Weather or not-Global climate databases: Reliable on tropical mountains?

Global, spatially interpolated climate datasets such as WorldClim and CHELSA, widely used in research, are based on station data, which are rare in tropical mountains. However, such biodiversity hotspots are of high ecological interest and require accurate data. Therefore, the quality of such gridded datasets needs to be assessed. This poses a kind of dilemma, as proving the reliability of these potentially weakly modelled data is usually not possible due to the lack of stations. Using a unique climate dataset with 170 stations, mainly from the montane and alpine zones of sixteen mountains in Tanzania including Kilimanjaro, we show that the accuracy of such datasets is very poor. Not only is the maximum amount of mean annual precipitation drastically underestimated (partly more than 50%), but also the elevation of the precipitation maximum deviates up to 850m. Our results show that, at least in tropical regions, they should be used with greater caution than before.

Diurnal temperature range as a key predictor of plants' elevation ranges globally.

A prominent hypothesis in ecology is that larger species ranges are found in more variable climates because species develop broader environmental tolerances, predicting a positive range size-temperature variability relationship. However, this overlooks the extreme temperatures that variable climates impose on species, with upper or lower thermal limits more likely to be exceeded. Accordingly, we propose the 'temperature range squeeze' hypothesis, predicting a negative range size-temperature variability relationship. We test these contrasting predictions by relating 88,000 elevation range sizes of vascular plants in 44 mountains to short- and long-term temperature variation. Consistent with our hypothesis, we find that species' range size is negatively correlated with diurnal temperature range. Accurate predictions of short-term temperature variation will become increasingly important for extinction risk assessment in the future.

Effects of land-use change and disturbance on the fine root biomass, dynamics, morphology, and related C and N fluxes to the soil of forest ecosystems at different elevations at Mt. Kilimanjaro (Tanzania).

Tropical forests are threatened by anthropogenic activities such as conversion into agricultural land, logging and fires. Land-use change and disturbance affect ecosystems not only aboveground, but also belowground including the ecosystems' carbon and nitrogen cycle. We studied the impact of different types of land-use change (intensive and traditional agroforestry, logging) and disturbance by fire on fine root biomass, dynamics, morphology, and related C and N fluxes to the soil via fine root litter across different ecosystems at different elevational zones at Mt. Kilimanjaro (Tanzania). We found a decrease in fine root biomass (80-90%), production (50%), and C and N fluxes to the soil via fine root litter (60-80%) at all elevation zones. The traditional agroforestry 'Chagga homegardens' (lower montane zone) showed enhanced fine root turnover rates, higher values of acquisitive root morphological traits, but similar stand fine root production, C and N fluxes compared to the natural forest. The decrease of C and N fluxes with forest disturbance was particularly strong at the upper montane zone (60 and 80% decrease, respectively), where several patches of Podocarpus forest had been disturbed by fire in the previous years. We conclude that changes on species composition, stand structure and land management practices resulting from land-use change and disturbance have a strong impact on the fine root system, modifying fine root biomass, production and the C and N supply to the soil from fine root litter, which strongly affects the ecosystems' C and N cycle in those East African tropical forest ecosystems.

The Lichen Genus Sticta (Lobariaceae, Peltigerales) in East African Montane Ecosystems.

The lichen flora of Africa is still poorly known. In many parts of the tropics, recent studies utilizing DNA methods have revealed extraordinary diversity among various groups of lichenized fungi, including the genus Sticta. In this study, East African Sticta species and their ecology are reviewed using the genetic barcoding marker nuITS and morphological characters. The studied regions represent montane areas in Kenya and Tanzania, including the Taita Hills and Mt. Kilimanjaro, which belong to the Eastern Afromontane biodiversity hotspot. Altogether 14 Sticta species are confirmed from the study region, including the previously reported S. fuliginosa, S. sublimbata, S. tomentosa, and S. umbilicariiformis. Sticta andina, S. ciliata, S. duplolimbata, S. fuliginoides, and S. marginalis are reported as new to Kenya and/or Tanzania. Sticta afromontana, S. aspratilis, S. cellulosa, S. cyanocaperata, and S. munda, are described as new to science. The abundance of new diversity detected and the number of taxa represented by only few specimens show that more comprehensive sampling of the region may be needed to reveal the true diversity of Sticta in East Africa. More generally, our results highlight the need for further taxonomic studies of lichenized fungi in the region.

The potential impact of future climate change on the production of a major food and cash crop in tropical (sub)montane homegardens.

Tropical agroforestry systems support the wellbeing of many smallholder farmers. These systems provide smallholders with crops for consumption and income through their ecological interactions between their tree, soil, and crop components. These interactions, however, could be vulnerable to changes in climate conditions; yet a reliable understanding of how this could happen is not well documented. The aim of this study is to understand how tree-soil-crop interactions and crop yield are affected by changes in climate conditions, which has implications for recognising how these systems could be affected by climate change. We used a space-for-time climate analogue approach, in conjunction with structural equation modelling, to empirically examine how warmer and drier climate conditions affects tree-soil-crop interactions and banana yield in Mt. Kilimanjaro's homegarden agroforest. Overall, the change in climate conditions negatively affected ecological interactions in the homegardens by destabilizing soil nutrient cycles. Banana yield, however, was mainly directly influenced by the climate. Banana yields could initially benefit from the warmer climate before later declining under water stress. Our findings imply that under increasingly warmer and drier climate conditions, homegarden agroforestry may not be a robust long-term farming practice which can protect smallholder's wellbeing unless effective irrigation measures are implemented.

The contribution of insects to global forest deadwood decomposition.

The amount of carbon stored in deadwood is equivalent to about 8 per cent of the global forest carbon stocks1. The decomposition of deadwood is largely governed by climate2-5 with decomposer groups-such as microorganisms and insects-contributing to variations in the decomposition rates2,6,7. At the global scale, the contribution of insects to the decomposition of deadwood and carbon release remains poorly understood7. Here we present a field experiment of wood decomposition across 55 forest sites and 6 continents. We find that the deadwood decomposition rates increase with temperature, and the strongest temperature effect is found at high precipitation levels. Precipitation affects the decomposition rates negatively at low temperatures and positively at high temperatures. As a net effect-including the direct consumption by insects and indirect effects through interactions with microorganisms-insects accelerate the decomposition in tropical forests (3.9% median mass loss per year). In temperate and boreal forests, we find weak positive and negative effects with a median mass loss of 0.9 per cent and -0.1 per cent per year, respectively. Furthermore, we apply the experimentally derived decomposition function to a global map of deadwood carbon synthesized from empirical and remote-sensing data, obtaining an estimate of 10.9 ± 3.2 petagram of carbon per year released from deadwood globally, with 93 per cent originating from tropical forests. Globally, the net effect of insects may account for 29 per cent of the carbon flux from deadwood, which suggests a functional importance of insects in the decomposition of deadwood and the carbon cycle.

Species richness is more important for ecosystem functioning than species turnover along an elevational gradient.

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.

High aboveground carbon stock of African tropical montane forests.

Tropical forests store 40-50 per cent of terrestrial vegetation carbon1. However, spatial variations in aboveground live tree biomass carbon (AGC) stocks remain poorly understood, in particular in tropical montane forests2. Owing to climatic and soil changes with increasing elevation3, AGC stocks are lower in tropical montane forests compared with lowland forests2. Here we assemble and analyse a dataset of structurally intact old-growth forests (AfriMont) spanning 44 montane sites in 12 African countries. We find that montane sites in the AfriMont plot network have a mean AGC stock of 149.4 megagrams of carbon per hectare (95% confidence interval 137.1-164.2), which is comparable to lowland forests in the African Tropical Rainforest Observation Network4 and about 70 per cent and 32 per cent higher than averages from plot networks in montane2,5,6 and lowland7 forests in the Neotropics, respectively. Notably, our results are two-thirds higher than the Intergovernmental Panel on Climate Change default values for these forests in Africa8. We find that the low stem density and high abundance of large trees of African lowland forests4 is mirrored in the montane forests sampled. This carbon store is endangered: we estimate that 0.8 million hectares of old-growth African montane forest have been lost since 2000. We provide country-specific montane forest AGC stock estimates modelled from our plot network to help to guide forest conservation and reforestation interventions. Our findings highlight the need for conserving these biodiverse9,10 and carbon-rich ecosystems.

Metagenomic insights into soil microbial communities involved in carbon cycling along an elevation climosequences.

Diversity and community composition of soil microorganisms along the elevation climosequences have been widely studied, while the microbial metabolic potential, particularly in regard to carbon (C) cycling, remains unclear. Here, a metagenomic analysis of C related genes along five elevations ranging from 767 to 4190 m at Mount Kilimanjaro was analysed to evaluate the microbial organic C transformation capacities in various ecosystems. The highest gene abundances for decomposition of moderate mineralizable compounds, i.e. carbohydrate esters, chitin and pectin were found at the mid-elevations with hump-shaped pattern, where the genes for decompositions of recalcitrant C (i.e. lignin) and easily mineralizable C (i.e. starch) showed the opposite trend (i.e. U-shaped pattern), due to high soil pH and seasonality in both low and high elevations. Notably, the gene abundances for the decompositions of starch, carbohydrate esters, chitin and lignin had positive relationships with corresponding C compounds, indicating the consistent responses of microbial functional profiles and metabolites to elevation climosequences. Understanding of adaptation of microbial communities, potential function and metabolites to elevation climosequences and their influencing factors provided a new insight for the regulation of terrestrial C storage.

Climate implications on forest above- and belowground carbon allocation patterns along a tropical elevation gradient on Mt. Kilimanjaro (Tanzania).

Tropical forests represent the largest store of terrestrial biomass carbon (C) on earth and contribute over-proportionally to global terrestrial net primary productivity (NPP). How climate change is affecting NPP and C allocation to tree components in forests is not well understood. This is true for tropical forests, but particularly for African tropical forests. Studying forest ecosystems along elevation and related temperature and moisture gradients is one possible approach to address this question. However, the inclusion of belowground productivity data in such studies is scarce. On Mt. Kilimanjaro (Tanzania), we studied aboveground (wood increment, litter fall) and belowground (fine and coarse root) NPP along three elevation transects (c. 1800-3900 m a.s.l.) across four tropical montane forest types to derive C allocation to the major tree components. Total NPP declined continuously with elevation from 8.5 to 2.8 Mg C ha-1 year-1 due to significant decline in aboveground NPP, while fine root productivity (sequential coring approach) remained unvaried with around 2 Mg C ha-1 year-1, indicating a marked shift in C allocation to belowground components with elevation. The C and N fluxes to the soil via root litter were far more important than leaf litter inputs in the subalpine Erica forest. Thus, the shift of C allocation to belowground organs with elevation at Mt. Kilimanjaro and other tropical forests suggests increasing nitrogen limitation of aboveground tree growth at higher elevations. Our results show that studying fine root productivity is crucial to understand climate effects on the carbon cycle in tropical forests.

Diversity of Leptogium (Collemataceae, Ascomycota) in East African Montane Ecosystems.

Tropical mountains and especially their forests are hot spots of biodiversity threatened by human population pressure and climate change. The diversity of lichens in tropical Africa is especially poorly known. Here we use the mtSSU and nuITS molecular markers together with morphology and ecology to assess Leptogium (Peltigerales, Ascomycota) diversity in the tropical mountains of Taita Hills and Mt. Kasigau in Kenya and Mt. Kilimanjaro in Tanzania. The sampled habitats cover a wide range of ecosystems from savanna to alpine heath vegetation and from relatively natural forests to agricultural environments and plantation forests. We demonstrate that Leptogium diversity in Africa is much higher than previously known and provide preliminary data on over 70 putative species, including nine established species previously known from the area and over 60 phylogenetically, morphologically, and/or ecologically defined Operational Taxonomic Units (OTUs). Many traditional species concepts are shown to represent morphotypes comprised of several taxa. Many of the species were only found from specific ecosystems and/or restricted habitats and are thus threatened by ongoing habitat fragmentation and degradation of the natural environment. Our results emphasize the importance of molecular markers in species inventories of highly diverse organism groups and geographical areas.

Contrasting patterns and drivers of soil bacterial and fungal diversity across a mountain gradient.

Microbial elevational diversity patterns have been extensively studied, but their shaping mechanisms remain to be explored. Here, we examined soil bacterial and fungal diversity and community compositions across a 3.4 km elevational gradient (consists of five elevations) on Mt. Kilimanjaro located in East Africa. Bacteria and fungi had different diversity patterns across this extensive mountain gradient-bacterial diversity had a U shaped pattern while fungal diversity monotonically decreased. Random forest analysis revealed that pH (12.61% importance) was the most important factor affecting bacterial diversity, whereas mean annual temperature (9.84% importance) had the largest impact on fungal diversity, which was consistent with results obtained from mixed-effects model. Meanwhile, the diversity patterns and drivers of those diversity patterns differ among taxonomic groups (phyla/classes) within bacterial or fungal communities. Taken together, our study demonstrated that bacterial and fungal diversity and community composition responded differently to climate and edaphic properties along an extensive mountain gradient, and suggests that the elevational diversity patterns across microbial groups are determined by distinct environmental variables. These findings enhanced our understanding of the formation and maintenance of microbial diversity along elevation, as well as microbial responses to climate change in montane ecosystems.

Biomass, Morphology, and Dynamics of the Fine Root System Across a 3,000-M Elevation Gradient on Mt. Kilimanjaro.

Fine roots (≤2 mm) consume a large proportion of photosynthates and thus play a key role in the global carbon cycle, but our knowledge about fine root biomass, production, and turnover across environmental gradients is insufficient, especially in tropical ecosystems. Root system studies along elevation transects can produce valuable insights into root trait-environment relationships and may help to explore the evidence for a root economics spectrum (RES) that should represent a trait syndrome with a trade-off between resource acquisitive and conservative root traits. We studied fine root biomass, necromass, production, and mean fine root lifespan (the inverse of fine root turnover) of woody plants in six natural tropical ecosystems (savanna, four tropical mountain forest types, tropical alpine heathland) on the southern slope of Mt. Kilimanjaro (Tanzania) between 900 and 4,500 m a.s.l. Fine root biomass and necromass showed a unimodal pattern along the slope with a peak in the moist upper montane forest (~2,800 m), while fine root production varied little between savanna and upper montane forest to decrease toward the alpine zone. Root:shoot ratio (fine root biomass and production related to aboveground biomass) in the tropical montane forest increased exponentially with elevation, while it decreased with precipitation and soil nitrogen availability (decreasing soil C:N ratio). Mean fine root lifespan was lowest in the ecosystems with pronounced resource limitation (savanna at low elevation, alpine heathland at high elevation) and higher in the moist and cool forest belt (~1,800-3,700 m). The variation in root traits across the elevation gradient fits better with the concept of a multi-dimensional RES, as root tissue density and specific root length showed variable relations to each other, which does not agree with a simple trade-off between acquisitive and conservative root traits. In conclusion, despite large variation in fine root biomass, production, and morphology among the different plant species and ecosystems, a general belowground shift in carbohydrate partitioning is evident from 900 to 4,500 m a.s.l., suggesting that plant growth is increasingly limited by nutrient (probably N) shortage toward higher elevations.

Specialization of plant-pollinator interactions increases with temperature at Mt. Kilimanjaro.

AIM: Species differ in their degree of specialization when interacting with other species, with significant consequences for the function and robustness of ecosystems. In order to better estimate such consequences, we need to improve our understanding of the spatial patterns and drivers of specialization in interaction networks. METHODS: Here, we used the extensive environmental gradient of Mt. Kilimanjaro (Tanzania, East Africa) to study patterns and drivers of specialization, and robustness of plant-pollinator interactions against simulated species extinction with standardized sampling methods. We studied specialization, network robustness and other network indices of 67 quantitative plant-pollinator networks consisting of 268 observational hours and 4,380 plant-pollinator interactions along a 3.4 km elevational gradient. Using path analysis, we tested whether resource availability, pollinator richness, visitation rates, temperature, and/or area explain average specialization in pollinator communities. We further linked pollinator specialization to different pollinator taxa, and species traits, that is, proboscis length, body size, and species elevational ranges. RESULTS: We found that specialization decreased with increasing elevation at different levels of biological organization. Among all variables, mean annual temperature was the best predictor of average specialization in pollinator communities. Specialization differed between pollinator taxa, but was not related to pollinator traits. Network robustness against simulated species extinctions of both plants and pollinators was lowest in the most specialized interaction networks, that is, in the lowlands. CONCLUSIONS: Our study uncovers patterns in plant-pollinator specialization along elevational gradients. Mean annual temperature was closely linked to pollinator specialization. Energetic constraints, caused by short activity timeframes in cold highlands, may force ectothermic species to broaden their dietary spectrum. Alternatively or in addition, accelerated evolutionary rates might facilitate the establishment of specialization under warm climates. Despite the mechanisms behind the patterns have yet to be fully resolved, our data suggest that temperature shifts in the course of climate change may destabilize pollination networks by affecting network architecture.

Direct and plant-mediated effects of climate on bird diversity in tropical mountains.

AIM: Although patterns of biodiversity across the globe are well studied, there is still a controversial debate about the underlying mechanisms and their generality across biogeographic scales. In particular, it is unclear to what extent diversity patterns along environmental gradients are directly driven by abiotic factors, such as climate, or indirectly mediated through biotic factors, such as resource effects on consumers. LOCATION: Andes, Southern Ecuador; Mt. Kilimanjaro, Tanzania. METHODS: We studied the diversity of fleshy-fruited plants and avian frugivores at the taxonomic level, that is, species richness and abundance, as well as at the level of functional traits, that is, functional richness and functional dispersion. We compared two important biodiversity hotspots in mountain systems of the Neotropics and Afrotropics. We used field data of plant and bird communities, including trait measurements of 367 plant and bird species. Using structural equation modeling, we disentangled direct and indirect effects of climate and the diversity of plant communities on the diversity of bird communities. RESULTS: We found significant bottom-up effects of fruit diversity on frugivore diversity at the taxonomic level. In contrast, climate was more important for patterns of functional diversity, with plant communities being mostly related to precipitation, and bird communities being most strongly related to temperature. MAIN CONCLUSIONS: Our results illustrate the general importance of bottom-up mechanisms for the taxonomic diversity of consumers, suggesting the importance of active resource tracking. Our results also suggest that it might be difficult to identify signals of ecological fitting between functional plant and animal traits across biogeographic regions, since different species groups may respond to different climatic drivers. This decoupling between resource and consumer communities could increase under future climate change if plant and animal communities are consistently related to distinct climatic drivers.

Eleven years' data of grassland management in Germany.

BACKGROUND: The 150 grassland plots were located in three study regions in Germany, 50 in each region. The dataset describes the yearly grassland management for each grassland plot using 116 variables.General information includes plot identifier, study region and survey year. Additionally, grassland plot characteristics describe the presence and starting year of drainage and whether arable farming had taken place 25 years before our assessment, i.e. between 1981 and 2006. In each year, the size of the management unit is given which, in some cases, changed slightly across years.Mowing, grazing and fertilisation were systematically surveyed: Mowing is characterised by mowing frequency (i.e. number of cuts per year), dates of cutting and different technical variables, such as type of machine used or usage of conditioner.For grazing , the livestock species and age (e.g. cattle, horse, sheep), the number of animals, stocking density per hectare and total duration of grazing were recorded. As a derived variable, the mean grazing intensity was then calculated by multiplying the livestock units with the duration of grazing per hectare [LSU days/ha]. Different grazing periods during a year, partly involving different herds, were summed up to an annual grazing intensity for each grassland.For fertilisation , information on the type and amount of different types of fertilisers was recorded separately for mineral and organic fertilisers, such as solid farmland manure, slurry and mash from a bioethanol factory. Our fertilisation measures neglect dung dropped by livestock during grazing. For each type of fertiliser, we calculated its total nitrogen content, derived from chemical analyses by the producer or agricultural guidelines (Table 3).All three management types, mowing, fertilisation and grazing, were used to calculate a combined land use intensity index (LUI) which is frequently used to define a measure for the land use intensity. Here, fertilisation is expressed as total nitrogen per hectare [kg N/ha], but does not consider potassium and phosphorus.Information on additional management practices in grasslands was also recorded including levelling, to tear-up matted grass covers, rolling, to remove surface irregularities, seed addition, to close gaps in the sward. NEW INFORMATION: Investigating the relationship between human land use and biodiversity is important to understand if and how humans affect it through the way they manage the land and to develop sustainable land use strategies. Quantifying land use (the 'X' in such graphs) can be difficult as humans manage land using a multitude of actions, all of which may affect biodiversity, yet most studies use rather simple measures of land use, for example, by creating land use categories such as conventional vs. organic agriculture. Here, we provide detailed data on grassland management to allow for detailed analyses and the development of land use theory. The raw data have already been used for > 100 papers on the effect of management on biodiversity (e.g. Manning et al. 2015).

Climate-land-use interactions shape tropical mountain biodiversity and ecosystem functions.

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.

Plant and animal functional diversity drive mutualistic network assembly across an elevational gradient.

Species' functional traits set the blueprint for pair-wise interactions in ecological networks. Yet, it is unknown to what extent the functional diversity of plant and animal communities controls network assembly along environmental gradients in real-world ecosystems. Here we address this question with a unique dataset of mutualistic bird-fruit, bird-flower and insect-flower interaction networks and associated functional traits of 200 plant and 282 animal species sampled along broad climate and land-use gradients on Mt. Kilimanjaro. We show that plant functional diversity is mainly limited by precipitation, while animal functional diversity is primarily limited by temperature. Furthermore, shifts in plant and animal functional diversity along the elevational gradient control the niche breadth and partitioning of the respective other trophic level. These findings reveal that climatic constraints on the functional diversity of either plants or animals determine the relative importance of bottom-up and top-down control in plant-animal interaction networks.

Broken bridges: The isolation of Kilimanjaro's ecosystem.

Biodiversity studies of global change mainly focus on direct impacts such as losses in species numbers or ecosystem functions. In this study, we focus on the long-term effects of recent land-cover conversion and subsequent ecological isolation of Kilimanjaro on biodiversity in a paleobiogeographical context, linking our findings with the long-standing question whether colonization of African mountains mainly depended on long-distance dispersal, or whether gradual migration has been possible through habitat bridges under colder climates. For this, we used Orthoptera as bioindicators, whose patterns of endemism and habitat demands we studied on about 500 vegetation plots on Kilimanjaro and Mt. Meru (Tanzania) since 1996. Land-cover changes in the same area were revealed using a supervised classification of Landsat images from 1976 to 2000. In 1976, there was a corridor of submontane forest vegetation linking Kilimanjaro with Mt. Meru, replaced by human settlements and agriculture after 2000. Until recently, this submontane forest bridge facilitated the dispersal of forest animals, illustrated by the large number of endemic submontane forest Orthoptera shared by both mountains. Furthermore, the occurrence of common montane endemics suggests the existence of a former forest corridor with montane vegetation during much earlier times under climatic conditions 2-7°C cooler and 400-1,700 mm wetter than today. Based on the endemicity patterns of forest Orthoptera, negative consequences are predicted due to the effects of isolation, in particular for larger forest animals. Kilimanjaro is becoming an increasingly isolated ecosystem with far reaching consequences for diversity and endemism. Forest bridges between East African mountains acted as important migratory corridors and are not only a prehistoric phenomenon during periods with other climatic conditions but also disappeared in some places recently due to increasing and direct anthropogenic impact.