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.

Dining on the dead

Inger, R., Per, E., Cox, D.T.C., Norton, B. & Gaston, K.J. 2017. Role of vertebrate scavengers in urban ecosystems in the UK. Ecology and Evolution, online early. shutterstock_147173099 [Image from Shutterstock]

Recent research has demonstrated how scavenging, the act of consuming dead animals, plays a key role in ecosystem structure, functioning, and stability. A growing number of studies suggest that vertebrate scavengers also provide key ecosystem services, the benefits humans gain from the natural world, particularly in the removal of carcasses from the environment. An increasing proportion of the human population is now residing in cities and towns, many of which, despite being highly altered environments, contain significant wildlife populations, and so animal carcasses. Indeed, non-predation fatalities may be higher within urban than natural environments. Despite this, the fate of carcasses in urban environments and the role vertebrate scavengers play in their removal have not been determined. In this study, we quantify the role of vertebrate scavengers in urban environments in three towns in the UK. Using experimentally deployed rat carcasses and rapid fire motion-triggered cameras, we determined which species were scavenging and how removal of carcass biomass was partitioned between them. Of the 63 experimental carcasses deployed, vertebrate scavenger activity was detected at 67%. There was a significantly greater depletion in carcass biomass in the presence (mean loss of 194 g) than absence (mean loss of 14 g) of scavengers. Scavenger activity was restricted to three species, Carrion crows Corvus corone, Eurasian magpies Pica pica, and European red foxes Vulpes vulpes. From behavioural analysis, we estimated that a maximum of 73% of the carcass biomass was removed by vertebrate scavengers. Despite having low species richness, the urban scavenger community in our urban study system removed a similar proportion of carcasses to those reported in more pristine environments. Vertebrate scavengers are providing a key urban ecosystem service in terms of carcass removal. This service is, however, often overlooked, and the species that provide it are among some of the most disliked and persecuted.

Weeds on the web

Robinson, B.S., Inger, R., Crowley, S.L. & Gaston, K.J. 2016. Weeds on the web: conflicting management advice about invasive non-native plants. Journal of Applied Ecology, online early. shutterstock_149062910 [Image from Shutterstock]

1. Invasive non-native plants (INNPs) can have serious and widespread negative ecological and socio-economic impacts. It is therefore important they are managed appropriately. Within domestic gardens management decisions, which will tend to be made by individual members of the public, are likely to vary depending on (a) understanding of problems caused by INNP, and (b) knowledge of best practice.
2. Using content analysis, an approach seldom employed in an ecological context, this study analysed variation in internet-based information sources regarding INNP to determine how this collective discourse might influence risk perceptions and management decisions for domestic garden owners/managers. We used Japanese knotweed Fallopia japonica in the UK, as a case study, as it is one of the most ecologically and economically damaging INNP in the region. Our analysis categorized the types of author disseminating information about Japanese knotweed, the relative frequency of documents between author categories, and variation in content and style between and within author categories.
3. We identified five author categories: environmental NGOs, control companies, government, media and the property market. There was extensive variation in document structure, topics discussed, references and links to other sources, and language style; sometimes this variation was between author categories and sometimes within author categories. The most significant variation in topics discussed between author categories was indirect socio-economic problems, with control companies discussing these most. The number of pieces of legislation referenced and the proportion of militaristic words used were also highly significantly different between author categories. Some documents used neutral terminology and were more circumspect, whilst others were more forceful in expressing opinions and sensational.
4. The author category returning the highest number of documents was the subcategory local government, the shortest of which contained neither links to other information nor referenced any organizations. Further analysis of local government documents revealed conflicting advice regarding the disposal of Japanese knotweed waste material; confusion about this topic could result in decisions being made that spread Japanese knotweed further and are potentially unlawful.
5. The potential implications of our findings for the management of INNP in domestic gardens and societal perceptions of risks posed by INNP are discussed.
6. Synthesis and applications. To help prevent inappropriate management of invasive nonnative plants (INNPs), for example Japanese knotweed Fallopia japonica in domestic gardens, we recommend that local and national authorities collaborate and work towards disseminating more consistent messages about (a) the potential socio-economic and ecological problems caused by INNP, whilst avoiding hyperbole, and (b) the most appropriate management techniques.

Latitude in gene expression

Porcelli, D., Westram, A.M., Pascual, M., Gaston, K.J., Butlin, R.K. & Snook, R.R. 2017. Gene expression clines reveal local adaptation and associated trade-offs at a continental scale. Scientific Reports 6, 32975.drosophila_subobscura_800 [Image from D. Obbard]

Local adaptation, where fitness in one environment comes at a cost in another, should lead to spatial variation in trade-offs between life history traits and may be critical for population persistence. Recent studies have sought genomic signals of local adaptation, but often have been limited to laboratory populations representing two environmentally different locations of a species’ distribution. We measured gene expression, as a proxy for fitness, in males of Drosophila subobscura, occupying a 20° latitudinal and 11 °C thermal range. Uniquely, we sampled six populations and studied both common garden and semi-natural responses to identify signals of local adaptation. We found contrasting patterns of investment: transcripts with expression positively correlated to latitude were enriched for metabolic processes, expressed across all tissues whereas negatively correlated transcripts were enriched for reproductive processes, expressed primarily in testes. When using only the end populations, to compare our results to previous studies, we found that locally adaptive patterns were obscured. While phenotypic trade-offs between metabolic and reproductive functions across widespread species are well-known, our results identify underlying genetic and tissue responses at a continental scale that may be responsible for this. This may contribute to understanding population persistence under environmental change.

Connection to nature in cities

Shanahan, D.F., Cox, D.T.C, Fuller, R.A., Hancock, S., Lin, B.B., Anderson, K., Bush, R. & Gaston, K.J. (2017) Variation in experiences of nature across gradients of tree cover in compact and sprawling cities. Landscape and Urban Planning 157, 231-238. (Image from Shutterstock) shutterstock_309919712

Urban environments are expanding globally, and by 2050 nearly 70% of the world’s population will live in towns and cities, where opportunities to experience nature are more limited than in rural areas. This transition could have important implications for health and wellbeing given the diversity of benefits that nature delivers. Despite these issues, there is a lack of information on whether or how the experience of nature changes as green space becomes less available. We explore this question for residents of two case study cities of varying urban designs, sprawling (Brisbane, Australia) and compact (three English towns, U.K). Second, we examine how people’s feelings of connection to nature (measured using the Nature Relatedness scale) vary across this same gradient of nature availability. Despite climatic and cultural differences we found substantial similarities between the two locations. Lower levels of neighbourhood tree cover were associated with a reduced frequency of visits to private and public green spaces, and a similar pattern was found for the duration of time spent in private and public green spaces for Brisbane. Residents of both urban areas showed similar levels of nature relatedness, and there was a weak but positive association between tree cover and Nature Relatedness. These results suggest that regardless of the style of urban design, maintaining the availability of nature close to home is a critical step to protect people’s experiences of nature and their desire to seek out those experiences.

Getting more benefits from your garden

Lin, B.B., Gaston, K.J., Fuller, R.A., Wu, D.S., Bush, R., Shanahan, D.F. 2017. How green is your garden?: Urban form and socio-demographic factors influence yard vegetation, visitation, and ecosystem service benefits. Landscape and Urban Planning 157, 239-246. (Image from Shutterstock) shutterstock_77993656

Private yards provide city residents with access to ecosystem services that can be realized through passive (vegetation availability) and active (time spent in yards: frequency and duration) means. However, urban densification is leading to smaller yards with less vegetation. Here, we examine how urban form and socio-demographic factors affect the potential ecosystem service benefits people can gain via passive (e.g. climate regulation) and active (e.g. recreation) pathways. Two measures of vegetation cover (0.15–2 m, >2 m) are used as a proxy for passive ecosystem service benefits, and two measures of yard use (use frequency, total time spent across a week) are used for active ecosystem service benefits. We use survey and GIS data to measure personal and physical predictors that could influence these variables for 520 residents of detached housing in Brisbane, Australia. We found house age and yard size were positively correlated with vegetation cover, and people with a greater nature relatedness and lower socio-economic disadvantage also had greater vegetation cover. Yard size was an important predictor of yard use, as was nature relatedness, householder age, and presence of children in the home. Vegetation cover showed no relationship, indicating that greater cover alone does not promote ecosystem service delivery through the active use pathway. Together our results show that people who have higher nature relatedness may receive greater benefits from their yards via both passive and active means as they have more vegetation available to them in their yards and they interact with this space more frequently and for longer time periods.

Why do people feed birds?

Cox, D.T.C. & Gaston, K.J. 2016. Urban bird feeding: connecting people with nature. PLoS One 11, e0158717. shutterstock_254521675 [Image from Shutterstock]

At a time of unprecedented biodiversity loss, researchers are increasingly recognizing the broad range of benefits provided to humankind by nature. However, as people live more urbanized lifestyles there is a progressive disengagement with the natural world that diminishes these benefits and discourages positive environmental behaviour. The provision of food for garden birds is an increasing global phenomenon, and provides a readily accessible way for people to counter this trend. Yet despite its popularity, quite why people feed birds remains poorly understood. We explore three loosely defined motivations behind bird feeding: that it provides psychological benefits, is due to a concern about bird welfare, and/or is due to a more general orientation towards nature. We quantitatively surveyed households from urban towns in southern England to explore attitudes and actions towards garden bird feeding. Each household scored three Likert statements relating to each of the three motivations. We found that people who fed birds regularly felt more relaxed and connected to nature when they watched garden birds, and perceived that bird feeding is beneficial for bird welfare while investing time in minimising associated risks. Finally, feeding birds may be an expression of a wider orientation towards nature. Overall, we found that the feelings of being relaxed and connected to nature were the strongest drivers. As urban expansion continues both to threaten species conservation and to change peoples’ relationship with the natural world, feeding birds may provide an important tool for engaging people with nature to the benefit of both people and conservation.

Crows clean up

Inger, R., Per, E., Cox, D.T.C. & Gaston, K.J. 2016. Key role in ecosystem functioning of scavengers reliant on a single common species. Scientific Reports 6, 29641.IMG_0184

The importance of species richness in maintaining ecosystem function in the field remains unclear.Recent studies however have suggested that in some systems functionality is maintained by a few abundant species. Here we determine this relationship by quantifying the species responsible for a key ecosystem role, carcass removal by scavengers. We find that, unlike those within largely unaltered environments, the scavenger community within our highly altered system is dominated by a single species, the Carrion crow, despite the presence of a number of other scavenging species. Furthermore, we find no relationship between abundance of crows and carcass removal. However, the overall activity of crows predicts carcass biomass removal rate in an asymptotic manner, suggesting that a relatively low level of abundance and scavenging activity is required to maintain this component of ecosystem function.

Benefits of doses of nature experience

Shanahan, D.F., Bush, R., Gaston, K.J., Lin, B.B., Dean, J., Barber, E. & Fuller, R.A. 2016. Health benefits from nature experiences depend on dose. Scientific Reports 6, 28551. (Image from Shutterstock) shutterstock_228348913

Nature within cities will have a central role in helping address key global public health challenges associated with urbanization. However, there is almost no guidance on how much or how frequently people need to engage with nature, and what types or characteristics of nature need to be incorporated in cities for the best health outcomes. Here we use a nature dose framework to examine the associations between the duration, frequency and intensity of exposure to nature and health in an urban population. We show that people who made long visits to green spaces had lower rates of depression and high blood pressure, and those who visited more frequently had greater social cohesion. Higher levels of physical activity were linked to both duration and frequency of green space visits. A dose-response analysis for depression and high blood pressure suggest that visits to outdoor green spaces of 30 minutes or more during the course of a week could reduce the population prevalence of these illnesses by up to 7% and 9% respectively. Given that the societal costs of depression alone in Australia are estimated at AUD$12.6 billion per annum, savings to public health budgets across all health outcomes could be immense.