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Agriculture and the exploitation of natural resources have transformed tropical mountain ecosystems across the world, and the consequences of these transformations for biodiversity and ecosystem functioning are largely unknown1-3. Conclusions that are derived from studies in non-mountainous areas are not suitable for predicting the effects of land-use changes on tropical mountains because the climatic environment rapidly changes with elevation, which may mitigate or amplify the effects of land use4,5. It is of key importance to understand how the interplay of climate and land use constrains biodiversity and ecosystem functions to determine the consequences of global change for mountain ecosystems. Here we show that the interacting effects of climate and land use reshape elevational trends in biodiversity and ecosystem functions on Africa's largest mountain, Mount Kilimanjaro (Tanzania). We find that increasing land-use intensity causes larger losses of plant and animal species richness in the arid lowlands than in humid submontane and montane zones. Increases in land-use intensity are associated with significant changes in the composition of plant, animal and microorganism communities; stronger modifications of plant and animal communities occur in arid and humid ecosystems, respectively. Temperature, precipitation and land use jointly modulate soil properties, nutrient turnover, greenhouse gas emissions, plant biomass and productivity, as well as animal interactions. Our data suggest that the response of ecosystem functions to land-use intensity depends strongly on climate; more-severe changes in ecosystem functioning occur in the arid lowlands and the cold montane zone. Interactions between climate and land use explained-on average-54% of the variation in species richness, species composition and ecosystem functions, whereas only 30% of variation was related to single drivers. Our study reveals that climate can modulate the effects of land use on biodiversity and ecosystem functioning, and points to a lowered resistance of ecosystems in climatically challenging environments to ongoing land-use changes in tropical mountainous regions.

Many experiments have shown that biodiversity enhances ecosystem functioning. However, we have little understanding of how environmental heterogeneity shapes the effect of diversity on ecosystem functioning and to what extent this diversity effect is mediated by variation in species richness or species turnover. This knowledge is crucial to scaling up the results of experiments from local to regional scales. Here we quantify the diversity effect and its components-that is, the contributions of variation in species richness and species turnover-for 22 ecosystem functions of microorganisms, plants and animals across 13 major ecosystem types on Mt Kilimanjaro, Tanzania. Environmental heterogeneity across ecosystem types on average increased the diversity effect from explaining 49% to 72% of the variation in ecosystem functions. In contrast to our expectation, the diversity effect was more strongly mediated by variation in species richness than by species turnover. Our findings reveal that environmental heterogeneity strengthens the relationship between biodiversity and ecosystem functioning and that species richness is a stronger driver of ecosystem functioning than species turnover. Based on a broad range of taxa and ecosystem functions in a non-experimental system, these results are in line with predictions from biodiversity experiments and emphasize that conserving biodiversity is essential for maintaining ecosystem functioning.

Agriculture and the exploitation of natural resources have transformed tropical mountain ecosystems across the world, and the consequences of these transformations for biodiversity and ecosystem functioning are largely unknown

Land-use intensification has consequences for biodiversity and ecosystem functioning, with various taxonomic groups differing widely in their sensitivity. As land-use intensification alters habitat structure and resource availability, both factors may contribute to explaining differences in animal species diversity. Within the local animal assemblages the flying vertebrates, bats and birds, provide important and partly complementary ecosystem functions. We tested how bats and birds respond to land-use intensification and compared abundance, species richness, and community composition across a land-use gradient including forest, traditional agroforests (home garden), coffee plantations and grasslands on Mount Kilimanjaro, Tanzania. Furthermore, we asked how sensitive different habitat and feeding guilds of bats and birds react to land-use intensification and the associated alterations in vegetation structure and food resource availability. In contrast to our expectations, land-use intensification had no negative effect on species richness and abundance of all birds and bats. However, some habitat and feeding guilds, in particular forest specialist and frugivorous birds, were highly sensitive to land-use intensification. Although the habitat guilds of both, birds and bats, depended on a certain degree of vegetation structure, total bat and bird abundance was mediated primarily by the availability of the respective food resources. Even though the highly structured southern slopes of Mount Kilimanjaro are able to maintain diverse bat and bird assemblages, the sensitivity of avian forest specialists against land-use intensification and the dependence of the bat and bird habitat guilds on a certain vegetation structure demonstrate that conservation plans should place special emphasis on these guilds.

In fragmented areas, the persistence of different species depends on their ability to use the surrounding matrix either as a corridor or as a foraging habitat. We assessed how species richness and abundance of Neotropical bats differ among forest fragments and rubber plantations under different management regimes. Our study site was located in a heterogeneous agricultural area in the Atlantic Forest of Bahia, northeastern Brazil. By combining mist netting and acoustic monitoring as complementary techniques, we caught 28 phyllostomid species and recorded 21 aerial insectivorous species, which either forage in open space or close to forests. Open space species were equally abundant and diverse in all land use types. In contrast, assemblages of phyllostomid and aerial insectivorous forest species differed significantly among habitats, with the highest species richness recorded in forest fragments. We identified a number of forest specialists in forest fragments, which indicates a relatively intact bat fauna. In intensively used rubber-cacao plantation, we found surprisingly high bat abundance and diversity, despite the shortage of resources for bats. Our results also indicate that patches of secondary vegetation around rubber plantations are important landscape features for bats and might contribute to the persistence of highly diverse bat assemblages. We suggest that bats do not perceive plantations as a hostile matrix, but probably use them as corridors between forest fragments and patches of secondary vegetation. Em áreas fragmentadas, a persistência de diferentes espécies depende da habilidade delas em usar a matriz ao redor como um corredor ou hábitat de forrageio. Nós avaliamos como a riqueza de espécies e abundância de morcegos neotropicais diferem entre fragmentos de mata e seringais sob diferentes regimes de manejo. Nossa área de estudo estava localizada em uma área agrícola heterogênea na Mata Atlântica da Bahia, nordeste do Brasil. Combinando capturas em redes com monitoramento acústico como técnicas complementares, capturamos 28 espécies de morcegos filostomídeos e 21 espécies de morcegos insetívoros aéreos, que forrageiam em espaço aberto ou perto de florestas. As espécies de espaço aberto foram igualmente abundantes e diversas em todas as categorias de uso da terra. Por outro lado, comunidades de filostomídeos e insetívoros aéreos de florestas diferiram significativamente entre hábitats, com a maior riqueza de espécies tendo sido registrada em fragmentos de mata. Identificamos muitos especialistas em florestas nos fragmentos de mata, o que sugere que a fauna de morcegos ainda está relativamente intacta. Em plantações mistas de cacau e seringais intensivamente usadas, encontramos uma abundância e riqueza de morcegos surpreendentemente altas, apesar da escassez de recursos para morcegos. Nossos resultados indicam que manchas de vegetação secundária ao redor de seringais são importantes elementos da paisagem para morcegos e podem contribuir para a persistência de comunidades altamente diversas. Sugerimos que morcegos não percebem as plantações como uma matriz hostil, mas provavelmente as usam como corredores entre fragmentos de mata e manchas de vegetação secundária.