This paper reports the alarming increase in wildfires in the Amazon rainforest during the severe 2023/2024 drought leading to an increase in large-scale forest degradation. It is highly relevant as the fire-driven forest degradation impacted also intact forests and released large amounts of carbon dioxide to the atmosphere pushing the Amazon rainforest closer to a potential tipping point.

Rapid changes to the climate of the boreal zone have resulted in large-scale 'greening' and range shifts. Feng and others explain these changes at a global scale and with unprecedented spatial and temporal resolution, demonstrating a change in boreal forest demography toward younger stands, an increase in areal extent of boreal forests, and a northward gain that outpaced losses on it southern fringe. These ongoing changes further emphasize the importance of boreal forests to earth system processes and the work in the present manuscript presents a path forward for detailed studies of large-scale land cover changes.

This publication provides a comprehensive review of the use of GDGTs (Glycerol Dialkyl Glycerol Tetraethers) for reconstructing past temperatures, with a particular focus on marine applications. It covers the full research workflow — from sample collection and processing to analytical methodologies, data interpretation, and data archiving. Importantly, the authors highlight best practices and propose recommendations to standardize approaches across the field. This review therefore serves as a valuable reference for both the paleoclimatology and organic geochemistry communities.

This paper reveals a previously unrecognized bias in the marine sediment record, challenging conventional interpretations of long-term carbon sequestration and weathering trends. While biases in the fossil and geological records are well-studied, this study demonstrates that deep-sea sedimentation data are also systematically skewed, necessitating a critical reevaluation of widely used paleoceanographic proxies. As a comprehensive meta-analysis of marine core data, these findings have far-reaching implications, highlighting the need to account for age-dependent biases in sedimentation-related proxies to refine our understanding of Earth's past climate and carbon cycle dynamics.

This study presents new insights into autotrophic carbon fixation in shallow-water hydrothermal systems, emphasizing the dominance of reductive tricarboxylic acid (rTCA) cycle-utilizing Campylobacteria. Low isotopic fractionation values in vent fluids, possibly due to very acidic pH levels, extend the isotopic fractionation range of rTCA. The study also highlights the ecological significance of chemosynthetically fixed carbon, observed in higher trophic levels like the vent endemic crab Xenograpsus testudinatus, improving our understanding of carbon cycling in extreme environments and the interplay between microbial chemosynthesis and higher organisms.

The manuscript by Pohle and Co-Workers describes an innovative approach for reconstructing patterns of geochemical data across evolutionary trees of life. The authors combine geochemical information with phylogenetic methods in a way that is new, provocative, and has the potential to open up a new sub-field concerning similar types of analyses on other groups of carbonate-producing organisms.

This paper discusses the carbon capture by poorly studied cold-water corals. These coral mounds represent a lesser known part of the carbon cycle and the outcomes of the study highlight the importance of these structures for natural carbon capture and storage at the sea floor.

Recent findings by Viljoen et al. (2024, Nature Climate Change) reveal contrasting phytoplankton trends above and below the mixed layer depth in the Sargasso Sea between 2011 and 2022, linked to ongoing ocean warming. Building on these observations, the current study by Zheng et al. seeks to replicate the detected patterns and unravel the drivers of these decadal changes. To this end, the authors develop a two-layer ecosystem model that conceptualizes stratified ocean systems as comprising two distinct ecological regimes: one within the surface mixed layer and another beneath it. Their results offer valuable insights into how phytoplankton communities may respond to future climate-driven stratification and highlight the critical need for improved monitoring efforts capable of capturing subsurface biological dynamics beyond the reach of satellite observations.

Based on the analysis of sedimentary ancient DNA, the authors show that Antarctic foraminiferal communities are diverse in open marine environments and significantly less diverse along slopes of submarine moraines. In both cases, DNA analysis reveals a high abundance of soft-walled monothalamids, which are not preserved in the fossil record. No foraminiferal DNA was found in tills, suggesting its destruction during glacial redeposition. A promising new foraminiferal mini-barcode marker is proposed, which merits further validation for application in future paleoecological investigations.

This study is the first to measure marine snow morphologies, sinking speeds, and midwater attenuation in export plumes using a BGC-Argo float equipped with optical and imaging sensors, offering new insights into the effects of morphology on particle sinking. The findings emphasize the need to move beyond size-based models by incorporating morphological properties to improve understanding of particle sinking and enhance flux estimates, with potential applications for monitoring natural and human-induced export events at high spatio-temporal resolution.

The study analyzed lake sediments from the southwest Maya lowlands to track past land use and population size. The authors found that over 3,300 years, land use was highly variable, with more fire and maize agriculture earlier (3500-2000 BP) with a denser population but less burning in a later period (1600-1000 BP). Surprisingly, their hydrogen isotope data showed no strong signature of drought locally, suggesting that climate in that area remained relatively stable. Therefore, the authors argue that collapse or population decline in the southwest Maya lowlands was likely driven more by social, political, or regional factors than by local drought.

Mercury emissions from artisanal and small-scale gold mining (ASGM) are one of the main sources of mercury (Hg) release into the environment, yet they are by far the least understood. This, together with the fact that ASGM emissions (besides their global implications) also directly/locally affect the poorest communities makes this a critical research topic. The authors demonstrate that bioaccumulation pathways in globally important crops are often overlooked, with implications for interventions, international collaborations, and emerging technologies.

The magnitude of the soil sink is a major uncertainty of the atmospheric molecular hydrogen (H2) budget. This manuscript provides critical data for understanding this process, though a yearlong set of H2 flux measurements at a deciduous woodland and a managed grassland in Scotland. Net fluxes are related to soil temperature, moisture and type, major factors that regulate the biological uptake of H2. While soil moisture is the dominant control on H2 fluxes in the grassland site, the variability of the larger magnitude fluxes at the woodland site illustrates that more work needs to be done to identify local controllers on H2 soil uptake.

This study combines an impressive dataset of tree ring radiocarbon measurements to quantify the balance between upwelling-related CO2 degassing from and CO2 uptake by the Southern Ocean, which is a crucial flux of of carbon between atmosphere and ocean and an important component of our climate system. These results benefit the broad climatology community both for its approach and for its important conclusions about the latitudinal variability in CO2 flux in the Southern Ocean.

Peltigera clouds? This fascinating manuscript demonstrates the potential of Peltigera lichens from across a range of ecosystems to generate potent biological ice nucleators. These Peltigera lichen ice nucleators can be more potent than the bacteria Pseudomonas syringae, which is often viewed as the most efficient biological ice nucleators. Given the widespread occurrence of Peltigera across the globe, these lichen may be important contributors to biological ice nucleation.

This study represents a pioneering step in the development of in situ monitoring, reporting, and verification (MRV) frameworks for ocean alkalinity enhancement (OAE), a leading marine carbon dioxide removal strategy. The authors conducted one of the first open-ocean rhodamine tracer release experiments explicitly designed to simulate alkalinity enhancement, demonstrating a scalable and practical approach for tracking the fate of alkalinity additions in dynamic marine environments. By moving beyond theoretical modeling and implementing real world testing, this work establishes a critical methodological foundation for future field trials and offers a replicable strategy for validating carbon removal through OAE.

In aquatic ecosystems, the production of nitrous oxide (N2O), an important greenhouse gas, was until recently mostly ascribed to the activity of nitrifiers and denitrifiers. Recent research has revealed that a range of other organisms are also capable of producing N2O, but quantifying their contribution has remained challenging. Plouviez et al. present a novel approach based on the stable nitrogen and oxygen isotope composition of N2O, combined with the intramolecular distribution of 15N ("site preference"). They found that various microalgae grown in darkness present distinct stable isotope patterns, which paves the way for improving our ability to distinguish the contribution of different microbial groups to N2O production in aquatic ecosystems.

This study presents a novel view on water vapour dynamics and the role it plays for atmospheric composition and transport mechanisms.