Sharp decline in future productivity of tropical reforestation above 29°C mean annual temperature

Resilience response of China's terrestrial ecosystem gross primary productivity under environmental stress

Climate change perturbations contribute to the alteration of ecosystem functions and the reduction of their resilience. Understanding this reduction in resilience is fundamental for formulating strategies for sustainable ecosystem management. Consequently, a systematic evaluation of factors influencing ecosystem resilience is imperative. This involves elucidating the resilience trends and stress conditions within Chinese ecosystems spatially, thereby enabling a holistic assessment of their health status. This study assesses resilience across China by analyzing the one-month lagged time autocorrelation of terrestrial Gross Primary Production (GPP) across China. It differentiates between various stress states within the study region and employs interpretable machine learning methods to examine the relationship between terrestrial ecosystem resilience and environmental changes under different stress conditions. The findings reveal that approximately 20 % of Chinese regions are undergoing a decrease in ecosystem resilience, with over half experiencing stressed conditions. This is particularly pronounced in the northeastern and central regions of China, where a more significant and widespread decrease in resilience is observed. In the stressed areas of China, the effect of each environmental factor on the decrease in resilience is greater, where attention needs to be paid to areas with higher maximum temperature, precipitation, vapor pressure deficit, and radiation. The study highlights the variability in ecosystem resilience under different environmental conditions and their varied responses to environmental changes. This provides a scientific basis for protecting ecological balance and promoting the sustainable development of ecosystems.

Increasing severity of large-scale fires prolongs recovery time of forests globally since 2001

Ongoing and sharply increased global forest fires, especially extreme large-scale fires (LFs) with their greater destructiveness, have significantly altered forest structures and functions. However, long-term variations in the severity of LFs and corresponding effects on the natural post-LF recovery time of global forests remain unclear. Here, we rigorously identified 3,281 global large-scale (>10 km2) single-time fire events (LSFs) from 2001 to 2021, and used multiple indicators to understand the post-LSF recovery dynamics from different perspectives and comprehensively reveal major driving factors across regions and forests types based on multiple models. Compared with pre-2010, LSFs after 2010 caused greater forest damage, with the fire severity expanding further from low to high latitudes and from humid to arid regions, particularly affecting evergreen needleleaf forests. Fewer than one-third of the forests recovered successfully within 7 years, and most of these were tropical, moisture-rich broadleaf forests. The average time required for three indicators to recover to pre-fire conditions increased by 7.5% (vegetation density), 11.1% (canopy structure) and 27.3% (gross primary productivity). Moreover, the positive sensitivity of recovery time to increased fire severity was significantly intensified. Notably, more forests experienced recovery stagnation with increased severity, especially in boreal forests, further extending recovery time. The negative impact of the severity of LSFs on forest recovery was much stronger than that of post-LSF climate conditions. Soil moisture after LSFs was identified as the primary facilitating factor. Temperature generally had a positive role before 2010, but a strong negative influence on post-LSF forest recovery after 2010. These findings provide a useful reference for better understanding global forest recovery mechanisms, estimating forest carbon sinks and implementing post-LSF management accordingly.

Differential thresholds of net ecosystem productivity in karst and non-karst regions for identifying their potential carbon sinks areas

Within ecosystems, habitat influences structure, and structure determines function, forming a habitat-structure-function framework (HSFF). Net ecosystem productivity (NEP) is a key indicator for assessing regional or global carbon dynamics. However, the response thresholds of NEP to habitat and structural factors, along with management strategies based on these thresholds, remain under-explored. Therefore, this study examines the response thresholds of NEP to habitat and structural factors in the karst and non-karst regions of southwest China, which exhibit strong surface heterogeneity, based on the HSFF using a restricted cubic spline method. The results are, (1) The interannual NEP increase rate and carbon storage per unit area were notably greater in karst regions than in non-karst ones. However, compared to non-karst regions, karst regions show greater NEP variability and lower stability. (2) Significant nonlinear relationships were identified between NEP and nine habitat factors and six structural factors. NEP thresholds due to habitat and structural factors were smaller in karst regions than in non-karst regions. (3) Habitat factors had greater relative importance and marginal contribution than structural factors in karst and non-karst regions, with energy and water as the main influences on NEP. (4) Using the potential carbon sinks areas determined by the threshold, the karst areas in the entire study will play an important role in carbon sinks in the future. Overall, this study not only deepens the understanding of the differences in ecosystem NEP between karst and non-karst regions, but also provides new perspectives and strategies for optimizing ecosystem management based on habitat and structural characteristics.

Scenario analysis of supply- and demand-side solutions for circular economy and climate change mitigation in the global building sector

Residential and non-residential buildings are a major contributor to human well-being. At the same time, buildings cause 30% of final energy use, 18% of greenhouse gas emissions (GHGE), and about 65% of material accumulation globally. With electrification and higher energy efficiency of buildings, material-related emissions gain relevance. The circular economy (CE) strategies, narrow, slow, and close, together with wooden buildings, can reduce material-related emissions. We provide a comprehensive set of building stock transformation scenarios for 10 world regions until 2060, using the resource efficiency climate change model of the stock-flow-service nexus and including the full CE spectrum plus wood-intensive buildings. The 2020-2050 global cumulative new construction ranges from 150 to 280 billion m2 for residential and 70-120 billion m2 for non-residential buildings. Ambitious CE reduces cumulative 2020-2050 primary material demand from 80 to 30 gigatons (Gt) for cement and from 35 to 15 Gt for steel. Lowering floor space demand by 1 m2 per capita leads to global savings of 800-2500 megatons (Mt) of cement, 300-1000 Mt of steel, and 3-10 Gt CO2-eq, depending on industry decarbonization and CE roll-out. Each additional Mt of structural timber leads to savings of 0.4-0.55 Mt of cement, 0.6-0.85 Mt of steel, and 0.8-1.8 Mt CO2-eq of system-wide GHGE. CE reduces 2020-2050 cumulative GHGE by up to 44%, where the highest contribution comes from the narrow CE strategies, that is, lower floorspace and lightweight buildings. Very low carbon emission trajectories are possible only when combining supply- and demand-side strategies. This article met the requirements for a gold-gold JIE data openness badge described at http://jie.click/badges.

Assessing multi-decadal climatic variability and its impact on cardamom cultivation in the Indian Cardamom Hills

This study examines the multi-decadal variability and trends of surface air temperature and precipitation in the Indian Cardamom Hills (ICH), a degraded tropical rainforest area unique for cardamom cultivation. Utilizing observed long-term climatic data (1958-2017), statistical methods such as the Mann-Kendall test (MKT), Sen's Slope Estimator (SSE), and Incremental Trend Analysis (ITA) were applied to assess the impact of surface air temperature, rainfall, and the number of rainy days on cardamom yield. The analysis revealed a significant decline in annual rainfall by approximately 13.62 mm per year, with pronounced seasonal declines 0.87 mm for winter, 12.33 mm for pre-monsoon, 24.93 mm for southwest monsoon, and 18.10 mm for post-monsoon. Simultaneously, the number of rainy days dropped by nearly 19.75 days over the 40-year period. A noticeable increase in decadal minimum and average temperatures was observed, highlighting potential adverse effects on cardamom yield and irrigation water resources. The findings suggest that excessive rainfall during the southwest monsoon negatively correlates with cardamom yield, while slightly warmer temperatures show a weak positive correlation. The study also emphasizes the need for adaptive agricultural practices and climate-resilient policies to mitigate the effects of changing climatic conditions on cardamom production. This research contributes valuable insights for farmers and other stakeholders as well as policymakers aiming to ensure sustainable cardamom cultivation amidst climate change.

The stomatal response to vapor pressure deficit drives the apparent temperature response of photosynthesis in tropical forests

As temperature rises, net carbon uptake in tropical forests decreases, but the underlying mechanisms are not well understood. High temperatures can limit photosynthesis directly, for example by reducing biochemical capacity, or indirectly through rising vapor pressure deficit (VPD) causing stomatal closure. To explore the independent effects of temperature and VPD on photosynthesis we analyzed photosynthesis data from the upper canopies of two tropical forests in Panama with Generalized Additive Models. Stomatal conductance and photosynthesis consistently decreased with increasing VPD, and statistically accounting for VPD increased the optimum temperature of photosynthesis (Topt) of trees from a VPD-confounded apparent Topt of c. 30-31°C to a VPD-independent Topt of c. 33-36°C, while for lianas no VPD-independent Topt was reached within the measured temperature range. Trees and lianas exhibited similar temperature and VPD responses in both forests, despite 1500 mm difference in mean annual rainfall. Over ecologically relevant temperature ranges, photosynthesis in tropical forests is largely limited by indirect effects of warming, through changes in VPD, not by direct warming effects of photosynthetic biochemistry. Failing to account for VPD when determining Topt misattributes the underlying causal mechanism and thereby hinders the advancement of mechanistic understanding of global warming effects on tropical forest carbon dynamics.

Warming exacerbates global inequality in forest carbon and nitrogen cycles

Forests are invaluable natural resources that provide essential services to humanity. However, the effects of global warming on forest carbon and nitrogen cycling remain uncertain. Here we project a decrease in total nitrogen input and accumulation by 7 ± 2 and 28 ± 9 million tonnes (Tg), respectively, and an increase in reactive nitrogen losses to the environment by 9 ± 3 Tg for 2100 due to warming in a fossil-fueled society. This would compromise the global carbon sink capacity by 0.45 ± 0.14 billion tonnes annually. Furthermore, warming-induced inequality in forest carbon and nitrogen cycles could widen the economic gap between the Global South and Global North. High-income countries are estimated to gain US$179 billion in benefits from forest assets under warming, while other regions could face net damages of US$31 billion. Implementing climate-smart forest management, such as comprehensive restoration and optimizing tree species composition, is imperative in the face of future climate change.

Biocultural diversity and crop improvement

Biocultural diversity is the ever-evolving and irreplaceable sum total of all living organisms inhabiting the Earth. It plays a significant role in sustainable productivity and ecosystem services that benefit humanity and is closely allied with human cultural diversity. Despite its essentiality, biodiversity is seriously threatened by the insatiable and inequitable human exploitation of the Earth's resources. One of the benefits of biodiversity is its utilization in crop improvement, including cropping improvement (agronomic cultivation practices) and genetic improvement (plant breeding). Crop improvement has tended to decrease agricultural biodiversity since the origins of agriculture, but awareness of this situation can reverse this negative trend. Cropping improvement can strive to use more diverse cultivars and a broader complement of crops on farms and in landscapes. It can also focus on underutilized crops, including legumes. Genetic improvement can access a broader range of biodiversity sources and, with the assistance of modern breeding tools like genomics, can facilitate the introduction of additional characteristics that improve yield, mitigate environmental stresses, and restore, at least partially, lost crop biodiversity. The current legal framework covering biodiversity includes national intellectual property and international treaty instruments, which have tended to limit access and innovation to biodiversity. A global system of access and benefit sharing, encompassing digital sequence information, would benefit humanity but remains an elusive goal. The Kunming-Montréal Global Biodiversity Framework sets forth an ambitious set of targets and goals to be accomplished by 2030 and 2050, respectively, to protect and restore biocultural diversity, including agrobiodiversity.