KEVIN J GASTON

Dallimer, M., Tinch, D., Hanley, N., Irvine, K.N., Rouquette, J.R., Warren, P.H., Maltby, L., Gaston, K.J. & Armsworth, P.R. 2014. Quantifying preferences for the natural world using monetary and non-monetary assessments of value. Conservation Biology 28, 404-413.

Given that funds for biodiversity conservation are limited, there is a need to understand people’s preferences for its different components. To date, such preferences have largely been measured in monetary terms. However, how people value biodiversity may differ from economic theory, and there is little consensus over whether monetary metrics are always appropriate or the degree to which other methods offer alternative and complementary perspectives on value. We used a choice experiment to compare monetary amounts recreational visitors to urban green spaces were willing to pay for biodiversity enhancement (increases in species richness for birds, plants, and aquatic macroinvertebrates) with self-reported psychological gains in well-being derived from visiting the same sites. Willingness-to-pay (WTP) estimates were significant and positive, and respondents reported high gains in well-being across three axes derived from environmental psychology theories (reflection, attachment, continuity with past). The two metrics were broadly congruent. Participants with abovemedian self-reported well-being scores were willing to pay significantly higher amounts for enhancing species richness than those with below-median scores, regardless of taxon. The socio-economic and demographic background of participants played little role in determining either their well-being or the probability of choosing a paying option within the choice experiment. Site-level environmental characteristics were only somewhat related to WTP, but showed strong associations with self-reported well-being. Both approaches are likely to reflect a combination of the environmental properties of a site and unobserved individual preference heterogeneity for the natural world. Our results suggest that either metric will deliver mutually consistent results in an assessment of environmental preferences, although which approach is preferable depends on why one wishes to measure values for the natural world.

Bonnington, C., Gaston, K.J. & Evans, K.L. 2014. Squirrels in suburbia: influence of urbanisation on occurrence and distribution of a common exotic mammal. Urban Ecosystems 17, 533-546.

Urbanisation is widely considered to promote the establishment of non-native species, but there is limited empirical evidence of the ecological factors driving their responses. The grey squirrel Sciurus carolinensis (Gmelin 1788) is native to North America, but is widespread in the UK and is starting to spread across Europe. It is regarded as one of the world’s worst invasive animals due to its adverse impacts on native biodiversity. We use the non-native grey squirrel population in Sheffield (UK) as a case study to assess which factors limit its distribution and abundance in urban environments. In 2010 the city-wide population of adult squirrels peaked at an estimated 6539 in autumn (0.46 squirrels/ha), with maximum local densities of 8.29/ha. These densities appear to be slightly lower than those recorded in urban environments in the species’ native range. Grey squirrels occurred more frequently at urban sites with larger amounts of green-space in the surrounding region. Local habitat characteristics were, however, more powerful predictors of urban grey squirrel occurrence and abundance than regional availability of green space. Canopy cover, seed bearing trees and supplementary feeders, provided for garden birds, positively influenced grey squirrels. The potential for grey squirrels to connect city dwellers with nature thus appears to be highest in urban locations that have considerable capacity to support native biodiversity. The beneficial impacts of supplementary feeding on grey squirrel populations is notable given concerns that squirrels can adversely influence bird populations. These habitat associations also imply that grey squirrels typically respond negatively to urbanisation, which challenges arguments that urbanisation favours exotic species.

Bonnington, C., Gaston, K.J. & Evans, K.L. 2014. Assessing the potential for Grey squirrels Sciurus carolinensis to compete with birds at supplementary feeding stations. Ibis 156, 220-226.

Supplementary feeding of birds, particularly in urban areas, is often associated with increased population size and fecundity. In the UK, the non-native Grey Squirrel Sciurus carolinensis is common in rural and urban habitats. It exploits supplementary feeders and may induce interference competition by excluding birds, but empirical evidence of this is unavailable. Using controlled model presentation experiments, we demonstrate that Grey Squirrels could reduce bird use of supplementary feeders and induce interference competition. Total bird resource use was reduced by 98% and most species exhibited similar sensitivities. The likelihood and magnitude of interference competition will depend on how rapidly displaced birds find alternative food sources; it will be greatest where there are high Grey Squirrel densities and few supplementary feeders. Other studies suggest that supplementary feeding increases Grey Squirrel numbers, and the species is also predicted to expand its non-native range across most of Europe. Our data indicate that Grey Squirrels may eventually alter the net effect of supplementary feeding on bird populations across the European continent; increased use of squirrelproof feeders may help to minimize such effects.

Cantú-Salazar, L., Orme, C.D.L., Rasmussen, P.C., Blackburn, T.M. & Gaston, K.J. 2013. The performance of the global protected area system in capturing vertebrate geographic ranges. Biodiversity and Conservation 22, 1033-1047.

Given the heavy reliance placed on and investment in protected areas for biological conservation, there has been much debate as to how effective these are in representing biodiversity features within their boundaries. The majority of studies addressing this issue have been conducted on a regional or national basis, precluding a broad picture of patterns of representation at the species level. We present a global assessment of the representation of the terrestrial geographic ranges of complete taxonomic groups: all known extant amphibians, birds and mammals (20,736 species) within the current global system of protected areas. We conclude that it is necessary substantially to improve the levels of coverage of the geographic ranges of the majority of species, even the widespread ones. This is particularly true for rare species, which might be assumed to be foci for protected area systems. To improve on the low levels of coverage of vertebrate ranges attained by the existing areas, key regions should be targeted, but heavy reliance will also have to be placed on approaches to sustaining populations in the wider, unprotected landscape.

Anderson, K. & Gaston, K.J. 2013. Lightweight unmanned aerial vehicles will revolutionize spatial ecology. Frontiers in Ecology and Environment 11, 138-146.

Ecologists require spatially explicit data to relate structure to function. To date, heavy reliance has been placed on obtaining such data from remote-sensing instruments mounted on spacecraft or manned aircraft, although the spatial and temporal resolutions of the data are often not suited to local-scale ecological investigations. Recent technological innovations have led to an upsurge in the availability of unmanned aerial vehicles (UAVs) – aircraft remotely operated from the ground – and there are now many lightweight UAVs on offer at reasonable costs. Flying low and slow, UAVs offer ecologists new opportunities for scale-appropriate measurements of ecological phenomena. Equipped with capable sensors, UAVs can deliver fine spatial resolution data at temporal resolutions defined by the end user. Recent innovations in UAV platform design have been accompanied by improvements in navigation and the miniaturization of measurement technologies, allowing the study of individual organisms and their spatiotemporal dynamics at close range.