The “internally” generated intraseasonal variability of the Indian Summer Monsoon is characterized by intermittent periods of enhanced (“active”) and deficient (“break”) precipitation, which produce a quasi east‐west precipitation dipole over the Indian subcontinent. Here we present multicentennial‐length and near annually‐resolved reconstructions of monsoon precipitation, inferred from absolute‐dated and instrumentally calibrated speleothem oxygen isotope records from regions (central and northeast India) that have diametric responses to active‐break monsoon circulation patterns. On centennial timescales (AD 1400–2008), precipitation variability from these two regions exhibit opposing behavior, oscillating between periods with a persistently “active‐dominated” (AD ∼1700 to 2007) and a “break‐dominated” (AD 1400 to ∼1700) regime. The switch between these regimes occurs abruptly (within decades) at a time (AD ∼ 1650–1700) when a proxy record of upwelling intensity from the Arabian Sea suggest an abrupt increase in the monsoon winds. On the basis of these observations, we hypothesize that the frequency distribution of active‐break periods varies on centennial timescales, implying a leading role of internal dynamics in governing the ISM response to slowly‐evolving changes in the external boundary conditions.

Observations show that summer rainfall over large parts of South Asia has declined over the past five to six decades. It remains unclear, however, whether this trend is due to natural variability or increased anthropogenic aerosol loading over South Asia. Here we use stable oxygen isotopes in speleothems from northern India to reconstruct variations in Indian monsoon rainfall over the last two millennia. We find that within the long-term context of our record, the current drying trend is not outside the envelope of monsoon's oscillatory variability, albeit at the lower edge of this variance. Furthermore, the magnitude of multi-decadal oscillatory variability in monsoon rainfall inferred from our proxy record is comparable to model estimates of anthropogenic-forced trends of mean monsoon rainfall in the 21st century under various emission scenarios. Our results suggest that anthropogenicforced changes in monsoon rainfall will remain difficult to detect against a backdrop of large natural variability.

Madagascar and the Mascarene Islands of Mauritius and Rodrigues underwent catastrophic ecological and landscape transformations, which virtually eliminated their entire endemic vertebrate megafauna during the past millennium. These ecosystem changes have been alternately attributed to either human activities, climate change, or both, but parsing their relative importance, particularly in the case of Madagascar, has proven difficult. Here, we present a multimillennial (approximately the past 8000 years) reconstruction of the southwest Indian Ocean hydroclimate variability using speleothems from the island of Rodrigues, located ∼1600 km east of Madagascar. The record shows a recurring pattern of hydroclimate variability characterized by submillennial-scale drying trends, which were punctuated by decadal-to-multidecadal megadroughts, including during the late Holocene. Our data imply that the megafauna of the Mascarenes and Madagascar were resilient, enduring repeated past episodes of severe climate stress, but collapsed when a major increase in human activity occurred in the context of a prominent drying trend.

The evolutionary adaptations of the organisms which inhabit the unusual and fragile ecosystems within caves are of inherent interest to both biologists and laymen. Cave organisms generally develop a high degree of physiological and behavioural adaptation for survival in the subterranean environment. The Kotumsar Cave is biologically the best known cave in India and has attracted interest from researchers from all over the world. This paper assesses the ecological community and overall habitat of the cave. This is based on long-term field observations and the review of the extensive literature on Kotumsar. For each species, features indicative of evolutionary adaptation to the cave environment are noted and conclusions drawn regarding the status of the species as a cavernicole. Several species of this cave are yet to get a proper study for correct taxonomic position although they have apparent troglomorphic dispositions. Several species which are highly endemic to this cave are probably in verge of its extinction. A serious measure to conserve the whole biodiversity has been suggested.

Abstract. The “4.2 ka event” is frequently described as a major global climate anomaly between 4.2 and 3.9 ka, which defines the beginning of the current Meghalayan age in the Holocene epoch. The “event” has been disproportionately reported from proxy records from the Northern Hemisphere, but its climatic manifestation remains much less clear in the Southern Hemisphere. Here, we present highly resolved and chronologically well-constrained speleothem oxygen and carbon isotopes records between ∼6 and 3 ka from Rodrigues Island in the southwestern subtropical Indian Ocean, located ∼600 km east of Mauritius. Our records show that the 4.2 ka event did not manifest itself as a period of major climate change at Rodrigues Island in the context of our record's length. Instead, we find evidence for a multi-centennial drought that occurred near-continuously between 3.9 and 3.5 ka and temporally coincided with climate change throughout the Southern Hemisphere.