Global change is increasing river drying and transforming surrounding landscapes through human land use, with important consequences for freshwater biodiversity. Yet how river drying and land use jointly influence biodiversity across spatial scales remains poorly understood. Using macroinvertebrate data from 49 riverine metacommunities in southeastern France, we examined how river drying and land use affect biodiversity across spatial scales and the metacommunity properties underlying these patterns. We estimated species-area relationship (SAR), with intercept and slope of SAR curve representing patterns analogous to alpha- and beta-diversity, respectively, and fitted structural equation models to assess how flow intermittence, land use (% of non-natural surface), and network size affected the metacommunity properties underlying these patterns, including intraspecific aggregation, species abundance distribution, total abundance, and regional species pool. Flow intermittence increased intraspecific aggregation and reduced evenness, leading to a lower SAR intercept and a steeper slope, reflecting lower local diversity but greater compositional differentiation among non-perennial rivers, and revealing strong scale-dependent responses of biodiversity to drying. Trait analyses further showed that flow intermittence favored aerial passive dispersers while reducing the relative abundance of aquatic active dispersers, suggesting that altered dispersal dynamics in non-perennial river networks contribute to biodiversity organization. In addition, land use primarily influenced biodiversity through nonlinear effects on the metacommunity species pool, with intermediate levels of land use associated with the highest regional diversity. Moreover, land use weakened the positive effect of flow intermittence on aggregation, indicating that anthropogenic pressures can homogenize metacommunities in drying regimes. Our findings demonstrate that flow intermittence strongly influences biodiversity across spatial scales through different mechanisms rather than uniformly reducing it. As climate change is forecast to increase the proportion of non-perennial rivers worldwide, our results highlight the importance of incorporating metacommunity processes and multi-scale diversity patterns into the conservation and management of these ecosystems.
Drylands store most of the global soil inorganic carbon (SIC), yet the extent to which this pool interacts with contemporary carbon (C) cycling remains poorly understood. To test whether SIC behaves primarily as an inert geological reservoir or instead bears a modern carbon imprint, we quantified SIC content and radiocarbon (∆14C) at 42 dryland sites spanning broad aridity gradients across Eurasia. We also evaluated the climatic, edaphic, and biotic factors associated with variation in ∆14C-SIC. Across all sites, topsoil SIC (~0-10 cm) was strongly depleted in 14C but consistently enriched relative to 14C-dead carbonates, indicating that it contains a measurable component derived from modern carbon inputs. In the Chinese drylands, ∆14C-SIC declined with increasing aridity, consistent with weaker modern carbon exchange under drier conditions and a greater contribution of inherited or 14C-depleted carbonate carbon. Soil pH and ∆14C of soil organic carbon were the strongest predictors of ∆14C-SIC, suggesting that carbonate dissolution-reprecipitation and the age of carbon entering soil CO2 play key roles in determining SIC origins. At a subset of nine Chinese sites, ∆14C-SIC declined sharply with depth and approached 14C-dead values in subsoils, indicating little influence of modern carbon in deeper carbonate pools. The presence of mixed 14C-depleted and modern 14C signatures in SIC potentially complicates the use of SIC isotopic signatures as proxies of environmental conditions. Together, our results indicate that dryland topsoil SIC commonly carries a measurable modern carbon signature that is tightly linked to contemporary carbon cycling. This coupling weakens with increasing aridity and soil depth, suggesting that environmental change in drylands may reshape one of the planet's largest carbon pools not only through changes in SIC stocks, but also through shifts in carbonate radiocarbon signatures and sources.
Accounting for spatial structure within populations is critical for defining appropriate scales of management, particularly in the Arctic, where habitats of ice-dependent species such as the polar bear (Ursus maritimus) are being transformed at an accelerated rate. We examined broad-scale patterns of space use and finer-scale habitat selection by adult female polar bears in James Bay, located at the southernmost extent of the species' global range. Using satellite telemetry data collected during the annual on-ice period from 2012 to 2017, we estimated individual- and population-level utilization distributions (UDs) and applied hierarchical clustering to assess whether individuals formed distinct spatial groups based on the degree of UD overlap. We also fit step-selection functions (SSFs) to evaluate selection for sea-ice concentration, ocean depth, and distance to coast. Fifteen bears with data spanning at least one complete on-ice period had individual 95% UDs averaging 74,770 km2 (SE = 11,663). Results of hierarchical clustering identified two distinct spatial groups: three "resident" bears remained within southern James Bay, whereas 12 "non-resident" bears had larger UDs extending into Hudson Bay. Overlap between groups remained near zero throughout winter, including during the breeding season. Step-selection analyses, which included an additional four bears (ntotal = 19), indicated consistent positive selection for high sea-ice concentration, with individual variation in selection strength. For non-resident bears, selection for distance to coast and ocean depth varied seasonally, with bears selecting areas farther from the Ontario coast during freeze-up, closer to the coast during April-May, and deeper offshore areas during breakup. Together with previous genetic evidence, our results suggest resident southern James Bay bears represent a spatially structured component of the broader subpopulation that warrants continued monitoring and explicit consideration in future harvest-risk assessments and conservation planning, particularly as sea-ice loss continues to alter habitat availability.
Anthropogenic habitat transformation has led to population declines and increasing isolation of populations of many species, particularly top predators, where small and fragmented populations often experience limited dispersal and reduced genetic diversity. Jaguars (Panthera onca), for example, have lost half of their historical range and most populations outside the Amazon biome are small, isolated and highly threatened. Here, we assess jaguar population connectivity across the species' range by identifying and ranking core areas and dispersal corridors, including linkages among Protected Areas and Indigenous Lands (hereafter, PAs). We used cumulative resistant kernels and factorial Least-Cost Paths (fLCP) in two complementary approaches: core area-based and PA-based connectivity. We identified 307 core areas for jaguar movement, covering ~7.75 million km2 (55% of the current range), of which approximately half lies within PAs. The largest and highest-ranked core area spans ~6.5 million km2 across four biomes (Amazon, Llanos, Chaco and Pantanal). We identified 176 dispersal corridors connecting core areas, although connectivity was not continuous across the entire range. Northern populations (Mexico and Central America) showed several connectivity gaps, whereas South America displayed a large, highly interconnected network linking the Amazon, Llanos, Chaco, Pantanal, Cerrado, Caatinga, Iberá and the Atlantic Forest's Green Corridor. In contrast, coastal Atlantic Forest patches appeared largely isolated. The PA-based analysis predicted 507 potential corridors connecting 905 PAs, including potential links absent from the core area model, particularly across Central America and between the Darién Gap, Amazon and coastal Atlantic Forest. The core-area approach provides a more biologically realistic representation of current connectivity, while the PA-based approach complements it by identifying pragmatic opportunities for long-term connectivity conservation. Together, these approaches identify priority areas and regions of uncertainty, providing a spatial framework to guide jaguar conservation and connectivity planning under accelerating global change.
Tropical wetlands have historically been resilient to fire, but ongoing climate and hydrological changes are undermining this stability. Here, we provide robust multi-decadal evidence (1985-2024) of structural changes in the contemporary fire regime of the Pantanal, the world's largest wetland, associated with hydroclimatic disruption. We investigated changes in burned area, mean fire size, and fire seasonality using hydrological, climatic, and fuel-condition predictors. To identify the major drivers of fire dynamics, we applied trend analyses and Elastic Net models across multiple temporal and spatial scales. Although no significant monotonic trend was detected for annual burned area across the entire time series, change point analysis identified 2014 as the onset of a significant upward trend. Mean fire size exhibited a significant long-term upward trend across the full period, which intensified after 2018, suggesting larger fire sizes in recent years. Across models, reduced precipitation, shorter seasonal wetland flood pulses, and higher atmospheric and fuel dryness emerged as the strongest predictors of burned area and fire size. These changes have expanded the duration of the fire season, particularly in the northern and central Pantanal, by delaying the onset of rains and shortening the flood pulse period. Our findings suggest a weakening of the hydroclimatic coupling that has regulated ignition and fuel availability in the Pantanal. Broader environmental changes in the upper basin and regional climate may be reinforcing this transition. These results highlight the Pantanal's increasing vulnerability to drought-driven fires and underscore the urgent need for integrated water and fire management strategies to preserve the resilience of the Pantanal and other tropical wetlands under intensifying global change pressures.
Climate change is reshaping marine fish habitats. Yet the future habitats' redistribution of fishes that are both critically endangered (CR) and globally commercially exploited remains poorly understood. Here, we assessed current and future suitable habitats for 24 CR commercial coastal demersal fishes selected on the IUCN Red List. Using ensemble species distribution models (SDMs), we projected habitat suitability under SSP1-2.6 and SSP5-8.5 by the 2100 s, and combined the projections with exclusive economic zones (EEZs), marine protected areas (MPAs), and fishing pressure. Most species were projected to experience net habitat contraction by the 2100 s, with stronger losses under SSP5-8.5 and pronounced declines in tropical and subtropical coastal waters. Across 145 coastal EEZs, projected species richness showed marked spatial heterogeneity, with Asia retaining the highest mean richness and Europe showing a net increase. Low-income and lower-middle-income countries supported substantial current species richness but faced stronger relative declines under SSP5-8.5. Projected habitats of CR commercial fishes intersected MPAs in only 49% of coastal countries, indicating substantial protection gaps. Overall, this study quantitatively delineates climate-driven habitat redistribution patterns of CR commercial fishes, suggesting potential implications for optimizing MPAs networks and advancing transboundary conservation strategies to promote marine biodiversity and sustainable fisheries development.
Malaria remains a major public health challenge, causing an estimated 600,000 deaths and 250 million infections annually. Most malaria control efforts focus on freshwater mosquito vectors, leaving saltwater-tolerant vector mosquitoes inhabiting coastal ecosystems like mangrove forests understudied. Historically, the role of mangrove forests as breeding grounds for malaria vectors often motivated their destruction. However, mangroves provide crucial ecosystem services, and their impact on malaria transmission remains poorly understood. This study presents the first multi-country analysis linking African mangrove forests to prevalence of malaria (Plasmodium falciparum). We employed piecewise structural equation models to examine the relationships among mangrove land cover and mangrove vegetation greenness across coastal settlements in 27 African countries. We combined satellite-derived land cover, vegetation, and weather data with malaria prevalence records from 11 years, ranging from 1996 to 2020. We found two key associations. First, increasing mangrove land cover is associated with decreasing malaria prevalence at coarse spatial resolution, refuting the traditional view of mangroves as disease-promoting environments. We hypothesise that this relationship may reflect ecological factors such as reduced larval development due to shading, or the presence of predators. Second, at fine and coarse spatial resolutions, increasing mangrove health (i.e., greener vegetation) is associated with increasing malaria prevalence. This trend may be driven by higher mosquito abundance and biodiversity in vegetation-rich mangrove areas, consistent with studies showing vegetation as a positive predictor of mosquito population density. Our findings constitute continent-wide patterns derived from observational data, whereas the precise impact of mangrove vegetation likely depends on the geographic location, configuration of the forests, and the identity and competence of host and vector species. We conclude that mangrove conservation needs to be integrated with locally adapted, context-specific vector management strategies.
Microbial necromass carbon (MNC) is increasingly recognized as a major contributor to persistent soil organic carbon (SOC), yet its response to climate warming and the underlying regulatory mechanisms remain poorly understood. Here, we conducted a global meta-analysis to assess how total MNC, fungal necromass carbon (FNC), and bacterial necromass carbon (BNC) respond to warming and to identify the key drivers. Overall, warming had no significant net effect on total MNC, FNC, or BNC across all observations, although publication bias-corrected analyses revealed a significant 8.6% increase in FNC. However, warming effects varied substantially among ecosystems, increasing MNC accumulation in permafrost (+25.4%), grassland (+8.2%), and cropland (+9.9%) soils, while decreasing it in forests (-12.4%) and showing no significant effect in wetlands. Warming effects were further influenced by warming method, soil depth, climatic conditions, and initial soil properties. Meta-regression analyses showed that warming-induced changes in microbial biomass were the strongest predictor of MNC responses, highlighting the central role of microbial growth and turnover in regulating necromass dynamics. Moreover, shifts in nutrient availability, soil pH, and extracellular enzyme activities significantly influenced the balance between necromass production and decomposition. Positive coupling between MNC and SOC responses suggests that microbial necromass formation represents an important mechanism linking microbial processes to soil carbon persistence under warming. Overall, our findings demonstrate that warming affects MNC by altering microbial traits and nutrient availability, thereby regulating the balance between necromass production and decomposition. Ecosystem-specific conditions further determine the magnitude and direction of these responses. These findings highlight the need to incorporate microbial necromass dynamics into predictions of soil carbon-climate feedbacks under future warming scenarios.
Extreme climatic perturbations are becoming increasingly frequent, with substantial and long-lasting legacy effects on biodiversity and ecosystems that may be compounded by human pressures such as illegal hunting. It is therefore vital to develop a better understanding of how best to manage and enhance ecosystem recovery. Using 15 years of data (2005-2019) from subtropical China, we investigated how an extreme ice storm event (2008) degraded mammal communities and how recovery was enhanced by subsequent anti-poaching enforcement (2012). Prior to the storm, communities were temporally stable, with a diversity of conservation-priority species in primary forests, while less protected species dominated degraded forests. Overall, the storm caused a 35% loss in species richness and abundance, with a 50% decline in conservation-priority species, all of which were obligate herbivores. Community properties in degraded forests recovered much more slowly than those in primary forests. Mammal communities did not regain dynamic stability when they reached their pre-storm levels; instead, legal enforcement in 2012 caused a shift toward a greater proportion of conservation-priority species, especially in degraded habitats, indicating that long-term reductions in abundance and species richness among conservation-priority mammal species were exacerbated by illegal poaching after this extreme storm event. These findings highlight that adaptive restoration management following extreme climatic events is essential for directing recovery trajectories toward achieving conservation and biodiversity targets, particularly for conservation-priority species, and especially in areas most vulnerable to human disturbance.
Simulated manipulation experiments, such as nitrogen addition to mimic atmospheric nitrogen deposition, are widely used in global change research. However, experimental manipulations may differ from real-world environmental change in their intensity, duration, and co-occurrence, leaving long-term changes in soil microbial communities and soil health insufficiently understood. To address this gap, we resampled soils from 38 forest and grassland ecosystems across eastern China in 2009 and 2019 and assessed microbial taxonomic and functional diversity using shotgun metagenomics. Microbial diversity increased by 17% over the decade, accompanied by clear shifts in community composition. Among the environmental variables considered, nitrogen deposition (~19 kg nitrogen ha-1 year-1 across ecosystems) was the strongest predictor of changes in seven of 12 microbial community metrics. Larger nitrogen deposition was also associated with increased relative abundances of nitrogen-cycling genes and reduced spatial turnover in microbial community composition. These effects were consistent with a potential alleviation of nitrogen limitation and weakening of deterministic community assembly, although these mechanisms could not be directly established. In addition, increases in genes associated with carbon degradation and phosphorus cycling, together with declines in the relative abundances of pathogens, antibiotic resistance genes, and DNA viruses, coincided with the raise of the composite soil health index. Our findings demonstrate widespread decadal increases in soil microbial diversity and soil health across eastern China, with nitrogen deposition emerging as their strongest environmental factor. These results highlight that microbial responses to long-term ambient environmental change can differ markedly from responses inferred from short-term or high-intensity manipulation experiments.
Combined increases in atmospheric CO2 and warming temperatures impact photosynthesis in complex yet mechanistically predictable ways. Seminal work in this area showed that temperatures above a thermal optimum reduce photosynthesis primarily by increasing photorespiration, but that elevated CO2 and higher temperature can act synergistically to raise the thermal optimum of photosynthesis and increase absolute photosynthetic rates. The modeling work that led to this prediction outlined both the synergistic effects of CO2 and temperature and hypothesized scenarios that could deviate from theory. Here, the assumptions underlying models of CO2 × temperature interactions in photosynthesis are reviewed, with emphasis on advances in in vivo enzyme kinetics, diffusive limitations, photosynthetic acclimation, and atmospheric feedbacks. Advances in Rubisco biochemistry, mesophyll conductance, field experiments, and canopy-scale modeling show why photosynthetic responses under future climates often deviate from the theoretical CO2 × temperature response. Scaling from leaf-level physiology to canopy carbon uptake is addressed to identify priorities for next-generation experiments and models. Together, this review highlights the work of the late Prof. Stephen P. Long, beginning with his pioneering manuscript that first addressed the synergistic effects of CO2 and temperature on photosynthesis.
Soil microbial communities underpin ecosystem functions critical for sustainable agriculture, yet our understanding of how long-term management of tropical agroecosystems shapes these communities remains limited. This is particularly the case in sub-Saharan Africa where soil health challenges are most acute for food security. Using four long-term (~20 years) experiments across contrasting agroecological zones in Kenya, we studied how organic inputs (farmyard manure, Tithonia diversifolia, Zea mays stover; applied at 4 Mg C ha-1 year-1) and nitrogen fertilizer (±120 kg N ha-1 per season as calcium ammonium nitrate) affect soil microbial communities. We combined amplicon sequencing of prokaryotic (16S rRNA) and fungal (ITS2) communities with quantification of nitrogen-cycling functional genes to examine microbial diversity, community composition, and functional potential. Site-level edaphic properties were the main correlate of community variation, namely 30% and 28% of prokaryotic and fungal β-diversity, respectively. Despite this strong environmental control, farmyard manure created distinguishable community patterns across all sites, significantly affecting 65 prokaryotic genera and achieving 96% reclassification success for fungal communities. Prokaryotic and fungal communities exhibited contrasting response patterns: prokaryotes responded predominantly to farmyard manure through enrichment of copiotrophic Bacillota (formerly Firmicutes), while fungi were sensitive to both farmyard manure and T. diversifolia green manure, recruiting distinct decomposer guilds based on substrate biochemistry. Functional gene responses were amplified at the driest, most nutrient-poor site, where farmyard manure led to a 30-fold increase in the abundance of ammonia-oxidizing bacteria compared to the control treatment. Mineral nitrogen fertilization alone did not produce distinct community composition but modestly reduced specific nitrogen-cycling genes. This demonstrates that organic resource management, not mineral inputs, drives long-term microbial community development. These findings provide decadal-scale evidence that sustained organic amendments can generate predictable microbial responses across environmentally heterogeneous tropical landscapes, informing integrated soil fertility management strategies for sub-Saharan Africa.
The equatorial western-central Pacific (WCP), characterized by low marine heatwave (MHW) occurrence and weak MHW intensity, is generally considered a refuge from MHWs. However, by integrating satellite observations with in situ measurements from BGC-Argo floats and TAO/TRITON buoys, this study reveals that the WCP exhibits the strongest phytoplankton response to MHWs in the global ocean, with near-surface chlorophyll concentration (CHL) declining by up to 50% per unit MHW intensity. This extreme response primarily arises from a concurrent reduction in both horizontal and vertical nutrient supply during MHWs. Eastward current anomaly inhibits zonal advection of nutrient-rich water from the east, while enhanced salinity stratification and shoaled mixed layer hamper vertical nutrient supply. Contrary to the near-surface, subsurface phytoplankton increase substantially during MHWs, mainly resulting from the improvement in nutrient and light conditions at depths below the shoaled mixed layer and near the base of the deepened euphotic layer. As the WCP hosts the world's most productive tuna fisheries and intense subsurface MHWs, our findings reveal a previously unrecognized ecological vulnerability with important implications for fishery management and carbon cycle in this vital marine system.
Warming and elevated CO2 (eCO2) are two potentially opposing climate-carbon (C) feedback mechanisms that modulate the magnitude of the land C sink, with warming decreasing and eCO2 increasing C sequestration. However, their net effect on soil organic C (SOC)-the largest terrestrial C stock-remains uncertain. Here, we quantify how warming, eCO2, and their interactions influence SOC by using 5558 paired observations from 1392 global studies across ecosystem types. Our study shows that warming reduces SOC by 8.0%, primarily by suppressing aboveground C inputs (-1.0%) and decreasing microbial C use efficiency (-9.9%). Concurrent warming and eCO2 increase SOC by 7.6%-a synergistic effect larger than eCO2 alone (+4.8%), primarily contributed by croplands. This outcome may result from increases in plant C inputs and soil nitrogen availability under eCO2, which facilitate microbial C assimilation and necromass formation (+3.9%). These processes promote the accumulation of mineral-associated C (+9.9%) and offset the negative effects of warming. The combined effect of warming and eCO2 is projected to increase SOC by 27.4 Pg C by 2100. Our findings highlight that synergistic interaction between warming and eCO2 increases SOC sequestration and enhances SOC stability under future climate change.
Ocean warming and acidification pose significant threats to marine biodiversity and human nutrition by fundamentally altering the biochemical composition of marine organisms. A primary concern is the potential decline in omega-3 fatty acids (FAs) that are essential to human health and primarily obtained through seafood consumption. The influence of these climate stressors on FA content across marine food webs remains poorly understood. To address this critical knowledge gap, we conducted a global meta-analysis of 489 experiments across 143 publications and 132 marine species, quantifying the effects of warming and acidification on nutritionally important FAs in marine primary producers, invertebrates and fishes. Under warmer conditions, we detected reductions of up to 34% and 50% in omega-3 FA proportions and concentrations, respectively, and up to 53% in omega-3: omega-6 ratios, together with increases of up to 22% and 17% in saturated FA proportions and concentrations, respectively across taxa groups. Critically, these effects were intensified as warming increased. The most severe reductions in omega-3 FAs were observed in primary producers, suggesting that climate-driven changes at the base of the food web could impair trophic transfer of these micronutrients, limiting nutrient availability for higher trophic levels and ultimately humans. Ocean acidification, conversely, demonstrated a minor overall effect on FA levels, although this result was based on substantially fewer studies. Furthermore, we identified species from environments with broader temperature ranges, diatoms, herbivorous invertebrates and low-resilience fish to display larger reductions in omega-3 FA proportions under warming. Our meta-analysis further highlighted the need for long-term studies under ecologically realistic conditions to improve predictions of nutritional responses to climate change. These findings are essential for understanding how the nutritional value of species change under climate change, and can inform fisheries management, aquaculture and public health policy aimed at securing the future availability of these vital micronutrients.
Microplastics (MPs) and their associated chemical additives are pervasive contaminants whose ecological impacts extend beyond organismal toxicity to fundamentally alter ecosystem processes. We synthesize current understanding of how MPs affect three interconnected dimensions of ecosystem integrity: ecosystem structure, ecosystem function, and ecosystem signaling. Across terrestrial, freshwater, and marine ecosystems, MPs alter biodiversity, community composition, trophic interactions, and habitat complexity, driving cascading changes in food-web architecture. They also impair key ecosystem functions, including primary production, decomposition, nutrient and carbon cycling, bioturbation, filtration, and energy transfer, with consequences for ecosystem productivity and resilience. We further identify ecosystem signaling as an emerging but underappreciated dimension of plastic pollution. MPs and their additives disrupt chemical, microbial, and sensory communication by altering semiochemicals, pheromones, quorum sensing, predator-prey recognition, host-microbiome interactions, and plant-soil feedbacks, thereby modifying behaviors and ecological processes that regulate ecosystem dynamics. Climate change further amplifies these effects through warming, altered hydrology, hypoxia, ocean acidification, ultraviolet radiation, and extreme weather events, which increase plastic fragmentation, additive release, bioavailability, and organismal susceptibility. We propose an integrated conceptual framework linking structural, functional, and signaling pathways to explain how MPs reshape ecosystem resilience under global change. Recognizing ecosystem signaling alongside ecosystem structure and function provides a more comprehensive framework for predicting ecosystem responses and identifying priorities for future research, conservation, and environmental management.
The Arctic cryosphere is undergoing dramatic changes, including declines in sea ice extent and thickness, ice sheets and glaciers, snow cover and duration and permafrost depth. These changes are having alarming direct and indirect consequences for terrestrial species, habitats and ecosystems. Such impacts are well documented and discussed for plants, birds and mammals, and we are beginning to understand the extent of links between cryospheric changes and terrestrial systems generally. However, terrestrial arthropods are rarely included in studies and reviews on this topic despite their taxonomic diversity and importance to ecosystem functions. In this mini-review, we aim to redress this imbalance and raise awareness of the impact of ice and snow decline on terrestrial arthropods and the ecological functions they perform. In addition, we highlight the recent methodological advances for arthropod monitoring and discuss their use in addressing gaps in our understanding of responses to multiple stressors.
Tropical forest restoration is an important nature-based solution that can sequester carbon as a means to mitigate climate change. Restoration approaches range from natural regeneration to intensive tree planting, but few studies have compared aboveground biomass (AGB) stocks over decadal time scales across multiple restoration treatments implemented at the same sites. Here we leverage data from a two-decade restoration experiment in southern Costa Rica; in 2004-2006, we established restoration plots representing a gradient of intervention intensity: natural regeneration (no planting), applied nucleation (planting tree clusters), and plantation (full planting). We compare 18-20 years of AGB across treatments of the four planted tree species and naturally recruited trees. We also examine the relationships between AGB pools and structural metrics derived from UAV-borne LiDAR data collected after 16-18 years. Because most AGB was in planted trees, AGB was about 6.5 times greater in plantations compared to natural regeneration, and double in plantations compared to applied nucleation after two decades, despite substantial mortality of planted trees. However, the plantation treatment suppressed naturally recruited AGB and accumulated only half the amount of the natural regeneration treatment. Natural recruits comprised four times the proportion of AGB in applied nucleation compared to plantation. LiDAR-quantified LAI was more tightly correlated with total AGB in natural regeneration plots, whereas canopy height was more strongly correlated with planted biomass in plantation and applied nucleation. Our results highlight that tree planting accelerates AGB accumulation at degraded sites and illustrate that practitioners should select species with complementary life history strategies that enable carbon to be sequestered beyond the first decade. Given the tradeoff between planted tree biomass and naturally recruited biomass, spatially patterned methods that plant fewer trees may better balance restoration goals beyond carbon accumulation, leading to more structurally and biologically diverse reforested systems.
Mangroves are characterized by high carbon sequestration rates, and future changes in mangrove biomass will be impacted by factors such as climate change, sea level rise, and management strategies. Here, we produce a map of present-day global mangrove aboveground biomass (AGB) based on extensive field observations and satellite data, giving a global mangrove AGB of 1.76 Pg dry matter (DM). After accounting for potential growth to maturity, future changes in climatic and hydrological conditions, possible restoration strategies, and sea-level rise, the global total mangrove AGB is projected to increase by 16.7% under the low-warming scenario (Shared Socioeconomic Pathway 1 and Representative Concentration Pathway 2.6, SSP126) and decrease by 19.3% under the high-warming scenario (SSP585) by 2100. Sea-level rise encroaching upon the growth space of mangroves will cause a biomass loss of 41.6% in the high-warming scenario, whereas restoration strategies would only increase AGB by 2.0%. Our study shows that sea-level rise limits the potential of mangrove restoration to maintain carbon stocks, and regions less constrained by sea-level rise offer greater potential for the long-term permanence.
CH4 emissions from mangrove, saltmarsh, and seagrass ecosystems partially offset carbon sequestration, potentially diminishing the climate mitigation capacity of these blue carbon habitats. However, a mechanistic understanding of the processes governing CH4 production potential across large spatial scales remains limited. By integrating incubation-based measurements from 116 sites, we reveal significant ecosystem-specific differences in CH4 production potential, with saltmarshes emerging as CH4 production hotspot relative to mangroves and seagrass meadows. Using an integrated analytical approach encompassing more than 30 environmental, biogeochemical, and microbial parameters, we demonstrate that CH4 production potential converges on sediment organic carbon availability, particularly plant-derived carbon, as a key regulatory axis. Additionally, metagenome-assembled genomes (MAGs) recovered from saltmarshes show a functional bias toward lignin degradation, thereby fueling downstream CH4 production via methylotrophic pathways. Lignin-addition and stable carbon isotope experiments further provide supportive evidence that lignin decomposition enhances Chinese saltmarsh CH4 production potential, revealing a pathway that may reduce net blue carbon benefit. Together, these findings underscore that saltmarsh plant-derived lignin is less stable than conventionally assumed, as microbial processing redirects stored carbon toward CH4 production, challenging current blue carbon accounting frameworks at a continental scale within China.
