Abstract Agricultural systems depend on Nature's Contributions to People (NCP), but their management often diminishes biodiversity, potentially undermining their sustainability. Thus, understanding the relationships between biodiversity, human capital (labour and physical inputs) and crop yields is essential for sustainable management, particularly in biodiverse ecosystems. We investigated the relationships between biodiversity, human capital and crop productivity across 15 long‐term monitoring plots spanning three cropping systems (coffee, banana and intercropped maize and beans) on the southern slopes of Mount Kilimanjaro, Tanzania. Using ecological surveys, semi‐structured farmer interviews and detailed yield assessments, we quantified crop yield (both mass and economic value), human capital and a multidiversity index (MDI) encompassing the species richness of birds, bats, bees, dung beetles and trees. Structural equation models were used to estimate the direct and indirect effects of climate, biodiversity and human capital on yield value. Labour capital was strongly and positively associated with crop yield value. Meanwhile, physical capital, which included costs for agrochemicals such as fertilizers and pesticides, was negatively associated with the MDI but showed no positive association with yield value. Biodiversity, as measured by the MDI, was not significantly associated with yield value, which may reflect low statistical power, a dominant role of agricultural inputs in driving yields or weak ecological contributions. Among cropping systems, intercropped maize and beans exhibited the highest MDI, while coffee plantations showed the lowest. Practical implications . These findings suggest that reducing agrochemical dependence could offer opportunities to enhance biodiversity without necessarily compromising productivity, though uncertainty remains. Nevertheless, in line with global calls for sustainable, biodiversity‐friendly agriculture and other regional research, we recommend policy and economic incentives for low‐input systems, the integration of agroecological practices and the use of precision input management. Overall, our results highlight the potential for ‘win‐win’ strategies that balance agricultural productivity, biodiversity and rural livelihoods on Mount Kilimanjaro.

Biodiversity can influence forest productivity, but this does not necessarily translate into higher provision of wood-based Nature's contributions to people (NCP), as only a subset of the wood produced is used for each NCP. Biodiversity-NCP relationships therefore require further assessment. Using forest inventory and plant trait data, and local socio-economic information from Mt Kilimanjaro, Tanzania, we examined how different biodiversity components affect the supply of wood-based NCP namely; timber, charcoal and firewood, compared to standing tree above-ground biomass. Confounding environmental variables such as climate and land-use intensity (LUI) were also incorporated in a structural equation modeling framework. Tree biomass, timber, charcoal and firewood supply peaked at intermediate elevations and low LUI, particularly in lower montane, Ocotea and Podocarpus-dominated forests within protected areas. Supply dropped to zero at the highest and lowest elevations, where herbaceous vegetation and agricultural land covers dominate. The role of biodiversity components varied across NCP and all three NCP showed a different response than total aboveground biomass to biodiversity components. Timber supply was positively associated with tree taxonomic diversity, most likely because the species selected for logging are found in diverse forests but was unrelated to community-weighted mean (CWM) tree height. In contrast, charcoal supply was influenced positively by both taxonomic diversity and CWM tree height. Firewood supply did not respond to either taxonomic diversity or CWM tree height. Our results suggest that relationships between biodiversity and NCP differ from those linking biodiversity to ecosystem functioning due to selective human use. This has implications for the transferability of biodiversity-ecosystem functioning research and the management of biodiversity and NCP.

Mount Kilimanjaro, with its steep elevational gradient (770-5886 m a.s.l.) and pronounced land-use heterogeneity, supports high biodiversity and diverse nature's contributions to people (NCP), but it is underrepresented in global spatial assessments. We address this gap by mapping NCP supply across 12 ecosystem types on the southern slopes identifying hotspots and coldspots and quantifying synergies and trade-offs among NCP categories. We use 25 context-specific NCP categories that integrate local and scientific knowledge with field measurements and remote-sensing-derived proxies. Combining long-term field data with remote sensing and machine learning, we upscaled plot-scale indicators into standardized supply maps. Total NCP supply is strongly concentrated in mid-elevation ecosystems: the 1100-2200 m band alone accounted for similar to 59% of total supply compared with similar to 18% in the lowlands (700-1100 m), and the 1100-2800 m belts together provide similar to 73%, whereas high-elevation zones (2800-4600 m) contribute <9%. Hotspots clustered in lower montane forest, Ocotea forest and homegardens at mid-elevations, while coldspots occur in Erica forest and Helichrysum vegetation at high elevations and in maize fields and savanna at low elevations. We detected moderate (r = 0.55) to strong synergies (r = 0.83) among the three NCP groups (material, regulating, non-material). After accounting for climatic co-variation, the correlations among NCP groups weakened (r = 0.23-0.44), underscoring the critical role of climate for NCP supply. Our study maps NCP hotspots and coldspots across Mt. Kilimanjaro and provides a decision-support layer for conservation, restoration and agroforestry management, as well as a blueprint for spatially-explicit NCP mapping and analyses.

Old-growth tropical forests store vast amounts of carbon in their aboveground biomass (AGB), yet the relative roles of abiotic factors such as climate, soil, and topography in governing its spatial distribution remain poorly understood. In particular, the degree to which climate acts on AGB through forest structure is still poorly quantified at the pantropical scale. Using a pantropical dataset of more than 2,000 old-growth forest plots and a structure-explicit framework, we assess how climate influences AGB through its effects on four structural attributes: basal area, mean diameter, stem density, and basal area-weighted wood density. We find that climate shapes AGB primarily through its effects on forest structure. However, structural attributes respond to climate in opposite directions, so climate’s net effect on AGB largely cancels out, and no clear climate-AGB relationship emerges across tropical regions. Moreover, only wood density responds consistently, decreasing with annual precipitation and increasing with precipitation seasonality, whereas all other attributes respond to climate differently from one region to another. This geographical variation further obscures any global climatic signal on AGB and points to the role of biogeographic history in shaping forest structure. Our findings highlight the central role of the climate-structure nexus in explaining AGB variation, and call for structure-explicit models to improve carbon stock predictions and inform climate adaptation strategies.

Montane forests are biodiversity hotspots that provide important ecosystem services, including temperature buffering for numerous species underneath forest canopies. In recent decades, montane forests have been under increasing pressure from small-and large-scale deforestation, yet associated spatio-temporal changes in temperature buffering capacity remain unclear. Here, we studied the changes in temperature buffering capacity due to forest loss from 2003 to 2022 in three montane forest ecosystems in Africa (Mount Kilimanjaro, Mount Bale, and the Taita Hills). We modeled the temperature buffering changes based on in situ microclimate measurements inside forests and in open areas, climate data, airborne laser scanning data, and satellite observations. We found that during the study period montane forests were lost at a rate of 2–9% across the study areas. This loss led to an annual average microclimate air temperature warming ranging from 2.0 ± 0.8 °C to 5.6 ± 2.1 °C across the three montane forests. The warming reduced the maximum air temperature buffering by an average of 3 ± 1.5 °C. Locally, the temperature buffering disappeared over time and transitioned to a mesoclimate amplification. Our findings demonstrate that microclimate buffering capacity was markedly diminished as a result of microclimate warming driven by recent forest loss.

Plant functional traits play an important role in shaping plant ecological responses to environmental conditions and influencing ecosystem functioning. However, how whole-plant functional strategies manifest at the community level to influence aboveground and below-ground carbon storage across environmental gradients remains poorly understood. We measured above-ground and below-ground carbon stocks and the variation in whole-plant (above- and below-ground) functional strategies at the community level in twelve ecosystem types across a broad savanna-forest-alpine elevational gradient of climate and land use on Mt. Kilimanjaro, Tanzania. Using Structural Equation Models, we disentangled the direct and land-use-mediated influences of climate on carbon storage from indirect influences mediated by variation in plant functional strategies. We found strong coordination between above- and below-ground functional traits at the whole community level, which corresponded with functional strategies related to two major trade-offs: a slow-conservation to fast resource-acquisition axis represented by a spectrum from high leaf dry matter content to high fine root nitrogen concentration; and a size-related woody to grassy community axis represented by a spectrum spanning high canopy height to high specific root length. The slow-fast and woody-grassy strategy axes were primarily driven by precipitation and land-use intensity, respectively. Both functional strategies mediated the effects of climate on carbon storage. The slow-fast strategy axis was strongly and positively associated with above-ground carbon stocks. Meanwhile, the woody-grassy strategy axis was negatively associated with both above-ground carbon stocks and soil organic carbon stocks. Synthesis. We demonstrate that major plant functional strategies manifest at the community level along elevational gradients. These strategies also explain variation in carbon storage, although above-ground storage is mostly driven by trait effects, and below-ground storage by direct effects of climate. Together, these results underscore the importance of incorporating community functional trait data into future analysis of climate change impacts on carbon storage, which would enhance our ability to predict shifts in ecosystem functioning.

Tropical mountains such as Kilimanjaro are biodiversity hotspots providing ecosystem services for millions of people, but many are under great pressure. Effective policies to halt biodiversity loss require an understanding of which anthropogenic factors are the main direct causes. While previous research focused mainly on climate change and on the effects rather than the causes, we investigated the effects of multiple drivers on biodiversity. The focus is on floristic and vegetation diversity, as vegetation is closely related to the diversity of other taxa and plays a fundamental role in ecosystem functioning. We show that land-use change caused by rapid population growth was the main direct driver on Kilimanjaro between 1911 and 2022, when 75% of natural species per km2 disappeared from the lower slopes. Climate change, on the other hand, had no apparent influence on the observed trends in biodiversity. The significant increase in traditional and diverse agroforestry and the establishment of protected areas show possibilities for mitigation. Kilimanjaro is thus an example of the challenges of global change, but also of the prospects and opportunities for other tropical regions.

Aim: Progress has been made in understanding the relationship between biodiversity and ecosystem functioning (BEF) in both experimental and real-world ecosystems. Yet, we have a limited understanding of the extent to which biodiversity affects ecosystem functioning in heterogeneous environments and whether variation in ecosystem functioning between communities is related to variation in species richness or turnover. Here, we quantify the relative contribution of variation in species richness and species turnover to variation in ecosystem functioning between communities (i.e., the diversity effect) along two tropical elevational gradients. Location: Andes (Ecuador) and Mt. Kilimanjaro (Tanzania).Taxa Studied Woody plants, springtails, soil arthropods, ants and frugivorous birds. Methods: We collected data on seven ecosystem functions, including biomass and process rates, across six ecosystem types along the two elevational gradients. We then combine the ecological Price equation with the concept of beta-diversity to quantify how the diversity effect is shaped by environmental heterogeneity within and across ecosystem types, and whether the effect of environmental heterogeneity is primarily mediated by variation in species richness or species turnover. Results: The diversity effect on ecosystem functioning increased consistently with environmental heterogeneity on both mountains. Species richness and turnover, on average, contributed similarly to the diversity effect on ecosystem functioning in both mountain regions, but effect sizes varied across functions. The increase in the diversity effect with environmental heterogeneity was primarily mediated by species richness, while species turnover played a secondary role in mediating the effects of environmental heterogeneity. Main Conclusions: Our study reveals that the diversity effect on ecosystem functioning increases with environmental heterogeneity and that species richness, rather than species turnover, primarily drives this relationship. The dominant role of species richness in mediating the effect of environmental heterogeneity indicates that BEF relationships along environmental gradients are strongly influenced by environmental filters that limit local species coexistence.

Trees can differ enormously in their crown architectural traits, such as the scaling relationships between tree height, crown width and stem diameter. Yet despite the importance of crown architecture in shaping the structure and function of terrestrial ecosystems, we lack a complete picture of what drives this incredible diversity in crown shapes. Using data from 374,888 globally distributed trees, we explore how climate, disturbance, competition, functional traits, and evolutionary history constrain the height and crown width scaling relationships of 1914 tree species. We find that variation in height-diameter scaling relationships is primarily controlled by water availability and light competition. Conversely, crown width is predominantly shaped by exposure to wind and fire, while also covarying with functional traits related to mechanical stability and photosynthesis. Additionally, we identify several plant lineages with highly distinctive stem and crown forms, such as the exceedingly slender dipterocarps of Southeast Asia, or the extremely wide crowns of legume trees in African savannas. Our study charts the global spectrum of tree crown architecture and pinpoints the processes that shape the 3D structure of woody ecosystems.

Climate, forest successional stage, and soil substrate age can alter herbivore communities and their effects on biogeochemical cycling, but the size and spatial variability of these effects are poorly quantified. To address this knowledge gap, we established a globally distributed network of 50 broadleaved old‐growth forests across six continents, encompassing well‐constrained local‐scale gradients in mean annual temperature (MAT), mean annual precipitation (MAP), succession, and soil substrate age. We used this network to investigate how these variables impact insect foliar herbivory and the associated carbon, nitrogen, phosphorus, and silica fluxes in forest ecosystems. Over 1 to 2 years, we measured stand‐level foliar biomass production, leaf‐level herbivory, and foliar element concentrations. At the global scale, insect herbivores liberated higher amounts of elements from the canopies of warmer and drier sites than those of cooler and wetter sites with patterns for phosphorus being most pronounced. MAT exerted a stronger influence over insect‐mediated element fluxes than MAP. Foliar biomass production and leaf‐level herbivory responses to MAT and MAP were mainly responsible for the observed changes in insect‐mediated element fluxes; we also observed minor effects of foliar phosphorus concentration on phosphorus fluxes. Local‐scale trends were mixed and successional stage or soil substrate age did not appear to influence insect herbivore‐mediated element fluxes. These results demonstrate that climate effects on plant‐herbivore interactions are stronger at large than small scales, at which herbivory rates and nutrient fluxes appear to be more strongly affected by a diversity of non‐climate factors.

Non‐material Nature's Contributions to People (NCP), such as spirituality and aesthetic enjoyment, arise from interactions between people and entities of nature. However, their intangible and context‐specific nature makes them challenging to identify and quantify. We analysed Twitter posts (now known as ‘X’) from tourists across different habitats at Mount Kilimanjaro, Tanzania, using a mixed‐method approach. Based on the terms and expressions used by tourists, we identified the non‐material NCP and entities of nature they perceived. We then assessed cross‐habitat differences and investigated factors associated with the number of non‐material NCP perceived. Tourists perceived 15 non‐material NCP, four of which were previously not described in the literature: Sense of Achievement, Affective Experiences, Sensory Experiences and Iconic Places & Charismatic Experiences . Tourists used a wide range of terms to describe nature, which we grouped into 15 types of entities of nature. These included generic biotic and landscape entities (e.g. ‘wildlife’, ‘wilderness’), as well as specific abiotic entities like geological ones (e.g. ‘volcano’). These entities of nature were associated with perception of more non‐material NCP than specific biotic entities (e.g. ‘chameleon’, ‘monkey’, ‘flower’). Importantly, non‐material NCP perception did not align with the mountain's most biodiverse habitats. Instead, it peaked at the high‐ and low‐elevation habitats, and it was lowest in the biodiversity‐rich mid‐elevation. Moreover, perception of biotic entities increased towards low‐elevation habitats. Our findings suggest a priming effect on biodiversity perception, driven by the type of nature engagement: summit‐focused activities may overshadow tourists' attention to biodiversity along the trail, whereas other experiences at lower elevations may foster greater appreciation of it. Synthesis and applications . Our fine‐grained, context‐specific approach reveals important details about people's interactions with nature. By understanding where and how people interact with nature, we can provide guidance on interventions that strengthen biodiversity awareness and engagement, enhance nature connectedness and ultimately support conservation efforts. Read the free Plain Language Summary for this article on the Journal blog.

Extensive forest exploitation decreases ecosystem integrity and forces species to adapt to changes in their habitats. Following thousands of years of human settlement in the Pare Mountains, less than 3% of the area remains covered with natural forests. We studied nocturnal and arboreal eastern tree hyraxes Dendrohyrax validus in North and South Pare. We compared their calls and songs from the Pare Mountains with calls from the Taita Hills (Kenya) and Mt. Kilimanjaro (Tanzania) and found some similar calls indicating that these populations are closely related. D. validus in the Pare Mountains mostly inhabit steep rocky outcrops with crevices, demonstrating that this species is not obligately arboreal or entirely dependent on old-growth forests.

Species' traits and environmental conditions determine the abundance of tree species across the globe. The extent to which traits of dominant and rare tree species differ remains untested across a broad environmental range, limiting our understanding of how species traits and the environment shape forest functional composition. We use a global dataset of tree composition of >22,000 forest plots and 11 traits of 1663 tree species to ask how locally dominant and rare species differ in their trait values, and how these differences are driven by climatic gradients in temperature and water availability in forest biomes across the globe. We find three consistent trait differences between locally dominant and rare species across all biomes; dominant species are taller, have softer wood and higher loading on the multivariate stem strategy axis (related to narrow tracheids and thick bark). The difference between traits of dominant and rare species is more strongly driven by temperature compared to water availability, as temperature might affect a larger number of traits. Therefore, climate change driven global temperature rise may have a strong effect on trait differences between dominant and rare tree species and may lead to changes in species abundances and therefore strong community reassembly.

Recent losses in the abundance and diversity of arthropods have been documented in many regions and ecosystems. In grasslands, such insect declines are largely attributed to land use, including modern machinery and mowing regimes. However, the effects of different mowing techniques on arthropods remain poorly understood. Using 11 years of data from 111 agricultural grassland plots across Germany, we analyzed the influence of various grassland management variables on the abundance and abundance-accounted species richness of four arthropod orders: Araneae, Coleoptera, Hemiptera, and Orthoptera. The analysis focused on detailed mowing information, for example, days after mowing and mower type, and compared their effect with other aspects of grassland management, that is, rolling, leveling, fertilization, and grazing. We found strong negative effects of mowing on all four arthropod orders, with arthropod abundance being lowest directly after mowing and steadily increasing to three to seven times the abundance after 100 days post-mowing. Likewise, Hemiptera and Coleoptera species richness was 30% higher 100 days after mowing. Mower width showed a positive effect on Orthoptera abundance, but not on the other arthropods. Arthropod abundance and Coleoptera species richness were lowest when a mulcher was used compared to rotary or bar mowers. In addition to mowing, intensive grazing negatively affected Orthoptera abundance but not the other orders. Mowing represents a highly disturbing and iterative stressor with negative effects on arthropod abundance and diversity, likely contributed by mowing-induced mortality and habitat alteration. While modifications of mowing techniques such as mower type or mowing height and width may help to reduce the negative impact of mowing on arthropods, our results show that mowing itself has the most substantial negative effect. Based on our results, we suggest that reduced mowing frequency, omission of mowing in parts of the grassland (refuges), or extensive grazing instead of mowing have the greatest potential to promote arthropod populations.

AimTo determine the relationships between the functional trait composition of forest communities and environmental gradients across scales and biomes and the role of species relative abundances in these relationships.LocationGlobal.Time periodRecent.Major taxa studiedTrees.MethodsWe integrated species abundance records from worldwide forest inventories and associated functional traits (wood density, specific leaf area and seed mass) to obtain a data set of 99,953 to 149,285 plots (depending on the trait) spanning all forested continents. We computed community-weighted and unweighted means of trait values for each plot and related them to three broad environmental gradients and their interactions (energy availability, precipitation and soil properties) at two scales (global and biomes).ResultsOur models explained up to 60% of the variance in trait distribution. At global scale, the energy gradient had the strongest influence on traits. However, within-biome models revealed different relationships among biomes. Notably, the functional composition of tropical forests was more influenced by precipitation and soil properties than energy availability, whereas temperate forests showed the opposite pattern. Depending on the trait studied, response to gradients was more variable and proportionally weaker in boreal forests. Community unweighted means were better predicted than weighted means for almost all models.Main conclusionsWorldwide, trees require a large amount of energy (following latitude) to produce dense wood and seeds, while leaves with large surface to weight ratios are concentrated in temperate forests. However, patterns of functional composition within-biome differ from global patterns due to biome specificities such as the presence of conifers or unique combinations of climatic and soil properties. We recommend assessing the sensitivity of tree functional traits to environmental changes in their geographic context. Furthermore, at a given site, the distribution of tree functional traits appears to be driven more by species presence than species abundance.

AimEcological and anthropogenic factors shift the abundances of dominant and rare tree species within local forest communities, thus affecting species composition and ecosystem functioning. To inform forest and conservation management it is important to understand the drivers of dominance and rarity in local tree communities. We answer the following research questions: (1) What are the patterns of dominance and rarity in tree communities? (2) Which ecological and anthropogenic factors predict these patterns? And (3) what is the extinction risk of locally dominant and rare tree species?LocationGlobal.Time period1990-2017.Major taxa studiedTrees.MethodsWe used 1.2 million forest plots and quantified local tree dominance as the relative plot basal area of the single most dominant species and local rarity as the percentage of species that contribute together to the least 10% of plot basal area. We mapped global community dominance and rarity using machine learning models and evaluated the ecological and anthropogenic predictors with linear models. Extinction risk, for example threatened status, of geographically widespread dominant and rare species was evaluated.ResultsCommunity dominance and rarity show contrasting latitudinal trends, with boreal forests having high levels of dominance and tropical forests having high levels of rarity. Increasing annual precipitation reduces community dominance, probably because precipitation is related to an increase in tree density and richness. Additionally, stand age is positively related to community dominance, due to stem diameter increase of the most dominant species. Surprisingly, we find that locally dominant and rare species, which are geographically widespread in our data, have an equally high rate of elevated extinction due to declining populations through large-scale land degradation.Main conclusionsBy linking patterns and predictors of community dominance and rarity to extinction risk, our results suggest that also widespread species should be considered in large-scale management and conservation practices.

AbstractTropical montane forest ecosystems are pivotal for sustaining biodiversity and essential terrestrial ecosystem services, including the provision of high-quality fresh water. Nonetheless, the impact of montane deforestation and climate change on the capacity of forests to deliver ecosystem services is yet to be fully understood. In this study, we offer observational evidence demonstrating the response of air temperature and cloud base height to deforestation in African montane forests over the last two decades. Our findings reveal that approximately 18% (7.4 ± 0.5 million hectares) of Africa’s montane forests were lost between 2003 and 2022. This deforestation has led to a notable increase in maximum air temperature (1.37 ± 0.58 °C) and cloud base height (236 ± 87 metres), surpassing shifts attributed solely to climate change. Our results call for urgent attention to montane deforestation, as it poses serious threats to biodiversity, water supply, and ecosystem services in the tropics.