Where to find aliens

Dyer, E.E., Cassey, P., Redding, D.W., Collen, B., Franks, V., Gaston, K.J., Jones, K.E., Kark, S., Orme, C.D.L. & Blackburn, T.M. 2017. The global distribution and drivers of alien bird species richness. PLoS Biology 15, e2000942. [Image from Shutterstock] shutterstock_289070456

Alien species are a major component of human-induced environmental change. Variation in the numbers of alien species found in different areas is likely to depend on a combination of anthropogenic and environmental factors, with anthropogenic factors affecting the number of species introduced to new locations, and when, and environmental factors influencing how many species are able to persist there. However, global spatial and temporal variation in the drivers of alien introduction and species richness remain poorly understood. Here, we analyse an extensive new database of alien birds to explore what determines the global distribution of alien species richness for an entire taxonomic class. We demonstrate that the locations of origin and introduction of alien birds, and their identities, were initially driven largely by European (mainly British) colonialism. However, recent introductions are a wider phenomenon, involving more species and countries, and driven in part by increasing economic activity. We find that, globally, alien bird species richness is currently highest at midlatitudes and is strongly determined by anthropogenic effects, most notably the number of species introduced (i.e., colonisation pressure). Nevertheless, environmental drivers are also important, with native and alien species richness being strongly and consistently positively associated. Our results demonstrate that colonisation pressure is key to understanding alien species richness, show that areas of high native species richness are not resistant to colonisation by alien species at the global scale, and emphasise the likely ongoing threats to global environments from introductions of species.

Allotments are good for you

Soga, M., Cox, D.T.C., Yamaura, Y., Gaston, K.J., Kurisu, K. & Hanaki, K. 2017. Health benefits of urban allotment gardening: improved physical and psychological wellbeing and social integration. International Journal of Environmental Research and Public Health 14,71. Screen Shot 2017-01-12 at 22.58.11

With an ever-increasing urban population, promoting public health and well-being in towns and cities is a major challenge. Previous research has suggested that participating in allotment gardening delivers a wide range of health benefits. However, evidence from quantitative analyses is still scarce. Here, we quantify the effects, if any, of participating in allotment gardening on physical, psychological and social health. A questionnaire survey of 332 people was performed in Tokyo, Japan. We compared five self-reported health outcomes between allotment gardeners and non-gardener controls: perceived general health, subjective health complaints, body mass index (BMI), mental health and social cohesion. Accounting for socio-demographic and lifestyle variables, regression models revealed that allotment gardeners, compared to non-gardeners, reported better perceived general health, subjective health complaints, mental health and social cohesion. BMI did not differ between gardeners and non-gardeners. Neither frequency nor duration of gardening significantly influenced reported health outcomes. Our results highlight that regular gardening on allotment sites is associated with improved physical, psychological and social health. With the recent escalation in the prevalence of chronic diseases, and associated healthcare costs, this study has a major implication for policy, as it suggests that urban allotments have great potential for preventative healthcare.

Losing contact with nature

Cox, D.T.C., Hudson, H.L., Shanahan, D.F., Fuller, R.A. & Gaston, K.J. 2017. The rarity of direct experiences of nature in an urban population. Landscape and Urban Planning 160, 79-84. [Image from Shutterstock] shutterstock_149634605

As people live more urbanised lifestyles there is potential to lose daily contact with nature, diminishing access to the wide range of associated health benefits of interacting with nature. Experiences of nature vary widely across populations, but this variation is poorly understood. We surveyed 1023 residents of an urban population in the UK to measure four distinctly different nature interactions: indirect (viewing nature through a window at work and at home), incidental (spending time outside at work), intentional (time spent in private gardens) and intentional (time spent in public parks). Scaled-up to the whole study population, accumulation curves of the total number of hours per week that people were exposed to each type of nature interaction showed that 75% of nature interactions were experienced by half the population. Moreover, 75% of the interactions of a type where people were actually present in nature were experienced by just 32% of the population. The average hours each individual experienced nature per week varied across interactions: indirect (46.0 ± 27.3 SD), incidental (6.4 ± 12.7 SD), intentional-gardens (2.5 ± 2.9 SD) and intentional-parks (2.3 ± 2.7 SD). Experiencing nature regularly appears to be the exception rather than the norm, with a person’s connection to nature being positively associated with incidental and intentional experiences. This novel study provides baseline information regarding how an urban population experiences different types of nature. Deconstructing nature experience will pave the way for developing recommendations for targeted health outcomes.

Scanning the horizon

Sutherland, W.J., Barnard, P., Broad, S., Clout, M., Connor, B., Côté, I.M., Dicks, L.V., Doran, H., Entwistle, A.C., Fleishman, E., Fox, M., Gaston, K.J., Gibbons, D.W., Jiang, Z., Keim, B., Lickorish, F.A., Markillie, P., Monk, K.A., Pearce-Higgins, J.W., Peck, L.S., Pretty, J., Spalding, M.D., Tonneijck, F.H., Wintle, B.C. & Ockendon, N. A 2017 horizon scan of emerging issues for global conservation and biological diversity. Trends in Ecology and Evolution, in press. [Image from Shutterstock] shutterstock_84255913

We present the results of our eighth annual horizon scan of emerging issues likely to affect global biological diversity, the environment, and conservation efforts in the future. The potential effects of these novel issues might not yet be fully recognized or understood by the global conservation community, and the issues can be regarded as both opportunities and risks. A diverse international team with collective expertise in horizon scanning, science communication, and conservation research, practice, and policy reviewed 100 potential issues and identified 15 that qualified as emerging, with potential substantial global effects. These issues include new developments in energy storage and fuel production, sand extraction, potential solutions to combat coral bleaching and invasive marine species, and block chain technology.

Local adaptation of reproductive performance

Porcelli, D., Gaston, K.J., Butlin, R.K. & Snook, R.R. 2017. Local adaptation of reproductive performance during thermal stress. Journal of Evolutionary Biology, in press. [Image from Shutterstock] shutterstock_137256881

Considerable evidence exists for local adaptation of critical thermal limits in ectotherms following adult temperature stress, but fewer studies have tested for local adaptation of sublethal heat stress effects across life-history stages. In organisms with complex life cycles, such as holometabolous insects, heat stress during juvenile stages may severely impact gametogenesis, having downstream consequences on reproductive performance that may be mediated by local adaptation, although this is rarely studied. Here, we tested how exposure to either benign or heat stress temperature during juvenile and adult stages, either independently or combined, influences egg-to-adult viability, adult sperm motility and fertility in high- and low-latitude populations of Drosophila subobscura. We found both population- and temperature-specific effects on survival and sperm motility; juvenile heat stress decreased survival and subsequent sperm motility and each trait was lower in the northern population. We found an interaction between population and temperature on fertility following application of juvenile heat stress; although fertility was negatively impacted in both populations, the southern population was less affected. When the adult stage was also subject to heat stress, the southern population exhibited positive carry-over effects whereas the northern population’s fertility remained low. Thus, the northern population is more susceptible to sublethal reproductive consequences following exposure to juvenile heat stress. This may be common in other organisms with complex life cycles and current models predicting population responses to climate change, which do not take into account the impact of juvenile heat stress on reproductive performance, may be too conservative.

A dose of gardening

Soga, M., Gaston, K.J. & Yamaura, Y. 2017. Gardening is beneficial for health: a meta-analysis. Preventive Medicine Reports 5, 92-99. [Image from Shutterstock] shutterstock_303853934

There is increasing evidence that gardening provides substantial human health benefits. However, no formal statistical assessment has been conducted to test this assertion. Here, we present the results of a meta-analysis of research examining the effects of gardening, including horticultural therapy, on health. We performed a literature search to collect studies that compared health outcomes in control (before participating in gardening or non-gardeners) and treatment groups (after participating in gardening or gardeners) in January 2016. The mean difference in health outcomes between the two groups was calculated for each study, and then the weighted effect size determined both across all and sets of subgroup studies. 22 case studies (published after 2001) were included in the meta-analysis, which comprised 74 comparisons between control and treatment groups. Most studies came from the United States, followed by Europe, Asia, and the Middle East. Studies reported a wide range of health outcomes, such as reductions in depression, anxiety and body mass index, as well as increases in life satisfaction, quality of life and sense of community. Meta analytic estimates showed a significant positive effect of gardening on the health outcomes both for all and sets of subgroup studies, whilst effect sizes differed among eight subgroups. Although Egger’s test indicated the presence of publication bias, significant positive effects of gardening remained after adjusting for this using trim and fill analysis. This study has provided robust evidence for the positive effects of gardening on health. A regular dose of gardening can improve public health.

Tracking garden birds

Cox, D.T.C., Inger, R., Hancock, S., Anderson, K. & Gaston, K.J. 2016. Movement of feeder-using songbirds: the influence of urban features. Scientific Reports 6, 37669. [Image from Shutterstock] shutterstock_240027928

Private gardens provide vital opportunities for people to interact with nature. The most popular form of interaction is through garden bird feeding. Understanding how landscape features and seasons determine patterns of movement of feeder-using songbirds is key to maximising the well-being benefits they provide. To determine these patterns we established three networks of automated data loggers along a gradient of greenspace fragmentation. Over a 12-month period we tracked 452 tagged blue tits Cyantistes caeruleus and great tits Parus major moving between feeder pairs 9,848 times, to address two questions: (i) Do urban features within different forms, and season, influence structural (presence-absence of connections between feeders by birds) and functional (frequency of these connections) connectivity? (ii) Are there general patterns of structural and functional connectivity across forms? Vegetation cover increased connectivity in all three networks, whereas the presence of road gaps negatively affected functional but not structural connectivity. Across networks structural connectivity was lowest in the summer when birds maintain breeding territories, however patterns of functional connectivity appeared to vary with habitat fragmentation. Using empirical data this study shows how key urban features and season influence movement of feeder-using songbirds, and we provide evidence that this is related to greenspace fragmentation.

3D vegetation structure measured from a plane

Hancock, S., Anderson, K., Disney, M. & Gaston, K.J. 2017. Measurement of fine-spatial-resolution 3D vegetation structure with airborne waveform lidar: Calibration and validation with voxelised terrestrial lidar. Remote Sensing of Environment 18, 37-50. screen-shot-2016-11-16-at-12-25-49

Vegetation structure controls habitat availability, ecosystem services, weather, climate and microclimate, but current landscape scale vegetation maps have lacked details of understorey vegetation and within canopy structure at resolutions finer than a few tens of metres. In this paper, a novel signal processing method is used to correctly measure 3D voxelised vegetation cover from full-waveform ALS data at 1.5 m
horizontal and 50 cm vertical resolution, including understorey vegetation and within-canopy structure. A new method for calibrating and validating the instrument specific ALS processing using high resolution TLS data is also presented and used to calibrate and validate the ALS derived data products over a wide range of land cover types within a heterogeneous urban area, including woodland, gardens and streets. This showed the method to accurately retrieve voxelised canopy cover maps with less than 0.4% of voxels containing false negatives, 10% of voxels containing false positives and a canopy cover accuracy within voxels of 24%. The method was applied across 100 km2 and the resulting structure maps were compared to the more widely used discrete return ALS and Gaussian decomposed waveform ALS data products. These products were found to give little information on the within-canopy structure and so are only capable of deriving coarse resolution, plot-scale structure metrics. The detailed 3D canopy maps derived from the new method allow landscape scale ecosystem processes to be examined in more detail than has previously been possible, and the new method reveals details about the canopy understorey, creating opportunities for ecological investigations. The calibration method can be applied to any waveform ALS instrument and processing method. All code used in this paper is freely available online through bitbucket (https://bitbucket.org/StevenHancock/voxel_lidar).

Cooled by plants

Edmondson, J.L., Stott, I., Davies, Z.G., Gaston, K.J. & Leake, J.R. 2016. Soil surface temperatures reveal moderation of the urban heat island effect by trees and shrubs. Scientific Reports 6, 33708. shutterstock_270038441[Image from Shutterstock]

Urban areas are major contributors to air pollution and climate change, causing impacts on human health that are amplified by the microclimatological effects of buildings and grey infrastructure through the urban heat island (UHI) effect. Urban greenspaces may be important in reducing surface temperature extremes, but their effects have not been investigated at a city-wide scale. Across a midsize UK city we buried temperature loggers at the surface of greenspace soils at 100 sites, stratified by proximity to city centre, vegetation cover and land-use. Mean daily soil surface temperature over 11 months increased by 0.6 °C over the 5 km from the city outskirts to the centre. Trees and shrubs in non-domestic greenspace reduced mean maximum daily soil surface temperatures in the summer by 5.7 °C compared to herbaceous vegetation, but tended to maintain slightly higher temperatures in winter. Trees in domestic gardens, which tend to be smaller, were less effective at reducing summer soil surface temperatures. Our findings reveal that the UHI effects soil temperatures at a city-wide scale, and that in their moderating urban soil surface temperature extremes, trees and shrubs may help to reduce the adverse impacts of urbanization on microclimate, soil processes and human health.

Loss of connection to nature matters

Soga, M., Gaston, K.J., Koyanagi, T.F., Kurisu, K. & Hanaki, K. 2016. Urban residents’ perceptions of neighbourhood nature: does the extinction of experience matter? Biological Conservation 203, 143-150.shutterstock_151363640 [Image from Shutterstock]

Today’s children have less direct contact with nature than ever before, resulting in an “extinction of experience”. Research has suggested that such loss of daily interactions decreases people’s appreciation of the natural world, but this remains quantitatively unexplored. We conducted a questionnaire survey of undergraduate university students in Tokyo, Japan, and determined the effects of frequency of contact with nature on emotional connect- edness to nature and perceptions of neighbourhood nature. A total of 255 students participated in the surveys. Students’ perceptions of neighbourhood nature were measured by to what extent they valued cultural ecosystem services derived from neighbourhood natural environments, birds and butterflies. Results showed that students valued neighbourhood natural environments, birds and butterflies for many different reasons, such as relaxation, beauty of natural scenes, an indicator of seasonality, and opportunities for education. Linear mixed models revealed that both current and childhood frequencies of contact with nature were positively related not only to students’ emotional connectedness to nature but also their perceptions of neighbourhood nature. Students’ emotional connection to nature and perceptions of neighbourhood nature were positively associated with each other. Our results suggest that, given the rapid decrease in children’s daily contact with nature, public appreciation of the value of the natural world is likely gradually also to decrease. This can be a major obstacle to reversing global environmental challenges. People should therefore be encouraged to experience neighbourhood natural environments and biodiversity, and city planners and policy makers will play a vital role in connecting people with nature.