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

137 results found

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

Journal article

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

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

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

Chapman P, Loveridge R, Rowcliffe JM, Carbone C, Bernard H, Davison CW, Ewers RMet al., 2019, Minimal spillover of native small mammals from Bornean tropical forests into adjacent oil palm plantations, Frontiers in Forests and Global Change, Vol: 2, ISSN: 2624-893X

In the face of rapid tropical agricultural expansion, preservation of tropical forest remnants is crucially important. Forest remnants often abut the edges of new or established plantations, so landscape-level conservation requires an understanding of the balance between ecosystem services and disservices provided by forest, including potential crop yield reductions caused by species such as rodents, an important pest group in oil palm plantations. However, very little is known about the scale of any spillover of native species which inhabit forest into adjacent agricultural areas. We examined the distribution and behaviour of small mammals across an edge separating logged tropical forest and oil palm plantations in Sabah, Malaysian Borneo, using a dual approach. We used a trapping grid to reveal patterns of species relative abundance across the forest-plantation edge, and tracked individuals of forest species using a spool-and-line. We uncovered little evidence that the native forest small mammal community crosses the edge and uses the plantation, although two invasive small mammal species were found across the whole edge gradient. Of 10 forest species detected, we found only the adaptable murid Maxomys whiteheadi in the plantation, where it persisted at low abundances across all sampling points, including in the plantation interior control site. This pattern is more consistent with persistence of M. whiteheadi throughout plantations than with spill-over from forest fragments. On the forest side, observed species richness of small mammals increased with distance into the interior, suggesting a negative edge effect may exist within forest remnants. Of 23 successfully tracked small mammals, only one M. whiteheadi crossed the forest-plantation edge, and overall, this species was significantly repelled from crossing into plantation habitat. Our results suggest that spillover of native small mammals contributes little to oil palm damage close to forest-plantation edges

Journal article

Gregory N, Ewers RM, Chung AYC, Cator LJet al., 2019, El Niño drought and tropical forest conversion synergistically determine mosquito development rate, Environmental Research Letters, Vol: 14, ISSN: 1748-9326

Extreme warming events can profoundly alter the transmission dynamics of mosquito–borne diseases by affecting the physiology of mosquito vectors. At local scales, temperatures are determined largely by vegetation structure and can be dramatically altered by drivers of land-use change (e.g. forest conversion). Disturbance activities can also hinder the buffering capacity of natural habitats, making them more susceptible to seasonal climate variation and extreme weather events (e.g. droughts). Using experiments spanning three years, we demonstrate that variation in microclimates due to forest conversion dramatically increases development rates in Aedes albopictus mosquitoes. However, this effect was mediated by an El Niño Southern Oscillation (ENSO) drought event. In normal years, mean temperatures did not differ between land-use types, however mosquitoes reared in oil palm plantations typically emerged 2-3 days faster than in logged forests. During an ENSO drought, mean temperatures did differ between land-use types, but surprisingly this did not result in different mosquito development rates. Driving this idiosyncratic response may be the differences in daily temperature fluctuations between the land-use types that either push mosquito larvae towards optimal development, or over the thermal optimum, thereby reducing fitness. This work highlights the importance of considering the synergistic effects of land-use and seasonal climate variations for predicting a key disease transmission-relevant mosquito trait.

Journal article

Woon JS, Boyle MJW, Ewers RM, Chung A, Eggleton Pet al., 2019, Termite environmental tolerances are more linked to desiccation than temperature in modified tropical forests, INSECTES SOCIAUX, Vol: 66, Pages: 57-64, ISSN: 0020-1812

Journal article

Galan-Acedo C, Arroyo-Rodriguez V, Andresen E, Verde Arregoitia L, Vega E, Peres CA, Ewers RMet al., 2019, The conservation value of human-modified landscapes for the world's primates, Nature Communications, Vol: 10, ISSN: 2041-1723

Land-use change pushes biodiversity into human-modified landscapes, where native ecosystems are surrounded by anthropic land covers (ALCs). Yet, the ability of species to use these emerging covers remains poorly understood. We quantified the use of ALCs by primates worldwide, and analyzed species’ attributes that predict such use. Most species use secondary forests and tree plantations, while only few use human settlements. ALCs are used for foraging by at least 86 species with an important conservation outcome: those that tolerate heavily modified ALCs are 26% more likely to have stable or increasing populations than the global average for all primates. There is no phylogenetic signal in ALCs use. Compared to all primates on Earth, species using ALCs are less often threatened with extinction, but more often diurnal, medium or large-bodied, not strictly arboreal, and habitat generalists. These findings provide valuable quantitative information for improving management practices for primate conservation worldwide.

Journal article

Qie L, Elsy A, Stumvoll A, Kwasnicka M, Peel A, Sullivan JA, Ettinger MS, Robertson AJ, Brisbane JK, Sawyer AL, Lui YN, Ow SN, Sebastianelli M, Majcher B, Duan M, Vigus H, Pounsin G, Nilus R, Ewers Ret al., 2019, Impending regeneration failure of the IUCN vulnerable Borneo ironwood (Eusideroxylon zwageri), Tropical Conservation Science, Vol: 12, Pages: 1-6, ISSN: 1940-0829

The regeneration of many climax species in tropical forest critically depends on adequate seed dispersal and seedling establishment. Here, we report the decreased abundance and increased spatial aggregation of younger trees of the Borneo ironwood (Eusideroxylon zwageri) in a protected forest in Sabah Malaysia. We observed a high level of seedling herbivory with strong density dependence, likely exacerbated by local aggregation and contributing to the progressively shrinking size distribution. We also note the largely undocumented selective herbivory by sambar deer on E. zwageri seedlings. This study highlights the combined impact of altered megafauna community on a tree population through interlinked ecological processes and the need for targeted conservation intervention for this iconic tropical tree species.

Journal article

Wearn OR, Carbone C, Rowcliffe JM, Pfeifer M, Bernard H, Ewers RMet al., 2019, Land-use change alters the mechanisms assembling rainforest mammal communities in Borneo, Journal of Animal Ecology, Vol: 88, Pages: 125-137, ISSN: 0021-8790

1.The assembly of species communities at local scales is thought to be driven by environmental filtering, species interactions, and spatial processes such as dispersal limitation. Little is known about how the relative balance of these drivers of community assembly changes along environmental gradients, especially man-made environmental gradients associated with land-use change. 2.Using concurrent camera- and live-trapping, we investigated the local-scale assembly of mammal communities along a gradient of land-use intensity (old-growth forest, logged forest and oil palm plantations) in Borneo. We hypothesised that increasing land-use intensity would lead to an increasing dominance of environmental control over spatial processes in community assembly. Additionally, we hypothesised that competitive interactions among species might reduce in concert with declines in α-diversity (previously documented) along the land-use gradient. 3.To test our first hypothesis, we partitioned community variance into the fractions explained by environmental and spatial variables. To test our second hypothesis, we used probabilistic models of expected species co-occurrence patterns, in particular focussing on the prevalence of spatial avoidance between species. Spatial avoidance might indicate competition, but might also be due to divergent habitat preferences. 4.We found patterns that are consistent with a shift in the fundamental mechanics governing local community assembly. In support of our first hypothesis, the importance of spatial processes (dispersal limitation and fine-scale patterns of home-ranging) appeared to decrease from low to high intensity land-uses, whilst environmental control increased in importance (in particular due to fine-scale habitat structure). Support for our second hypothesis was weak: whilst we found that the prevalence of spatial avoidance decreased along the land-use gradient, in particular between congeneric species pairs most likely to be in compet

Journal article

Sethi S, Ewers R, Jones N, Orme D, Picinali Let al., 2018, Robust, real-time and autonomous monitoring of ecosystems with an open, low-cost, networked device, Methods in Ecology and Evolution, Vol: 9, Pages: 2383-2387, ISSN: 2041-210X

1. Automated methods of monitoring ecosystems provide a cost-effective way to track changes in natural system's dynamics across temporal and spatial scales. However, methods of recording and storing data captured from the field still require significant manual effort. 2. Here we introduce an open source, inexpensive, fully autonomous ecosystem monitoring unit for capturing and remotely transmitting continuous data streams from field sites over long time-periods. We provide a modular software framework for deploying various sensors, together with implementations to demonstrate proof of concept for continuous audio monitoring and time-lapse photography. 3. We show how our system can outperform comparable technologies for fractions of the cost, provided a local mobile network link is available. The system is robust to unreliable network signals and has been shown to function in extreme environmental conditions, such as in the tropical rainforests of Sabah, Borneo. 4. We provide full details on how to assemble the hardware, and the open-source software. Paired with appropriate automated analysis techniques, this system could provide spatially dense, near real-time, continuous insights into ecosystem and biodiversity dynamics at a low cost.

Journal article

Nainar A, Tanaka N, Bidin K, Annammala KV, Ewers RM, Reynolds G, Walsh RPDet al., 2018, Hydrological dynamics of tropical streams on a gradient of land-use disturbance and recovery: A multi-catchment experiment, Journal of Hydrology, Vol: 566, Pages: 581-594, ISSN: 0022-1694

Although erosional impacts of rainforest logging are well established, changes in hydrological dynamics have been less explored especially in the post-logging recovery phase following repeat-logging cycles and mature phase of oil palm plantation cycles. This study addresses this gap by comparing hydrological characteristics of five catchments in a steep land area of Sabah, Malaysian Borneo on a gradient of disturbance and recovery – twice-logged forest, 22 years recovery (LF2); multiple-logged forest, 8 years recovery (LF3); mature oil palm, 20 years old (OP); and two primary forests (PF and VJR) as controls. Each catchment was instrumented with water depth (converted to discharge), conductivity, temperature, and turbidity sensors, and a raingauge connected to a solar-powered datalogger recording data at 5-minute intervals from November 2011 to August 2013. Data were analysed via the flow-duration curve (FDC) supplemented by the runoff coefficient (RR) and coefficient of variation in discharge (QVAR) for aggregated characteristics, as well as via a combination of the Dunn's test and multiple-regression at the storm event scale for focused hydrological dynamics. Results show that OP is characterised by a relatively low RR (0.357) but with high responsiveness during storm events and very low baseflow (38.4% of total discharge). Discharge in the LF3 (RR = 0.796) is always the highest while having an intermediate level of responsiveness. LF2 with longer-term recovery shown a reduction in terms of discharge (RR = 0.640). Being the benchmark, the undisturbed forest (PF) has the most buffered storm response with the highest baseflow (67.9% of total discharge). Stormflow and baseflow are anomalously high and low respectively in the near-primary VJR catchment, but this probably reflects the shallow soils and short-stature rainforest associated with its igneous and metamorphic lithology. From a management aspect, although hydrological recovery is more advanced in the 22

Journal article

Jucker T, Hardwick SR, Both S, Elias DMO, Ewers RM, Milodowski DT, Swinfield T, Coomes DAet al., 2018, Canopy structure and topography jointly constrain the microclimate of human-modified tropical landscapes, Global Change Biology, Vol: 24, Pages: 5243-5258, ISSN: 1354-1013

Local-scale microclimatic conditions in forest understoreys play a key role in shaping the composition, diversity and function of these ecosystems. Consequently, understanding what drives variation in forest microclimate is critical to forecasting ecosystem responses to global change, particularly in the tropics where many species already operate close to their thermal limits and rapid land-use transformation is profoundly altering local environments. Yet our ability to characterize forest microclimate at ecologically meaningful scales remains limited, as understorey conditions cannot be directly measured from outside the canopy. To address this challenge, we established a network of microclimate sensors across a land-use intensity gradient spanning from old-growth forests to oil-palm plantations in Borneo. We then combined these observations with high-resolution airborne laser scanning data to characterize how topography and canopy structure shape variation in microclimate both locally and across the landscape. In the processes, we generated high-resolution microclimate surfaces spanning over 350 km2 , which we used to explore the potential impacts of habitat degradation on forest regeneration under both current and future climate scenarios. We found that topography and vegetation structure were strong predictors of local microclimate, with elevation and terrain curvature primarily constraining daily mean temperatures and vapour pressure deficit (VPD), whereas canopy height had a clear dampening effect on microclimate extremes. This buffering effect was particularly pronounced on wind-exposed slopes but tended to saturate once canopy height exceeded 20 m-suggesting that despite intensive logging, secondary forests remain largely thermally buffered. Nonetheless, at a landscape-scale microclimate was highly heterogeneous, with maximum daily temperatures ranging between 24.2 and 37.2°C and VPD spanning two orders of magnitude. Based on this, we estimate that

Journal article

Banks-Leite C, Fletcher R, Didham R, Barlow J, Ewers RM, Rosindell JL, Holt RD, Gonzalez A, Pardini R, Damschen E, Melo FPL, Ries L, Prevedello JA, Tscharntke WF, Laurance WF, Lovejoy T, Haddad NMet al., 2018, Is habitat fragmentation good for biodiversity?, Biological Conservation, Vol: 226, Pages: 9-15, ISSN: 0006-3207

Habitat loss is a primary threat to biodiversity across the planet, yet contentious debate has ensued on the importance of habitat fragmentation ‘per se’ (i.e., altered spatial configuration of habitat for a given amount of habitat loss). Based on a review of landscape-scale investigations, Fahrig (2017; Ecological responses to habitat fragmentation per se. Annual Review of Ecology, Evolution, and Systematics 48:1-23) reports that biodiversity responses to habitat fragmentation ‘per se’ are more often positive rather than negative and concludes that the widespread belief in negative fragmentation effects is a ‘zombie idea’. We show that Fahrig's conclusions are drawn from a narrow and potentially biased subset of available evidence, which ignore much of the observational, experimental and theoretical evidence for negative effects of altered habitat configuration. We therefore argue that Fahrig's conclusions should be interpreted cautiously as they could be misconstrued by policy makers and managers, and we provide six arguments why they should not be applied in conservation decision-making. Reconciling the scientific disagreement, and informing conservation more effectively, will require research that goes beyond statistical and correlative approaches. This includes a more prudent use of data and conceptual models that appropriately partition direct vs indirect influences of habitat loss and altered spatial configuration, and more clearly discriminate the mechanisms underpinning any changes. Incorporating these issues will deliver greater mechanistic understanding and more predictive power to address the conservation issues arising from habitat loss and fragmentation.

Journal article

Wilkinson CL, Yeo DCJ, Tan HH, Fikri AH, Ewers RMet al., 2018, The availability of freshwater fish resources is maintained across a land-use gradient in Sabah, Borneo, AQUATIC CONSERVATION-MARINE AND FRESHWATER ECOSYSTEMS, Vol: 28, Pages: 1044-1054, ISSN: 1052-7613

Freshwater fish are a vital resource for local communities across the rural tropics. In Southeast Asia, biodiversity‐rich forests are being logged and converted to extensive oil palm monocultures. This clearly has impacts on associated freshwater ecosystems, but the impact on their biodiversity remains largely understudied and poorly understood, despite the important provisioning service that freshwater fishes provide for human well‐being. This study quantifies the biomass stocks of freshwater fish across a land‐use gradient encompassing primary forest, twice‐logged forest, and oil palm plantations in Sabah, Malaysia, in an area where local communities are known to harvest freshwater fish. Stream fish were sampled using a cast net, the dominant technique used by local fishermen, in 200‐m‐long transects in 16 streams over three sampling years (2011, 2013, and 2015). Unexpectedly, no impact from land use on total fish availability was detected. There were no significant differences in fish species richness or, most importantly, biomass per unit fishing effort across the land‐use gradient. There was variation in the responses of five known food species (Tor tambra, Hampala sabana, Barbodes sealei, Barbonymus balleroides, and Gastromyzon lepidogaster), and these small differences are attributed to variation in species habitat selection that co‐vary with land‐use change. Despite evidence to suggest that freshwater fish communities are resilient to land‐use change, they still face risks associated with disturbance, such as invasion by alien species; furthermore, several of the more stenotopic species were only present in primary forest catchments. Nonetheless, freshwater fish in small headwater streams appear to represent a sustainable food resource for villages established in human‐modified forests or in developed oil palm plantations.

Journal article

Chapman P, Wearn OR, Riutta T, Carbone C, Rowcliffe M, Bernard H, Ewers RMet al., 2018, Inter-annual dynamics and persistence of small mammal communities in a selectively logged tropical forest in Borneo, Biodiversity and Conservation, Vol: 27, Pages: 3155-3169, ISSN: 1572-9710

Understanding temporal change and long-term persistence of species and communities is vital if we are to accurately assess the relative values of human-modified habitats for biodiversity. Despite a large literature and emerging consensus demonstrating a high conservation value of selectively logged tropical rainforests, few studies have taken a long-term perspective. We resampled small mammals (≤1kg) in a heavily logged landscape in Sabah, Borneo between 2011 and 2016 to investigate temporal patterns of species-level changes in population density. We found that small mammal population density in heavily logged forest was highly variable among years, consistent with patterns previously observed in unlogged forest, and uncovered evidence suggesting that one species is potentially declining towards local extinction. Across nine species, population densities varied almost sevenfold during our six-year study period, highlighting the extremely dynamic nature of small mammal communities in this ecosystem. Strictly terrestrial murid species tended to exhibit strong temporal dynamics, whereas semi-arboreal foraging species such as treeshrews had more stable dynamics. We found no relationships between population density and fruit/seed mass, and therefore no evidence that our patterns represent responses to inter-annual mast fruiting of the dominant canopy dipterocarp trees. This may be due to the removal of most of the canopy during logging, and hence the dipterocarp seed resource, although it possibly also reflects spatiotemporal limitations of our data. Our results underline the importance of understanding long-term variability in animal communities before developing conservation and management recommendations for human-altered ecosystems.

Journal article

Ewers RM, 2018, Boring speakers talk for longer, NATURE, Vol: 561, Pages: 464-464, ISSN: 0028-0836

Journal article

Marsh C, Feitosa R, Louzada J, Ewers Ret al., 2018, Is β-diversity of Amazonian ant and dung beetles communities elevated at rainforest edges?, Journal of Biogeography, Vol: 45, Pages: 1966-1979, ISSN: 0305-0270

AimThousands of kilometres of rainforest edges are created every year through forest fragmentation, but we have little knowledge of the impacts of edges on spatial patterns of species turnover and nestedness components of β‐diversity.LocationA quasi‐experimental landscape in the north‐east Brazilian Amazon.MethodsWe sampled dung beetles and ants using a sampling design based on a fractal series of equilateral triangles that naturally allows examination at multiple spatial scales. We sampled two edge types (primary‐secondary and primary‐Eucalyptus forest) and three control sites immersed in primary, secondary and Eucalyptus forest. We measured β‐diversity between communities across the primary forest‐matrix edge and within communities at up to 1 km from the forest edge. We examined β‐diversity at multiple scales by partitioning the dissimilarity matrix into fractal orders representing inter‐point distances of ~32, ~100, ~316 and ~1,000 m and into turnover and nestedness components.ResultsTurnover but not nestedness was greater across the primary‐Eucalyptus forest than primary‐secondary forest edge. There was spillover of species across edges in both directions. Across edges and within controls, turnover was the main driver of β‐diversity. Within community, β‐diversity was increased for dung beetles at large scales (~300–1,000 m) at both edge types. This increase, however, was driven by elevated nestedness. Levels of β‐diversity were affected even ~300 m into habitat interiors, but appeared to be at control levels by 1 km.Main conclusionsThe effects of edges on the spatial dynamics of community composition penetrated far beyond the typical distances at which forest structure and microclimate are altered. This indicates that for a significant proportion of Amazonian communities, the underlying processes determining diversity may be impacted by deforestation.

Journal article

Riutta T, Malhi Y, Kho LK, Marthews TR, Huaraca Huasco W, Khoo M, Tan S, Turner E, Reynolds G, Both S, Burslem DFRP, Teh YA, Vairappan CS, Majalap N, Ewers RMet al., 2018, Logging disturbance shifts net primary productivity and its allocation in Bornean tropical forests., Global Change Biology, Vol: 24, Pages: 2913-2928, ISSN: 1354-1013

Tropical forests play a major role in the carbon cycle of the terrestrial biosphere. Recent field studies have provided detailed descriptions of the carbon cycle of mature tropical forests, but logged or secondary forests have received much less attention. Here we report the first measures of total net primary productivity (NPP) and its allocation along a disturbance gradient from old-growth forests to moderately and heavily logged forests in Malaysian Borneo. We measured the main NPP components (woody, fine root and canopy NPP) in old-growth (n=6) and logged (n=5) 1 ha forest plots. Overall, the total NPP did not differ between old-growth and logged forest (13.5 ± 0.5 and 15.7 ± 1.5 Mg C ha-1 year-1 , respectively). However, logged forests allocated significantly higher fraction into woody NPP at the expense of the canopy NPP (42% and 48% into woody and canopy NPP, respectively, in old-growth forest vs. 66% and 23% in logged forest). When controlling for local stand structure, NPP in logged forest stands was 41% higher, and woody NPP was 150% higher than in old-growth stands with similar basal area, but this was offset by structure effects (higher gap frequency and absence of large trees in logged forest). This pattern was not driven by species turnover: the average woody NPP of all species groups within logged forest (pioneers, non-pioneers, species unique to logged plots and species shared with old-growth plots) was similar. Hence, below a threshold of very heavy disturbance, logged forests can exhibit higher NPP and higher allocation to wood; such shifts in carbon cycling persist for decades after the logging event. Given that the majority of tropical forest biome has experienced some degree of logging, our results demonstrate that logging can cause substantial shifts in carbon production and allocation in tropical forests. This article is protected by copyright. All rights reserved.

Journal article

Jucker T, Asner GP, Dalponte M, Brodrick PG, Philipson CD, Vaughn NR, Teh YA, Brelsford C, Burslem DFRP, Deere NJ, Ewers RM, Kvasnica J, Lewis SL, Malhi Y, Milne S, Nilus R, Pfeifer M, Phillips OL, Qie L, Renneboog N, Reynolds G, Riutta T, Struebig MJ, Svatek M, Turner EC, Coomes DAet al., 2018, Estimating aboveground carbon density and its uncertainty in Borneo's structurally complex tropical forests using airborne laser scanning, BIOGEOSCIENCES, Vol: 15, Pages: 3811-3830, ISSN: 1726-4170

Borneo contains some of the world's most biodiverse and carbon-dense tropical forest, but this 750 000 km2 island has lost 62 % of its old-growth forests within the last 40 years. Efforts to protect and restore the remaining forests of Borneo hinge on recognizing the ecosystem services they provide, including their ability to store and sequester carbon. Airborne laser scanning (ALS) is a remote sensing technology that allows forest structural properties to be captured in great detail across vast geographic areas. In recent years ALS has been integrated into statewide assessments of forest carbon in Neotropical and African regions, but not yet in Asia. For this to happen new regional models need to be developed for estimating carbon stocks from ALS in tropical Asia, as the forests of this region are structurally and compositionally distinct from those found elsewhere in the tropics. By combining ALS imagery with data from 173 permanent forest plots spanning the lowland rainforests of Sabah on the island of Borneo, we develop a simple yet general model for estimating forest carbon stocks using ALS-derived canopy height and canopy cover as input metrics. An advanced feature of this new model is the propagation of uncertainty in both ALS- and ground-based data, allowing uncertainty in hectare-scale estimates of carbon stocks to be quantified robustly. We show that the model effectively captures variation in aboveground carbon stocks across extreme disturbance gradients spanning tall dipterocarp forests and heavily logged regions and clearly outperforms existing ALS-based models calibrated for the tropics, as well as currently available satellite-derived products. Our model provides a simple, generalized and effective approach for mapping forest carbon stocks in Borneo and underpins ongoing efforts to safeguard and facilitate the restoration of its unique tropical forests.

Journal article

Wilkinson CL, Yeo DCJ, Hui TH, Fikri AH, Ewers RMet al., 2018, Land-use change is associated with a significant loss of freshwater fish species and functional richness in Sabah, Malaysia, Biological Conservation, Vol: 222, Pages: 164-171, ISSN: 0006-3207

Global biodiversity is being lost due to extensive anthropogenic land cover change. In Southeast Asia, biodiversity-rich forests are being extensively logged and converted to oil-palm monocultures. The impacts of this land-use change on freshwater ecosystems, and particularly on freshwater biodiversity, remain largely understudied and poorly understood. We assessed the differences between fish communities in headwater stream catchments across an established land-use gradient in Sabah, Malaysia (protected forest areas, twice-logged forest, salvage-logged forest, oil-palm plantations with riparian reserves, and oil-palm plantations without riparian reserves). Stream fishes were sampled using an electrofisher, a cast net and a tray net in 100 m long transects in 23 streams in 2017. Local species richness and functional richness were both significantly reduced with any land-use change from protected forest areas, but further increases in land-use intensity had no subsequent impacts on fish biomass, functional evenness, and functional divergence. Any form of logging or land-use change had a clear and negative impact on fish communities, but the magnitude of that effect was not influenced by logging severity or time since logging on any fish community metric, suggesting that just two rounds of selective impact (i.e., logging) appeared sufficient to cause negative effects on freshwater ecosystems. It is therefore essential to continue protecting primary forested areas to maintain freshwater diversity, as well as to explore strategies to protect freshwater ecosystems during logging, deforestation, and conversion to plantation monocultures that are expected to continue across Southeast Asia.

Journal article

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