French Institute of Pondicherry

<strong class="journal-contentHeaderColor">Abstract.</strong> The tropical dry evergreen forest (TDEF) is a vital but endangered ecosystem in India, crucial for supporting cultural services, biodiversity, and organic carbon storage. The oxalate-carbonate pathway (OCP) is an understudied process in which plants and oxalotrophic microorganisms convert atmospheric CO₂ into calcium carbonate (CaCO₃) within plant tissues or tree-adjacent soils. Yet, despite its significance, the OCP has not been studied in the TDEF of India. This study aimed to assess novel OCP systems associated with three TDEF diagnostic species (<em>Diospyros ebenum, Lepisanthes tetraphylla</em>, <em>Sapindus emarginatus</em>) and one local agroforestry species (<em>Artocarpus heterophyllus</em>) in the restored- and primary-TDEF of Tamil Nadu. Surface soil samples (0&ndash;10 cm) were collected from an adjacent and control distance away from trees, along with tree biomass samples, and investigated for oxalate production (microscopy and enzymatic assays), oxalotrophic microbial communities (<em>frc</em> gene sequencing), and tree-induced shifts in soil biogeochemistry. Oxalate was detected in all species (4.4&plusmn;3.2 % dry weight), accompanied by CaCO₃precipitation on biomass. Oxalotrophic microbial communities were dominated by Actinomycetota (86 %), which were also identified in electron micrographs. Soil biogeochemical shifts indicative of active OCPs were also observed, particularly in the hollowed-out trunks of the TDEF trees. However, differences between adjacent and control soils were less pronounced, suggesting that monsoon conditions leached OCP precipitated CaCO₃ from the adjacent soils. This research provides the first evidence of active OCPs in Indian TDEF, highlighting a previously unrecognized mechanism for organic and inorganic carbon cycling in this threatened ecosystem.

The time interval between 4 Ma and 0.8 Ma is pivotal for the evolutionary history of hominids in eastern Africa, and particularly in the Turkana Depression (East African Rift System, Kenya / Ethiopia). It coincides with a number of major evolutionary events, including the evolution and disappearance of the genus Australopithecus, the appearance of the genus Homo, the first expansions to Eurasia, and many technological innovations, especially the Lomekwian, Oldowayan and Acheulean lithic industries. This period is also marked by pronounced environmental changes, relatively well constrained at the global scale using marine records, but still poorly documented on the continents. Indeed, little information exists on their impact on landscapes, whose configuration, dynamics, spatial expansion are inevitably intertwined with other factors at play at the regional and local scale.In this contribution, we aim at reconstructing the evolution of sedimentary environments and landscapes in the Lower Omo Valley (Ethiopia) for the past four million years to provide a better understanding of the physical environments in which local biological and cultural evolutions took place. To do so, we investigated the evolution of sedimentary systems and landscape dynamics in the Lower Omo Valley combining a Landscape Evolution Model (Landlab) to constrain the input sediment flux with a stratigraphic forward model (DionisosFlow, Beicip-Franlab). To assess the consistency of model reconstructions, we compare model outputs to sedimentary architectures, volumes of eroded and deposited sediments and facies distribution derived from field observations and seismic data. Subsequently, we will present and discuss the roles of the different forcings, such as changes in precipitation and tectonic uplift, that drove the evolution of the sedimentary system.

While it is accepted that the tropical hydrological cycle has intensified during past interglacial periods due to changes in insolation, greenhouse gases, and ice volume, variations in the intensity and spatial distribution of rainfall in the South Asian monsoon domain, as well as the respective influence of these forcings during past warm periods, remain uncertain. Here, we present a pollen record from the Bay of Bengal (IODP Site U1446, located off the Mahanadi river exit, outside the influence of the Bengal fan) that allows reconstruction of vegetation changes in the core monsoon zone of India during two warm periods, the current and last interglacial periods. We compare the data with numerical model simulations (HadCM3 and LOVECLIM1.3) to assess the influence of different forcing mechanisms on the response of summer monsoon rainfall during past interglacials characterized by different levels of warming (Cl&amp;#233;ment et al., 2024). We also present a pollen record from cores (SO93) taken at 16&amp;#176;N from the Ganges-Brahmaputra-Meghna (G-B-M) river-fed Bengal fan, covering the current interglacial period.Results from IODP Site U1446 show tropical forest expansion between 11.7-5 ka and 127-120 ka, defining two Indian humid periods, with the last interglacial showing the strongest monsoon activity, consistent with salinity reconstructions. During the last five millennia of both interglacial periods, moist tropical forest largely declined in favor of savanna marking a significant decrease in summer monsoon rainfall. Although the pollen assemblages from sites SO93 and U1446 show substantial differences in Holocene vegetation cover between the basins, the maximum expansion of the evergreen component of the tropical forest is recorded contemporaneously in both sequences. This suggests a similar Holocene evolution of the summer monsoon from central to northern India. The model-data comparison highlights boreal summer insolation as the primary driver of vegetation dynamics and monsoon intensity during interglacial periods, with CO2 and ice-sheets having a limited effect. These results also show that vegetation remains unaffected by pre-industrial CO2 variations above 250 ppmv, a threshold value that characterizes most interglacials of the last million years.Cl&amp;#233;ment, C., Martinez, P., Yin, Q., Clemens, S., Thirumalai, K., Prasad, S., Anupama, K., Su, Q., Lyu, A., Gr&amp;#233;mare, A., Desprat, S., 2024. Greening of India and revival of the South Asian summer monsoon in a warmer world. Commun. Earth Environ. 5, 685.

<strong class="journal-contentHeaderColor">Abstract.</strong> Marine Isotope Stage (MIS) 11 has long been considered a unique Quaternary interglacial due to its orbital similarities with the Holocene, persistence of high atmospheric CO₂ concentrations and extended duration triggering unusual polar ice-sheet loss. Despite its importance, Indian summer monsoon (ISM) variability within the core monsoon zone (CMZ), as well as its impacts on vulnerable tropical forests, remain unexplored. Here, we document, for the first time, MIS 11 ISM-driven vegetation changes and their underlying forcings by combining pollen analysis from IODP Site U1446, strategically retrieved from the Bay of Bengal to represent the CMZ, with model simulations. Our results reveal the distinct roles of insolation, CO₂, ice volume, and millennial-scale variability in driving coupled ISM-vegetation changes, depending on the changing boundary conditions through MIS 11. Orbital- and millennial-scale tropical forest changes mirror southern European vegetation and atmospheric methane variability, ultimately reflecting shifts in the Intertropical Convergence Zone (ITCZ) that impact the tropical regions, a primary source of CH₄ emissions. Our proxy and model reconstructions show that ISM-vegetation changes during MIS 11c closely followed boreal summer insolation, revealing its dominant role under warm background conditions with high CO₂ and reduced ice volume. Conversely, during MIS 11b-a, ISM-vegetation decreased while insolation remained high, indicating that its influence was overshadowed by expanding ice sheets, lower CO₂, and the interaction of orbital and millennial-scale variations. Millennial-scale climate variability during the younger MIS 11b-a substages is expressed by prominent forest contractions tied to southward ITCZ shifts, Atlantic meridional overturning circulation (AMOC) reductions and high-latitude ice sheet dynamics, which were rapidly followed by abrupt forest expansions associated with northward ITCZ shifts, AMOC strengthening and CH₄ overshoots. Conspicuously, the first and most severe forest setback interrupted MIS 11 full interglacial conditions, suggesting that extreme ISM weakening could also occur under similarly warm future conditions. Our findings provide new insights into ISM behavior during MIS 11, highlighting its high sensitivity to climate changes in the context of projected ISM intensification and its effect on the extent and composition of the tropical forest, which is key component of both global carbon and methane cycles.

In this paper, I reflect on what presence is all about, leaning on personal experiences and my fieldwork in Bhubaneswar, capital of the Indian State of Odisha, from September 2021 onwards.The particular context of the COVID-19 pandemic has multiplied our encounters with disembodied modalities of presence.This poses the question of what differences it makes to engage with somebody's presence virtually or physically.While the fieldwork I undertook during this period was marked by the constraints to which both I and my research participants were subjected, forcing me to adapt my fieldwork, modifying the ways in which physical contact could be established, it also raised into prominence the differences that arose from an appraisal of virtual or physical presences of dance practitioners.I analyse these differences utilizing the particular example of my assessment of Odissi dance activity in the early 2020s in Bhubaneswar, based on both virtual sources and physical encounters with the material world.As I assess the perception of these presences, I show the relational nature of this phenomenon within a network of both human and non-human, living and non-living beings, as well as the different ways it engages the (human) perceiver in emotional and sensory manners.

&lt;p&gt;Flowing parallel to the sea, sand is subject to erosive, accretive, and extractive processes and is intertwined with the socio-ecological dynamics at the land–sea interface. Human interventions, climate change, and societal responses to it are constantly reshaping the morphology of coastal areas and thus disrupting sand flows, for example, through the construction of harbours or groins to prevent erosion. In this article, we ask how disrupted sand flows shape the interaction and social dynamics between different coastal actors in the making of coastal protection. Empirically, we ground our research in the Pondicherry region of southern India, characterised by a sandy morphology and numerous fishing communities. Building on the literature on “geosocialities,” we argue that engaging with the materialities of ocean sand and the social implications of sediment loss for artisanal fishers is crucial to reducing maladaptation. Following sand as a non-human actor unravels the social entanglements with ocean sand that underpin the implementation of protective measures and that shape access to sandy beaches for artisanal fishers. By exploring these contestations, we show how the reclamation of sand through groins is embedded in unequal power relations over shrinking beaches. While migration to other sandy beaches becomes a necessary means of adaptation, this leads to local conflicts over coastal space. We conclude by highlighting the need to understand coastal adaptation as a geophysical and socially intertwined process, in which ocean sand must be critically considered for future adaptation strategies.&lt;/p&gt;