Global Change Biology最新文献

Unvegetated tidal flats, despite accounting for approximately 24.9% of global blue carbon ecosystem area, remain underrepresented in blue carbon budgets. Here, we synthesize data from 184 sites across 23 countries to quantify their carbon stocks, carbon accumulation rate (CAR) and greenhouse gas (GHG, CO₂ and CH₄) emissions. Our results reveal that tidal flats sequester 8.6 (4.5–9.9) Tg C yr⁻¹ and store 1.2 (0.7–2.0) Pg C in the top meter of sediments, increasing global blue carbon estimates by 6%–17%. However, they simultaneously emit 0.073 Tg CH₄ yr⁻¹ (3.3 Tg CO₂eq yr⁻¹), 27.9% of the CH₄ emissions from salt marshes, offsetting 14.1% (1.8%–20.4%) of their carbon sequestration benefits. Mudflats exhibit the highest carbon stocks and CO₂ fluxes among different sediment types, primarily due to their abundant binding sites of fine-grained particles and stronger microbial activities. Both CAR and CH₄ fluxes decline poleward, with tropical zone as hotspots. Our findings highlight the urgency of integrating tidal flats into climate mitigation strategies, particularly given their vulnerability to land-use changes and sea-level rise. Conservation efforts must balance carbon sequestration gains against CH₄ trade-offs to optimize their climate regulation potential.

Tropical landscapes are undergoing rapid transformation due to human activities and global change. Forest restoration has emerged as a key strategy to mitigate biodiversity loss and climate warming. However, a standardized assessment of how different restoration methods contribute to biodiversity recovery and conservation remains lacking. Here, we present the first comprehensive comparison of tree diversity restoration and the drivers of recovery across five main reforestation methods (naturally regenerating forests, biodiverse restoration plantings, short- and long-rotation tree monocultures, agroforests) relative to three reference systems (agropastoral lands, degraded and conserved forest remnants). Tree inventories were conducted in 519 plots (900 m² each) across two forest types (rainforest and seasonally dry forest) in the Atlantic forest of São Paulo state, Brazil, encompassing over 39,000 trees and 869 species. We found that: (1) all reforestation methods except short-rotation monoculture plots supported tree diversity recovery. In the rainforest, conserved remnant plots maintained the highest average Shannon diversity (Hill 1 = 29 ± 14), while naturally regenerating forests and restoration plantings approached the diversity of degraded remnant plots (15 ± 5). In seasonally dry forest, biodiverse restoration plantings and agroforests reached diversity levels comparable to conserved remnants (15 ± 6). Additionally, (2) recovery was influenced by forest age, climate (water availability), soil fertility, and landscape context, though the relative importance of these factors varied by method. Climate and landscape context were more influential for recovery in naturally regenerating forests, while soil conditions played a greater role in biodiverse restoration plantings. Lastly, (3) species composition in naturally regenerating forests most closely resembled that of conserved remnants. Conversely, restoration plantings and agroforests exhibited high compositional overlap across sites, reducing overall species richness. Our findings underscore the wide variation in biodiversity outcomes among and within reforestation methods, emphasizing that goals and strategies must align with local conditions to maximize benefits in complex tropical landscapes.

Soil microorganisms constitute the largest portion of Earth's biodiversity. However, soil microorganisms are also highly sensitive to on-going global change, and the influence of an increasing number of stressors on common, rare, and unknown taxa across large environmental gradients remains virtually unknown. Here, we combined a large-scale spatial field survey across multiple different ecosystems and found that the diversity and abundance of soil rare taxa were significantly reduced under high environmental stressor number (i.e., a high number of stressors passing a 75% stressor threshold). Strikingly, the abundance of unknown soil taxa and unknown genes increased with increasing environmental stress number. We further identified the metagenome-assembled genomes (MAGs) that were considered as relatively common taxa using metagenomics. Compared to 9% of negative responders, 32% of common MAGs were resistant or positively responsive to multiple stress, displaying a reduced potential for cellular processes and an enhanced potential for environmental, genetic, and metabolic processes. Our study suggests that as stress increases, we would have less rare, but more unknown microorganisms and unique genomes of resistant common taxa, suggesting major changes in the soil microbiome in a world subjected to multiple global change stressors.

Harmful algal blooms (HABs) are an escalating global threat to aquatic ecosystems, reducing biodiversity, degrading water quality, and compromising human health. Climate-driven warming and excessive nutrient inputs are key drivers of HABs in global lakes. However, as nutrient reduction strategies gain traction, the relative contributions of rising water temperatures and nutrient enrichment remain unclear. Here, we compiled a dataset spanning 40 years from 156 lakes worldwide and analyzed the nonlinear response relationship between chlorophyll-a (Chl-a) and water temperature using a combination of empirical mode decomposition (EMD) and a random forest (RF) model. EMD demonstrated strong adaptability in extracting long-term stable signals from non-stationary records, revealing that over 40% of the lakes are eutrophic, with substantial spatial heterogeneity in HAB intensity; mean Chl-a concentrations reached as high as 26 μg L⁻¹ in tropical regions. As warming continues, water temperature emerges as a progressively stronger driver of HABs, surpassing the influences of nutrient availability and stoichiometric balance. Rising water temperatures diminish the reliance of HABs on nutrient availability, while the nitrogen-to-phosphorus ratio consistently explains variation in Chl-a concentrations throughout the warming process. Furthermore, RF-based scenario projections indicate that under current warming and nutrient scenarios, the mean annual Chl-a concentrations of global lakes are projected to rise to 17.7 μg L⁻¹ under RCP 4.5 and 18.4 μg L⁻¹ under RCP 8.5 by the end of the 21st century. These findings highlight the urgent need to incorporate temperature effects into lake HAB management strategies.

Global amphibian declines outpace the loss of most organisms on Earth. The panzootic fungal disease chytridiomycosis, caused by Batrachochytrium dendrobatidis (Bd), is widely regarded as a predominant driver behind amphibian biodiversity erosion. However, a comprehensive global-scale analysis of the relationship between Bd and extinction risk remains lacking. Using a global database of Bd-detections and IUCN Red List extinction risk, we show that current amphibian declines are associated with Bd in temperate regions only, whereas historical analyses reveal a past peak of Bd-related declines across more equatorial areas during 1980–2004, that has diminished in intensity in recent decades (2004–2020). In contrast, temperate species show a lack of Bd-related declines during 1980–2004 but significant declines are currently ongoing. We suggest that the shorter activity seasons in temperate regions may have acted as ‘natural lockdowns’ that delayed the annihilating effects of Bd in susceptible species. Conversely, year-round activity in more amphibian-dense, equatorial areas may have triggered a faster transition into post-epizootic dynamics, characterised by a continuous high-intensity outbreak followed by amphibian population stabilisation and pathogen persistence at lower levels.