Response of vegetation phenology to urbanization in the conterminous United States

The influence of urbanization on vegetation phenology is gaining considerable attention due to its implications for human health, cycling of carbon and other nutrients in Earth system. In this study, we examined the relationship between change in vegetation phenology and urban size, an indicator of urbanization, for the conterminous United States. We studied more than 4500 urban clusters of varying size to determine the impact of urbanization on plant phenology, with the aids of remotely sensed observations since 2003–2012. We found that phenology cycle (changes in vegetation greenness) in urban areas starts earlier (start of season, SOS) and ends later (end of season, EOS), resulting in a longer growing season length (GSL), when compared to the respective surrounding urban areas. The average difference of GSL between urban and rural areas over all vegetation types, considered in this study, is about 9 days. Also, the extended GSL in urban area is consistent among different climate zones in the United States, whereas their magnitudes are varying across regions. We found that a tenfold increase in urban size could result in an earlier SOS of about 1.3 days and a later EOS of around 2.4 days. As a result, the GSL could be extended by approximately 3.6 days with a range of 1.6–6.5 days for 25th ~ 75th quantiles, with a median value of about 2.1 days. For different vegetation types, the phenology response to urbanization, as defined by GSL, ranges from 1 to 4 days. The quantitative relationship between phenology and urbanization is of great use for developing improved models of vegetation phenology dynamics under future urbanization, and for developing change indicators to assess the impacts of urbanization on vegetation phenology.     

Gardening and urban landscaping: significant players in global change

Global warming leads to shifts in vegetation types in given temperate environments. The fastest species movement is due to the globalized supply and use of exotic plants in gardening and urban landscaping. These standard practices circumvent dispersal limitations and biological and environmental stresses; they have three major global impacts: (i) the enhancement of biological invasions, (ii) the elevation of volatile organic compound emissions and the resulting increase in photochemical smog formation, and (iii) the enhancement of CO(2) fixation and water use by gardened plants. These global effects, none of which are currently considered in global-change scenarios, are increasingly amplified with further warming and urbanization. We urge for quantitative assessment of the global effects of gardening and urban landscaping.     

Urban environments provide new perspectives for forecasting vegetation phenology responses under climate warming

Given that already-observed temperature increase within cities far exceeds the projected global temperature rise by the end of the century, urban environments often offer a unique opportunity for studying ecosystem response to future warming. However, the validity of thermal gradients in space serving as a substitute for those in time is rarely tested. Here, we investigated vegetation phenology dynamics in China's 343 cities and empirically test whether phenological responses to spatial temperature rise in urban settings can substitute for those to temporal temperature rise in their natural counterparts based on satellite-derived vegetation phenology and land surface temperature from 2003 to 2018. We found prevalent advancing spring phenology with “high confidence” and delaying autumn phenology with “medium confidence” under the context of widespread urban warming. Furthermore, we showed that space cannot substitute for time in predicting phenological shifts under climate warming at the national scale and for most cities. The thresholds of ~11°C mean annual temperature and ~600 mm annual precipitation differentiated the magnitude of phenological sensitivity to temperature across space and through time. Below those thresholds, there existed stronger advanced spring phenology and delayed autumn phenology across the spatial urbanization gradients than through time, and vice versa. Despite the complex and diverse relationships between phenological sensitivities across space and through time, we found that the directions of the temperature changes across spatial gradients were converged (i.e., mostly increased), but divergent through temporal gradients (i.e., increased or decreased without a predominant direction). Similarly, vegetation phenology changes more uniformly over space than through time. These results suggested that the urban environments provide a real-world condition to understand vegetation phenology response under future warming.     

城市化鸟类群落变化及其与城市植被的关系

持续而快速的城市化进程正在助长全球生物多样性的丧失,其中鸟类是城市生态系统的重要环节和城市生物多样性保护的重点目标,同时也是研究的热点内容。从城市环境变化压力下,鸟类群落组成与结构、空间分布和繁殖营巢方式的改变分析,重点介绍了支持城市地区鸟类多样性的植物环境因素与影响机制的最新研究成果。结果表明：1）城市中的植被和绿色空间为城市鸟类提供生存空间和食物资源,是城市鸟类最主要的栖息地。2）保留原生乡土植物和大型树木的地区能支持更丰富的鸟类物种。3）植被的结构和盖度对鸟类群落有显著影响。林冠覆盖率增加,复杂的垂直空间和多样的植物种类的组合产生各种不同类型的植物空间和栖息地类型,吸引不同的鸟类物种,相应地也会导致更丰富的鸟类群落。总之,保持和加强城市中植物环境良好和稳定是保护城市生物多样性的有效手段。据此,提出城市环境与鸟类群落关系研究的未来发展方向,指出了其在鸟类多样性保护和城市可持续发展等领域的应用前景。     

Simulated responses of potential vegetation to doubled-CO2 climate change and feedbacks on near-surface temperature

Increases in the atmospheric concentration of carbon dioxide and associated changes in climate may exert large impacts on plant physiology and the density of vegetation cover. These may in turn provide feedbacks on climate through a modification of surface‐atmosphere fluxes of energy and moisture. This paper uses asynchronously coupled models of global vegetation and climate to examine the responses of potential vegetation to different aspects of a doubled‐CO₂ environmental change, and compares the feedbacks on near‐surface temperature arising from physiological and structural components of the vegetation response. Stomatal conductance reduces in response to the higher CO₂ concentration, but rising temperatures and a redistribution of precipitation also exert significant impacts on this property as well as leading to major changes in potential vegetation structure. Overall, physiological responses act to enhance the warming near the surface, but in many areas this is offset by increases in leaf area resulting from greater precipitation and higher temperatures. Interactions with seasonal snow cover result in a positive feedback on winter warming in the boreal forest regions.     

Climate controls on vegetation phenological patterns in northern mid- and high latitudes inferred from MODIS data

Recent studies using both field measurements and satellite-derived-vegetation indices have demonstrated that global warming is influencing vegetation growth and phenology. To accurately predict the future response of vegetation to climate variation, a thorough understanding of vegetation phenological cycles and their relationship to temperature and precipitation is required. In this paper, vegetation phenological transition dates identified using data from the moderate-resolution imaging spectroradiometer (MODIS) in 2001 are linked with MODIS land surface temperature (LST) data from the northern hemisphere between 35°N and 70°N. The results show well-defined patterns dependent on latitude, in which vegetation greenup gradually migrates northward starting in March, and dormancy spreads southward from late September. Among natural vegetation land-cover types, the growing-season length for forests is strongly correlated with variation in mean annual LST. For urban areas, the onset of greenup is 4–9 days earlier on average, and the onset of dormancy is about 2–16 days later, relative to adjacent natural vegetation. This difference (especially for urban vs. forests) is apparently related to urban heat island effects that result in both the average spring temperature and the mean annual temperature in urban areas being about 1–3°C higher relative to rural areas. The results also indicate that urban heat island effects on vegetation phenology are stronger in North America than in Europe and Asia. Finally, the onset of forest greenup at continental scales can be effectively described using a thermal time-chilling model, which can be used to infer the delay or advance of greenup onset in relation to climatic warming at global scale.     

Noise pollution and decreased size of wooded areas reduces the probability of occurrence of Tawny Owl Strix aluco

At present, urban areas cover almost 3% of the Earth's land surface, and this proportion is constantly increasing along with human population growth. Although urbanization leads to biodiversity decline, at the same time it creates a novel and extensive environment that is exploited by whole assemblages of organisms. These include predators, which use the matrix of different habitat types within the urban environment for breeding and/or foraging. This study investigated how attributes of the urban landscape influence the distribution pattern of a nocturnal acoustic predator, the Tawny Owl Strix aluco. The probability of occurrence of this species was correlated with the presence of natural forests, and the increasing size of wooded habitat patches within the urban landscape; however, Tawny Owls were less likely to occur at sites with high noise levels at night. Our study suggests that the distribution pattern of acoustic predators is shaped by the availability of primary habitat but reduced by noise intensity (which may decrease hunting efficiency). The Tawny Owl is a top predator in the urban environment and its presence/absence may therefore affect populations of other species; this provides clear evidence of the indirect effect of noise pollution on animal populations inhabiting urban environments.     

城市化对鸟类的影响：从群落到个体

世界范围急剧的城市化进程所带来的生态问题,尤其是城市化对鸟类的影响引起了生态学家越来越多的关注。关注点从最初的群落水平,逐渐向种群水平和个体水平深入。在群落水平上,现有的研究展示了城市化对鸟类群落组成、物种的丰富度、多度、生物量和多样性等多方面存在的不同程度的影响;而物种水平的研究探讨了城市化影响鸟类群落格局的内在原因:不同的鸟类物种对城市化具有不同的反应;而个体水平的研究,更是进一步从鸟类行为、生活史特征等方面揭示城市化压力和鸟类的适应对策。大量的证据说明,城市化所带来的土地使用的改变、人为干扰、热岛效应、食物资源改变、巢捕食、夜间灯光等,不同程度地对城市鸟类产生了影响。     

长三角地区植被覆盖演变城乡差异及其原因

城市生态环境和城市化之间的关系是城市可持续发展的关键。研究不同城市化水平下植被覆盖的长时间演变趋势,对理解城市化过程对植被生长动态的影响,城市更新以及推进城市绿化的科学管理具有重要意义。然而,目前对城市内部沿城乡梯度植被生长趋势差异的认识还比较有限。以我国城市化发展最为强烈的长三角地区为研究对象,基于2000-2020年长三角归一化植被指数数据,采用趋势分析和地理探测器方法,探究了长三角地区城市内部植被覆盖演变城乡差异,并从土地利用/覆被变化和城市化发展的角度解析其成因。研究结果表明：（1）2000-2020年长三角地区植被总体呈绿化趋势,植被明显绿化占最大比例（52.06%）,轻微绿化与稳定不变地区占31.68%,零星分布的褐化区占6.82%。（2）城市老城区植被覆盖变化总体呈现返绿趋势（0.016/10 a）,新城区褐化明显（-0.019/10 a）,农郊区绿化突出（0.023/10 a）。在上海、南京和杭州等人口城市化水平较高的城市中,老城区土地利用变化强度最高,其绿化趋势也最高,体现了城市更新过程对绿地空间的促进作用;而在人口城市化水平相对较低的宣城、蚌埠和阜阳等城市,土地利用变化强度相对较低的农郊区也呈现明显的绿化趋势,更多的是受到区域生态保护的影响。（3）土地城市化是长三角地区老城区和新城区植被覆盖变化的主导因子,而城市化因子对农郊区解释程度总体不显著。从长三角总体区域看,城镇人口比重、不透水面积/总面积以及地区生产总值三者对植被覆盖演变存在显著影响,其中城镇人口比重影响最大。     

Responses of wasp communities to urbanization: effects on community resilience and species diversity

Urbanization is one of the most extreme and rapidly growing anthropogenic pressures on the natural world. It is linked to significant impacts on biodiversity and disruptions to ecological processes in remnant vegetation. We investigated the richness and abundance of wasps in a highly fragmented urban landscape in Sydney, Australia, comparing assemblages in small urban remnants to edges and interiors of continuous areas of vegetation. We detected no difference in wasp abundance or species richness between remnant types indicating that communities are highly resilient to the effects of urbanization at this scale. However, Chao 2 estimates of predicted species richness indicate that edge sites would support a greater richness and abundance of species compared to small and interior sites. Although families were represented evenly across the sites, interior and edge sites supported more species within families. Wasp composition was significantly affected by the temporal variation and trap location (arboreal or ground), particularly at the family level demonstrating high species turnover and discrimination in vertical space. These sampling effects and temporal inconsistencies highlight the hazards of relying on one-off snapshot surveys and uncorrected datasets for assessments of diversity and responses to urban landscapes. The strong resilience of wasp communities to urbanization when assessed at coarse scales indicates that responses at finer spatial and taxonomic scales are critical to understanding the maintenance of ecosystem function in highly modified landscapes.     

京津冀城市群人-地、人-水与人-碳交互胁迫关系及其叠加效应

随着社会、经济效益的不断增加及国际影响力的不断增大,京津冀正在向世界级城市群迈进。而快速的城市增长与资源环境的交互胁迫效应严重制约了京津冀地区的可持续发展,因此,明确城市增长与不同资源环境要素的相互作用机制并采用有效的措施,是实现京津冀地区发展和保护共生的关键。目前针对城镇化与单一种资源环境要素交互作用的研究较多,但对城镇化与不同资源环境要素相互作用的叠加效应的关注很少。针对土地、水资源与能源这三种明显限制京津冀地区发展的资源要素,综合考虑了供给侧与需求侧特征,分析了人-地、人-水与人-碳的相互作用关系,解析了京津冀地区城镇发展与不同资源环境要素交互胁迫作用及其叠加效应。结果表明：2002-2017年,1、城市群整体水平上,人-地、人-水和人-碳关系总体上均呈"强协调"或"弱协调"交替变化的状态;2、城市尺度上,不同城市的人-地、人-水和人-碳交互关系存在明显时空分异。多数城市都曾面临土地、水资源或能源的胁迫影响,尤其是河北的一些城市（石家庄、邯郸、承德、衡水、邢台、唐山及保定等）在有些年份面临土地、水资源或能源的"强胁迫"影响;3、从京津冀地区整体水平上看,不存在多种资源要素的叠加胁迫影响,但是,城市群内部多数城市在有的年份同时面临土地、水资源或能源两种以上资源要素的叠加胁迫影响。因此,要协同改善京津冀地区资源环境的胁迫,需要全面考虑不同空间尺度之间,不同城市之间,以及不同资源要素之间的叠加影响机制,有针对性的提出政策与措施。     

Assessing the impact of revegetation and weed control on urban sensitive bird species

Nature in cities is concentrated in urban green spaces, which are key areas for urban biodiversity and also important areas to connect people with nature. To conserve urban biodiversity within these natural refugia, habitat restoration such as weed control and revegetation is often implemented. These actions are expected to benefit biodiversity, although species known to be affected by urbanization may not be interacting with restoration in the ways we anticipate. In this study, we use a case study to explore how urban restoration activities impact different bird species. Birds were grouped into urban sensitivity categories and species abundance, and richness was then calculated using a hierarchical species community model for individual species responses, with “urban class” used as the hierarchical parameter. We highlight variable responses of birds to revegetation and weed control based on their level of urban sensitivity. Revegetation of open grassy areas delivers significant bird conservation outcomes, but the effects of weed control are neutral or in some cases negative. Specifically, the species most reliant on remnant vegetation in cities seem to remain stable or decline in abundance in areas with weed control, which we suspect is the result of a simplification of the understorey. The literature reports mixed benefits of weed control between taxa and between locations. We recommend, in our case study site, that weed control be implemented in concert with replanting of native vegetation to provide the understory structure preferred by urban sensitive birds. Understanding the impacts of revegetation and weed control on different bird species is important information for practitioners to make restoration decisions about the allocation of funds for conservation action. This new knowledge can be used both for threatened species and invasive species management.     

大气污染对城市植被的生态胁迫效应综述

快速的城市化进程使得城市大气污染日趋严重,造成了城市植被的退化及其生态服务功能的下降。大气中的O₃、紫外(UV-B)辐射、重金属、SO₂等污染物及其复合污染从分子、细胞、个体、种群、群落和生态系统各个水平上都对城市植被造成了胁迫效应。本文从微观实验法和宏观高光谱遥感法两方面对已有的研究方法进行了分析和总结后,提出了以下几个今后需要关注的研究领域:开展野外和长期胁迫实验、植物受胁迫机理及多种因子复合胁迫研究等;同时指出应重视建筑物在城市大气污染生态胁迫中的重要作用,并在今后加强城市行道树相关方面的研究。     

城市扩张与水污染物排放的伴生效应与交互机理——基于2011-2015年长三角地区的实证检验

揭示城市扩张与水污染物排放之间的伴生效应与空间交互机理是城市化水环境效应研究的重要议题。以长三角地区为例,选取COD和NH₃-N两项特征污染物指标,在2011—2015年快速城市化时期的水污染物排放格局分析基础上,优选空间杜宾模型估计城市扩张与水污染物排放的伴生效应,采用直接效应和间接效应分解定量测度二者的空间交互机理。研究结果表明：2011—2015年长三角地区水污染物排放规模显著下降,县域排放强度等级整体降低,高强度排放格局由连片式分布收缩为零散式分布;城市扩张与水污染物排放的伴生效应显著而稳定,高扩张-高排放型县域在上海及其周边、苏北地区集中分布,沿海和沿江区位是城市扩张通常会选择的布局指向,在排污距离成本和环境规制强度双重作用下,距海岸线和长江干流距离越远,水污染物排放强度越呈对数曲线式降低;城市扩张与水污染物排放的空间交互作用具有两面性,城市扩张规模每提升1%,使本地COD、NH₃-N排放分别增加0.274%、0.368%的同时,还会造成邻近县域排放降低1.017%、0.650%。因此,为缓解城市扩张与水污染物排放的伴生效应和交互作...     

Urban expansion dynamics and natural habitat loss in China: a multiscale landscape perspective

China's extensive urbanization has resulted in a massive loss of natural habitat, which is threatening the nation's biodiversity and socioeconomic sustainability. A timely and accurate understanding of natural habitat loss caused by urban expansion will allow more informed and effective measures to be taken for the conservation of biodiversity. However, the impact of urban expansion on natural habitats is not well‐understood, primarily due to the lack of accurate spatial information regarding urban expansion across China. In this study, we proposed an approach that can be used to accurately summarize the dynamics of urban expansion in China over two recent decades (1992–2012), by integrating data on nighttime light levels, a vegetation index, and land surface temperature. The natural habitat loss during the time period was evaluated at the national, ecoregional, and local scales. The results revealed that China had experienced extremely rapid urban growth from 1992 to 2012 with an average annual growth rate of 8.74%, in contrast with the global average of 3.20%. The massive urban expansion has resulted in significant natural habitat loss in some areas in China. Special attention needs to be paid to the Pearl River Delta, where 25.79% or 1518 km² of the natural habitat and 41.99% or 760 km² of the local wetlands were lost during 1992–2012. This raises serious concerns about species viability and biodiversity. Effective policies and regulations must be implemented and enforced to sustain regional and national development in the context of rapid urbanization.     

Satellite Evidence of Phenological Differences Between Urbanized and Rural Areas of the Eastern United States Deciduous Broadleaf Forest

We used a 10-year record (1990–99) of composited and cloud-screened reflectances from the Advanced Very High Resolution Radiometer (AVHRR) to test for phenological differences between urban and rural areas in the eastern United States deciduous broadleaf forest (DBF). We hypothesized that well-documented urban heat island effects would be associated with alterations in temperature-sensitive vegetation phenology. Our objectives were thus (a) to investigate possible differences in the start of the growing season (SOS) and end of the growing season (EOS) between the urban and DBF land covers, (b) to investigate related differences in greenness amplitude and fractional cover, and (c) to develop a generalized additive model (GAM) to predict the spatial variation of observed differences. By analyzing individual 1° latitude by 1° longitude blocks, we found that, on average, urbanization is associated with a growing season expansion of 7.6 days. Most of this effect is caused by an earlier SOS in urban areas. In all cases, urban regions had lower fractional cover and greenness amplitude. The GAM model failed to produce a viable model for differences in EOS, probably because it is dominated by photoperiod controls with only a minor temperature impact. SOS differences were predicted with an accuracy of about 2.4 days, with a GAM consisting of smoothed functions of mean annual average temperature, urban fractional cover, and the urban vs DBF greenness amplitude difference. We speculate that evidence of a phenological response to warming indicates that global warming, without reduction in DBF vegetation cover and greenness amplitude, may increase carbon sequestration in mesic deciduous forests. Received 6 June 2001; accepted 23 October 2001.     

The Nexus of Carbon,Nitrogen, and Biodiversity Impacts from Urban Metabolism

Methodology is developed for linking the urban metabolism (UM) to global environmental stresses on the carbon (C) cycle, nitrogen (N) cycle, and biodiversity loss. UM variables are systematically mapped to the drivers of carbon, nitrogen, and biodiversity impacts. Change in mean species abundance is used as metric of biodiversity loss, by adopting the dose‐response relationships from the GLOBIO model. The main biodiversity drivers related to UM included here are land‐use change (LUC) and atmospheric N deposition. The methodology is demonstrated by studying the nexus for Shanghai in 2006, based on energy and soybean consumption. Results for Shanghai show a strong nexus between C, N, and biodiversity impact due to electricity consumption and energy used in manufacturing industries and construction. Prioritization of the shift away from coal energy will therefore lead to lowering the urban growth impact on all three dimensions. Road transportation, domestic aviation, and the metal industry impact only the C footprint highly, whereas district energy impacts only biodiversity loss highly, showing a weak nexus. Among the global impacts of soybean consumption in Shanghai on biodiversity loss (due to LUC only), the highest impact occurs in Uruguay (0.52%) followed by Brazil (0.05%) and Argentina (0.02%). The local impact on biodiversity loss (i.e., within China) of soybean consumption in Shanghai is 1.03%. However, the methodology and results are limited due to the partial inclusion of drivers, a carbon footprint based on carbon dioxide emissions only, and limitations of biodiversity loss models. Potential to overcome methodological limitations is discussed.     

Urbanization drives cross‐taxon declines in abundance and diversity at multiple spatial scales

The increasing urbanization process is hypothesized to drastically alter (semi‐)natural environments with a concomitant major decline in species abundance and diversity. Yet, studies on this effect of urbanization, and the spatial scale at which it acts, are at present inconclusive due to the large heterogeneity in taxonomic groups and spatial scales at which this relationship has been investigated among studies. Comprehensive studies analysing this relationship across multiple animal groups and at multiple spatial scales are rare, hampering the assessment of how biodiversity generally responds to urbanization. We studied aquatic (cladocerans), limno‐terrestrial (bdelloid rotifers) and terrestrial (butterflies, ground beetles, ground‐ and web spiders, macro‐moths, orthopterans and snails) invertebrate groups using a hierarchical spatial design, wherein three local‐scale (200 m × 200 m) urbanization levels were repeatedly sampled across three landscape‐scale (3 km × 3 km) urbanization levels. We tested for local and landscape urbanization effects on abundance and species richness of each group, whereby total richness was partitioned into the average richness of local communities and the richness due to variation among local communities. Abundances of the terrestrial active dispersers declined in response to local urbanization, with reductions up to 85% for butterflies, while passive dispersers did not show any clear trend. Species richness also declined with increasing levels of urbanization, but responses were highly heterogeneous among the different groups with respect to the richness component and the spatial scale at which urbanization impacts richness. Depending on the group, species richness declined due to biotic homogenization and/or local species loss. This resulted in an overall decrease in total richness across groups in urban areas. These results provide strong support to the general negative impact of urbanization on abundance and species richness within habitat patches and highlight the importance of considering multiple spatial scales and taxa to assess the impacts of urbanization on biodiversity.     

Lean birds in the city: body size and condition of house sparrows along the urbanization gradient

1. Urbanized habitats differ from natural ones in several ecological features, including climate, food availability, strength of predation and competition. Although the effects of urbanization on avian community composition are well known, there is much less information about how individual birds are affected by these human-generated habitat differences. 2. In this study we investigated the relationships between the morphological characteristics and the degree of habitat urbanization in house sparrows, Passer domesticus (Linne 1758) . We collected data for more than 1000 non-breeding adult birds in Hungary between 1997 and 2006, from seven sites including farmlands, suburban areas and city centres. 3. We found that the body mass, tarsus length and body condition of free-living sparrows differed among the sites: birds in more urbanized habitats were consistently smaller and in worse condition than birds in more rural habitats. A composite measure of habitat urbanization (based on building density, road density and vegetation cover) explained over 75% of variance between sites in the studied traits, after we controlled for the effects of sex, year, season and time of capture. 4. The difference in body mass between rural and urban sparrows was significant when birds were kept in aviaries under identical conditions, with constant ad libitum food availability. It is therefore unlikely that the reduced body size and condition of urban sparrows are a consequence of reduced access to food for adults (e.g. due to strong competition), or their short-term responses to high food predictability (e.g. by strategic mass regulation). 5. We suggest that habitat differences in nestling development or adaptive divergence of sparrow populations due to distinct environmental conditions (such as differing predation pressure) may account for the differences along the urbanization gradient.     

Urban-associated habitat alteration promotes brood parasitism of Acadian Flycatchers

ABSTRACT.   High rates of brood parasitism are generally associated with agricultural landscapes, but recent evidence suggests that urbanization may also increase the likelihood of brood parasitism. I evaluated the extent to which brood parasitism by Brown-headed Cowbirds ( Molothrus ater ) was explained by differences in (1) body size of adult hosts, presumably relating to the ability to defend nest from cowbirds, (2) nest placement in substrate and relative to habitat edges, (3) habitat structure surrounding nests, (4) host density, (5) cowbird abundance, both absolute and relative to host numbers, (6) landscape composition, and (7) Julian date. From 2001 to 2006, I monitored nest fate and measured vegetation characteristics surrounding nests of Acadian Flycatcher ( Empidonax virescens ) breeding in mature riparian forests in central Ohio, USA. The likelihood that a nest would be parasitized was best explained by the number of understory stems surrounding the nest and, to a lesser extent, by the amount of urbanization in the surrounding 1-km-radius landscape. Parasitized nests were surrounded by 1.6 times more stems and nearly twice the amount of urbanization than nonparasitized nests. Numbers of understory stems were positively associated with increasing urbanization, primarily due to invasion of urban forests by Amur honeysuckle ( Lonicera maackii ). Thus, urban-associated changes in habitat characteristics around nests may be important contributors to the greater vulnerability of urban nests to brood parasitism than nests in more rural landscapes. This pattern suggests that ecological restoration, such as removing exotic shrubs, may be an effective strategy to ameliorate certain negative consequences of urbanization near wooded reserves.