Artificial light and lockdown

Bustamante-Calabria, M., Sánchez de Miguel, A., Martín-Ruiz, S., Ortiz, J-L., Vílchez, J.M., Pelegrina, A., García, A., Zamorano, J., Bennie, J. & Gaston, K.J. 2021. Effects of the COVID-19 lockdown on urban light emissions: ground and satellite comparison. Remote Sensing, 13, 258.

‘Lockdown’ periods in response to COVID-19 have provided a unique opportunity to study the impacts of economic activity on environmental pollution (e.g., NO2, aerosols, noise, light). The effects on NO2 and aerosols have been very noticeable and readily demonstrated, but that on light pollution has proven challenging to determine. The main reason for this difficulty is that the primary source of nighttime satellite imagery of the earth is the SNPP-VIIRS/DNB instrument, which acquires data late at night after most human nocturnal activity has already occurred and much associated lighting has been turned off. Here, to analyze the effect of lockdown on urban light emissions, we use ground and satellite data for Granada, Spain, during the COVID-19 induced confinement of the city’s population from 14 March until 31 May 2020. We find a clear decrease in light pollution due both to a decrease in light emissions from the city and to a decrease in anthropogenic aerosol content in the atmosphere which resulted in less light being scattered. A clear correlation between the abundance of PM10 particles and sky brightness is observed, such that the more polluted the atmosphere the brighter the urban night sky. An empirical expression is determined that relates PM10 particle abundance and sky brightness at three different wavelength bands.

Variability and suitability

Gardner, A.S., Gaston, K.J. & Maclean, I.M.D. 2021. Accounting for inter-annual variability alters long-term estimates of climate suitability. Journal of Biogeography [online early].

Aim: Species respond to environmental conditions and so reliable assessments of climate suitability are important for predicting how climate change could alter their distributions. Long-term average climate data are often used to evaluate the climate suitability of an area, but in these aggregated climate datasets, inter-annual variability is lost. Due to non-linearity in species’ biological responses to climate, estimates of long-term climate suitability from average climate data may be biased and so differ from estimates derived from the average annual suitability over the same period (average response). We investigate the extent to which such differences manifest in a regional assessment of climate suitability for 255 plant species across two 17-year time periods.

Location: Cornwall in South-West England provides a case study.

Taxon: Plantae.

Methods: We run a simple mechanistic climate suitability model and derive quantitative estimates of climate suitability for 1984–2000 and 2001–2017. For each period, we run the model using climate data representing average monthly values for that period. We then run the model for each year using monthly climate data for that year and average the annual suitability scores across each period (average response). We compare estimates of climate suitability from these two approaches.

Results: Average climate data gave higher estimates of suitability than the average response, suggesting bias against years of poor suitability in temporally aggregated climate datasets. Differences between suitability estimates were larger in areas of high climate variability and correlated with species’ environmental requirements, being larger for species with small thermal niches and narrow ranges of precipitation tolerance.

Main Conclusions: Incorporating inter-annual variability into climate suitability assessments or understanding the extent to which average climate data might obscure this variance will be important to predict reliably the impacts of climate change on species distributions and should be considered when using mechanistic species distribution models.

Nature interactions vary between cities

Oh, R.R.Y., Fielding, K.S., Nghiem, L.T.P., Chang, C.C., Shanahan, D.F., Gaston, K.J., Carrasco, L.R. & Fuller, R.A. 2021. Factors influencing nature interactions vary between cities and types of nature interactions. People and Nature 3, 405-417.

1. There is mounting concern that people living more urbanised, modern lifestyles have fewer and lower quality interactions with nature, and therefore have limited access to the associated health and well-being benefits. Yet, variation in the different types of nature interactions and the factors that influence these interactions across populations are poorly understood.

2. We compared four types of nature interactions by administering surveys across two cities that differ markedly in urbanisation pattern and population density – Singapore and Brisbane – : (a) indirect (viewing nature through a window at work or at home); (b) incidental (spending time in nature as part of work); (c) intentional interactions in gardens; and (d) intentional interactions in public urban greenspace.

3. Our results show that Singapore respondents spent about half as much time (25.8 hr/week) interacting with nature as Brisbane respondents (52.3 hr/week), and indirect interactions were the most prevalent across both cities.

4. Nature orientation, age, income and gender significantly predicted the duration of nature interactions in both cities, while self-reported health, education and ethnicity additionally predicted the duration of nature interactions only for Brisbane. Also, the relationship(s) between each factor and duration could differ in direction and effect size between the types of nature interactions.

5. As such, we conclude that there is much local variation in the dynamics of interactions between people and nature, and that focused studies are needed to develop effective interventions addressing declines in nature interactions in different locations.


McNaughton, E.J., Beggs, J.R., Gaston, K.J., Jones, D.N. & Stanley, M.C. 2021. Retrofitting streetlights with LEDs has limited impacts on urban wildlife. Biological Conservation 254, 108944.

Artificial light at night (ALAN) causes a wide range of ecological impacts across diverse ecosystems. Most concentrated in urban areas, ALAN poses a particular risk to associated wildlife by disrupting physiology, behaviour and ultimately survival. This risk is predicted to shift as nighttime lightscapes in many cities undergo change. Globally, streetlights are currently being retrofitted with newer technologies that differ in the spectrum and intensity of their emissions, but there is a dearth of in situ urban experiments on the ecological impacts of this change. We monitored timing of dawn and dusk bird song; frequency of owl vocalisations; avian diversity, relative abundance and community composition; small invasive mammal and ground insect activity; and invertebrate relative abundance at 26 residential properties over an 18-month period that coincided with a retrofit from high-pressure sodium (HPS) to white light-emitting diode (LED) streetlights. Initiation time of dawn song was advanced or delayed for two bird species following the retrofit and backyard avian community composition was altered. Avian species richness, relative abundances of three bird species and ground insect activity increased in the presence of LED streetlights. No other retrofit effects were found. Our study suggests that retrofitting streetlights with white LEDs may lead to both positive and negative conservation outcomes for urban wildlife, but direct impacts are relatively small and may be mitigated by changes in lighting characteristics, such as dimming. Streetlight retrofits could provide an opportunity to reduce the impacts of ALAN on urban wildlife if intentionally designed with conservation benefits in mind.

Green exercise

Tan, C.L.Y., Chang, C.-C., Nghiem, T.P.L., Zhang, Y., Oh, R.R.Y., Shanahan, D.F., Lin, B.B., Gaston, K.J., Fuller, R.A. & Carrasco, L.R. 2021. The right mix: residential urban green-blue space combinations are correlated with physical exercise in a tropical city-state. Urban Forestry & Urban Greening 57, 126947. [Image from NASA]

Growing recognition of nature’s benefits to many aspects of human wellbeing has prompted the incorporation of both urban green and blue natural outdoor environments (NOEs) into cities. Amongst the many purposes of NOEs, promotion of physical exercise has been garnering interest, given the increasingly sedentary lifestyles of urban dwellers. However, studies rarely consider how different types of NOEs, let alone the combination of them, might affect the type and frequency of physical exercise conducted by urban residents. We use Singapore, a highly urbanised tropical nation with a considerable number of NOEs, as a case-study to address these gaps. We used a market research survey (n = 1519), geographic information systems, and generalised linear regression models to investigate the relationship between residential NOE cover, exercise-influencing sociodemographic factors, and outdoor exercise choice (i.e., if respondents exercised or not) and frequency of four types of physical exercises: walking, individual-based, team-sports, and overall exercise. For exercise choice, more people walked in areas with higher forest and scrub cover, and less in areas with just scrub. Less conducted individual-based exercise in areas with high unmanaged vegetation cover, and more conducted team-sports in areas with higher open-canopy managed vegetation cover. Amongst those who engaged in these exercises, managed vegetation cover is positively correlated with walking (open- and closed-canopy combined) and team-sports (open-canopy) frequency. Individual-based exercise frequency rose in areas with a mix of high open-canopy managed vegetation and blue space cover within 250 m from one’s home, and a mix of high managed treescape and forest cover 500 m from one’s home. Findings suggest that a specific mix of NOEs can promote the participation of different types of physical exercise. Integrating the right NOE types and combinations into urban residential spaces may thus help to mitigate sedentary lifestyles, boosting public health outcomes in city populations.

Crop futures

Gardner, A.S., Maclean, I.M.D., Gaston, K.J. & Bütikofer, L. 2021. Forecasting future crop suitability with microclimate data. Agricultural Systems 190, 103084.

Context: Against a background of unprecedented climate change, humanity faces the challenge of how to increase global food production without compromising the natural environment. Crop suitability models can indicate the best locations to grow different crops and, in doing so, support efficient use of land to leave space for, or share space with, nature. However, challenges in downscaling the climate data needed to drive these models to make predictions for the future has meant that they are often run using national or regional climate projections. At finer spatial scales, variation in climate conditions can have a substantial influence on yield and so the continued use of coarse resolution climate data risks maladaptive agricultural decisions. Opportunities to grow novel crops, for which knowledge of local variation in microclimate may be critical, may be missed.

Objective: We demonstrate how microclimate information can be acquired for a region and used to run a mechanistic crop suitability model under present day and possible future climate scenarios.

Methods: We use microclimate modelling techniques to generate 100 m spatial resolution climate datasets for the south-west of the UK for present day (2012-2017) and predicted future (2042-2047) time periods. We use these data to run the mechanistic crop model WOrld FOod STudies (WOFOST) for 56 crop varieties, which returns information on maximum crop yields for each planting month.

Results and conclusions: Over short distances, we find that the highest attainable yields vary substantially and discuss how these differences mean that field-level assessments of climate suitability could support land-use decisions, enabling food production whilst protecting biodiversity.

Significance: We provide code for running WOFOST in the WofostR R package, thus enabling integration with microclimate models and meaning that our methodology could be applied anywhere in the world. As such, we make available to anyone the tools to predict climate suitability for crops at high spatial resolution for both present day and possible future climate scenarios.

Novel crops in a warming world

Gardner, A.S., Gaston, K.J. & Maclean, I.M.D. 2021. Combining qualitative and quantitative methodology to assess prospects for novel crops in a warming climate. Agricultural Systems, 190, 103083.

Context: Climate change will alter the global distribution of climatically suitable space for many species, including agricultural crops. In some locations, warmer temperatures may offer opportunities to grow novel, high value crops, but non-climatic factors also inform agricultural decision-making. These non-climatic factors can be difficult to quantify and incorporate into suitability assessments, particularly for uncertain futures. 

Objective: To demonstrate how qualitative and quantitative techniques can be combined to assess crop suitability with consideration for climatic and non-climatic factors.

Methods: We carried out a horizon scanning exercise that used Delphi methodology to identify possible novel crops for a region in south-west England. We show how the results of the expert panel assessment could be combined with a crop suitability model that only considered climate to identify the best crops to grow in the region. 

Results and conclusions: Whilst improving climate and crop models will enhance the ability to identify environmental constraints to growing novel crops, we propose horizon scanning as a useful tool to understand constraints on crop suitability that are beyond the parameterisation of these models and that may affect agricultural decisions.

Significance: A similar combination of qualitative and quantitative approaches to assessing crop suitability could be used to identify potential novel crops in other regions and to support more holistic assessments of crop suitability in a changing world.

Moving out of the night

Cox, D.T.C., Gardner, A.S. & Gaston, K.J. 2021. Diel niche variation in mammals associated with expanded trait space. Nature Communications 12, 1753.

Mammalian life shows huge diversity, but most groups remain nocturnal in their activity pattern. A key unresolved question is whether mammal species that have diversified into different diel niches occupy unique regions of functional trait space. For 5,104 extant mammals we show here that daytime-active species (cathemeral or diurnal) evolved trait combinations along different gradients from those of nocturnal and crepuscular species. Hypervolumes of five major functional traits (body mass, litter size, diet, foraging strata, habitat breadth) reveal that 30% of diurnal trait space is unique, compared to 55% of nocturnal trait space. Almost half of trait space (44%) of species with apparently obligate diel niches is shared with those that can switch, suggesting that more species than currently realised may be somewhat flexible in their activity patterns. Increasingly, conservation measures have focused on protecting functionally unique species; for mammals, protecting functional distinctiveness requires a focus across diel niches.

Biomass of aliens

Blackburn, T.M. & Gaston, K.J. 2021. Contribution of non-native galliforms to annual variation in biomass of British birds. Biological Invasions, 23, 1549-1562.

Millions of individuals of two species of non-native galliform birds, the Common Pheasant (Phasianus colchicus) and Red-legged Partridge (Alectoris rufa) are released into the British countryside annually in late summer, supplementing established breeding populations of these two species. The biomass of birds involved in these releases has been compared to the British breeding bird biomass. However, the validity of this comparison is compromised because the biomass of wild birds varies across the year due to reproduction, mortality and migration. How the biomass of Common Pheasants and Redlegged Partridges compares to that of other British bird species in late summer, or across the whole year, is currently unknown. Here, we produce estimates of how British bird biomass varies across the year, to assess the contribution of the two non-native galliforms to this variation. We show that overall British bird biomass is probably lowest around the start of the breeding season in April, and peaks in late summer and autumn. We estimate that around a quarter of British bird biomass annually is contributed by Common Pheasants and Red-legged Partridges, and that at their peak in August these two species represent about half of all wild bird biomass in Britain.

Roads, pollutants & pollinators

Phillips, B.B, Bullock, J.M., Gaston, K.J., Hudson-Edwards, K.A., Bamford, M., Cruse, C., Dicks, L.V., Falagan, C., Wallace, C. & Osborne, J.L.2021. Impacts of multiple pollutants on pollinator activity in road verges. Journal of Applied Ecology 58, 1017-1029.

1. To tackle pollinator declines, there is a major need to increase the quantity of flower-rich habitats. Road verges offer one such opportunity but are exposed to diverse forms of pollution from roads and road traffic.

2. We carried out a broad initial assessment to establish if and how pollution affects the quality of road verges as pollinator foraging environments. We assessed the spatial distribution of pollution, flowers and pollinators in road verges, then used field experiments to simulate and measure the impacts of four ubiquitous and little studied forms of road pollution (noise, turbulence, dust and metals) on pollinator densities and foraging behaviour.

3. We found that pollinators in road verges were exposed to noise, turbulence, dust and metal pollution, which decreased with distance from the road edge but, with the exception of turbulence, extended more than 8 m into road verges.

4. Pollinator densities were lower closer to the road edge – particularly within first 2 m (55% lower than at 7-9 m) – where pollution is greatest. This was despite a similar density and species richness of flowers.

5. Simulated turbulence deterred pollinators by causing intermittent disturbance (reducing visit duration by up to 54%), and some pollinator taxa preferentially avoided concentrations of metals that were more frequently found in flowers within 2 m of roads (resulting in up to 75% fewer visits), while noise and dust had no apparent effect.

6. Synthesis and applications. Pollinators in road verges are exposed to many forms of pollution, and we found impacts of roadside-realistic levels of turbulence and metals on pollinator densities and foraging behaviour. Although the findings suggest that road verges are largely suitable for pollinator conservation, management enhancements should prioritise areas more than 2 m from the road edge, and verges along roads with relatively lower traffic densities.