‘Lake’ Alaotra, Madagascar: A late Quaternary wetland regulated by the tectonic regime

Miétton, Michel; Gunnell, Yanni; Nicoud, Gérard; Ferry, Luc; Razafimahefa, Reine; Grandjean, Philippe

doi:10.1016/j.catena.2018.01.021

Cited by 17 publications

(35 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The travertine blocks at the base of Level 2 may be associated with heightened activity of the Vakinankaratra volcanic field around 19 000 years ago (19 000 ± 2000 ca al BP; Rufer et al, 2014). Mietton et al (2018) correlated these volcanics with the time of deposition of late glacial deposits at Lake Tritrivakely, when the incidence of heath pollen at this site was very high and grasses scarce. At Lake Tritrivakely, the transition from glacial (cold) to postglacial (warm) conditions occurred in two steps, first at~16 900 cal a BP and next at~15 100 cal a BP, with a significant drop in heath plants and rise in grasses at each (Gasse & Van Campo, 1998).…”

Section: Discussionmentioning

confidence: 95%

A new late Pleistocene subfossil site (Tsaramody, Sambaina basin, central Madagascar) with implications for the chronology of habitat and megafaunal community change on Madagascar's Central Highlands

Samonds

Crowley

Rasolofomanana

et al. 2019

J Quaternary Science

View full text Add to dashboard Cite

Madagascar is a complex ‘biodiversity hotspot’ with a rapidly dwindling biota. The Late Quaternary subfossil record includes many extinct species whose loss is attributed to natural climate change and human impacts. Investigation of the chronology of these events is challenging because few localities document pre‐Holocene communities not impacted by humans. Caves with extinct lemurs of large body size comprise some of Madagascar's richest subfossil sites, but provide only a limited window into the island's past. Open highland sites may have fewer primates, but may better document other megafauna, and allow the analysis of the role of the Central Highlands as refugia and as corridors for the dispersal of vertebrates before and after human arrival. Here we present a new subfossil site, Tsaramody (Sambaina basin, Central Madagascar), a high‐altitude wetland area that preserves a diverse late glacial and postglacial vertebrate community. Tsaramody bears testimony to fluctuations in the highland flora during the transition from glacial to postglacial conditions, and the composition of a highland vertebrate community before humans arrived. We compare its biota to those of other sites to begin to document the decline and disappearance of megafauna from some of Madagascar's open ecosystems – wetlands dominated by hippopotamuses and crocodylians. © 2019 John Wiley & Sons, Ltd.

show abstract

Section: Discussionmentioning

confidence: 95%

A new late Pleistocene subfossil site (Tsaramody, Sambaina basin, central Madagascar) with implications for the chronology of habitat and megafaunal community change on Madagascar's Central Highlands

Samonds

Crowley

Rasolofomanana

et al. 2019

J Quaternary Science

View full text Add to dashboard Cite

show abstract

“…This vegetation was replaced by Ericaceae (adapted to survive strong seasonal droughts) [ 31 , 32 ] during the LGM as a result of the abrupt decrease in temperature (~ 4 ℃ cooler than today) [ 31 , 74 ]. Multiple paleoenvironmental records from other parts of the island and corresponding to more recent periods confirmed substantially drier and cooler conditions during the LGM (e.g., [ 18 , 30 , 75 , 76 ] but see [ 77 ]), suggesting that a general contraction of forest habitats across Madagascar at that time period is likely [ 30 ]. Such conditions during the LGM probably induced lowland forests to contract, possibly to riverine refugia, as those areas would have secured access to water and generated rather mesic local conditions [ 33 ].…”

Section: Discussionmentioning

confidence: 99%

Impact of model assumptions on demographic inferences: the case study of two sympatric mouse lemurs in northwestern Madagascar

et al. 2021

View full text Add to dashboard Cite

Background Quaternary climate fluctuations have been acknowledged as major drivers of the geographical distribution of the extraordinary biodiversity observed in tropical biomes, including Madagascar. The main existing framework for Pleistocene Malagasy diversification assumes that forest cover was strongly shaped by warmer Interglacials (leading to forest expansion) and by cooler and arid glacials (leading to forest contraction), but predictions derived from this scenario for forest-dwelling animals have rarely been tested with genomic datasets. Results We generated genomic data and applied three complementary demographic approaches (Stairway Plot, PSMC and IICR-simulations) to infer population size and connectivity changes for two forest-dependent primate species (Microcebus murinus and M. ravelobensis) in northwestern Madagascar. The analyses suggested major demographic changes in both species that could be interpreted in two ways, depending on underlying model assumptions (i.e., panmixia or population structure). Under panmixia, the two species exhibited larger population sizes across the Last Glacial Maximum (LGM) and towards the African Humid Period (AHP). This peak was followed by a population decline in M. ravelobensis until the present, while M. murinus may have experienced a second population expansion that was followed by a sharp decline starting 3000 years ago. In contrast, simulations under population structure suggested decreasing population connectivity between the Last Interglacial and the LGM for both species, but increased connectivity during the AHP exclusively for M. murinus. Conclusion Our study shows that closely related species may differ in their responses to climatic events. Assuming that Pleistocene climatic conditions in the lowlands were similar to those in the Malagasy highlands, some demographic dynamics would be better explained by changes in population connectivity than in population size. However, changes in connectivity alone cannot be easily reconciled with a founder effect that was shown for M. murinus during its colonization of the northwestern Madagascar in the late Pleistocene. To decide between the two alternative models, more knowledge about historic forest dynamics in lowland habitats is necessary. Altogether, our study stresses that demographic inferences strongly depend on the underlying model assumptions. Final conclusions should therefore be based on a comparative evaluation of multiple approaches.

show abstract

“…The average annual rainfall is between 950 and 1250 mm, with the maximum taking place in January [35]. These heavy rainfalls can be accompanied by cyclones, further leading to flooding, destruction of shelters, and a deterioration of soil quality due to heavy deposits [22,36].…”

Section: Methodsmentioning

confidence: 99%

Biting the Bullet: Dealing with the Annual Hunger Gap in the Alaotra, Madagascar

Stoudmann¹,

Reibelt

Kull

et al. 2019

Sustainability

View full text Add to dashboard Cite

The hunger gap (the annual period of hardship when most crops are growing but not yet ready for harvest) remains a reality for many smallholder farmers throughout the globe. With a population largely relying on agriculture, and high poverty and malnutrition rates continuously afflicting the country, farmers in Madagascar are particularly vulnerable to the impacts of the hunger gap, further putting pressure on already fragile ecosystems. Using a case study in the Alaotra region, we examine the seasonal trends of climate and agricultural resource dynamics, as well as characterize farmers’ experiences of and strategies used in response to the hunger gap, in order to assess how conservation may better consider the hunger gap to align its objectives with local needs. Results show that farmers are vulnerable to climatic events during a large part of the year, exacerbating the impacts of the hunger gap. The hunger gap appears to have varying degrees of impact on communities around Lake Alaotra, linked to factors such as road quality and agrarian structures—for example, land tenure and size of parcels—contributing to growing environmental degradation. We end by discussing various past and present responses aimed at improving the resilience of farmers of the Alaotra region, including improved accessibility, agricultural intensification, and conservation agriculture.

show abstract

‘Lake’ Alaotra, Madagascar: A late Quaternary wetland regulated by the tectonic regime

Cited by 17 publications

References 26 publications

A new late Pleistocene subfossil site (Tsaramody, Sambaina basin, central Madagascar) with implications for the chronology of habitat and megafaunal community change on Madagascar's Central Highlands

A new late Pleistocene subfossil site (Tsaramody, Sambaina basin, central Madagascar) with implications for the chronology of habitat and megafaunal community change on Madagascar's Central Highlands

Impact of model assumptions on demographic inferences: the case study of two sympatric mouse lemurs in northwestern Madagascar

Biting the Bullet: Dealing with the Annual Hunger Gap in the Alaotra, Madagascar

Contact Info

Product

Resources

About