Horizon scanning

Sutherland, W.J., Bennett, C.., Brotherton, P.N.M. Butterworth, H.M., Clout, M.N., Côté, I.M., Dinsdale, J., Esmail, N., Fleishman, E., Gaston, K.J., Herbert-Read, J.E., Hughes, A., Kaartokallio, H., Le Roux, X., Lickorish, F.A., Matcham, W., Noor, N., Palardy, J.E., Pearce-Higgins, J.W., Peck, L.S., Pettorelli, N., Pretty, J., Scobey, R., Spalding, M.D., Tonneijck, F.H., Tubbs, N., Watson, J.E.M., WentworthJ.E., Wilson, J.D & Thornton, A. 2023. A global biological conservation horizon scan of issues for 2023. Trends in Ecology and Evolution 38, 96-107.

We present the results of our 14th horizon scan of issues we expect to influence biological conservation in the future. From an initial set of 102 topics, our global panel of 30 scientists and practitioners identified 15 issues we consider most urgent for societies worldwide to address. Issues are novel within biological conservation or represent a substantial positive or negative step change at global or regional scales. Issues such as submerged artificial light fisheries and accelerating upper ocean currents could have profound negative impacts on marine or coastal ecosystems. We also identified potentially positive technological advances, including energy production and storage, improved fertilisation methods, and expansion of biodegradable materials. If effectively managed, these technologies could realise future benefits for biological diversity.

Multiple environmental consequences of artificial lighting

Gaston, K.J. & Sánchez de Miguel, A. 2022. Environmental impacts of artificial light at night. Annual Review of Environment and Resources 47, 373-398.

The nighttime is undergoing unprecedented change across much of the world, with natural light cycles altered by the introduction of artificial light emissions. Here we review the extent and dynamics of artificial light at night (ALAN), the benefits that ALAN provides, the environmental costs ALAN creates, approaches to mitigating these negative effects, and how costs are likely to change in the future. We particularly highlight the consequences of the increasingly widespread use of light-emitting diode (LED) technology for new lighting installations and to retrofit pre-existing ones. Although this has been characterized as a technological lighting revolution, it also constitutes a revolution in the environmental costs and impacts of ALAN, particularly because the LEDs commonly used for outdoor lighting have significant emissions at the blue wavelengths to which many biological responses are particularly sensitive. It is clear that a very different approach to the use of artificial lighting is required. [Image from Earth Science and Remote Sensing Unit, NASA Johnson Space Center]

Colouring Europe by night

Sánchez de Miguel, A., Bennie, J., Rosenfeld, E., Dzurjak, S. & Gaston, K.J. 2022. Environmental risks from artificial nighttime lighting widespread and increasing across Europe. Science Advances 8, eabl6891.

The nighttime environment of much of Earth is being changed rapidly by the introduction of artificial lighting. While data on spatial and temporal variation in the intensity of artificial lighting have been available at a regional and global scale, data on variation in its spectral composition have only been collected for a few locations, preventing variation in associated environmental and human health risks from being mapped. Here, we use imagery obtained using digital cameras by astronauts on the International Space Station to map variation in the spectral composition of lighting across Europe for 2012–2013 and 2014–2020. These show a regionally widespread spectral shift, from that associated principally with high-pressure sodium lighting to that associated with broad white light-emitting diodes and with greater blue emissions. Reexpressing the color maps in terms of spectral indicators of environmental pressures, we find that this trend is widely increasing the risk of harmful effects to ecosystems.[Image from Earth Science and Remote Sensing Unit, NASA Johnson Space Center]

Losing who does what when

Cox, D.T.C., Gardner, A.S. & Gaston, K.J. 2022. Global and regional erosion of mammalian functional diversity across the diel cycle. Science Advances 8, eabn6008.

Biodiversity is declining worldwide. When species are physically active (i.e., their diel niche) may influence their risk of becoming functionally extinct. It may also affect how species losses affect ecosystems. For 5033 terrestrial mammals, we predict future changes to diel global and local functional diversity through a gradient of progressive functional extinction scenarios of threatened species. Across scenarios, diurnal species were at greater risk of becoming functionally extinct than nocturnal, crepuscular, and cathemeral species, resulting in deep functional losses in global diurnal trait space. Redundancy (species with similar roles) will buffer global nocturnal functional diversity; however, across the land surface, losses will mostly occur among functionally dispersed species (species with distinct roles). Functional extinctions will constrict boundaries of cathemeral trait space as megaherbivores, and arboreal foragers are lost. Variation in the erosion of functional diversity across the daily cycle will likely profoundly affect the partitioning of ecosystem functioning between night and day.

Bites, stings and phobias

Soga, M. & Gaston, K.J. 2022. The dark side of nature experience: typology, dynamics and implications of negative sensory interactions with nature. People and Nature, online early.

1. The human health benefits of direct sensory interactions with nature (hereafter direct human–nature interactions) are increasingly recognised. However, these interactions can also have various negative health and well-being impacts on people, some of which may be severe. Compared to positive ones, there has been relatively little investigation of such negative direct human–nature interactions beyond the medical literature, and what has been done is widely scattered across disciplines.

2. Here, we provide an overview of the typology, characteristics and dynamics of negative direct sensory interactions with nature and suggest management implications and future research directions.

3. We highlight the breadth of forms that negative direct human–nature interactions occur, and evidence that the incidences of some have recently grown rapidly in many parts of the world.

4. Our review also suggests that more intense negative direct human–nature interactions can sometimes occur simultaneously or sequentially with more positive ones, and there may be trade-offs between the two.

5. Such serious implications highlight the importance of focusing research and public policy on improving the understanding of negative direct human–nature interactions, taking a more balanced view of the benefits and costs of nature experiences, and developing appropriate mitigation strategies.

Nature & social cohesion

Oh, R.R.Y., Zhang, Y., Nghiem, L.T.P., Chang, C.-C., Tan, C.L.Y., Quazi, S.A., Shanahan, D.F., Lin, B.B., Gaston, K.J., Fuller, R.A. & Carrasco, R.L. 2022. Connection to nature and time spent in gardens predicts social cohesion. Urban Forestry and Urban Greening 74, 127655.

A person’s health and wellbeing are contingent on the amount of social support that they receive. Similarly, experiencing nature has been shown to improve people’s health and wellbeing. However, we do not know how relationships between social cohesion, nature experiences and nature connection could interrelate and vary across different types of urban green spaces, and in non-Westernised cultures. We conducted a study on 1249 residents in Singapore, a tropical city-state, and measured three dimensions of social cohesion (i.e. general social cohesion; trust and sense of community; and social interactions), various types of nature experiences (i.e. amount of green space around one’s residence; frequency and duration of urban green space visits; frequency and duration of visits to gardens), and three dimensions of one’s connection to nature: self-identity with nature, desire to experience nature, and environmental concern (using the nature relatedness scale). We found that people who strongly identify with nature, who enjoy being in nature, and who had more frequent gardens visits were more likely to have a stronger sense of social cohesion across two dimensions. However, those with stronger environmental concern reported an overall weaker sense of social cohesion, possibly due to the perception that society’s contributions to conserve environmental problems was insufficient. Further, people who gardened more frequently were also more likely to visit green spaces, self-identify with nature and exhibit a stronger desire to experience nature. We propose that strategies targeted at encouraging people to engage in nature-related, collaborative activities at the local community level, such as spending time in local gardens, will increase urban residents’ daily nature experiences and its associated benefits such as improving social cohesion. 

Lighting up plant communities

Anic, V., Gaston, K.J., Davies, T.W. & Bennie, J. 2022. Long-term effects of artificial nighttime lighting and trophic complexity on plant biomass and foliar carbon and nitrogen in a grassland community. Ecology and Evolution 12, e9157.

The introduction of artificial nighttime lighting due to human settlements and transport networks is increasingly altering the timing, intensity, and spectra of natural light regimes worldwide. Much of the research on the impacts of nighttime light pollution on organisms has focused on animal species. Little is known about the impacts of daylength extension due to outdoor lighting technologies on wild plant communities, despite the fact that plant growth and development are under photoperiodic control. In a five-year field experiment, artificial ecosystems (“mesocosms”) of grassland communities both alone or in combination with invertebrate herbivores and predators were exposed to light treatments that simulated street lighting technologies (low-pressure sodium, and light-emitting diode [LED]-based white lighting), at ground-level illuminance. Most of the plant species in the mesocosms did not exhibit changes in biomass accumulation after 5 years of exposure to the light treatments. However, the white LED treatment had a significant negative effect on biomass production in the herbaceous species Lotus pedunculatus. Likewise, the interaction between the white LED treatment and the presence of herbivores significantly reduced the mean shoot/root ratio of the grass species Holcus lanatus. Artificial nighttime lighting had no effect on the foliar carbon or nitrogen in most of the grassland species. Nevertheless, the white LED treatment significantly increased the leaf nitrogen content in Lotus corniculatus in the presence of herbivores. Long-term exposure to artificial light at night had no general effects on plant biomass responses in experimental grassland communities. However, species-specific and negative effects of cool white LED lighting at ground-level illuminance on biomass production and allocation in mixed plant communities are suggested by our findings. Further studies on the impacts of light pollution on biomass accumulation in plant communities are required as these effect could be mediated by different factors, including herbivory, competition, and soil nutrient availability.

Monitoring nature engagement

Phillips, B.B., Burgess, K., Willis, C. & Gaston, K.J. 2022. Monitoring public engagement with nature using Google Trends. People and Nature, online early.

1. How humans interact with nature affects the health of both people and ecosystems. Yet, long-term data on nature engagement are scarce because traditional survey methods are expensive, time consuming and require commitment over multiple years. Digital data sources (e.g. aggregated data from online searches) have major potential as a supplementary source of information and, in the absence of available data, as a proxy for more direct measurement of nature engagement.

2. Using Google Trends, we created a list of refined and relevant search terms relating to diverse outdoor spaces and activities. We then compared trends in Google search volumes in England across both a 1-year and 10-year period to those from Google Community Mobility Reports, and from nationally representative survey data (Natural England’s People and Nature Survey and the Monitor of Engagement with the Natural Environment).

3. Search, survey and mobility data all support a general increase in public engagement with nature since 2009, and a more substantial increase during, or following, the initial national ‘lockdown’ period of the COVID-19 pandemic in England. Search volumes increased for many urban and rural outdoor green spaces (e.g. woodlands), blue spaces (e.g. reservoirs), exercise activities (e.g. walking, running and hiking) and explicitly nature-based activities (e.g. fishing, wild swimming and encouraging wildlife).

4. Overall, volumes of Google searches were more closely related with longer-term (10-year) trends from survey data, than shorter-term changes during the COVID-19 pandemic. There were statistically significant relationships between search volumes, survey data (self-reported past behaviour) and mobility data (movement trends) for around half of comparisons. Of these, an average of 13–44% of variation in the data was explained.

5. The findings show that Google Trends provides valuable information about public engagement with nature, which can help to supplement existing survey data by providing new insights about behavioural trends. The paper also provides a proof of concept for using Google Trends to understand changes in public engagement with nature, which could be applied to the many countries that lack long-term survey monitoring.

Lighting up food webs

Sanders, S., Baker, D.J., Cruse, D., Bell, F., van Veen, F.J.F. & Gaston, K.J. 2022. Spectrum of artificial light at night drives impact of a diurnal species in insect food web. Science of the Total Environment 831, 154893.

Artificial light at night (ALAN) has become a profound form of global anthropogenic environmental change differing in from natural light regimes in intensity, duration, distribution and spectra. It is clear that ALAN impacts individual organisms, however, population level effects, particularly of spectral changes, remain poorly understood. Here we exposed experimental multigenerational aphid-parasitoid communities in the field to seven different light spectra at night ranging from 385 to 630 nm and compared responses to a natural day-night light regime. We found that while aphid population growth was initially unaffected by ALAN, parasitoid efficiency declined under most ALAN spectra, leading to reduced top-down control and higher aphid densities. These results differ from those previously found for white light, showing a strong impact on species’ daytime performance. This highlights the importance of ALAN spectra when considering their environmental impact. ALAN can have large impacts on the wider ecological community by influencing diurnal species.

Losing rural darkness

Cox, D.T.C., Sánchez de Miguel, A., Bennie, J., Dzurjak, S.A., & Gaston, K.J. 2022. Majority of artificially lit Earth surface associated with non-urban, non-industrial population. Science of the Total Environment 841, 156782.

Key to understanding the negative impacts of artificial light at night (ALAN) on human health and the natural environment is its relationship with human density. ALAN has often primarily been considered an urban issue, however although over half of the population is urbanized, the 46 % that are not inhabit a dispersed array of smaller settlements. Here, we determine the global relationships between two dimensions of ALAN, namely direct emissions (radiance) and skyglow, and human density, and howthese relationships vary across continents.We correct the Visible Infrared Imaging Radiometer Suite Day/Night Band (VIIRS DNB) product for albedo, skyglow, airglow, the aurora and permanent snow and ice to represent upward radiance overland at 1.61 ∗ 2.12 km resolution from artificial sources only. For skyglow we use the World Atlas of Artificial Sky Brightness. Globally (between 59°N and 55°S), direct emissions were detected over 26.5 % and skyglow over 46.9 % of land area. Over half of all cumulative direct emissions (54.9 %) were emitted at low levels by the non-urban population, whilst these populations experienced the negative impacts of over two-thirds of all cumulative skyglow (69.8 %). This emphasises the extent of ALAN outside of urban areas, and its similarity in this regard to a number of other forms of pollution. Although powerful sources of rural direct emissions (e.g., industry, recreation) are important contributors of light pollution, cumulatively they only contributed 10% to total direct emissions. The relationship between each dimension of ALAN and population density varied across continents, driven by powerful rural emissions, non-urban populations and urban design. These relationships reflect the unique socio-economic and geographical make-up of each region and inform on where best to target light pollution mitigation strategies, not only in urban areas but also in rural ones.