Reducing the ecological consequences of night-time light pollution: options and developments

Much concern has been expressed about the ecological consequences of night‐time light pollution. This concern is most often focused on the encroachment of artificial light into previously unlit areas of the night‐time environment, but changes in the spectral composition, duration and spatial pattern of light are also recognized as having ecological effects.

Here, we examine the potential consequences for organisms of five management options to reduce night‐time light pollution. These are to (i) prevent areas from being artificially lit; (ii) limit the duration of lighting; (iii) reduce the ‘trespass’ of lighting into areas that are not intended to be lit (including the night sky); (iv) change the intensity of lighting; and (v) change the spectral composition of lighting.

Maintaining and increasing natural unlit areas is likely to be the most effective option for reducing the ecological effects of lighting. However, this will often conflict with other social and economic objectives. Decreasing the duration of lighting will reduce energy costs and carbon emissions, but is unlikely to alleviate many impacts on nocturnal and crepuscular animals, as peak times of demand for lighting frequently coincide with those in the activities of these species. Reducing the trespass of lighting will maintain heterogeneity even in otherwise well‐lit areas, providing dark refuges that mobile animals can exploit. Decreasing the intensity of lighting will reduce energy consumption and limit both skyglow and the area impacted by high‐intensity direct light. Shifts towards ‘whiter’ light are likely to increase the potential range of environmental impacts as light is emitted across a broader range of wavelengths.

Synthesis and applications. The artificial lightscape will change considerably over coming decades with the drive for more cost‐effective low‐carbon street lighting solutions and growth in the artificially lit area. Developing lighting strategies that minimize adverse ecological impacts while balancing the often conflicting requirements of light for human utility, comfort and safety, aesthetic concerns, energy consumption and carbon emission reduction constitute significant future challenges. However, as both lighting technology and understanding of its ecological effects develop, there is potential to identify adaptive solutions that resolve these conflicts.

The artificial lightscape will change considerably over coming decades with the drive for more cost‐effective low‐carbon street lighting solutions and growth in the artificially lit area. Developing lighting strategies that minimize adverse ecological impacts while balancing the often conflicting requirements of light for human utility, comfort and safety, aesthetic concerns, energy consumption and carbon emission reduction constitute significant future challenges. However, as both lighting technology and understanding of its ecological effects develop, there is potential to identify adaptive solutions that resolve these conflicts.

Animal body size distributions: patterns, mechanisms and implications

Documenting the shape of the frequency distribution of species body sizes for an animal taxon appears at first sight a straightforward task. However, a variety of patterns has been reported, and a consensus is only now being reached through an understanding of how potential biases may affect observed shapes of distributions. A new body of evidence suggests that, at large scales, size distributions are right-skewed, even on logarithmic axes. If body size distributions can be described with certainty, this will allow assessment of the mechanisms proposed to generate them, and will be an important step towards understanding the structure and dynamics of animal assemblages.

Household factors influencing participation in bird feeding activity: a national scale analysis

Ameliorating pressures on the ecological condition of the wider landscape outside of protected areas is a key focus of conservation initiatives in the developed world. In highly urbanized nations, domestic gardens can play a significant role in maintaining biodiversity and facilitating human-wildlife interactions, which benefit personal and societal health and well-being. The extent to which sociodemographic and socioeconomic factors are associated with engagement in wildlife gardening activities remain largely unresolved. Using two household-level survey datasets gathered from across Britain, we determine whether and how the socioeconomic background of a household influences participation in food provision for wild birds, the most popular and widespread form of human-wildlife interaction. A majority of households feed birds (64% across rural and urban areas in England, and 53% within five British study cities). House type, household size and the age of the head of the household were all important predictors of bird feeding, whereas gross annual household income, the occupation of the head of the household, and whether the house is owned or rented were not. In both surveys, the prevalence of bird feeding rose as house type became more detached and as the age of the head of the household increased. A clear, consistent pattern between households of varying size was less evident. When regularity of food provision was examined in the study cities, just 29% of households provided food at least once a week. The proportion of households regularly feeding birds was positively related to the age of the head of the household, but declined with gross annual income. As concerns grow about the lack of engagement between people and the natural environment, such findings are important if conservation organizations are successfully to promote public participation in wildlife gardening specifically and environmentally beneficial behaviour in society more generally.

Street lighting changes the composition of invertebrate communities

Artificial lighting has been used to illuminate the nocturnal environment for centuries and continues to expand with urbanization and economic development. Yet, the potential ecological impact of the resultant light pollution has only recently emerged as a major cause for concern. While investigations have demonstrated that artificial lighting can influence organism behaviour, reproductive success and survivorship, none have addressed whether it is altering the composition of communities. We show, for the first time, that invertebrate community composition is affected by proximity to street lighting independently of the time of day. Five major invertebrate groups contributed to compositional differences, resulting in an increase in the number of predatory and scavenging individuals in brightly lit communities. Our results indicate that street lighting changes the environment at higher levels of biological organization than previously recognized, raising the potential that it can alter the structure and function of ecosystems.

The cost of policy simplification in conservation incentive programs

Incentive payments to private landowners provide a common strategy to conserve biodiversity and enhance the supply of goods and services from ecosystems. To deliver cost-effective improvements in biodiversity, payment schemes must trade-off inefficiencies that result from over-simplified policies with the administrative burden of implementing more complex incentive designs. We examine the effectiveness of different payment schemes using field parameterized, ecological economic models of extensive grazing farms. We focus on profit maximising farm management plans and use bird species as a policy-relevant indicator of biodiversity. Common policy simplifications result in a 49-100% loss in biodiversity benefits depending on the conservation target chosen. Failure to differentiate prices for conservation improvements in space is particularly problematic. Additional implementation costs that accompany more complicated policies are worth bearing even when these constitute a substantial proportion (70% or more) of the payments that would otherwise have been given to farmers.

The Fynbos and sUcculent Karoo biomes do not have exceptional local ant richness

BACKGROUND

The Fynbos (FB) and Succulent Karoo biomes (SKB) have high regional plant diversity despite relatively low productivity. Local diversity in the region varies but is moderate. For insects, previous work suggests that strict phytophages, but not other taxa, may have high regional richness. However, what has yet to be investigated is whether the local insect species richness of FB and SKB is unusual for a region of this productivity level at this latitude, and whether regional richness is also high. Here we determine whether this is the case for ants.

METHODOLOGY/PRINCIPAL FINDINGS

We use species richness data from pitfall traps in the FB and SKB in the Western Cape Province, South Africa and a global dataset of local ant richness extracted from the literature. We then relate the globally derived values of local richness to two energy-related predictors--productive energy (NDVI) and temperature, and to precipitation, and compare the data from the FB and SKB with these relationships. We further compare our local richness estimates with that of similar habitats worldwide, and regional ant richness with estimates derived from other regions. The local ant species richness of the FB and SKB falls within the general global pattern relating ant richness to energy, and is similar to that in comparable habitats elsewhere. At a regional scale, the richness of ants across all of our sites is not exceptional by comparison with other regional estimates from across the globe.

CONCLUSIONS/SIGNIFICANCE

Local richness of ants in the FB and SKB is not exceptional by global standards. Initial analyses suggest that regional diversity is also not exceptional for the group. It seems unlikely that the mechanisms which have contributed to the development of extraordinarily high regional plant diversity in these biomes have had a strong influence on the ants.

Spatial covariation between freshwater and terrestrial ecosystem services

To inform the design and implementation of land-use policies that consider the variety of goods and services people derive from ecosystems, it is essential to understand spatial patterns of individual services, how multiple services relate to each other, and how these relationships vary across spatial scales and localities. Despite the importance of freshwater as a determinant of regional economic and human demographic patterns, there are surprisingly few studies that map the provision of a range of services associated with the quality of the aquatic environment. Here we examine relationships between indicators of riverine water and associated habitat quality, freshwater biodiversity, three terrestrial ecosystem services, and terrestrial biodiversity across England and Wales. The results indicate strong associations between our indicators of freshwater services. However, a comparison of these indicators of freshwater services with other ecosystem services (carbon storage, agricultural production, recreation) and biodiversity of species of conservation concern in the surrounding terrestrial landscape shows no clear relationships. While there are potential policy "win-wins" for the protection of multiple services shown by associations between indicators of freshwater services and carbon storage in upland areas of Britain, the other ecosystem services showed either negative or no relationships with the indicators of freshwater services. We also consider the influence that spatial scale has on these relationships using River Basin Districts. Our results indicate that relationships between indicators of services can change dramatically depending on the societal pressures and other regional conditions. Thus, the delivery of multiple ecosystem services requires the development of regional strategies, or of national strategies that take account of regional variation.

Balancing alternative land uses in conservation prioritization

Pressure on ecosystems to provide various different and often conflicting services is immense and likely to increase. The impacts and success of conservation prioritization will be enhanced if the needs of competing land uses are recognized at the planning stage. We develop such methods and illustrate them with data about competing land uses in Great Britain, with the aim of developing a conservation priority ranking that balances between needs of biodiversity conservation, carbon storage, agricultural value, and urban development potential. While both carbon stocks and biodiversity are desirable features from the point of view of conservation, they compete with the needs of agriculture and urban development. In Britain the greatest conflicts exist between biodiversity and urban areas, while the largest carbon stocks occur mostly in Scotland in areas with low agricultural or urban pressure. In our application, we were able successfully to balance the spatial allocation of alternative land uses so that conflicts between them were much smaller than had they been developed separately. The proposed methods and software, Zonation, are applicable to structurally similar prioritization problems globally.

Effectiveness of protected areas in maintaining plant production

Given the central importance of protected area systems in local, regional and global conservation strategies, it is vital that there is a good understanding of their effectiveness in maintaining ecological functioning. Here, we provide, to our knowledge, the first such global analysis, focusing on plant production, a “supporting” ecosystem function necessary for multiple other ecosystem services. We use data on the normalized difference vegetation index (NDVI) as a measure of variation in plant production in the core, boundary and surroundings of more than 1000 large protected areas over a 25 year period. Forested protected areas were higher (or similar), and those non-forested were lower (or similar), in NDVI than their surrounding areas, and these differences have been sustained. The differences from surrounding areas have increased for evergreen broadleaf forests and barren grounds, decreased for grasslands, and remained similar for deciduous forests, woodlands, and shrublands, reflecting different pressures on those surroundings. These results are consistent with protected areas being effective both in the representation and maintenance of plant production. However, widespread overall increases in NDVI during the study period suggest that plant production within the core of non-forested protected areas has become higher than it was in the surroundings of those areas in 1982, highlighting that whilst the distinctiveness of protected areas from their surroundings has persisted the nature of that difference has changed.

Are soils in urban ecosystems compacted? A citywide analysis

Soil compaction adversely influences most terrestrial ecosystem services on which humans depend. This global problem, affecting over 68 million ha of agricultural land alone, is a major driver of soil erosion, increases flood frequency and reduces groundwater recharge. Agricultural soil compaction has been intensively studied, but there are no systematic studies investigating the extent of compaction in urban ecosystems, despite the repercussions for ecosystem function. Urban areas are the fastest growing land-use type globally, and are often assumed to have highly compacted soils with compromised functionality. Here, we use bulk density (BD) measurements, taken to 14 cm depth at a citywide scale, to compare the extent of surface soil compaction between different urban greenspace classes and agricultural soils. Urban soils had a wider BD range than agricultural soils, but were significantly less compacted, with 12 per cent lower mean BD to 7 cm depth. Urban soil BD was lowest under trees and shrubs and highest under herbaceous vegetation (e.g. lawns). BD values were similar to many semi-natural habitats, particularly those underlying woody vegetation. These results establish that, across a typical UK city, urban soils were in better physical condition than agricultural soils and can contribute to ecosystem service provision.

Global human footprint on the linkage between biodiversity and ecosystem functioning in reef fishes

Difficulties in scaling up theoretical and experimental results have raised controversy over the consequences of biodiversity loss for the functioning of natural ecosystems. Using a global survey of reef fish assemblages, we show that in contrast to previous theoretical and experimental studies, ecosystem functioning (as measured by standing biomass) scales in a non-saturating manner with biodiversity (as measured by species and functional richness) in this ecosystem. Our field study also shows a significant and negative interaction between human population density and biodiversity on ecosystem functioning (i.e., for the same human density there were larger reductions in standing biomass at more diverse reefs). Human effects were found to be related to fishing, coastal development, and land use stressors, and currently affect over 75% of the world's coral reefs. Our results indicate that the consequences of biodiversity loss in coral reefs have been considerably underestimated based on existing knowledge and that reef fish assemblages, particularly the most diverse, are greatly vulnerable to the expansion and intensity of anthropogenic stressors in coastal areas.

Temporal changes in greenspace in a highly urbanized region

The majority of the world's population now lives in towns and cities, and urban areas are expanding faster than any other land-use type. In response to this phenomenon, two opposing arguments have emerged: whether cities should 'sprawl' into the wider countryside, or 'densify' through the development of existing urban greenspace. However, these greenspaces are increasingly recognized as being central to the amelioration of urban living conditions, supporting biodiversity conservation and ecosystem service provision. Taking the highly urbanized region of England as a case study, we use data from a variety of sources to investigate the impact of national-level planning policy on temporal patterns in the extent of greenspace in cities. Between 1991 and 2006, greenspace showed a net increase in all but one of 13 cities. However, the majority of this gain occurred prior to 2001, and greenspace has subsequently declined in nine cities. Such a dramatic shift in land use coincides with policy reforms in 2000, which favoured densification. Here, we illustrate the dynamic and policy-responsive nature of urban land use, thereby highlighting the need for a detailed investigation of the trade-offs associated with different mechanisms of urban densification to optimize and secure the diverse benefits associated with greenspaces.

The impact of projected increases in urbanization on ecosystem services

Alteration in land use is likely to be a major driver of changes in the distribution of ecosystem services before 2050. In Europe, urbanization will probably be the main cause of land-use change. This increase in urbanization will result in spatial shifts in both supplies of ecosystem services and the beneficiaries of those services; the net outcome of such shifts remains to be determined. Here, we model changes in urban land cover in Britain based on large (16%) projected increases in the human population by 2031, and the consequences for three different services--flood mitigation, agricultural production and carbon storage. We show that under a scenario of densification of urban areas, the combined effect of increasing population and loss of permeable surfaces is likely to result in 1.7 million people living within 1 km of rivers with at least 10 per cent increases in projected peak flows, but that increasing suburban 'sprawl' will have little effect on flood mitigation services. Conversely, losses of stored carbon and agricultural production are over three times as high under the sprawl as under the 'densification' urban growth scenarios. Our results illustrate the challenges of meeting, but also of predicting, future demands and patterns of ecosystem services in the face of increasing urbanization.

Field-level bird abundances are enhanced by landscape-scale agri-environment scheme uptake

Despite two decades of agri-environment schemes (AESs) aimed at mitigating farmland biodiversity losses, the evidence that such programmes actually benefit biodiversity remains limited. Using field-level surveys, we assess the effectiveness of AESs in enhancing bird abundances in an upland area of England, where schemes have been operating for over 20 years. In such a region, the effects of AESs should be readily apparent, and we predict that bird abundances will co-vary with both field- and landscape-scale measures of implementation. Using an information theoretic approach, we found that, for abundances of species of conservation concern and upland specialists, measures of AES implementation and habitat type at both scales appear in the most parsimonious models. Field-level bird abundances are higher where more of the surrounding landscape is included in an AES. While habitat remains a more influential predictor, we suggest that landscape-scale implementation results in enhanced bird abundances. Hence, measures of the success of AESs should consider landscape-wide benefits as well as localized impacts.

The ecological research needs of business

1. Businesses have an unrivalled ability to mobilize human, physical and financial capital, often manage large land holdings, and draw on resources and supply products that impact a wide array of ecosystems. Businesses therefore have the potential to make a substantial contribution to arresting declines in biodiversity and ecosystem services. To realize this potential, businesses require support from researchers in applied ecology to inform how they measure and manage their impacts on, and opportunities presented to them by, biodiversity and ecosystem services.

2. We reviewed papers in leading applied ecology journals to assess the research contribution from existing collaborations involving businesses. We reviewed applications to, and grants funded by, the UK’s Natural Environment Research Council for evidence of public investment in such collaborations. To scope opportunities for expanding collaborations with businesses, we conducted workshops with three sectors (mining and quarrying, insurance and manufacturing) in which participants identified exemplar ecological research questions of interest to their sector.

3. Ten to fifteen per cent of primary research papers in Journal of Applied Ecology and Ecological Applications evidenced business involvement, mostly focusing on traditional rural industries (farming, fisheries and forestry). The review of UK research council funding found that 35% of applications mentioned business engagement, while only 1% of awarded grants met stricter criteria of direct business involvement.

4. Some questions identified in the workshops aim to reduce costs from businesses’ impacts on the environment and others to allow businesses to exploit new opportunities. Some questions are designed to inform long‐term planning undertaken by businesses, but others would have more immediate commercial applications. Finally, some research questions are designed to streamline and make more effective those environmental policies that affect businesses.

5. Business participants were forward‐looking regarding ecological questions and research. For example, representatives from mining and quarrying companies emphasized the need to move beyond biodiversity to consider how ecosystems function, while those from the insurance sector stressed the importance of ecology researchers entering into new types of interdisciplinary collaboration.

6.  Synthesis and applications. Businesses from a variety of sectors demonstrated a clear interest in managing their impacts on, and exploiting opportunities created by, ecosystem services and biodiversity. To achieve this, businesses are asking diverse ecological research questions, but publications in leading applied ecology journals and research council funding reveal limited evidence of direct engagement with businesses. This represents a missed opportunity for ecological research findings to see more widespread application.

A conceptual framework for the colonisation of urban areas: the blackbird Turdus merula as a case study

Despite increasing interest in urban ecology the factors limiting the colonisation of towns and cities by species from rural areas are poorly understood. This is largely due to the lack of a detailed conceptual framework for this urbanisation process, and of sufficient case studies. Here, we develop such a framework. This draws upon a wide range of ecological and evolutionary theory and the increasing number of studies of how the markedly divergent conditions in urban and rural areas influence the traits of urban populations and the structure of urban assemblages. We illustrate the importance of this framework by compiling a detailed case study of spatial and temporal variation in the urbanisation of the blackbird Turdus merula. Our framework identifies three separate stages in the urbanisation process: (i) arrival, (ii) adjustment, and (iii) spread. The rate of progress through each stage is influenced by environmental factors, especially human attitudes and socio-economic factors that determine the history of urban development and the quality of urban habitats, and by species' ecological and life-history traits. Some traits can positively influence progression through one stage, but delay progression through another. Rigorous assessment of the factors influencing urbanisation should thus ideally pay attention to the different stages. Urbanisation has some similarities to invasion of exotic species, but the two clearly differ. Invasion concerns geographic range expansion that is external to the species' original geographic range, whilst urbanisation typically relates to filling gaps within a species' original range. This process is exemplified by the blackbird which is now one of the commonest urban bird species throughout its Western Palearctic range. This is in stark contrast to the situation 150 years ago when the species was principally confined to forest. Blackbird urbanisation was first recorded in Germany in 1820, yet some European cities still lack urban blackbirds. This is especially so in the east, where urbanisation has spread more slowly than in the west. The timing of blackbird urbanisation exhibits a marked spatial pattern, with latitude and longitude explaining 76% of the variation. This strong spatial pattern contrasts with the weaker spatial pattern in timing of urbanisation exhibited by the woodpigeon Columba palumbus (with location explaining 39% of the variation), and with the very weak spatial pattern in timing of black-billed magpie Pica pica urbanisation (in which location explains 12% of the variation). Strong spatial patterns in timing of urbanisation are more compatible with the leap-frog urbanisation model, in which urban adapted or imprinted birds colonise other towns and cities, than with the independent urbanisation model, in which urban colonisation events occur independently of each other. Spatial patterns in isolation do not, however, confirm one particular model. Factors relating to the arrival and adjustment stages appear particularly likely to have influenced the timing of blackbird urbanisation. Spatial variation in the occurrence of urban populations and the timing of their establishment creates opportunities to assess the factors regulating urbanisation rates, and how the composition of urban assemblages develops as a result. These are major issues for urban ecology.