Global Change Biology最新文献

Mass coral bleaching has become a hallmark ecological signature of anthropogenic climate change, yet the structural mechanisms governing its spatial and temporal evolution remain poorly resolved. Traditional assessments emphasize surface thermal anomalies and strong El Niño phases but increasingly fail to explain the persistence of bleaching, its regional asymmetry, and the instability of ecological thresholds. Here, using long-term datasets (1993–2020) of ocean temperature, bleaching alerts, El Niño–Southern Oscillation (ENSO) indices, coral–algal cover, and subsurface thermal profiles, we identify a regime shift from episodic bleaching toward chronic thermal exposure. This shift reflects a reduced dependence of bleaching on ENSO intensity, as even moderate ENSO phases, including both El Niño and La Niña events, are now associated with widespread bleaching, suggesting progressive erosion of thermal thresholds under sustained ocean warming. We further propose a “Structure–Pathway–Response” framework to capture the structural reconfiguration of bleaching risk: (i) heat convergence along eastern continental margins (e.g., East Asian Seas, Caribbean); (ii) poleward transport and topographic retention of subsurface heat along continental slopes; and (iii) vertical accumulation through isotherm deepening that elevates bleaching risk. We identify two dominant heat-retention regimes: a current-deflection mode in the Northern Hemisphere and a thermal-stacking mode in the Southern Hemisphere. These patterns increase regional vulnerability by broadening the spatial extent and persistence of thermal anomalies, reflecting processes not fully captured by surface Sea Surface Temperature (SST) variability. Our findings highlight the limitations of surface-only monitoring systems and underscore the need for thermodynamically informed, region-specific early-warning frameworks. Protecting structural thermal refugia and managing heat pathways will be critical for sustaining coral reef resilience in a rapidly warming ocean.

Large soil organic carbon (SOC) stocks in alpine tundra play a critical role in the global carbon budget but are increasingly vulnerable to loss under climate warming. These losses are partly driven by vegetation shifts, such as the upward migration of herbaceous plants, which alter soil food web structure and influence SOC sequestration. Although interactive effects between these processes are expected, they remain largely unclear or hidden. Here, we conducted a ¹³C-labeled glucose tracing experiment in the alpine tundra of Changbai Mountain to investigate how upward migration of Deyeuxia angustifolia affects soil food web structure, energy flows, and ultimately SOC sequestration. Compared with soils without migration (NM), heavily herb-migrated (HM) soils showed intensified carbon fluxes within trophic cascade, increasing carbon transfer to higher trophic levels, including fungivores, omnivores-predators, plant-parasites, meso- and macrofauna. Predators in HM soils progressively increased ¹³C assimilation over the 30-day period, while microbivores showed a 5-day lag behind microbial ¹³C uptake. This predator-driven energy dissipation was 2–14 times greater in HM than in NM soils and constituted an inefficient carbon sequestration pathway that limited the formation of stable carbon pools. As a result, SOC turnover in HM soils was more than 50% lower than in NM soils, indicating a shift toward less stable organic matter forms and reduced net carbon accumulation. Overall, our findings demonstrate that soil food webs play a pivotal role in both “belowground shaping” and “aboveground feedback” processes during herbaceous plant migration and that strengthened trophic cascade effects redirect carbon flow toward inefficient pathways, thereby constraining SOC sequestration in alpine tundra ecosystems.

Arctic permafrost soils are increasingly subject to thermokarst that is, abrupt ground subsidence caused by thaw. Wetlands can form within these depressions, leading to changes in organic matter decomposition and gas fluxes (CO₂, CH₄, N₂O, NH₃). Thermokarst wetlands tend to be dominated by graminoids, while surrounding upland tussock tundra tends to be dominated by mixed communities of shrubs and graminoids. To investigate how thermokarst alters the land-atmosphere exchange of C and N gases in Arctic tundra, we analyzed soil, porewater, above- and belowground biomass, and measured gas fluxes across dominant plant functional types (PFTs) within a lowland thermokarst wetland and adjacent upland tussock tundra. Both locations were overall sinks of CO₂, sources of CH₄, and sources of both N₂O and NH₃. We found that thermokarst wetlands emitted enough CH₄ to generate a positive radiative forcing in CO₂ equivalents (+1.2 μmol m⁻² s⁻¹ CO₂-eq), counteracting the high CO₂ uptake. In contrast, the upland tussock tundra had a net negative radiative forcing (−1.2 μmol m⁻² s⁻¹ CO₂-eq). Differences in gas flux and soil chemistry between upland and lowland are primarily driven by flooded conditions present in thermokarst wetland. Additionally, root biomass from graminoids across both lowlands and uplands significantly correlated with CH₄ fluxes, supporting previous observations of plant-mediated transport of CH₄. Graminoid cover was correlated with increases in low molecular weight dissolved organic carbon, possibly associated with root exudates that fuel methanogenesis. Forb cover in the upland tussock tundra was significantly correlated with nine soil chemical variables, indicating that forbs may influence local soil chemistry or conversely, that soil chemistry controls where forbs grow. Overall, our findings indicate the variability in gas fluxes in the upland tussock tundra is partially controlled by PFT cover, while thermokarst wetlands emit enough CH₄ to counteract CO₂ uptake, with implications for carbon budget changes in Arctic systems.

Mangrove forests are recognized as plastic sequestration hotspots, particularly in urbanized areas, which may contain up to two orders of magnitude more plastic litter. Fiddler crab populations, known as ecosystem engineers, are thriving precisely in these expanding plastic-pollution hotspots, prompting inquiry into how these creatures navigate the substantial plastic loads within sediments they have evolved to inhabit and feed upon. To investigate this, we released two types of unaged, fluorescently labeled polyethylene microspheres (hereafter, “microspheres”)—green (20–27 μm diameter) and red (75–90 μm diameter)—into polluted urban mangroves inhabited by the fiddler crab Minuca vocator. The microsphere sizes were chosen to mimic the natural range of food particle sizes encountered by these crabs. This field experiment tracked the uptake and fate of microspheres in the crabs' hepatopancreas, gills, hindgut, and the sediments over 66 days. Microspheres were incorporated by most crabs (91 out of 95), with uptake markedly higher in the hindgut (26.04 ± 1.19 SE microspheres g⁻¹) and hepatopancreas (10.07 ± 1.19) than in the gills (0.86 ± 0.20). The average uptake of microplastics, 48.67 (±7.24 SE) per crab was more than 16 times higher than the density in the sediment (2.92 microspheres g⁻¹), and represents one of the highest uptakes ever recorded in nature. Approximately 15% of this load, primarily located in the hepatopancreas, was found in a fragmented state, suggesting degradation through digestive processes. Microspheres fragmented by digestive processes were detectable in mangrove sediments within just 14 days, challenging the notion that plastic degradation is a long-term process driven mainly by abiotic aging over decades. Combined with the widespread presence of fiddler crabs along coastlines acting as plastic sinks, these findings suggest that biotic fragmentation is an important pathway for the degradation of plastics entering the ocean.

Climate change poses a severe threat to desert ecosystems; however, understanding how specialized desert species respond to changing climate remains limited. These species are confronting extreme changes, including intensified droughts, altered precipitation, and temperature patterns. Here, we integrate population and ecogenomic approaches to examine population genetic structure, demographic history, and climate adaptation in two distantly related, sympatric rodent species in arid and semi-arid regions in East Asia. We further combine genomic offset analysis, ecological niche modeling, and landscape connectivity assessments to evaluate their climate change risks. Our results reveal that the two species have diverged into five geographically distinct lineages, each associated with a different arid region. Lineage divergence times are estimated between 20 and 400 thousand years ago, with population size declines occurring around the Last Glacial Maximum. While the two species exhibited distinct climate adaptation, evidenced by different key climatic variables and associated genes identified for each species, they exhibited congruent vulnerability to future climate change. This was indicated by parallel patterns of genomic offset and niche suitability loss. Under future climate change scenarios, eastern lineages in high precipitation seasonality areas (e.g., DB lineages in Horqin Sandy Land) face a higher risk due to substantial genomic offset, habitat loss, and reduced connectivity. In contrast, lineages on the west ranges with low precipitation seasonality (e.g., QH lineages in the Qaidam Basin and HL lineage in the Changtang Plateau) appear less vulnerable, characterized by lower genomic offset and the expansion of desert habitats. Overall, this study provides a comprehensive framework for identifying vulnerable populations and predicting responses to climate changes in desert species, offering critical insights for the conservation of desert ecosystems.

While China harbors rich biodiversity, it is facing concurrent challenges from rapid socio-economic growth and severe biodiversity loss. Additionally, critical gaps in knowledge about the country's biodiversity trends have persisted for a long time because of a lack of a national-scale biodiversity monitoring program. Using a decade (2011–2020) of avian monitoring data from 142 sites and 864 species under the China Biodiversity Observation Network, we evaluated temporal trends in alpha and beta diversity, examining both the taxonomic and functional facets of biodiversity, and assessed their drivers. We found that species richness remained stable over 10 years, with no directional trend at 84.5% of sites and a small mean effect size (Zr = 0.102, 95% CI = [−0.012; 0.216]). In contrast, functional richness increased significantly (Zr = 0.122, 95% CI = [0.016; 0.227]). Taxonomic multiple-site beta diversity decreased over time (p < 0.01), indicating a trend towards biotic homogenization. Bird communities in regions with pronounced precipitation seasonality and lower elevation exhibited larger increases in species and functional richness, whereas those at higher elevations and topographic heterogeneity showed greater biotic turnover through time. Our results reveal asynchronous changes in taxonomic and functional diversity, and decoupled trends in alpha and beta diversity, implying that stable species richness at the local scale may mask broader-scale trends in functional diversity and biotic homogenization. Therefore, it is crucial for long-term monitoring to track multi-dimensional biodiversity trends to better develop targeted conservation practices in the Anthropocene.