Search for: All records

Abstract Global environmental change is causing a decline in biodiversity with profound implications for ecosystem functioning and stability. It remains unclear how global change factors interact to influence the effects of biodiversity on ecosystem functioning and stability. Here, using data from a 24-year experiment, we investigate the impacts of nitrogen (N) addition, enriched CO₂(eCO₂), and their interactions on the biodiversity-ecosystem functioning relationship (complementarity effects and selection effects), the biodiversity-ecosystem stability relationship (species asynchrony and species stability), and their connections. We show that biodiversity remains positively related to both ecosystem productivity (functioning) and its stability under N addition and eCO₂. However, the combination of N addition and eCO₂diminishes the effects of biodiversity on complementarity and selection effects. In contrast, N addition and eCO₂do not alter the relationship between biodiversity and either species asynchrony or species stability. Under ambient conditions, both complementarity and selection effects are negatively related to species asynchrony, but neither are related to species stability; these links persist under N addition and eCO₂. Our study offers insights into the underlying processes that sustain functioning and stability of biodiverse ecosystems in the face of global change. 

Soil microbial diversity is crucial to sustaining ecosystem productivity and improving carbon sequestration. Global temperature continues to rise, but how climate warming affects microbial diversity and its capacity to sequester soil organic carbon (SOC) remains uncertain. Here, by conducting a global meta-analysis with 251 paired observations from 102 studies, we showed that, on average, warming reduced bacterial and fungal diversity (measured by richness and Shannon index) by 16.0 and 19.7%, respectively, and SOC by 18.1%. The negative responses of both soil bacterial and fungal diversity to warming became more pronounced with increasing warming magnitude, experimental duration, and decreasing soil nitrogen availability. Under the worst-case climate warming scenario (2010 to 2070, 3.4 increase in °C), soil bacterial diversity and fungal diversity are projected to reduce by 56% and 81%, respectively, over 60 y. Importantly, in addition to the direct impact of warming on SOC, warming-induced declines in microbial diversity also contributed to SOC losses. We highlight that prolonged warming could substantially reduce soil microbial diversity and decrease SOC sequestration, accelerating future warming and underscoring the urgent need for decisive actions to mitigate global climate change. 

ABSTRACT Biodiversity promotes ecosystem productivity and stability, positive impacts that often strengthen over time. But ongoing global changes such as rising atmospheric carbon dioxide (CO₂) levels and anthropogenic nitrogen (N) deposition may modulate the impact of biodiversity on ecosystem productivity and stability over time. Using a quarter‐century grassland biodiversity‐global change experiment we show that diversity increasingly enhanced productivity over time irrespective of global change treatments. In contrast, the positive influence of diversity on ecosystem stability strengthened over time under ambient conditions but weakened to varying degrees under global change treatments, largely driven by a greater reduction in species asynchrony under global changes. Thus, over 25 years, CO₂and N enrichment gradually eroded some of the positive effects of biodiversity on ecosystem stability. As elevated CO₂, N eutrophication, and biodiversity loss increasingly co‐occur in grasslands globally, our results raise concerns about their potential joint detrimental effects on long‐term grassland stability. 

Abstract Global changes such as nitrogen (N) enrichment and elevated carbon dioxide (CO₂) are known to exacerbate biodiversity loss in grassland ecosystems. They do so by modifying processes whose strength may vary at different spatial scales. Yet, whether and how global changes impact plant diversity at different spatial scales remains elusive.We collected data on species presence and cover at a high resolution in the third decade of a long‐term temperate grassland biodiversity—global change experiment. Based on the data, we constructed species—area relationships across three spatial orders of magnitude (from 0.01 to 3.24 m²) and compared them for the different global change treatments.We found that N enrichment, both under ambient and elevated CO₂levels, decreased species richness across almost all spatial scales, with proportional decreases being largest at the smallest spatial scales. Elevated CO₂also reduced richness at both ambient and enriched N supply rates but did so proportionally across all spatial scales. Suppression of diversity was stronger at all scales for diversity indices that include relative abundances than for species richness. Taken together, these results suggest that CO₂and N are re‐organizing this grassland system by increasingly favouring, at fine scales, a small subset of dominant species.Synthesis: Our results highlight the role of spatial scales in influencing biodiversity loss, especially when it is driven by anthropogenic resource changes that might influence species interactions differently across spatial scales. 

Mitigating climate change and social injustice are critical, interwoven challenges. Climate change is driven by grossly unequal contributions to elevated greenhouse gas emissions among individuals, socioeconomic groups, and nations. Yet, its deleterious impacts disproportionately affect poor and less powerful nations, and the poor and the less powerful within each nation. This climate injustice prompts a call for mitigation strategies that buffer the poorest and the most vulnerable against climate change impacts. Unfortunately, all emissions mitigation strategies also reshape social, economic, political, and ecological processes in ways that may create climate change mitigation injustices—i.e., a unique set of injustices not caused by climate change, but by the strategies designed to stem it. Failing to stop climate change is not an answer—this will swamp all adverse impacts of even unjust mitigation in terms of the scope and scale of disastrous consequences. However, mitigation without justice will create uniquely negative consequences for the more vulnerable. The ensuing analysis systematically assesses how climate change mitigation strategies can generate or ameliorate injustices. We first examine how climate science and social justice interact within and among countries. We then ask what there is to learn from the available evidence on how emissions reductions, well-being, and equity have unfolded in a set of countries. Finally, we discuss the intersection between emissions reduction and mitigation justice through actions in important domains including energy, technology, transport, and food systems; nature-based solutions; and policy and governance. 

ABSTRACT Potassium (K) is the second most abundant nutrient element in plants after nitrogen (N), and has been shown to limit aboveground production in some contexts. However, the role of N and phosphorus (P) availability in mediating K limitation in terrestrial production remains poorly understood; and it is unknown whether K also limits belowground carbon (C) stocks, which contain at least three times more C than those aboveground stocks. By synthesizing 779 global paired observations (528, 125, and 126 for aboveground productivity, root biomass, and soil organic C [SOC], respectively), we found that K addition significantly increased aboveground production and SOC by 8% and 5%, respectively, but did not significantly affect root biomass (+9%). Moreover, enhanced N and/or P availability (through N and P addition) did not further amplify the positive effect of K on aboveground productivity. In other words, K had a positive effect on aboveground productivity only when N and/or P were limiting, indicating that K could somehow substitute for N or P when they were limiting. Climate variables mostly explained the variations in K effects; specifically, stronger positive responses of aboveground productivity and SOC to K were found in regions with high mean annual temperature and wetness. Our results suggest that K addition enhances C sequestration by increasing both aboveground productivity and SOC, contributing to climate mitigation, but the positive effects of K on terrestrial C stocks are not further amplified when N and P limitations are alleviated. 

Plant litter decomposition is a primary control on carbon fluxes in terrestrial ecosystems around the world. Individually, the key mediators of decomposition rates—litter traits, temperature, and moisture—are relatively well understood. However, our understanding of how combined drivers influence decomposition remains limited. To test how multiple, interactive climate change factors directly alter decomposition rates and indirectly influence leaf litter decomposition rates by altering substrate chemistry, we conducted two decomposition experiments within the Boreal Forest Warming at an Ecotone in Danger (B4WarmED) study in Minnesota, USA. Our first experiment decomposed ambient-grown leaf litter from eight common tree species under a factorial combination of warming and rainfall reduction treatments. We found that the direct effects of combined warming and rainfall reduction increased litter half-life by 42% ± 11% in comparison to ambient plots with no warming or rainfall reduction. In contrast, only rainfall reduction influenced litter mean residence time, which increased by 37% ± 18% in comparison to ambient rainfall plots. Our second experiment decomposed ambient- and warm-grown leaf litter from the same eight species under ambient and warmed conditions. We found that warming slowed decomposition of both litter types, but warm-grown litter had a 22% ± 6.5% shorter half-life than ambient-grown leaf tissue under ambient environmental conditions. Warm grown litter half-life then increased by 36% ± 11% with warmed environmental conditions. Our results highlight that climate change could slow carbon and nutrient cycling in systems where moisture becomes a limiting factor. In addition, our study demonstrates that there may be an overlooked relationship between the growth conditions of plants and the temperature of decomposition. This nuanced understanding of decomposition can then support carbon cycling models and more effective nature-based climate mitigation efforts. 

Afforestation and reforestation, both of which refer to forestation strategies, are widely promoted as key tools to mitigate anthropogenic warming. However, the carbon sequestration potential of these efforts remains uncertain in satellite-based assessments, particularly when accounting for dynamic climate conditions, vegetation-climate feedback, fire-dominated disturbance, and the trade-offs associated with surface albedo changes. Leveraging a coupled Earth system model, we estimated that global forestation mitigates 31.3 to 69.2 Pg C_eq(carbon equivalent) during 2021–2100 under a sustainable shared socioeconomic pathway. Regionally, the highest carbon mitigation potential of forestation concentrates in tropical areas, while mid-high-latitude regions demonstrate higher heterogeneity, highlighting the need for region-specific strategies and further refinement of nature-based mitigation plans. Our findings underscore the importance of considering disturbances and minimizing adverse albedo changes when estimating the carbon mitigation potential of forestation initiatives. We also advocate for the development of consistent, high-resolution maps of suitable areas for targeted forestation, avoiding environmentally sensitive lands and potential conflicts with other human activities.