Pea aphids and artificial light

Bennie, J., Davies, T.W, Cruse, D., Inger, R. & Gaston, K.J (2015) Cascading effects of artificial light at night: resource-mediated control of herbivores in a grassland ecosystem. Philosophical Transactions of the Royal Society B 370, 20140131.

Artificial light at night has a wide range of biological effects on both plants and animals. Here, we review mechanisms by which artificial light at night may restructure ecological communities by modifying the interactions between species. Such mechanisms may be top-down (predator, parasite or grazer controlled), bottom-up (resource-controlled) or involve non-trophic processes, such as pollination, seed dispersal or competition. We present results from an experiment investigating both top-down and bottom-up effects of artificial light at night on the population density of pea aphids Acyrthosiphon pisum in a diverse artificial grassland community in the presence and absence of predators and under low-level light of different spectral composition. We found no evidence for top-down control of A. pisum in this system, but did find evidence for bottom-up effects mediated through the impact of light on flower head density in a leguminous food plant. These results suggest that physiological effects of light on a plant species within a diverse plant community can have detectable demographic effects on a specialist herbivore.

202 Words

Urban green space and public health

Shanahan, D.F., Lin, B.B., Bush, R., Gaston, K.J., Dean, J.H., Barber, E. & Fuller, R.A. (2015) Toward improved public health outcomes from urban nature. American Journal of Public Health, 105 (3), 470-477.

There is mounting concern for the health of urban populations as cities expand at an unprecedented rate. Urban green spaces provide settings for a remarkable range of physical and mental health benefits, and pioneering health policy is recognizing nature as a cost effective tool for planning healthy cities. Despite this, limited information on how specific elements of nature deliver health outcomes restricts its use for enhancing population health. We articulate a framework for identifying direct and indirect causal pathways through which nature delivers health benefits, and highlight current evidence. We see a need for a bold new research agenda founded on testing causality that transcends disciplinary boundaries between ecology and health. This will lead to cost-effective and tailored solutions that could enhance population health and reduce health inequalities.


163 Words

Artificial nighttime light pollution in natural ecosystems

Bennie, J., Duffy, J.P., Davies, T.W., Correa-Cano, M.E. & Gaston, K.J. (2015) Global trends in exposure to light pollution in natural terrestrial ecosystems. Remote Sensing 7, 2715-2730.

The rapid growth in electric light usage across the globe has led to increasing presence of artificial light in natural and semi-natural ecosystems at night. This occurs both due to direct illumination and skyglow – scattered light in the atmosphere. There is increasing concern about the effects of artificial light on biological processes, biodiversity and the functioning of ecosystems. We combine intercalibrated Defense Meteorological Satellite Program’s Operational Linescan System (DMSP/OLS) images of stable night-time lights for the period 1992 to 2012 with a remotely sensed landcover product (GLC2000) to assess recent changes in exposure to artificial light at night in 43 global ecosystem types. We find that Mediterranean-climate ecosystems have experienced the greatest increases in exposure, followed by temperate ecosystems. Boreal, Arctic and montane systems experienced the lowest increases. In tropical and subtropical regions, the greatest increases are in mangroves and subtropical needleleaf and mixed forests, and in arid regions increases are mainly in forest and agricultural areas. The global ecosystems experiencing the greatest increase in exposure to artificial light are already localized and fragmented, and often of particular conservation importance due to high levels of diversity, endemism and rarity. Night time remote sensing can play a key role in identifying the extent to which natural ecosystems are exposed to light pollution.

239 Words

The costs and benefits of artificial light

Gaston, K.J., Gaston, S., Bennie, J. & Hopkins, J. (2015) Benefits and costs of artificial nighttime lighting of the environment. Environmental Reviews 23, 14-23.

Artificial lighting has transformed the outdoor nighttime environment over large areas, modifying natural cycles of light in terms of timing, wavelength, and distribution. This has had widespread benefits and costs to humankind, impacting on health and wellbeing, vehicle accidents, crime, energy consumption and carbon emissions, aesthetics, and wildlife and ecosystems. Here, we review these effects, particularly in the context of ongoing developments in the extent of artificial lighting and in the prevalent technologies being employed. The key issue that emerges is how best to maximize the benefits of artificial nighttime lighting whilst limiting the costs. To do so, three main strategies are required. First, important knowledge gaps need to be filled. Second, there is an urgent need to connect the research being conducted in different disciplines, which to date has been very disjointed. Third, it is imperative that much firmer and well-developed links are made between research, policy, and practice.

172 Words

Worldwide night-time light pollution

Kyba, C.C.M., Tong, K.P., Bennie, J., Birriel, I., Birriel, J.J., Cool, A., Danielsen, A., Davies, T.W., den Outer, P.N., Edwards, W., Ehlert, R., Falchi, F., Fischer, J., Giacomelli, A., Guibbilini, F., Haaima, M., Hesse, C., Heygster, G., Holker, F., Inger, R., Jensen, L.J., Kuelchy, H.U., Kuehn, J., Langill, P., Lolkema, D.E., Nagy, M., Nievas, M., Ochi, N., Popow, E., Posch, T., Puschnig, J., Ruhtz, T., Schmidt, W., Schwarz, R., Schwope, A., Spoelstra, H., Tekatch, A., Trueblood, M., Walker, C.E., Weber, M., Welch, D.L., Zamorano, J. & Gaston, K.J. (2015) Worldwide variations in artificial skyglow. Scientific Reports 5, 8409.

Pages from Kyba et al SciRep 2015Despite constituting a widespread and significant environmental change, understanding of artificial nighttime skyglow is extremely limited. Until now, published monitoring studies have been local or regional in scope, and typically of short duration. In this first major international compilation of monitoring data we answer several key questions about skyglow properties. Skyglow is observed to vary over four orders of magnitude, a range hundreds of times larger than was the case before artificial light. Nearly all of the study sites were polluted by artificial light. A non-linear relationship is observed between the sky brightness on clear and overcast nights, with a change in behavior near the rural to urban landuse transition. Overcast skies ranged from a third darker to almost 18 times brighter than clear. Clear sky radiances estimated by the World Atlas of Artificial Night Sky Brightness were found to be overestimated by ~25%; our dataset will play an important role in the calibration and ground truthing of future skyglow models. Most of the brightly lit sites darkened as the night progressed, typically by ~5% per hour. The great variation in skyglow radiance observed from site-to-site and with changing meteorological conditions underlines the need for a long-term international monitoring program.

303 Words

Trends in abundance and biomass of European birds

Inger, R., Gregory, R., Duffy, J. P., Stott, I., Vorisek, P. & Gaston, K. J. (2015) Common European birds are declining rapidly while less abundant species’ numbers are rising. Ecology Letters 18, 28-36.

IMG_5491Biodiversity is undergoing unprecedented global decline. Efforts to slow this rate have focused foremost on rarer species, which are at most risk of extinction. Less interest has been paid to more common species, despite their greater importance in terms of ecosystem function and service provision. How rates of decline are partitioned between common and less abundant species remains unclear. Using a 30-year data set of 144 bird species, we examined Europe-wide trends in avian abundance and biomass. Overall, avian abundance and biomass are both declining with most of this decline being attributed to more common species, while less abundant species showed an overall increase in both abundance and biomass. If overall avian declines are mainly due to reductions in a small number of common species, conservation efforts targeted at rarer species must be better matched with efforts to increase overall bird numbers, if ecological impacts of birds are to be maintained.

180 Words

Tree cover in urban parks

Shanahan, D. F., Lin, B. B., Gaston, K. J., Bush, R. & Fuller, R. A. (2015) What is the role of trees and remnant vegetation in attracting people to urban parks? Landscape Ecology 30, 153-165.

P1030033Public parks commonly contain important habitat for urban biodiversity, and they also provide recreation opportunities for urban residents. However, the extent to which dual outcomes for recreation and conservation can be achieved in the same spaces remains unclear. We examine whether greater levels of (i) tree cover (i.e. park ‘greenness’) and (ii) native remnant vegetation cover (i.e. vegetation with high ecological value) attract or deter park visitors. This study is based on the park visitation behaviour of 670 survey respondents in Brisbane, Australia, detailing 1,090 individual visits to 324 urban parks. We first examined the presence of any clear revealed preferences for visiting parks with higher or lower levels of tree cover or remnant vegetation cover. We then examined the differences between each park visited by respondents and the park closest to their home, and used linear mixed models to identify socio-demographic groups who are more likely to travel further to visit parks with greater tree cover or remnant vegetation cover. Park visitation rates reflected the availability of parks, suggesting that people do not preferentially visit parks with greater vegetation cover despite the potential for improved nature-based experiences and greater wellbeing benefits. However, we discovered that people with a greater orientation towards nature (measured using the nature relatedness scale) tend to travel further for more vegetated parks. Our results suggest that to enhance recreational benefits from ecologically valuable spaces a range of social or educational interventions are required to enhance people’s connection to nature.

276 Words

Agricultural ecosystems for biodiversity conservation

Duran, A. P., Duffy, J. P. & Gaston, K. J. (2014) Exclusion of agricultural lands in spatial conservation prioritization strategies: consequences for biodiversity and ecosystem service representation. Proceedings of the Royal Society B 281 (1792), 20141529.

PastedGraphic-1Agroecosystems have traditionally been considered incompatible with biological conservation goals, and often been excluded from spatial conservation prioritization strategies. The consequences for the representativeness of identified priority areas have been little explored. Here, we evaluate these for biodiversity and carbon storage representation when agricultural land areas are excluded from a spatial prioritization strategy for South America. Comparing different prioritization approaches, we also assess how the spatial overlap of priority areas changes. The exclusion of agricultural lands was detrimental to biodiversity representation, indicating that priority areas for agricultural production overlap with areas of relatively high occurrence of species. By contrast, exclusion of agricultural lands benefits representation of carbon storage within priority areas, as lands of high value for agriculture and carbon storage overlap little. When agricultural lands were included and equally weighted with biodiversity and carbon storage, a balanced representation resulted. Our findings suggest that with appropriate management, South American agroecosystems can significantly contribute to biodiversity conservation.

187 Words

Vegetation cover along socio-economic gradients in Brisbane

Shanahan, D. F., Lin, B. B., Gaston, K. J., Bush, R. & Fuller, R. A. (2014) Socio-economic inequalities in access to nature on public and private lands: a case study from Brisbane, Australia. Landscape and Urban Planning 130, 14–23.

IMG_0550Opportunities to experience nature are important for human wellbeing, yet they are often inequitably distributed across society. Socio-economic variation can explain some of this inequity, but there has been relatively limited consideration of how access to different kinds of nature experiences varies across society. Here we examine how tree cover (as a measure of the general ‘greenness’ of urban environments) and native remnant vegetation cover (as a measure of access to higher quality natural areas) varies across the socio-economic gradient within public parkland and residential yards in Brisbane, Australia. We found that most tree cover was provided on residential land, and spatial regression models revealed that tree cover in both public parkland and private spaces was strongly positively related to socio-economic advantage. Conversely, most remnant vegetation cover was located on public parkland, and this was only weakly positively related to socio-economic status. These results suggest that municipal management of remnant vegetation can support equity in access to high quality nature experiences across the socio-economic gradient. However, the results also highlight the important role of residential yards in providing access to nature in general, as these areas provide the majority of overall tree cover. Thus, while public policy can enhance equity in access to nature on public lands, strategies such as social marketing and incentives that enhance nature within private spaces are important particularly within more disadvantaged neighbourhoods.

262 Words

Effects of artificial night-time light

Gaston, K. J., Duffy, J. P., Gaston, S., Bennie, J. & Davies, T. W. (2014) Human alteration of natural light cycles: causes and ecological consequences. Oecologia 176, 917–931.

Artificial light at night is profoundly altering natural light cycles, particularly as perceived by many organisms, over extensive areas of the globe. This alteration comprises the introduction of light at night at places and times at which it has not previously occurred, and with different spectral signatures. Given the long geological periods for which light cycles have previously been consistent, this constitutes a novel environmental pressure, and one for which there is evidence for biological effects that span from molecular to community level. Here we provide a synthesis of understanding of the form and extent of this alteration, some of the key consequences for terrestrial and aquatic ecosystems, interactions and synergies with other anthropogenic pressures on the environment, major uncertainties, and future prospects and management options. This constitutes a compelling example of the need for a thoroughly interdisciplinary approach to understanding and managing the impact of one particular anthropogenic pressure. The former requires insights that span molecular biology to ecosystem ecology, and the latter contributions of biologists, policy makers and engineers.

195 Words