Imperial College London

ProfessorRobertEwers

Faculty of Natural SciencesDepartment of Life Sciences (Silwood Park)

Professor of Ecology
 
 
 
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Contact

 

+44 (0)20 7594 2223r.ewers

 
 
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Location

 

1.4Centre for Population BiologySilwood Park

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Summary

 

Publications

Publication Type
Year
to

154 results found

Lyons-White J, Mikolo Yobo C, Ewers RM, Knight ATet al., 2022, Understanding zero deforestation and the High Carbon Stock Approach in a highly forested tropical country, Land Use Policy, Vol: 112, Pages: 1-12, ISSN: 0264-8377

“Zero deforestation” commitments are pledges by companies to avoid deforestation when producing palm oil. Zero deforestation can be implemented using the High Carbon Stock Approach (HCSA), a tool that distinguishes forests from degraded land which can be developed. In highly forested countries like Gabon, zero deforestation may conflict with national economic goals involving palm oil and other agricultural commodities. We investigated perspectives of stakeholders in Gabon about zero deforestation and the HCSA using Critical Systems Heuristics, a systems thinking methodology. In 25 interviews with government, NGOs, companies, and research institutions, and two focus groups with rural communities, we identified three contrasting perspectives on forest conservation and agro industrial development: international, national, and local. Zero deforestation represents an international perspective that marginalises issues from a national perspective. This may produce unintended consequences that undermine the legitimacy of zero deforestation, including conversion of Gabon’s savannahs and disincentives for sustainable business. From a local perspective, zero deforestation is embedded in an agro-industrial vision that may marginalise value judgments concerning forests and traditional livelihoods. Gabon’s National Land Use Plan could help reconcile the three perspectives but requires recognition by international standards. Adapting the HCSA to Gabon’s context should also be considered to promote legitimacy. Research is required to ensure proposed institutional arrangements deliver equitable multi-stakeholder participation in land-use planning. Gabon’s case shows the applicability of zero deforestation to all highly forested countries cannot be assumed. Improved international understanding of national contexts, and flexibility in applying “zero deforestation”, is important for designing effective and equitable international standard

Journal article

Lembrechts JJ, van den Hoogen J, Aalto J, Ashcroft MB, De Frenne P, Kemppinen J, Kopecký M, Luoto M, Maclean IMD, Crowther TW, Bailey JJ, Haesen S, Klinges DH, Niittynen P, Scheffers BR, Van Meerbeek K, Aartsma P, Abdalaze O, Abedi M, Aerts R, Ahmadian N, Ahrends A, Alatalo JM, Alexander JM, Nina Allonsius C, Altman J, Ammann C, Andres C, Andrews C, Ardö J, Arriga N, Arzac A, Aschero V, Assis RL, Johann Assmann J, Bader MY, Bahalkeh K, Barančok P, Barrio IC, Barros A, Barthel M, Basham EW, Bauters M, Bazzichetto M, Belelli Marchesini L, Bell MC, Benavides JC, Luis Benito Alonso J, Berauer BJ, Bjerke JW, Björk RG, Björkman MP, Björnsdóttir K, Blonder B, Boeckx P, Boike J, Bokhorst S, Brum BNS, Brůna J, Buchmann N, Buysse P, Luís Camargo J, Campoe OC, Candan O, Canessa R, Cannone N, Carbognani M, Carnicer J, Casanova-Katny A, Cesarz S, Chojnicki B, Choler P, Chown SL, Cifuentes EF, Čiliak M, Contador T, Convey P, Cooper EJ, Cremonese E, Curasi SR, Curtis R, Cutini M, Johan Dahlberg C, Daskalova GN, Angel de Pablo M, Della Chiesa S, Dengler J, Deronde B, Descombes P, Di Cecco V, Di Musciano M, Dick J, Dimarco RD, Dolezal J, Dorrepaal E, Dušek J, Eisenhauer N, Eklundh L, Erickson TE, Erschbamer B, Eugster W, Ewers RM, Exton DA, Fanin N, Fazlioglu F, Feigenwinter I, Fenu G, Ferlian O, Rosa Fernández Calzado M, Fernández-Pascual E, Finckh M, Finger Higgens R, Forte TGW, Freeman EC, Frei ER, Fuentes-Lillo E, García RA, García MB, Géron C, Gharun M, Ghosn D, Gigauri K, Gobin A, Goded I, Goeckede M, Gottschall F, Goulding K, Govaert S, Jessen Graae B, Greenwood S, Greiser C, Grelle A, Guénard B, Guglielmin M, Guillemot J, Haase P, Haider S, Halbritter AH, Hamid M, Hammerle A, Hampe A, Haugum SV, Hederová L, Heinesch B, Helfter C, Hepenstrick D, Herberich M, Herbst M, Hermanutz L, Hik DS, Hoffrén R, Homeier J, Hörtnagl L, Høye TT, Hrbacek F, Hylander K, Iwata H, Antoni Jackowicz-Korczynski M, Jactel H, Järveoja J, Jastrzębowski S, Jentsch A, Jiménez JJ, Jónsdóttir IS, Juckeret al., 2021, Global maps of soil temperature., Glob Chang Biol

Research in global change ecology relies heavily on global climatic grids derived from estimates of air temperature in open areas at around 2 m above the ground. These climatic grids do not reflect conditions below vegetation canopies and near the ground surface, where critical ecosystem functions occur and most terrestrial species reside. Here, we provide global maps of soil temperature and bioclimatic variables at a 1-km² resolution for 0-5 and 5-15 cm soil depth. These maps were created by calculating the difference (i.e., offset) between in-situ soil temperature measurements, based on time series from over 1200 1-km² pixels (summarized from 8500 unique temperature sensors) across all the world's major terrestrial biomes, and coarse-grained air temperature estimates from ERA5-Land (an atmospheric reanalysis by the European Centre for Medium-Range Weather Forecasts). We show that mean annual soil temperature differs markedly from the corresponding gridded air temperature, by up to 10°C (mean = 3.0 ± 2.1°C), with substantial variation across biomes and seasons. Over the year, soils in cold and/or dry biomes are substantially warmer (+3.6 ± 2.3°C) than gridded air temperature, whereas soils in warm and humid environments are on average slightly cooler (-0.7 ± 2.3°C). The observed substantial and biome-specific offsets emphasize that the projected impacts of climate and climate change on near-surface biodiversity and ecosystem functioning are inaccurately assessed when air rather than soil temperature is used, especially in cold environments. The global soil-related bioclimatic variables provided here are an important step forward for any application in ecology and related disciplines. Nevertheless, we highlight the need to fill remaining geographic gaps by collecting more in-situ measurements of microclimate conditions to further enhance the spatiotemporal resolution of global soil temperature products for ecological ap

Journal article

Sethi SS, Ewers RM, Jones NS, Sleutel J, Shabrani A, Zulkifli N, Picinali Let al., 2021, Soundscapes predict species occurrence in tropical forests, OIKOS, Pages: 1-9, ISSN: 0030-1299

Accurate occurrence data is necessary for the conservation of keystone or endangered species, but acquiring it is usually slow, laborious and costly. Automated acoustic monitoring offers a scalable alternative to manual surveys but identifying species vocalisations requires large manually annotated training datasets, and is not always possible (e.g. for lesser studied or silent species). A new approach is needed that rapidly predicts species occurrence using smaller and more coarsely labelled audio datasets. We investigated whether local soundscapes could be used to infer the presence of 32 avifaunal and seven herpetofaunal species in 20 min recordings across a tropical forest degradation gradient in Sabah, Malaysia. Using acoustic features derived from a convolutional neural network (CNN), we characterised species indicative soundscapes by training our models on a temporally coarse labelled point-count dataset. Soundscapes successfully predicted the occurrence of 34 out of the 39 species across the two taxonomic groups, with area under the curve (AUC) metrics from 0.53 up to 0.87. The highest accuracies were achieved for species with strong temporal occurrence patterns. Soundscapes were a better predictor of species occurrence than above-ground carbon density – a metric often used to quantify habitat quality across forest degradation gradients. Our results demonstrate that soundscapes can be used to efficiently predict the occurrence of a wide variety of species and provide a new direction for data driven large-scale assessments of habitat suitability.

Journal article

Heath BE, Orme DS, Sethi CSL, Ewers RM, Picinali Let al., 2021, How index selection, compression, and recording schedule impact the description of ecological soundscapes, Evolutionary Ecology, Vol: 11, Pages: 13206-13217, ISSN: 0269-7653

Acoustic indices derived from environmental soundscape recordings are being used to monitor ecosystem health and vocal animal biodiversity. Soundscape data can quickly become very expensive and difficult to manage, so data compression or temporal down-sampling are sometimes employed to reduce data storage and transmission costs. These parameters vary widely between experiments, with the consequences of this variation remaining mostly unknown.We analyse field recordings from North-Eastern Borneo across a gradient of historical land use. We quantify the impact of experimental parameters (MP3 compression, recording length and temporal subsetting) on soundscape descriptors (Analytical Indices and a convolutional neural net derived AudioSet Fingerprint). Both descriptor types were tested for their robustness to parameter alteration and their usability in a soundscape classification task.We find that compression and recording length both drive considerable variation in calculated index values. However, we find that the effects of this variation and temporal subsetting on the performance of classification models is minor: performance is much more strongly determined by acoustic index choice, with Audioset fingerprinting offering substantially greater (12%–16%) levels of classifier accuracy, precision and recall.We advise using the AudioSet Fingerprint in soundscape analysis, finding superior and consistent performance even on small pools of data. If data storage is a bottleneck to a study, we recommend Variable Bit Rate encoded compression (quality = 0) to reduce file size to 23% file size without affecting most Analytical Index values. The AudioSet Fingerprint can be compressed further to a Constant Bit Rate encoding of 64 kb/s (8% file size) without any detectable effect. These recommendations allow the efficient use of restricted data storage whilst permitting comparability of results between different studies.

Journal article

Bowler E, Lefebvre VA, Pfeifer M, Ewers RMet al., 2021, Optimising sampling designs for habitat fragmentation studies, Methods in Ecology and Evolution, ISSN: 2041-210X

Habitat fragmentation has become one of the largest areas of research in conservation biology. Empirical studies into habitat fragmentation impacts typically measure ecological responses to metrics describing fragmentation processes, for example ‘distance to the nearest forest edge’, ‘forest fragment area’ and ‘landscape habitat amount’. However, these studies often fail to sample across representative ranges of fragmentation metrics characterising the study region. They therefore lack the data to account for correlation among multiple fragmentation metrics and for spatial autocorrelation among sample sites, which reduces the strength of derived predictive models.Here, we draw on approaches used in the mining and soil science industry to develop standardised and repeatable protocols for designing optimised sampling schemes of biodiversity in fragmented landscapes that meet three criteria: the distance between sample sites is maximised to reduce spatial autocorrelation, the full range of values of the metrics of interest are sampled and the confounding effects of correlated metrics are minimised.We show that our computational methods can optimise the placement of sample sites in fragmented landscapes to minimise, and in some cases to entirely avoid, over- or under-sampling of fragmentation metrics. Our method is flexible enough to cater for any continuous (e.g. maps of percentage tree cover) or categorical (e.g. habitat and land use types) fragmentation metric, and to simultaneously handle combinations of multiple fragmentation metrics and habitat types. We implement our methods as open-source code which includes options to mask invalid or inaccessible regions, update designs to adapt to unforeseen constraints in the field and suggest optimal numbers of sample sites for given design criteria.Using a case study landscape, we demonstrate how the approach improves on manually generated sampling designs. We also show that the methods a

Journal article

Milodowski DT, Coomes DA, Swinfield T, Jucker T, Riutta T, Malhi Y, Svatek M, Kvasnica J, Burslem DFRP, Ewers RM, Teh YA, Williams Met al., 2021, The impact of logging on vertical canopy structure across a gradient of tropical forest degradation intensity in Borneo, JOURNAL OF APPLIED ECOLOGY, Vol: 58, Pages: 1764-1775, ISSN: 0021-8901

Journal article

Huaraca Huasco W, Riutta T, Girardin CAJ, Hancco Pacha F, Puma Vilca BL, Moore S, Rifai SW, del Aguila-Pasquel J, Araujo Murakami A, Freitag R, Morel AC, Demissie S, Doughty CE, Oliveras I, Galiano Cabrera DF, Durand Baca L, Farfan Amezquita F, Silva Espejo JE, da Costa ACL, Oblitas Mendoza E, Quesada CA, Evouna Ondo F, Edzang Ndong J, Jeffery KJ, Mihindou V, White LJT, N'ssi Bengone N, Ibrahim F, Addo-Danso SD, Duah-Gyamfi A, Djaney Djagbletey G, Owusu-Afriyie K, Amissah L, Mbou AT, Marthews TR, Metcalfe DB, Aragao LEO, Marimon-Junior BH, Marimon BS, Majalap N, Adu-Bredu S, Abernethy KA, Silman M, Ewers RM, Meir P, Malhi Yet al., 2021, Fine root dynamics across pantropical rainforest ecosystems, Global Change Biology, Vol: 27, Pages: 3657-3680, ISSN: 1354-1013

Fine roots constitute a significant component of the net primary productivity (NPP) of forest ecosystems but are much less studied than aboveground NPP. Comparisons across sites and regions are also hampered by inconsistent methodologies, especially in tropical areas. Here, we present a novel dataset of fine root biomass, productivity, residence time, and allocation in tropical old-growth rainforest sites worldwide, measured using consistent methods, and examine how these variables are related to consistently determined soil and climatic characteristics. Our pantropical dataset spans intensive monitoring plots in lowland (wet, semi-deciduous, and deciduous) and montane tropical forests in South America, Africa, and Southeast Asia (n = 47). Large spatial variation in fine root dynamics was observed across montane and lowland forest types. In lowland forests, we found a strong positive linear relationship between fine root productivity and sand content, this relationship was even stronger when we considered the fractional allocation of total NPP to fine roots, demonstrating that understanding allocation adds explanatory power to understanding fine root productivity and total NPP. Fine root residence time was a function of multiple factors: soil sand content, soil pH, and maximum water deficit, with longest residence times in acidic, sandy, and water-stressed soils. In tropical montane forests, on the other hand, a different set of relationships prevailed, highlighting the very different nature of montane and lowland forest biomes. Root productivity was a strong positive linear function of mean annual temperature, root residence time was a strong positive function of soil nitrogen content in montane forests, and lastly decreasing soil P content increased allocation of productivity to fine roots. In contrast to the lowlands, environmental conditions were a better predictor for fine root productivity than for fractional allocation of total NPP to fine roots, suggesting t

Journal article

Ewers RM, Nathan SKSS, Lee PAK, 2021, African swine fever ravaging Borneo's wild pigs, NATURE, Vol: 593, Pages: 37-37, ISSN: 0028-0836

Journal article

Boyle MJW, Bishop TR, Luke SH, van Breugel M, Evans TA, Pfeifer M, Fayle TM, Hardwick SR, Lane-Shaw RI, Yusah KM, Ashford ICR, Ashford OS, Garnett E, Turner EC, Wilkinson CL, Chung AYC, Ewers RMet al., 2021, Localised climate change defines ant communities in human-modified tropical landscapes, Functional Ecology, Vol: 35, Pages: 1094-1108, ISSN: 0269-8463

Logging and habitat conversion create hotter microclimates in tropical forest landscapes, representing a powerful form of localised anthropogenic climate change. It is widely believed that these emergent conditions are responsible for driving changes in communities of organisms found in modified tropical forests, although the empirical evidence base for this is lacking.Here we investigated how interactions between the physiological traits of genera and the environmental temperatures they experience lead to functional and compositional changes in communities of ants, a key organism in tropical forest ecosystems.We found that the abundance and activity of ant genera along a gradient of forest disturbance in Sabah, Malaysian Borneo, was defined by an interaction between their thermal tolerance (CTmax) and environmental temperature. In more disturbed, warmer habitats, genera with high CTmax had increased relative abundance and functional activity, and those with low CTmax had decreased relative abundance and functional activity.This interaction determined abundance changes between primary and logged forest that differed in daily maximum temperature by a modest 1.1°C, and strengthened as the change in microclimate increased with disturbance. Between habitats that differed by 5.6°C (primary forest to oil palm) and 4.5°C (logged forest to oil palm), a 1°C difference in CTmax among genera led to a 23% and 16% change in relative abundance, and a 22% and 17% difference in functional activity. CTmax was negatively correlated with body size and trophic position, with ants becoming significantly smaller and less predatory as microclimate temperatures increased.Our results provide evidence to support the widely held, but never directly tested, assumption that physiological tolerances underpin the influence of disturbance‐induced microclimate change on the abundance and function of invertebrates in tropical landscapes.

Journal article

Nunes MH, Jucker T, Riutta T, Svatek M, Kvasnica J, Rejzek M, Matula R, Majalap N, Ewers RM, Swinfield T, Valbuena R, Vaughn NR, Asner GP, Coomes DAet al., 2021, Recovery of logged forest fragments in a human-modified tropical landscape during the 2015-16 El Nino, Nature Communications, Vol: 12, Pages: 1-11, ISSN: 2041-1723

The past 40 years in Southeast Asia have seen about 50% of lowland rainforests converted to oil palm and other plantations, and much of the remaining forest heavily logged. Little is known about how fragmentation influences recovery and whether climate change will hamper restoration. Here, we use repeat airborne LiDAR surveys spanning the hot and dry 2015-16 El Niño Southern Oscillation event to measure canopy height growth across 3,300 ha of regenerating tropical forests spanning a logging intensity gradient in Malaysian Borneo. We show that the drought led to increased leaf shedding and branch fall. Short forest, regenerating after heavy logging, continued to grow despite higher evaporative demand, except when it was located close to oil palm plantations. Edge effects from the plantations extended over 300 metres into the forests. Forest growth on hilltops and slopes was particularly impacted by the combination of fragmentation and drought, but even riparian forests located within 40 m of oil palm plantations lost canopy height during the drought. Our results suggest that small patches of logged forest within plantation landscapes will be slow to recover, particularly as ENSO events are becoming more frequent.

Journal article

Gray REJ, Ewers RM, 2021, Monitoring forest phenology in a changing world, Forests, Vol: 12, Pages: 1-24, ISSN: 1999-4907

Plant phenology is strongly interlinked with ecosystem processes and biodiversity. Like many other aspects of ecosystem functioning, it is affected by habitat and climate change, with both global change drivers altering the timings and frequency of phenological events. As such, there has been an increased focus in recent years to monitor phenology in different biomes. A range of approaches for monitoring phenology have been developed to increase our understanding on its role in ecosystems, ranging from the use of satellites and drones to collection traps, each with their own merits and limitations. Here, we outline the trade-offs between methods (spatial resolution, temporal resolution, cost, data processing), and discuss how their use can be optimised in different environments and for different goals. We also emphasise emerging technologies that will be the focus of monitoring in the years to follow and the challenges of monitoring phenology that still need to be addressed. We conclude that there is a need to integrate studies that incorporate multiple monitoring methods, allowing the strengths of one to compensate for the weaknesses of another, with a view to developing robust methods for upscaling phenological observations from point locations to biome and global scales and reconciling data from varied sources and environments. Such developments are needed if we are to accurately quantify the impacts of a changing world on plant phenology.

Journal article

Aguirre-Gutierrez J, Rifal S, Shenkin A, Oliveras I, Bentley LP, Svatek M, Girardin CAJ, Both S, Riutta T, Berenguer E, Kissling WD, Bauman D, Raab N, Moore S, Farfan-Rios W, Simoes Figueiredo AE, Reis SM, Ndong JE, Ondo FE, Bengone NN, Mihindou V, Moraes de Seixas MM, Adu-Bredu S, Abemethy K, Asner GP, Barlow J, Burstem DFRP, Coomes DA, Cernusak LA, Dargle GC, Enquist BJ, Ewers RM, Ferreira J, Jeffery KJ, Joly CA, Lewis SL, Marimon-Junior BH, Martin RE, Morandi PS, Phillips OL, Quesada CA, Salinas N, Marimon BS, Silman M, Teh YA, White LJT, Malhi Yet al., 2021, Pantropical modelling of canopy functional traits using Sentinel-2 remote sensing data, REMOTE SENSING OF ENVIRONMENT, Vol: 252, ISSN: 0034-4257

Journal article

Banks-Leite C, Ewers R, Folkard-Tapp H, Fraser Aet al., 2020, Countering the effects of habitat loss, fragmentation, and degradation through habitat restoration, One Earth, Vol: 3, Pages: 672-676, ISSN: 2590-3322

Habitat loss, fragmentation and degradation impacts are the most direct threat to global biodiversity. In this Primer, we discuss how these three forms of habitat transformation are inextricably intertwined, and how their effects on biodiversity and ecosystems are often context-specific. We draw on recent analyses that have explored this context-dependence directly, to discuss how local-scale impacts of habitat transformation are mediated by biogeographic-scale variation in evolutionary histories and species’ geographic ranges. We also discuss how changes to ecosystem functions and services in modified habitats can be just as context-dependent – and how these changes are further obscured by high levels of ecological redundancy in species functions, which can confer resilience to habitat transformation. To avoid the impending extinction of millions of species, it is crucial that the impacts of habitat transformation are mitigated through a combination of preventing further habitat loss while simultaneously extending and repairing the habitats that remain.

Journal article

Sethi S, Ewers R, Jones N, Signorelli A, Picinali L, Orme CDLet al., 2020, SAFE Acoustics: an open-source, real-time eco-acoustic monitoring network in the tropical rainforests of Borneo, Methods in Ecology and Evolution, Vol: 11, Pages: 1182-1185, ISSN: 2041-210X

1. Automated monitoring approaches offer an avenue to unlocking large‐scale insight into how ecosystems respond to human pressures. However, since data collection and data analyses are often treated independently, there are currently no open‐source examples of end‐to‐end, real‐time ecological monitoring networks. 2. Here, we present the complete implementation of an autonomous acoustic monitoring network deployed in the tropical rainforests of Borneo. Real‐time audio is uploaded remotely from the field, indexed by a central database, and delivered via an API to a public‐facing website.3. We provide the open‐source code and design of our monitoring devices, the central web2py database, and the ReactJS website. Furthermore, we demonstrate an extension of this infrastructure to deliver real‐time analyses of the eco‐acoustic data. 4. By detailing a fully functional, open source, and extensively tested design, our work will accelerate the rate at which fully autonomous monitoring networks mature from technological curiosities, and towards genuinely impactful tools in ecology.

Journal article

Sethi SS, Ewers RM, Jones NS, Sleutel J, Shabrani A, Zulkifli N, Picinali Let al., 2020, Soundscapes predict species occurrence in tropical forests, Publisher: Cold Spring Harbor Laboratory

Accurate occurrence data is necessary for the conservation of keystone or endangered species, but acquiring it is usually slow, laborious, and costly. Automated acoustic monitoring offers a scalable alternative to manual surveys, but identifying species vocalisations requires large manually annotated training datasets, and is not always possible (e.g., for silent species). A new, intermediate approach is needed that rapidly predicts species occurrence without requiring extensive labelled data.We investigated whether local soundscapes could be used to infer the presence of 32 avifaunal and seven herpetofaunal species across a tropical forest degradation gradient in Sabah, Malaysia. We developed a machine-learning based approach to characterise species indicative soundscapes, training our models on a coarsely labelled manual point-count dataset.Soundscapes successfully predicted the occurrence of 34 out of the 39 species across the two taxonomic groups, with area under the curve (AUC) metrics of up to 0.87 (Bold-striped Tit-babbler Macronus bornensis). The highest accuracies were achieved for common species with strong temporal occurrence patterns.Soundscapes were a better predictor of species occurrence than above-ground biomass – a metric often used to quantify habitat quality across forest degradation gradients.Synthesis and applications: Our results demonstrate that soundscapes can be used to efficiently predict the occurrence of a wide variety of species. This provides a new direction for audio data to deliver large-scale, accurate assessments of habitat suitability using cheap and easily obtained field datasets.

Working paper

Wilkinson CL, Chua KWJ, Fiala R, Liew JH, Kemp V, Hadi Fikri A, Ewers RM, Kratina P, Yeo DCJet al., 2020, Forest conversion to oil palm compresses food chain length in tropical streams., Ecology, Vol: 102, Pages: 1-10, ISSN: 0012-9658

In Southeast Asia, biodiversity-rich forests are being extensively logged and converted to oil palm monocultures. Although the impacts of these changes on biodiversity are largely well documented, we know little about how these large-scale impacts affect freshwater trophic ecology. We used stable isotope analyses (SIA) to determine the impacts of land-use changes on the relative contribution of allochthonous and autochthonous basal resources in 19 stream food webs. We also applied compound-specific SIA and bulk-SIA to determine the trophic position of fish apex predators and meso-predators (invertivores and omnivores). There was no difference in the contribution of autochthonous resources in either consumer group (70-82%) among streams with different land-use type. There was no change in trophic position for meso-predators, but trophic position decreased significantly for apex predators in oil palm plantation streams compared to forest streams. This change in maximum food chain length was due to turnover in identity of the apex predator among land-use types. Disruption of aquatic trophic ecology, through reduction in food chain length and shift in basal resources, may cause significant changes in biodiversity as well as ecosystem functions and services. Understanding this change can help develop more focused priorities for mediating the negative impacts of human activities on freshwater ecosystems.

Journal article

Wiederkehr F, Wilkinson CL, Zeng Y, Yeo DCJ, Ewers RM, O'Gorman EJet al., 2020, Urbanisation affects ecosystem functioning more than structure in tropical streams, Biological Conservation, Vol: 249, Pages: 1-19, ISSN: 0006-3207

Urbanisation poses a clear threat to tropical freshwater streams, yet fundamental knowledge gaps hinder our ability to effectively conserve stream biodiversity and preserve ecosystem functioning. Here, we studied the impact of urbanisation on structural and functional ecosystem responses in low-order streams in Singapore, a tropical city with a mosaic landscape of protected natural forests, managed buffer zones (between forest and open-country habitats), and built-up urban areas. We quantified an urbanisation gradient based on landscape, in-stream, and riparian conditions, and found an association between urbanisation and pollution-tolerant macroinvertebrates (e.g. freshwater snail and worm species) in litter bags. We also found greater macroinvertebrate abundance (mean individuals bag−1; forest: 30.3, buffer: 70.1, urban: 109.0) and richness (mean taxa bag−1; forest: 4.53, buffer: 4.75, urban: 7.50) in urban streams, but similar diversity across habitats. Higher levels of primary productivity (measured from algal accrual on ceramic tiles) and microbial decomposition (measured from litter-mass loss in mesh bags) at urban sites indicate rapid microbial activity at higher light, temperature, and nutrient levels. We found that urbanisation affected function 32% more than structure in the studied tropical streams, likely driven by greater algal growth in urban streams. These changes in ecological processes (i.e. ecosystem functioning) possibly lead to a loss of ecosystem services, which would negatively affect ecology, society, and economy. Our results point to possible management strategies (e.g. increasing vegetation density through buffer park creation) to reduce the impacts of urbanisation, restore vital ecosystem functions in tropical streams, and create habitat niches for native species.

Journal article

Muscarella R, Emilio T, Phillips OL, Lewis SL, Slik F, Baker WJ, Couvreur TLP, Eiserhardt WL, Svenning J, AffumBaffoe K, Aiba S, Almeida EC, Almeida SS, Oliveira EA, ÁlvarezDávila E, Alves LF, AlvezValles CM, Carvalho FA, Guarin FA, Andrade A, Aragão LEOC, Murakami AA, Arroyo L, Ashton PS, Corredor GAA, Baker TR, Camargo PB, Barlow J, Bastin J, Bengone NN, Berenguer E, Berry N, Blanc L, BöhningGaese K, Bonal D, Bongers F, Bradford M, Brambach F, Brearley FQ, Brewer SW, Camargo JLC, Campbell DG, Castilho CV, Castro W, Catchpole D, Cerón Martínez CE, Chen S, Chhang P, Cho P, Chutipong W, Clark C, Collins M, Comiskey JA, Medina MNC, Costa FRC, Culmsee H, DavidHiguita H, Davidar P, AguilaPasquel J, Derroire G, Di Fiore A, Van Do T, Doucet J, Dourdain A, Drake DR, Ensslin A, Erwin T, Ewango CEN, Ewers RM, Fauset S, Feldpausch TR, Ferreira J, Ferreira LV, Fischer M, Franklin J, Fredriksson GM, Gillespie TW, Gilpin M, Gonmadje C, Gunatilleke AUN, Hakeem KR, Hall JS, Hamer KC, Harris DJ, Harrison RD, Hector A, Hemp A, Herault B, Pizango CGH, Coronado ENH, Hubau W, Hussain MS, Ibrahim F, Imai N, Joly CA, Joseph S K A, Kartawinata K, Kassi J, Killeen TJ, Kitayama K, Klitgård BB, Kooyman R, Labrière N, Larney E, Laumonier Y, Laurance SG, Laurance WF, Lawes MJ, Levesley A, Lisingo J, Lovejoy T, Lovett JC, Lu X, Lykke AM, Magnusson WE, Mahayani NPD, Malhi Y, Mansor A, Peña JLM, MarimonJunior BH, Marshall AR, Melgaco K, Bautista CM, Mihindou V, Millet J, Milliken W, Mohandass D, Mendoza ALM, Mugerwa B, Nagamasu H, Nagy L, Seuaturien N, Nascimento MT, Neill DA, Neto LM, Nilus R, Vargas MPN, Nurtjahya E, Araújo RNO, Onrizal O, Palacios WA, PalaciosRamos S, Parren M, Paudel E, Morandi PS, Pennington RT, Pickavance G, Pipoly JJ, Pitman NCA, Poedjirahajoe E, Poorter L, Poulsen JR, Rama Chandra Prasad P, Prieto A, Puyravaud J, Qie L, Quesada CA, RamírezAngulo H, Razafimahaimodison JC, Reitsma JM, RequenaRojas EJ, Correa ZR, Rodriguez CR, Roopsind A, Rovero F, Rozak A, Lleraset al., 2020, The global abundance of tree palms, Global Ecology and Biogeography, Vol: 29, Pages: 1495-1514, ISSN: 1466-822X

AimPalms are an iconic, diverse and often abundant component of tropical ecosystems that provide many ecosystem services. Being monocots, tree palms are evolutionarily, morphologically and physiologically distinct from other trees, and these differences have important consequences for ecosystem services (e.g., carbon sequestration and storage) and in terms of responses to climate change. We quantified global patterns of tree palm relative abundance to help improve understanding of tropical forests and reduce uncertainty about these ecosystems under climate change.LocationTropical and subtropical moist forests.Time periodCurrent.Major taxa studiedPalms (Arecaceae).MethodsWe assembled a pantropical dataset of 2,548 forest plots (covering 1,191 ha) and quantified tree palm (i.e., ≥10 cm diameter at breast height) abundance relative to co‐occurring non‐palm trees. We compared the relative abundance of tree palms across biogeographical realms and tested for associations with palaeoclimate stability, current climate, edaphic conditions and metrics of forest structure.ResultsOn average, the relative abundance of tree palms was more than five times larger between Neotropical locations and other biogeographical realms. Tree palms were absent in most locations outside the Neotropics but present in >80% of Neotropical locations. The relative abundance of tree palms was more strongly associated with local conditions (e.g., higher mean annual precipitation, lower soil fertility, shallower water table and lower plot mean wood density) than metrics of long‐term climate stability. Life‐form diversity also influenced the patterns; palm assemblages outside the Neotropics comprise many non‐tree (e.g., climbing) palms. Finally, we show that tree palms can influence estimates of above‐ground biomass, but the magnitude and direction of the effect require additional work.ConclusionsTree palms are not only quintessentially tropical, but they are also overwhelmingly Neotropical. Futur

Journal article

Sethi S, Jones NS, Fulcher B, Picinali L, Clink DJ, Klinck H, Orme CDLO, Wrege P, Ewers Ret al., 2020, Characterising soundscapes across diverse ecosystems using a universal acoustic feature set, Proceedings of the National Academy of Sciences of USA, Vol: 117, Pages: 17049-17055, ISSN: 0027-8424

Natural habitats are being impacted by human pressures at an alarming rate. Monitoring these ecosystem-level changes often requires labor-intensive surveys that are unable to detect rapid or unanticipated environmental changes. Here we have developed a generalizable, data-driven solution to this challenge using eco-acoustic data. We exploited a convolutional neural network to embed soundscapes from a variety of ecosystems into a common acoustic space. In both supervised and unsupervised modes, this allowed us to accurately quantify variation in habitat quality across space and in biodiversity through time. On the scale of seconds, we learned a typical soundscape model that allowed automatic identification of anomalous sounds in playback experiments, providing a potential route for real-time automated detection of irregular environmental behavior including illegal logging and hunting. Our highly generalizable approach, and the common set of features, will enable scientists to unlock previously hidden insights from acoustic data and offers promise as a backbone technology for global collaborative autonomous ecosystem monitoring efforts.

Journal article

Gregory N, 2020, Vectorial capacity across an environmental gradient

Disease transmitted by mosquitoes present some of the most pressing challenges facing human health today. Land-use change is a key driver of disease emergence, however the mechanisms linking environmental covariates of change, such as temperature, to the transmission potential of mosquitoes is poorly understood. Studies exploring these relationships have largely been correlative in nature, and thus have limited capacity to predict dynamics through space and time. Mechanistic approaches provide a valuable framework for understanding the processes underlying transmission, however they suffer from a dearth of field data on fundamental mosquito ecology. In both approaches, the environmental data used is typically coarse in scale and interpolated from weather stations located in open areas. In reality, local climatic conditions can vary considerably over fine spatial and temporal scales, particularly in dynamic working landscapes. Wild mosquitoes experience and respond to this highly dynamic environment, and failing to account for this variation may have significant implications for the accuracy of epidemiological models. This thesis uses an established epidemiological framework to explore the effects of tropical forest conversion to oil palm plantation on the potential for Ae. albopictus mosquitoes to transmit disease. Using field-derived microclimate data and published thermal responses of mosquito traits, I first examine how the scale of environmental data affects predictions of mosquito demography under land-use change. Next, I conduct field experiments to investigate whether microclimate heterogeneity across a land-use gradient drives variation in the rates of larval development. By pairing fine-scale microclimate data with temperature-dependent trait estimates, I find that forest conversion significantly increases the potential of Ae. albopictus to transmit disease. Together, these findings advance our understanding of Ae. albopictus ecology, and highlight the impo

Thesis dissertation

Gregory N, 2020, Vectorial capacity across an environmental gradient

Disease transmitted by mosquitoes present some of the most pressing challenges facing human health today. Land-use change is a key driver of disease emergence, however the mechanisms linking environmental covariates of change, such as temperature, to the transmission potential of mosquitoes is poorly understood. Studies exploring these relationships have largely been correlative in nature, and thus have limited capacity to predict dynamics through space and time. Mechanistic approaches provide a valuable framework for understanding the processes underlying transmission, however they suffer from a dearth of field data on fundamental mosquito ecology. In both approaches, the environmental data used is typically coarse in scale and interpolated from weather stations located in open areas. In reality, local climatic conditions can vary considerably over fine spatial and temporal scales, particularly in dynamic working landscapes. Wild mosquitoes experience and respond to this highly dynamic environment, and failing to account for this variation may have significant implications for the accuracy of epidemiological models. This thesis uses an established epidemiological framework to explore the effects of tropical forest conversion to oil palm plantation on the potential for Ae. albopictus mosquitoes to transmit disease. Using field-derived microclimate data and published thermal responses of mosquito traits, I first examine how the scale of environmental data affects predictions of mosquito demography under land-use change. Next, I conduct field experiments to investigate whether microclimate heterogeneity across a land-use gradient drives variation in the rates of larval development. By pairing fine-scale microclimate data with temperature-dependent trait estimates, I find that forest conversion significantly increases the potential of Ae. albopictus to transmit disease. Together, these findings advance our understanding of Ae. albopictus ecology, and highlight the impo

Thesis dissertation

Swinfield T, Both S, Riutta T, Bongalov B, Elias D, Majalap-Lee N, Ostle N, Svatek M, Kvasnica J, Milodowski D, Jucker T, Ewers RM, Zhang Y, Johnson D, Teh YA, Burslem DFRP, Malhi Y, Coomes Det al., 2019, Imaging spectroscopy reveals the effects of topography and logging on the leaf chemistry of tropical forest canopy trees, Global Change Biology, Vol: 26, Pages: 989-1002, ISSN: 1354-1013

Logging, pervasive across the lowland tropics, affects millions of hectares of forest, yet its influence on nutrient cycling remains poorly understood. One hypothesis is that logging influences phosphorus (P) cycling, because this scarce nutrient is removed in extracted timber and eroded soil, leading to shifts in ecosystem functioning and community composition. However, testing this is challenging because P varies within landscapes as a function of geology, topography and climate. Superimposed upon these trends are compositional changes in logged forests, with species with more acquisitive traits, characterized by higher foliar P concentrations, more dominant. It is difficult to resolve these patterns using traditional field approaches alone. Here, we use airborne light detection and ranging‐guided hyperspectral imagery to map foliar nutrient (i.e. P, nitrogen [N]) concentrations, calibrated using field measured traits, over 400 km2 of northeastern Borneo, including a landscape‐level disturbance gradient spanning old‐growth to repeatedly logged forests. The maps reveal that canopy foliar P and N concentrations decrease with elevation. These relationships were not identified using traditional field measurements of leaf and soil nutrients. After controlling for topography, canopy foliar nutrient concentrations were lower in logged forest than in old‐growth areas, reflecting decreased nutrient availability. However, foliar nutrient concentrations and specific leaf area were greatest in relatively short patches in logged areas, reflecting a shift in composition to pioneer species with acquisitive traits. N:P ratio increased in logged forest, suggesting reduced soil P availability through disturbance. Through the first landscape scale assessment of how functional leaf traits change in response to logging, we find that differences from old‐growth forest become more pronounced as logged forests increase in stature over time, suggesting exacerbated phosphorus limitation as

Journal article

Betts MG, Wolf C, Pfeifer M, Banks-Leite C, Arroyo-Rodríguez V, Ribeiro DB, Barlow J, Eigenbrod F, Faria D, Fletcher RJ, Hadley AS, Hawes JE, Holt RD, Klingbeil B, Kormann U, Lens L, Levi T, Medina-Rangel GF, Melles SL, Mezger D, Morante-Filho JC, Orme CDL, Peres CA, Phalan BT, Pidgeon A, Possingham H, Ripple WJ, Slade EM, Somarriba E, Tobias JA, Tylianakis JM, Urbina-Cardona JN, Valente JJ, Watling JI, Wells K, Wearn OR, Wood E, Young R, Ewers RMet al., 2019, Extinction filters mediate the global effects of habitat fragmentation on animals, Science, Vol: 366, Pages: 1236-1239, ISSN: 0036-8075

Habitat loss is the primary driver of biodiversity decline worldwide, but the effects of fragmentation (the spatial arrangement of remaining habitat) are debated. We tested the hypothesis that forest fragmentation sensitivity-affected by avoidance of habitat edges-should be driven by historical exposure to, and therefore species' evolutionary responses to disturbance. Using a database containing 73 datasets collected worldwide (encompassing 4489 animal species), we found that the proportion of fragmentation-sensitive species was nearly three times as high in regions with low rates of historical disturbance compared with regions with high rates of disturbance (i.e., fires, glaciation, hurricanes, and deforestation). These disturbances coincide with a latitudinal gradient in which sensitivity increases sixfold at low versus high latitudes. We conclude that conservation efforts to limit edges created by fragmentation will be most important in the world's tropical forests.

Journal article

Sethi S, Jones N, Fulcher B, Picinali L, Clink D, Klinck H, Orme D, Wrege P, Ewers Ret al., 2019, Combining machine learning and a universal acoustic feature-set yields efficient automated monitoring of ecosystems, Publisher: bioRxiv

Natural habitats are being impacted by human pressures at an alarming rate. Monitoring these ecosystem-level changes often requires labour-intensive surveys that are unable to detect rapid or unanticipated environmental changes. Here we developed a generalisable, data-driven solution to this challenge using eco-acoustic data. We exploited a convolutional neural network to embed ecosystem soundscapes from a wide variety of biomes into a common acoustic space. In both supervised and unsupervised modes, this allowed us to accurately quantify variation in habitat quality across space and in biodiversity through time. On the scale of seconds, we learned a typical soundscape model that allowed automatic identification of anomalous sounds in playback experiments, paving the way for real-time detection of irregular environmental behaviour including illegal activity. Our highly generalisable approach, and the common set of features, will enable scientists to unlock previously hidden insights from eco-acoustic data and offers promise as a backbone technology for global collaborative autonomous ecosystem monitoring efforts.

Working paper

Ewers RM, Barlow J, Banks-Leite C, Rahbek Cet al., 2019, Separate authorship categories to recognize data collectors and code developers, NATURE ECOLOGY & EVOLUTION, Vol: 3, Pages: 1610-1610, ISSN: 2397-334X

Journal article

Davison CW, Chapman PM, Wearn OR, Bernard H, Ewers RMet al., 2019, Shifts in the demographics and behavior of bearded pigs (Sus barbatus) across a land-use gradient, Biotropica, Vol: 51, Pages: 938-948, ISSN: 0006-3606

Beyond broad‐scale investigations of species diversity and abundance, there is little information on how land conversion in the tropics is affecting the behavior and demographics of surviving species. To fill these knowledge gaps, we explored the effects of land‐use change on the ecologically important and threatened bearded pig (Sus barbatus) over seven years in Borneo. Random placement of camera traps across a land‐use gradient of primary forest, logged forest, and oil palm plantations (32,542 trap nights) resulted in 2,303 independent capture events. Land‐use was associated with changes in the age structure and activity patterns of photographed individuals, alongside large changes in abundance shown previously. The proportion of adults recorded declined from 92% in primary forests to 76% in logged forests, and 67% in plantations, likely indicating increased fecundity in secondary forests. Activity level (capture rate) did not vary, but activity patterns changed markedly, from diurnal in primary forests, crepuscular in logged forests, to nocturnal in plantations. These changes corresponded with avoidance of diurnal human activity and may also protect bearded pigs from increased thermal stress in warmer degraded forests. The percentage of adult captures that were groups rather than individuals increased five‐fold from primary forests (4%) to logged forests (20%), possibly due to increased mating or in response to perceived threats from indirect human disturbance. We recommend further investigation of the demographic and behavioral effects of land‐use change on keystone species as altered population structure, activity patterns, and social behavior may have knock‐on effects for entire ecosystems.

Journal article

Sharp AC, Barclay MVL, Chung AYC, Ewers RMet al., 2019, Tropical logging and deforestation impacts multiple scales of weevil beta-diversity, Biological Conservation, Vol: 234, Pages: 172-179, ISSN: 0006-3207

Half of Borneo's forest has been logged and oil palm plantations have replaced millions of hectares of forest since the 1970's. While this extensive land-use change has been shown to reduce species richness across landscapes, there is limited current knowledge on how deforestation affects the spatial arrangement of ecological communities. Identifying responses of beta-diversity to land-use change may reveal processes which could mitigate total biodiversity loss. We sampled weevils (superfamily: Curculionoidea) at multiple spatial scales across a land-use gradient at the Stability of Altered Forest Ecosystems (SAFE) Project in Sabah, Malaysia, in 2011–2012. We caught 160 taxa of weevil and calculated the response of alpha-diversity (1-ha scale) and beta-diversity (10-, 100-, and 1000-ha scales) to disturbance. Alpha-diversity of weevils was greatest in unlogged forest but landscape-level beta-diversity (100- and 1000-ha scale) was maintained across logged and unlogged due to high rates of spatial turnover. Turnover at smallest spatial scales (10-ha) in unlogged forest was highest in rough, flat terrain but smooth, sloping terrain had highest turnover in logged forest. Logging of flat terrain at small spatial scales has potential to decrease beta-diversity at greater scales. Beta-diversity at landscape-level in oil palm plantation remained high but was propagated by abundance shifts of few species instead of spatial turnover of many species. High temporal beta-diversity in unlogged forest was evident through periodic fluxes in abundance of many weevil species. We conclude that unlogged forest is irreplaceable for high beetle biodiversity but increased spatial turnover in some terrains may help conserve beetle communities in heavily-degraded landscapes.

Journal article

Heon SP, Chapman PM, Bernard H, Ewers RMet al., 2019, Small logging roads do not restrict movements of forest rats in Bornean logged forests, Biotropica, Vol: 51, Pages: 412-420, ISSN: 0006-3606

Selective logging is driving the proliferation of roads throughout tropical rain forests, particularly narrow, unpaved logging roads. However, little is known about the extent of road edge effects or their influence on the movements of tropical understory animal species. Here, we used forest rats to address the following questions: (a) Does the occupancy of rats differ from road edges to forest interior within logged forests? (b) Do roads inhibit the movements of rats within these forests? We established trapping grids along a road edge‐to‐forest interior gradient at four roads and in three control sites within a logged forest in Sabah, Malaysia. To quantify the probability of road crossing, rats were captured, translocated across a road, and then recaptured on subsequent nights. We caught 216 individuals of eight species on 3,024 trap nights. Rat occupancy did not differ across the gradient from road edge to interior, and 48 percent of the 105 translocated individuals crossed the roads and were recaptured. This proportion was not significantly different from that of rats returning in control sites (38% of 60 individuals), suggesting that small roads were not barriers to rat movements within logged forests. Subadults were significantly more likely to return from translocation than adults in both road and control sites. Our results are encouraging for the ecology of small mammal communities in heavily logged forests, because small logging roads do not restrict the movements of rats and therefore are unlikely to create an edge effect or influence habitat selection.

Journal article

Qie L, Telford E, Massam MR, Tangki H, Nilus R, Hector A, Ewers Ret al., 2019, Drought cuts back regeneration in logged tropical forests, Environmental Research Letters, Vol: 14, ISSN: 1748-9326

Logged tropical forests represent a major opportunity for preserving biodiversity and sequestering carbon, playing a large role in meeting global forest restoration targets. Left alone, these ecosystems have been expected to undergo natural regeneration and succession towards old growth forests, but extreme drought events may challenge this process. While old growth forests possess a certain level of resilience, we lack understanding as to how logging may affect forest responses to drought. This study examines the drought–logging interaction in seedling dynamics within a landscape of logged and unlogged forests in Sabah Malaysia, based on 73 plots monitored before and after the 2015-16 El Niño drought. Drought increased seedling mortality in all forests, but the magnitude of this impact was modulated by logging intensity, with forests with lower canopy leaf area index (LAI) and above ground biomass (AGB) experiencing greater drought induced mortality. Moreover, community traits in more heavily logged forests shifted towards being more ruderal after drought, suggesting that the trajectory of forest succession had been reversed. These results indicate that with reoccurring strong droughts under a changing climate, logged forests that have had over half of their biomass removed may suffer permanently arrested succession. Targeted management interventions may therefore be necessary to lift the vulnerable forests above the biomass threshold.

Journal article

Wilkinson CL, Yeo DCJ, Tan HH, Hadi Fikri A, Ewers RMet al., 2019, Resilience of tropical, freshwater fish (Nematabramis everetti) populations to severe drought over a land-use gradient in Borneo, Environmental Research Letters, Vol: 14, ISSN: 1748-9326

Biodiversity-rich forests in tropical Southeast Asia are being extensively logged and converted to oil-palm monocultures. In addition, extreme climatic events such as droughts are becoming more common. Land-use change and extreme climatic events are thought to have synergistic impacts on aquatic biodiversity, but few studies have directly tested this. A severe El Niño drought in Southeast Asia in early 2016 caused 16 low-order hill streams across a land-use gradient encompassing primary forest, logged forest and oil palm plantations in Sabah, Malaysia, to dry up into series of disconnected pools. The resulting disturbance (specifically, increased water temperature and decreased dissolved oxygen concentration) tolerated by the fish during the drought exceeded any worst-case scenario for climate change-induced warming. We quantified the biomass, density and movement of the dominant freshwater fish species, Nematabramis everetti (Cyprinidae), in these streams across this land-use gradient before, during, and after the 2016 El Niño drought period. Density of N. everetti was significantly lower in logged forest streams than primary forest or oil palm streams, and the biomass of individuals captured was lower during drought than prior to the drought; however, there was no change in the biomass density of individuals during drought. The distance moved by N. everetti was significantly lower during and after the drought compared to before the drought. We detected a significant antagonistic interaction on biomass of captured fish, with the magnitude of the drought impact reduced according to land-use. Populations of N. everetti were surprisingly resilient to drought and seem most affected instead by land-use. Despite this resilience, it is important to monitor how this widespread and abundant species, which provides an important ecosystem service to local human communities, is affected by future land-use and climate change, as logging, deforestation and conversi

Journal article

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