Species distribution modelling of the endangered Mahogany Glider (Petaurus gracilis) reveals key areas for targeted survey and conservation

The Mahogany Glider (Petaurus gracilis) is one of the most endangered marsupials in Australia. Its known distribution is an approximately 120 km strip of fragmented coastal woodland in north-east Queensland, from north of Townsville to the Tully area. Records are clustered in a number of well-surveyed areas, with significant areas of lowland habitat unsurveyed. Around 30% of historic records fall in areas that were subsequently cleared for farmland, and ongoing clearing and fragmentation of lowland sclerophyll forest continues within the potential distribution. Resolving the distribution is an urgent requirement to guide conservation but Mahogany Gliders are difficult to detect in the field. Species distribution modelling offers a technique for estimating the fine-scale distribution and for targeting further field survey and conservation efforts. We used known occurrence records (N = 481) to predict the distribution of Mahogany Gliders across the Wet Tropics bioregion. We used climatic, topographic and other environmental predictors to generate distribution models using Maxent and Random Forest algorithms, each with two bias correction methods. The predictions revealed that many unknown populations may exist within the currently defined distribution and in important areas beyond this (e.g. Hinchinbrook Island). There was reasonable congruence between models, and we include syntheses of the models to present the most likely current distribution. The most important predictor variables across the models were precipitation seasonality (high seasonality), elevation (generally <100 m), soil type (hydrosols) and vegetation type (including Eucalyptus and Melaleuca woodlands). Our results identify core habitat and reveal key areas that require targeted field surveys. Importantly, the predicted suitable habitat is highly fragmented and ongoing conservation efforts need to improve habitat connectivity and limit further fragmentation.     

Identifying Hot Moments in Road-Mortality Risk for Freshwater Turtles

ABSTRACT Risk assessments can be used to identify threats, which vary both in space and time, to declining species. Just as hot spots describe locations where threat processes operate at a higher rate than in surrounding areas, hot moments refer to periods when threat rates are highest. However, the identification of hot moments can be challenging because the temporal complexity of some threat processes makes their effects on population viability difficult to predict. Declining throughout much of their range, Blanding's turtle (Emydoidea blandingii) populations are potentially most vulnerable to road mortality where road densities and traffic volumes are high. The temporal variations in road-mortality risk faced by these and other semiaquatic turtles at the population level are a consequence of several factors, including sex-specific movement characteristics and seasonal changes in traffic volume. We examined these risk factors for Blanding's turtle populations in Maine, USA, by integrating temporally explicit roadkill probabilities with demographic parameters informed by local and range-wide studies. Specifically, we used population simulations to estimate the relative risk for 14 2-week periods during the turtles’ active season. Our analysis clearly identified early summer as a period of elevated risk, with June through mid-July signaling a road-mortality hot moment for Blanding's turtles (for both M and F). These findings provide guidance for the implementation of temporally explicit conservation measures such as cautionary road signage, traffic management, and public outreach that, if timed strategically, could help to mitigate population impacts from road mortality.     

Do unpaved,low-traffic roads affect bird communities?

Unpaved, low traffic roads are often assumed to have minimal effects on biodiversity. To explore this assertion, we sampled the bird communities in fifteen randomly selected sites in Pafos Forest, Cyprus and used multiple regression to quantify the effects of such roads on the total species richness. Moreover, we classified birds according to their migratory status and their global population trends, and tested each category separately. Besides the total length of unpaved roads, we also tested: a. the site's habitat diversity, b. the coefficient of variation in habitat (patch) size, c. the distance to the nearest agricultural field, and d. the human population size of the nearest village. We measured our variables at six different distances from the bird point-count locations. We found a strong negative relationship between the total bird richness and the total length of unpaved roads. The human population size of the nearest village also had a negative effect. Habitat diversity was positively related to species richness. When the categories were tested, we found that the passage migrants were influenced more by the road network while resident breeders were influenced by habitat diversity. Species with increasing and stable populations were only marginally affected by the variables tested, but the effect of road networks on species with decreasing populations was large. We conclude that unpaved and sporadically used roads can have detrimental effects on the bird communities, especially on vulnerable species. We propose that actions are taken to limit the extent of road networks within protected areas, especially in sites designated for their rich avifauna, such as Pafos Forest, where several of the affected species are species of European and global importance.     

西南贫困山区路网扩张与生态环境压力的关系

交通路网建设在促进贫困地区经济发展的同时给生态环境带来了诸多影响，处理好两者之间的关系对实现经济-生态的协同发展具有十分重要的意义。基于重庆市贫困区县奉节县和非贫困区县涪陵区2010年、2014年和2018年3年的道路网络数据和生态足迹数据，构建道路网络通达度与生态环境压力两个指标体系，其中道路网络通达度选用道路密度和道路连通度两个指标表征，生态环境压力使用生态足迹表征，并将生态足迹中对路网扩张影响最大的"建设用地"和"化石能源用地"进行加和组成"建-化足迹"，通过计算增幅率指数比较道路密度、道路连通度及"建-化足迹"三者之间的变化趋势，以探究生态足迹内部与道路通达度之间的关系。结果显示：（1）西南山区贫困与非贫困区县道路连通度、道路密度、生态赤字、"建-化足迹"四项指标逐年增长，总体变化趋势一致，贫困区县在研究时段呈现更快速的增长趋势。（2）西南山区贫困与非贫困区县研究时段生态环境压力进一步扩大，表明经济-生态的发展整体处于不协调状态，且有持续恶化的趋势。（3）西南山区贫困区县"建-化足迹"与道路连通度两项指标研究时段内增幅率分别为0.40和0.42，故两者关系较为一致，表明其道路布局结构对生态环境压力更大；非贫困区县"建-化足迹"与道路密度两项指标研究时段内增幅率分别为0.34和0.33，故两者关系较为一致，表明其生态环境压力更多受到道路建设规模的影响。因此，研究结论对于制定山区贫困县交通基础设施建设、生态环境规划与区域发展战略等具有参考价值。     

Road verges as habitat for small mammals in Britain

There are 370 000 kilometres of roads in Great Britain, mostly bordered by a verge that is potential habitat for small mammals. The present study assessed the importance of road verges as small mammal habitat and investigated the influence of some key features on rodent abundance. Five rodent and three shrew species were live‐trapped on 14 road verges in late summer 1994 and nine verges in autumn 1996 in north Cambridgeshire, UK. On average, between three and four species were captured per verge. Bank Voles Clethrionomys glareolus, Wood Mice Apodemus sylvaticus and Field Voles Microtus agrestis were the most abundant species, with mean densities of 45.5, 40.2 and 29.5 animals km^–1 in summer and 52.8, 181.9 and 47.2 animals km^–1 in autumn. Numbers varied between verges and this was significantly correlated with particular features on the verge. Bank Vole and Field Vole numbers showed a significant positive correlation with the dimensions of hedges and the width of the tall grass area, respectively. Wood Mice were also more numerous on verges with big hedges but the relationship between mouse abundance and verge structure was complex. The number of mice in 1994 was positively and significantly correlated with hedge features and with the width of the short grass sightline, whereas, in autumn 1996, they were only significantly correlated with total verge width (positive association) and ditch width (negative association).     

Linkages between unpaved forest roads and streambed sediment: why context matters in directing road restoration

Unpaved forest roads remain a pervasive disturbance on public lands and mitigating sediment from road networks remains a priority for management agencies. Restoring roaded landscapes is becoming increasingly important for many native coldwater fishes that disproportionately rely on public lands for persistence. However, effectively targeting restoration opportunities requires a comprehensive understanding of the effects of roads across different ecosystems. Here, we combine a review and a field study to evaluate the status of knowledge supporting the conceptual framework linking unpaved forest roads with streambed sediment. Through our review, we specifically focused on those studies linking measures of the density of forest roads or sediment delivery with empirical streambed sediment measures. Our field study provides an example of a targeted effort of linking spatially explicit estimates of sediment production with measures of streambed sediment. Surprisingly, our review uncovered few studies (n = 8) that empirically tested the conceptual framework linking unpaved forest roads and streambed sediment, and the results varied considerably. Field results generally supported the conceptual model that unpaved forest roads can control streambed sediment quality, but demonstrated high‐spatial variability in the effects of forest roads on streambed sediment and the need to address hotspots of sediment sources. The importance of context in the effects of forest roads is apparent in both our review and field data, suggesting the need for in situ studies to avoid misdirected restoration actions.