, with the functional extinction occurring between 12,000 and 11,500 yr ago. Population declines coincided with wet events. The age of the final megafaunal decline is within the range of the first human occupation of the region. Our data are consistent with climate causing the population collapse, with humans preventing population recovery and inducing extinction. We did not observe some of the ecological repercussions documented at other sites and attributed to the megafaunal extinction. Habitat-specific ecological consequences of the extinction add to the heterogeneity of late Pleistocene and early Holocene landscapes.

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“…Whilst the technique has proven especially powerful in analysing patterns of megafaunal extinction (e.g. Burney et al 2003;Gill et al, 2009;Rule et al, 2012;Rozas-Davila et al, 2016), other workers have used it to estimate livestock densities and the effects of grazing pressure (e.g. Davis and Schafer, 2006;Mazier et al, 2009;Etienne et al, 2013;Gill et al, 2013, Baker et al, 2016.…”

Section: Introductionmentioning

confidence: 99%

Comparison of Sporormiella dung fungal spores and oribatid mites as indicators of large herbivore presence: evidence from the Cuzco region of Peru

Chepstow-Lusty

Frogley

Baker

2019

Journal of Archaeological Science

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The ability of sedimentary proxies (especially dung fungal spores) to reflect the past presence and density of large herbivores on a landscape has been receiving increasing scrutiny. Here we examine the Sporormiella spore record from a well-dated, multiproxy, highly organic sedimentary record from the small lake basin of Marcacocha in the Cuzco region of Peru. The basin, a wetland since ca. AD 1840, existed as a small lake for at least 4000 years prior. Previous work at Marcacocha has shown that changes in herbivore densities reflect the abundances of oribatid mites preserved in the lake sediments. This study tests the assumption that both the Sporormiella and the oribatid mite records responded in broadly the same way to changes in herbivore densities over the past 1200 years. Analysis reveals a very low covariance between concentrations of Sporormiella spores and the two major components of the oribatid mite assemblage: a single aquatic species of Hydrozetes and a less abundant, wider grouping comprising members of the mostly terrestrial superfamily Ceratozetoidea (referred to as the 'ceratozetoids'). Variations in the Hydrozetes assemblage clearly dovetail with known historical events, including the massive decline of indigenous and camelid populations following the collapse of the Inca Empire in the mid-sixteenth century. Comparison with other environmental proxies from the Marcacocha sequence, including diatoms and charophyte oospores, suggests that the ceratozetoids appear to reflect increasing terrestrialization. In contrast, although the Sporormiella record indicates the presence of livestock, it fails to register the major historical changes in herbivore presence, though reflects well episodes of lake-level lowering. In small lake settings, therefore, the use of Sporormiella to estimate the density of herbivores in the catchment might be considered a relatively blunt instrument when compared with some other indicators. Supporting Information: Appendix S1 Comparison of Sporormiella dung fungal spores and oribatid mites as indicators of large herbivore presence: evidence from the Cuzco region of Peru

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The functional extinction of Andean megafauna

Cited by 36 publications

References 35 publications

Polylepiswoodland dynamics during the last 20,000 years

Polylepiswoodland dynamics during the last 20,000 years

The collapse of megafaunal populations in southeastern Brazil

Comparison of Sporormiella dung fungal spores and oribatid mites as indicators of large herbivore presence: evidence from the Cuzco region of Peru

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