Travis Longcore

Ecological light pollution

Ecologists have long studied the critical role of natural light in regulating species interactions, but, with limited exceptions, have not investigated the consequences of artificial night lighting. In the past century, the extent and intensity of artificial night lighting has increased such that it has substantial effects on the biology and ecology of species in the wild. We distinguish “astronomical light pollution”, which obscures the view of the night sky, from “ecological light pollution”, which alters natural light regimes in terrestrial and aquatic ecosystems. Some of the catastrophic consequences of light for certain taxonomic groups are well known, such as the deaths of migratory birds around tall lighted structures, and those of hatchling sea turtles disoriented by lights on their natal beaches. The more subtle influences of artificial night lighting on the behavior and community ecology of species are less well recognized, and constitute a new focus for research in ecology and a pressing conservation challenge.

The Nightsat mission concept

Nightsat is a concept for a satellite system capable of global observation of the location, extent and brightness of night‐time lights at a spatial resolution suitable for the delineation of primary features within human settlements. Based on requirements from several fields of scientific inquiry, Nightsat should be capable of producing a complete cloud‐free global map of lights on an annual basis. We have used a combination of high‐resolution field spectra of outdoor lighting, moderate resolution colour photography of cities at night from the International Space Station, and high‐resolution airborne camera imagery acquired at night to define a range of spatial, spectral, and detection limit options for a future Nightsat mission. The primary findings of our study are that Nightsat should collect data from a near‐synchronous orbit in the early evening with 50 to 100 m spatial resolution and have detection limits of 2.5E−8 Watts cm−2sr−1µm−1 or better. Although panchromatic low‐light imaging data would be useful, multispectral low‐light imaging data would provide valuable information on the type or character of lighting; potentially stronger predictors of variables such as ambient population density and economic activity; and valuable information to predict response of other species to artificial night lighting. The Nightsat mission concept is unique in its focus on observing a human activity, in contrast to traditional Earth observing systems that focus on natural systems.

A framework to assess evolutionary responses to anthropogenic light and sound

Human activities have caused a near-ubiquitous and evolutionarily-unprecedented increase in environmental sound levels and artificial night lighting. These stimuli reorganize communities by interfering with species-specific perception of time-cues, habitat features, and auditory and visual signals. Rapid evolutionary changes could occur in response to light and noise, given their magnitude, geographical extent, and degree to which they represent unprecedented environmental conditions. We present a framework for investigating anthropogenic light and noise as agents of selection, and as drivers of other evolutionary processes, to influence a range of behavioral and physiological traits such as phenological characters and sensory and signaling systems. In this context, opportunities abound for understanding contemporary and rapid evolution in response to human-caused environmental change.

An Estimate of Avian Mortality at Communication Towers in the United States and Canada

Avian mortality at communication towers in the continental United States and Canada is an issue of pressing conservation concern. Previous estimates of this mortality have been based on limited data and have not included Canada. We compiled a database of communication towers in the continental United States and Canada and estimated avian mortality by tower with a regression relating avian mortality to tower height. This equation was derived from 38 tower studies for which mortality data were available and corrected for sampling effort, search efficiency, and scavenging where appropriate. Although most studies document mortality at guyed towers with steady-burning lights, we accounted for lower mortality at towers without guy wires or steady-burning lights by adjusting estimates based on published studies. The resulting estimate of mortality at towers is 6.8 million birds per year in the United States and Canada. Bootstrapped subsampling indicated that the regression was robust to the choice of studies included and a comparison of multiple regression models showed that incorporating sampling, scavenging, and search efficiency adjustments improved model fit. Estimating total avian mortality is only a first step in developing an assessment of the biological significance of mortality at communication towers for individual species or groups of species. Nevertheless, our estimate can be used to evaluate this source of mortality, develop subsequent per-species mortality estimates, and motivate policy action.

Analysis of Transect Counts to Monitor Population Size in Endangered Insects The Case of the El Segundo Blue Butterfly, Euphilotes Bernardino Allyni

Before, during and after habitat restoration from 1984 to 1994, we monitored population size of the federally listed endangered El Segundo blue butterfly, Euphilotes bernardino allyni (Shields). In the subsequent formalization of a recovery plan for the species, the U.S. Fish and Wildlife Service established several recovery criteria, including a requirement of ‘a scientifically credible monitoring plan’ to track population size annually. To avoid detrimental effects of the extensively used mark-release-recapture method on the delicate El Segundo blue butterfly, which would conflict with protection afforded by the Endangered Species Act, we chose instead to perform transect counts to estimate relative population size. Herein, we analyze the results of our transect counts by three different methods, developed by or modified from Pollard, Watt et al. and Zonneveld. Qualitatively, the three methods, which have different assumptions, produced similar results when applied to the same data. Zonnevelds model estimates death rate in addition to an index of population size, thus providing more information than the other two methods. The El Segundo blue butterflys sedentary nature and the close relationship of its adult and early stages to one foodplant permits extrapolation of the index of population size based on transect counts, to an estimate of actual population size. Our data document butterfly numbers increasing from 1984 to 1989, but then declining until the end of our observations in 1994. Based on analysis of our El Segundo blue butterfly data, we propose an implementation of a scientifically credible monitoring plan.

Tuning the white light spectrum of light emitting diode lamps to reduce attraction of nocturnal arthropods

Artificial lighting allows humans to be active at night, but has many unintended consequences, including interference with ecological processes, disruption of circadian rhythms and increased exposure to insect vectors of diseases. Although ultraviolet and blue light are usually most attractive to arthropods, degree of attraction varies among orders. With a focus on future indoor lighting applications, we manipulated the spectrum of white lamps to investigate the influence of spectral composition on number of arthropods attracted. We compared numbers of arthropods captured at three customizable light-emitting diode (LED) lamps (3510, 2704 and 2728 K), two commercial LED lamps (2700 K), two commercial compact fluorescent lamps (CFLs; 2700 K) and a control. We configured the three custom LEDs to minimize invertebrate attraction based on published attraction curves for honeybees and moths. Lamps were placed with pan traps at an urban and two rural study sites in Los Angeles, California. For all invertebrate orders combined, our custom LED configurations were less attractive than the commercial LED lamps or CFLs of similar colour temperatures. Thus, adjusting spectral composition of white light to minimize attracting nocturnal arthropods is feasible; not all lights with the same colour temperature are equally attractive to arthropods.

Height, Guy Wires, and Steady-Burning Lights Increase Hazard of Communication Towers to Nocturnal Migrants: A Review and Meta-Analysis

Abstract

A global inventory of coral reef stressors based on satellite observed nighttime lights

In this article, we present a satellite-based approach to gather information about the threat to coral reefs worldwide. Three chosen reef stressors – development, gas flaring and heavily lit fishing boat activity – are analysed using nighttime lights data derived from the Defense Meteorological Satellite Program (DMSP) produced at the National Oceanic & Atmospheric Administration, National Geophysical Data Center (NOAA/NGDC). Nighttime lights represent a direct threat to coral reef ecosystems and are an excellent proxy measure for associated human-caused stressors. A lights proximity index (LPI) is calculated, measuring the distance of coral reef sites to each of the stressors and incorporating the stressors intensity. Colourized maps visualize the results on a global scale. Area rankings clarify the effects of artificial night lighting on coral reefs on a regional scale. The results should be very useful for reef managers and for state administrations to implement coral reef conservation projects and for the scientific world to conduct further research.

Remote sensing to map influence of light pollution on Cory’s shearwater in São Miguel Island, Azores Archipelago

Global economic and population growth increase the extent and intensity of artificial night lighting. From an ecological perspective, this is light pollution, which causes changes in reproductive physiology, migration and foraging of many species and ultimately leads to loss of biodiversity. Some seabirds are intimately linked with the light features of their environments because they are nocturnally active. We report light-induced groundings of Cory’s shearwater (Calonectris diomedea) during a 2-year study (2008 and 2009) in São Miguel Island, in the Azores archipelago, and investigate the spatial correlation of locations of grounded birds with an annual composite of remotely sensed stable lights. Results indicate that 16.7% of fledglings are attracted to lights. The exposure of shearwater colonies in the study area to artificial night lighting is low overall. Four colonies account for 87% of the grounded birds. The distance each bird was found from the closest colony was best explained by the ratio of the satellite-measured light levels at the grounding spot to the light levels at the assigned colony of origin. These results demonstrate that satellite-observed nighttime lights are sufficient to assess risk to marine birds at the scale of oceanic islands and indicate their utility for monitoring the effectiveness of programs to manage lighting to reduce risk for these species and conducting global assessments of species vulnerability. To minimize the impact on Cory’s shearwater and other marine birds, we recommend measures such as reduction and control of lighting intensity near colony locations, while continuing and re-enforcing rescue campaigns.

Historical Ecology as a Tool for Assessing Landscape Change and Informing Wetland Restoration Priorities

Vast resources are devoted annually to watershed management and wetland restoration. Historical wetland losses are often cited as a motivation for prioritizing ambitious wetland restoration efforts. However, analysis of historical conditions is often underutilized in the planning process. In this paper we demonstrate historical ecological analysis of the San Gabriel River watershed in southern California. We integrate multiple disparate data sources collected at different spatial and temporal scales to describe historical wetland extent and distribution. We compare historic wetlands to contemporary conditions to calculate wetland losses. From the results of this analysis, we conclude that the widely held view of southern California as naturally dry and desert-like with mainly ephemeral and intermittent streams may be an over generalization. Historically, the San Gabriel watershed has supported complex expanses of channels, ponds, sloughs, seeps, marshes, and seasonal wetlands that alternated between wet and dry conditions on multi-year to decadal cycles. We estimate that >86% of historical wetlands have been lost since ca. 1870, with the greatest losses occurring to palustrine alkali meadows in the lower floodplain. Despite the extensive losses, the analysis reveals areas of the watershed conducive to wetland re-establishment and provides insight into the most appropriate wetland types to prioritize for specific watershed settings.