Diverse impacts of artificial light

Sanders, D., Frago, E., Kehoe, R., Patterson, C. & Gaston, K.J. 2020. A meta-analysis of biological impacts of artificial light at night. Nature Ecology and Evolution [online early].

Natural light cycles are being eroded over large areas of the globe by the direct emissions and sky brightening that result from sources of artificial night-time light. This is predicted to affect wild organisms, particularly because of the central role that light regimes play in determining the timing of biological activity. Although many empirical studies have reported such effects, these have focused on particular species or local communities and have thus been unable to provide a general evaluation of the overall frequency and strength of these impacts. Using a new database of published studies, we show that exposure to artificial light at night induces strong responses for physiological measures, daily activity patterns and life history traits. We found particularly strong responses with regards to hormone levels, the onset of daily activity in diurnal species and life history traits, such as the number of offspring, predation, cognition and seafinding (in turtles). So far, few studies have focused on the impact of artificial light at night on ecosystem functions. The breadth and often strength of biological impacts we reveal highlight the need for outdoor artificial night-time lighting to be limited to the places and forms—such as timing, intensity and spectrum—where it is genuinely required by the people using it to minimize ecological impacts.

Biodiversity and planning

Baker, D.J., Maclean, I.M.D., Goodall, M. & Gaston, K.J. 2021. Species distribution modelling is needed to support ecological impact assessments. Journal of Applied Ecology [online early].

1. Legislation commonly mandates the mitigation of impacts to biodiversity in planning and development processes, with potential impacts identified through some form of ecological impact assessment. Yet, protections for biodiversity are frequently undermined because the distributions of priority species are poorly known in most locations at the spatial scales required to inform planning decisions (i.e. c. 1-100 ha).

2. Planning applications are often screened against opportunistic records to determine potential impacts to priority species. However, raw occurrence records provide information only on where a species has been detected and cannot be used to indicate if a species is likely to be absent from a site.

3. Inferences drawn from these data on the likelihood of a species being present at a site can only be correctly interpreted through an appropriate species distribution modelling (SDM) framework that ensures assumptions about the data and models are formalised and documented. We argue that SDM frameworks must be integrated into ecological impact assessments to improve support for biodiversity protections within planning and development processes.

4. Biases and uncertainties in opportunistic data create modelling challenges, but recent methodological advances can minimise their impacts on predictions. We advocate co-production with practitioners of SDM tools, mapping products and best-practice guidelines specific to planning processes.

5. Policy implications. The integration of species distribution modelling frameworks into ecological impact assessments will strengthen biodiversity protections in planning and development processes by ensuring methodological transparency and rigour in the interpretation of species occurrence data.

Asymmetrical warming

Cox, D.T.C., Maclean, I.M.D., Gardner, A.S. & Gaston, K.J. 2020. Global variation in diurnal asymmetry in temperature, cloud cover, specific humidity and precipitation and its association with Leaf Area Index. Global Change Biology [online early].

The impacts of the changing climate on the biological world vary across latitudes, habitats and spatial scales. By contrast, the time of day at which these changes are occurring has received relatively little attention. As biologically significant organismal activities often occur at particular times of day, any asymmetry in the rate of change between the daytime and night-time will skew the climatic pressures placed on them, and this could have profound impacts on the natural world. Here we determine global spatial variation in the difference in the mean annual rate at which near-surface daytime maximum and night-time minimum temperatures and mean daytime and mean night-time cloud cover, specific humidity and precipitation have changed over land. For the years 1983–2017, we derived hourly climate data and assigned each hour as occurring during daylight or darkness. In regions that showed warming asymmetry of >0.5°C (equivalent to mean surface temperature warming during the 20th century) we investigated corresponding changes in cloud cover, specific humidity and precipitation. We then examined the proportional change in leaf area index (LAI) as one potential biological response to diel warming asymmetry. We demonstrate that where night-time temperatures increased by >0.5°C more than daytime temperatures, cloud cover, specific humidity and precipitation increased. Conversely, where daytime temperatures increased by >0.5°C more than night-time temperatures, cloud cover, specific humidity and precipitation decreased. Driven primarily by increased cloud cover resulting in a dampening of daytime temperatures, over twice the area of land has experienced night-time warming by >0.25°C more than daytime warming, and has become wetter, with important consequences for plant phenology and species interactions. Conversely, greater daytime relative to night-time warming is associated with hotter, drier conditions, increasing species vulnerability to heat stress and water budgets. This was demonstrated by a divergent response of LAI to warming asymmetry.

Extending the parasitic day

Kehoe, R., Sanders, D., Cruse, D., Silk, M., Gaston, K.J., Bridle, J.R. & van Veen, F. 2020. Longer photoperiods through range shifts and artificial light lead to a destabilising increase in host-parasitoid interaction strength. Journal of Animal Ecology [online early].

  1. Many organisms are experiencing changing daily light regimes due to latitudinal range shifts driven by climate change and increased artificial light at night (ALAN). Activity patterns are often driven by light cycles, which will have important consequences for species interactions.
  2. We tested whether longer photoperiods lead to higher parasitism rates by a day-active parasitoid on its host using a laboratory experiment in which we independently varied day length and the presence of ALAN. We then tested whether reduced nighttime temperature tempers the effect of ALAN.
  3. We found that parasitism rate increased with day length, with ALAN intensifying this effect only when the temperature was not reduced at night. The impact of ALAN was more pronounced under short day length. Increased parasitoid activity was not compensated for by reduced lifespan, indicating that increased day length leads to an increase in total parasitism effects on fitness.
  4. To test the significance of increased parasitism rate for population dynamics, we developed a host-parasitoid model. The results of the model predicted an increase in time-to-equilibrium with increased day length and, crucially, a threshold day length above which interactions are unstable, leading to local extinctions.
  5. Here we demonstrate that ALAN impact interacts with day length and temperature by changing the interaction strength between a common day-active consumer species and its host in a predictable way. Our results further suggest that range expansion or ALAN induced changes in light regimes experienced by insects and their natural enemies will result in unstable dynamics beyond key tipping points in day length.

Personal detection

Gaston, K.J. 2020. Personalised ecology and detection functions. People and Nature [online early].

1. Direct interactions with nature are important for people’s health, well-being and support for pro-nature policies. There is an urgent need better to understand the structure and dynamics of these interactions, and how they differ among individual people, human populations and the communities to which they belong.

2. The determinants of these interactions have two components. First are the factors that influence whether someone undertakes actions that may lead to interactions with nature (e.g. looking through a window, going for a walk, travelling to the countryside). These factors have attracted significant attention. Second are the factors that influence what nature interactions are obtained when someone is present in a situation in which these could occur. These have received little explicit attention.

3. One way of formalizing understanding, and identifying gaps in knowledge, of the second group of factors is to consider human–nature interactions in terms of detection functions. Rather than using such functions for the estimation of species abundances, the purpose for which they were originally developed, they can be reorganized as descriptors of influences on people’s nature interactions.

4. This paper considers how the different variables contained within detection functions influence human–nature interactions, and in particular how the number of nature interactions a person has in a given place and time is shaped both by clearly ‘nature’-associated variables, such as the number of organisms present, and also by variables that are strongly influenced by characteristics of the observer, such as how they use or explore an area and their personal nature detection abilities.

5. Many issues explored in the context of human–nature interactions are then seen to concern these component variables of detection functions, and approaches to improving the frequency of interactions seen, in effect, to be targeted at affecting change in different ones of these variables.

Bottom-up mapping of climate zones

Gardner, A.S., Maclean, I.M.D. & Gaston, K.J. 2020. A new system to classify global climate zones based on plant physiology and using high temporal resolution climate data. Journal of Biogeography, [online early].

Aim: Climate classification systems (CCSs) can be used to predict how species’ distributions might be altered by climate change and to increase the reliability of these estimates is an important goal in biogeographical research. We produce an objective, global climate classification system (CCS) at high temporal resolution based on plant physiology as a robust way to predict how climate change may impact terrestrial biomes.

Location: Global

Taxon: Plantae

Methods: We construct ten climate variables that capture the physiological processes that determine plant distributions and use cluster analysis to present a new global CCS which accounts for variation in these aspects of climate. We use Kappa statistics to compare the distribution of climate zones in a five- and six-cluster CCS constructed using the physiology variables to the popular Köppen-Geiger and Köppen-Trewartha CCSs, respectively, and find good correlation in both cases.

Results: Our CCS highlights ten climate zones for plants. We show that clustering of the physiologically relevant variables reproduces known, present-day patterns of vegetation but also indicates important areas where zone assignment in our physiological CCSs is different to that of the Köppen systems.

Main conclusions: The existing Köppen CCSs do not entirely reflect the physiological processes that determine plant distributions. Predictions of climate-driven changes in plant distributions may thus be unreliable in areas where zone assignment by clustering of physiologically relevant variables is different to that of the Köppen systems. Both the physiological relevance and temporal resolution of climate variables used to construct CCSs should be considered in order to predict reliably how climate change may alter plant distributions and to support an appropriate global response to conserve plant biodiversity for the future.

Pollinators on the verge

Phillips, B.B., Wallace, C., Roberts, B.R., Whitehouse, A.T., Gaston, K.J., Bullock, J.M., Dicks, L.V. & Osborne, J.L. 2020. Enhancing road verges to aid pollinator conservation: a review. Biological Conservation [online early].

Road verges provide habitats that have considerable potential as a tool for pollinator conservation, especially given the significant area of land that they collectively cover. Growing societal interest in managing road verges for pollinators suggests an immediate need for evidence-based management guidance. We used a formal, global literature review to assess evidence for the benefits of road verges for pollinators (as habitats and corridors), the potential negative impacts of roads on pollinators (vehicle-pollinator collisions, pollution, barriers to movement) and how to enhance road verges for pollinators through management. We identified, reviewed and synthesised 140 relevant studies. Overall, the literature review demonstrated that: (i) road verges are often hotspots of flowers and pollinators (well established), (ii) traffic and road pollution can cause mortality and other negative impacts on pollinators (well established), but available evidence suggests that the benefits of road verges to pollinators far outweigh the costs (established but incomplete), and (iii) road verges can be enhanced for pollinators through strategic management (well established). Future research should address the lack of holistic and large-scale understanding of the net effects of road verges on pollinators. We provide management recommendations for enhancing both individual road verges for pollinators (e.g. optimised mowing regimes) and entire road networks (e.g. prioritising enhancement of verges with the greatest capacity to benefit pollinators), and highlight three of the most strongly supported recommendations: (i) creating high quality habitats on new and existing road verges, (ii) reducing mowing frequency to 0–2 cuts/year and (iii) reducing impacts of street lighting.

Nature experiences and life satisfaction

Chang, C-C., Oh, R.R.Y., Nghiem, T.P.L., Zhang, Y., Tan, C.L.Y., Lin, B.B., Gaston, K.J., Fuller, R.A. & Carrasco, L.R. 2020. Life satisfaction linked to the diversity of nature experiences and nature views from the window. Landscape and Urban Planning 202, 103874.

The effects of nature interactions on multiple aspects of human subjective wellbeing are increasingly well understood. Although nature experience has been shown to be positively associated with life satisfaction, it remains unknown whether the diversity of nature experiences contributes to increased life satisfaction and whether the relationship is mediated by a person’s strength of connection with nature. We conducted a national survey in Singapore through online questionnaires (n = 1, 262), where we measured frequency, duration, diversity of nature experiences, and presence or absence of nature views from windows at home and at the workplace. We also measured participants’ strength of connection with nature (how strongly a person identifies with nature). We found that people who visited more diverse types of natural spaces (ranging from wild nature, managed parks, and beaches) had higher life satisfaction. The presence of nature views from windows at the home and/or at the workplace was also linked with higher life satisfaction. We also found that people with a stronger connection with nature had higher life satisfaction when they spent more than one hour in natural spaces per week, while this relationship was weak for people without a strong connection with nature. Our results suggest that urban planning should aim to provide a diversity of natural spaces to increase life satisfaction.

Understanding extinction of experience

Gaston, K.J. & Soga, M. 2020. Extinction of experience: the need to be more specific. People and Nature [online early].

1. Extinction of experience, the progressive loss of human–nature interactions, may prove to be one of the key environmental concepts of our times. Not only does this loss reduce the important benefits that people gain from these interactions, but it may also undermine their support for pro-biodiversity policies and management actions, and thus play an important role in shaping the future of biodiversity.

2. Here, to help improve understanding, encourage a more consistent approach and highlight research gaps, we consider some of the key features of the concept of extinction of experience, contentions that these have caused and propose some solutions.

3. We focus particularly on the importance of (a) the definition of nature employed; (b) whether direct or other human–nature interactions are considered; (c) the differences between the loss and the extinction of experience; (d) the timing of the loss of interactions that is considered; and (e) the difference between human–nature interactions and human–nature experiences.

4. Differentiating between narrow and broad senses of nature, between childhood and lifelong timings, and between interactions and experiences leads to a typology of eight different forms of extinction of experience. Such a classification can be useful for targeting research, furthering understanding of the processes and dynamics of the extinction of experience, and developing policies to reduce this phenomenon and minimize its negative consequences.