Global Change Biology最新文献

Three-quarters of the planet's land surface has been altered by humans, with consequences for animal ecology, movements and related ecosystem functioning. Species often occupy wide geographical ranges with contrasting human disturbance and environmental conditions, yet, limited data availability across species' ranges has constrained our understanding of how human pressure and resource availability jointly shape intraspecific variation of animal space use. Leveraging a unique dataset of 758 annual GPS movement trajectories from 375 brown bears (Ursus arctos) across the species' range in Europe, we investigated the effects of human pressure (i.e., human footprint index), resource availability and predictability, forest cover and disturbance, and area-based conservation measures on brown bear space use. We quantified space use at different spatiotemporal scales during the growing season (May–September): home range size; representing general space requirements, 10-day long-distance displacement distances, and routine 1-day displacement distances. We found large intraspecific variation in brown bear space use across all scales, which was profoundly affected by human footprint index, vegetation productivity, and recent forest disturbances creating opportunity for resource pulses. Bears occupied smaller home ranges and moved less in more anthropized landscapes and in areas with higher resource availability and predictability. Forest disturbances reduced space use while contiguous forest cover promoted longer daily movements. The amount of strictly protected and roadless areas within bear home ranges was too small to affect space use. Anthropized landscapes may hinder the expansion of small and isolated populations, such as the Apennine and Pyrenean, and obstruct population connectivity, for example between the Dinaric Pindos population and the Alpine or Carpathian population. Our findings call for actions to maintain bear movements across landscapes with high human footprint, for example by maintaining forest integrity, to support viable bear populations and their ecosystem functions.

Climate change poses an unprecedented threat to forest ecosystems, necessitating innovative adaptation strategies. Traditional assisted migration approaches, while promising, face challenges related to environmental constraints, forestry practices, phytosanitary risks, economic barriers, and legal constraints. This has sparked debate within the scientific community, with some advocating for the broader implementation of assisted migration despite these limitations, while others emphasize the importance of local adaptation, which may not keep pace with the rapid rate of climate change. This opinion paper proposes a novel pollen-based assisted migration strategy as a potential middle ground in this debate. By leveraging existing seed orchard infrastructure for controlled pollen transfer, this approach aims to enhance forest resilience through the introduction of genetic material from climatically suitable sources while acknowledging local adaptation. We assess the genetic implications of the proposed strategy through computer simulation. Additionally, we examine the ecological implications of assisted gene flow, discussing the potential benefits of heterosis and the risks of outbreeding depression in intra-specific hybrid populations. We further explore the advantages of pollen-based migration in mitigating phytosanitary risks, reducing economic barriers, and simplifying legal considerations compared to traditional seed or seedling transfer methods. Regional perspectives on adapting pollen-based assisted migration are provided, with specific examples from Northern and Central Europe. We highlight how this approach could be integrated into existing forestry practices and regulatory frameworks within the European Union. We conclude by advocating for the inclusion of pollen-based assisted migration in future international projects and operational forestry, emphasizing the need for adaptable policies that can support innovative forest management strategies in the face of climate change.

Temperate forests cover 25% of the world's forest area and most of them are managed for timber production. To increase yields, native deciduous trees have been commonly replaced by fast-growing conifers, especially in Western and Central Europe. Despite the importance of forest soils for a variety of ecosystem functions, the effects of forest management intensity on soil biological processes have not yet been sufficiently understood. Using a standardized sampling protocol that covers 200 plots across four regions with different abiotic site conditions, our study aims at disentangling the effects of individual components of forest management intensity such as (i) share of native deciduous trees, (ii) timber harvesting volume, and (iii) natural deadwood volume on soil biological processes. Our findings indicate that the effects of management practices on soil biological processes are as important as abiotic factors, such as subsoil pH value and soil texture. Piecewise structural equation modeling revealed that forest management has both direct and indirect effects on soil biological processes via humus form and topsoil pH. Generally, the ratio of deciduous and coniferous trees had the most significant effect on nutrient cycling and soil properties, followed by nutrient extraction through timber harvesting and natural deadwood volume. The strength of the observed effects was modified by regional variations in climate, topography, and bedrock. Our findings underline the high diagnostic value of humus form as an indicator of biological processes in mineral topsoil (particularly pH, C/N, and microbial characteristics can be predicted) that can guide forest managers in evaluating soil quality and identifying management impacts.

Agriculture serves as both a source and a sink of global greenhouse gases (GHGs), with agricultural intensification continuing to contribute to GHG emissions. Climate-smart agriculture, encompassing both nature- and technology-based actions, offers promising solutions to mitigate GHG emissions. We synthesized global data, between 1990 and 2021, from the Food and Agriculture Organization (FAO) of the United Nations to analyze the impacts of agricultural activities on global GHG emissions from agricultural land, using structural equation modeling. We then obtained predictive estimates of agricultural GHG emissions for the future period of 2022–2050 using deep-learning models. The FAO data show that, from 1990 to 2021, global livestock numbers, inorganic nitrogen (N) fertilizer use, crop residue, and irrigation area increased by 27%, 47%, 49%, and 37%, respectively. The increased livestock numbers contributed to the increases in CH₄ and N₂O emissions, while inorganic N fertilizer, crop residue, and irrigation mainly contributed to the increases in N₂O emissions. Emissions of CO₂ decreased because of a 29% reduction in net forest loss. As a result of the reduced deforestation emissions, the overall agricultural GHG emissions declined from 11.50 to 10.89 GtCO₂eq from 1990 to 2021 despite the increases in livestock numbers, inorganic N fertilizer, crop residue, and irrigation. Looking ahead, our model predicts that if current agricultural trends persist, GHG emissions will rise to 11.82 ± 0.07 GtCO₂eq in 2050. However, maintaining agricultural GHG emissions at the 2021 level through 2050 is possible if the rate of reduction in net forest loss is doubled. Furthermore, if the rate is tripled, agricultural GHG emissions can be limited to 9.85 ± 0.07 GtCO₂eq in 2050. Our findings suggest that reductions in agricultural GHG emissions, alongside sustainable agricultural intensification and climate-smart agricultural practices, can be achieved through parallel efforts emphasizing accelerated forest conservation.

In fire-prone regions such as the Mediterranean biome, fire seasons are becoming longer, and fires are becoming more frequent and severe. Post-fire recovery dynamics is a key component of ecosystem resilience and stability. Even though Mediterranean ecosystems can tolerate high exposure to extreme temperatures and recover from fire, changes in climate conditions and fire intensity or frequency might contribute to loss of ecosystem resilience and increase the potential for irreversible changes in vegetation communities. In this study, we assess the recovery rates of burned vegetation after recurrent fires across Mediterranean regions globally, based on remotely sensed Enhanced Vegetation Index (EVI) data, a proxy for vegetation status, from 2001 to 2022. Recovery rates are quantified through a statistical model of EVI time-series. This approach allows resolving recovery dynamics in time and space, overcoming the limitations of space-for-time approaches typically used to study recovery dynamics through remote sensing. We focus on pixels burning repeatedly over the study period and evaluate how fire severity, pre-fire vegetation greenness, and post-fire climate conditions modulate vegetation recovery rates of different vegetation types. We detect large contrasts between recovery rates, mostly explained by regional differences in vegetation type. Particularly, needle-leaved forests tend to recover faster following the second event, contrasting with shrublands that tend to recover faster from the first event. Our results also show that fire severity can promote a faster recovery across forested ecosystems. An important modulating role of pre-fire fuel conditions on fire severity is also detected, with pixels with higher EVI before the fire resulting in stronger relative greenness loss. In addition, post-fire climate conditions, particularly air temperature and precipitation, were found to modulate recovery speed across all regions, highlighting how direct impacts of fire can compound with impacts from climate anomalies in time and likely destabilise ecosystems under changing climate conditions.