Designing "Tiny Forests" as a lesson for transdisciplinary urban ecology learning.

The sustainability and livability of urban areas call for the next generation of scientists, practitioners and policy makers to understand the benefits, implementation and management of urban greenspaces. We harnessed the concept of "Tiny Forests©" - a restoration strategy for small wooded areas (~100-400 m2) - to create a transdisciplinary and experiential project for university forestry students that follows an ecology-with-cities framework. We worked with 16 students and a local municipality in the Munich, Germany metropolitan region to survey a community about its needs and desires and then used this information alongside urban environmental features and data collected by students (e.g., about soil conditions) to design a Tiny Forest. In this article, we describe the teaching concept, learning outcomes and activities, methodological approach, and instructor preparation and materials needed to adapt this project. Designing Tiny Forests provides benefits to students by having them approach authentic tasks in urban greening while experiencing the challenges and benefits of transdisciplinary communication and engagement with community members. Supplementary Information: The online version contains supplementary material available at 10.1007/s11252-023-01371-7.

Multiple ecosystem service synergies and landscape mediation of biodiversity within urban agroecosystems.

Ecosystem services (ESs) are essential for human well-being, especially in urban areas where 60% of the global population will live by 2030. While urban habitats have the potential to support biodiversity and ES, few studies have quantified the impact of local and landscape management across a diverse suite of services. We leverage 5 years of data (>5000 observations) across a network of urban community gardens to determine the drivers of biodiversity and ES trade-offs and synergies. We found multiple synergies and few trade-offs, contrasting previous assumptions that food production is at odds with biodiversity. Furthermore, we show that natural landscape cover interacts with local management to mediate services provided by mobile animals, specifically pest control and pollination. By quantifying the factors that support a diverse suite of ES, we highlight the critical role of garden management and urban planning for optimizing biodiversity and human benefit.

Vegetation complexity and nesting resource availability predict bee diversity and functional traits in community gardens.

Urban gardens can support diverse bee communities through resource provision in resource poor environments. Yet the effects of local habitat and landscape factors on wild bee communities in cities is still insufficiently understood, nor is how this information could be applied to urban wildlife conservation. Here we investigate how taxonomic and functional diversity of wild bees and their traits in urban community gardens are related to garden factors and surrounding landscape factors (e.g., plant diversity, amount of bare ground, amount of nesting resources, amount of landscape imperviousness). Using active and passive methods in 18 community gardens in Berlin, Germany, we documented 26 genera and 102 species of bees. We found that higher plant species richness and plant diversity as well as higher amounts of deadwood in gardens leads to higher numbers of wild bee species and bee (functional) diversity. Furthermore, higher landscape imperviousness surrounding gardens correlates with more cavity nesting bees, whereas a higher amount of bare ground correlates with more ground-nesting bees. Pollen specialization was positively associated with plant diversity, but no factors strongly predicted the proportion of endangered bees. Our results suggest that, aside from foraging resources, nesting resources should be implemented in management for more pollinator-friendly gardens. If designed and managed using such evidence-based strategies, urban gardens can create valuable foraging and nesting habitats for taxonomically and functionally diverse bee communities in cities.

'Tidy' and 'messy' management alters natural enemy communities and pest control in urban agroecosystems.

Agroecosystem management influences ecological interactions that underpin ecosystem services. In human-centered systems, people's values and preferences influence management decisions. For example, aesthetic preferences for 'tidy' agroecosystems may remove vegetation complexity with potential negative impacts on beneficial associated biodiversity and ecosystem function. This may produce trade-offs in aesthetic- versus production-based management for ecosystem service provision. Yet, it is unclear how such preferences influence the ecology of small-scale urban agroecosystems, where aesthetic preferences for 'tidiness' are prominent among some gardener demographics. We used urban community gardens as a model system to experimentally test how aesthetic preferences for a 'tidy garden' versus a 'messy garden' influence insect pests, natural enemies, and pest control services. We manipulated gardens by mimicking a popular 'tidy' management practice-woodchip mulching-on the one hand, and simulating 'messy' gardens by adding 'weedy' plants to pathways on the other hand. Then, we measured for differences in natural enemy biodiversity (abundance, richness, community composition), and sentinel pest removal as a result of the tidy/messy manipulation. In addition, we measured vegetation and ground cover features of the garden system as measures of practices already in place. The tidy/messy manipulation did not significantly alter natural enemy or herbivore abundance within garden plots. The manipulation did, however, produce different compositions of natural enemy communities before and after the manipulation. Furthermore, the manipulation did affect short term gains and losses in predation services: the messy manipulation immediately lowered aphid pest removal compared to the tidy manipulation, while mulch already present in the system lowered Lepidoptera egg removal. Aesthetic preferences for 'tidy' green spaces often dominate urban landscapes. Yet, in urban food production systems, such aesthetic values and management preferences may create a fundamental tension in the provision of ecosystem services that support sustainable urban agriculture. Though human preferences may be hard to change, we suggest that gardeners allow some 'messiness' in their garden plots as a "lazy gardener" approach may promote particular natural enemy assemblages and may have no downsides to natural predation services.

Rarity begets rarity: Social and environmental drivers of rare organisms in cities.

Cities are sometimes characterized as homogenous with species assemblages composed of abundant, generalist species having similar ecological functions. Under this assumption, rare species, or species observed infrequently, would have especially high conservation value in cities for their potential to increase functional diversity. Management to increase the number of rare species in cities could be an important conservation strategy in a rapidly urbanizing world. However, most studies of species rarity define rarity in relatively pristine environments where human management and disturbance is minimized. We know little about what species are rare, how many species are rare, and what management practices promote rare species in urban environments. Here, we identified which plants and species of birds and bees that control pests and pollinate crops are rare in urban gardens and assessed how social, biophysical factors, and cross-taxonomic comparisons influence rare species richness. We found overwhelming numbers of rare species, with more than 50% of plants observed classified as rare. Our results highlight the importance of women, older individuals, and gardeners who live closer to garden sites in increasing the number of rare plants within urban areas. Fewer rare plants were found in older gardens and gardens with more bare soil. There were more rare bird species in larger gardens and more rare bee species for which canopy cover was higher. We also found that in some cases, rarity begets rarity, with positive correlations found between the number of rare plants and bee species and between bee and bird species. Overall, our results suggest that urban gardens include a high number of species existing at low frequency and that social and biophysical factors promoting rare, planned biodiversity can cascade down to promote rare, associated biodiversity.

Experiences of gardening during the early stages of the COVID-19 pandemic.

Gardening has the potential to improve health and wellbeing, especially during crises. Using an international survey of gardeners (n = 3743), this study aimed to understand everyday gardening experiences, perspectives and attitudes during early stages of the COVID-19 pandemic in 2020. Our qualitative reflexive thematic and sentiment analyses show that during the first months of the COVID-19 pandemic, gardening seemed to create a safe and positive space where people could socially connect, learn and be creative. Participants had more time to garden during the pandemic, which led to enhanced connections with family members and neighbours, and the ability to spend time in a safe outdoor environment. More time gardening allowed for innovative and new gardening practices that provided enjoyment for many participants. However, our research also highlighted barriers to gardening (e.g. lack of access to garden spaces and materials). Our results illustrate the multiple benefits of gardening apparent during COVID-19 through a lens of the social-ecological model of health.

Thermal sensitivity and seasonal change in the gut microbiome of a desert ant, Cephalotes rohweri.

Microorganisms within ectotherms must withstand the variable body temperatures of their hosts. Shifts in host body temperature resulting from climate change have the potential to shape ectotherm microbiome composition. Microbiome compositional changes occurring in response to temperature in nature have not been frequently examined, restricting our ability to predict microbe-mediated ectotherm responses to climate change. In a set of field-based observations, we characterized gut bacterial communities and thermal exposure across a population of desert arboreal ants (Cephalotes rohweri). In a paired growth chamber experiment, we exposed ant colonies to variable temperature regimes differing by 5°C for three months. We found that the abundance and composition of ant-associated bacteria were sensitive to elevated temperatures in both field and laboratory experiments. We observed a subset of taxa that responded similarly to temperature in the experimental and observational study, suggesting a role of seasonal temperature and local temperature differences amongst nests in shaping microbiomes within the ant population. Bacterial mutualists in the genus Cephaloticoccus (Opitutales: Opitutaceae) were especially sensitive to change in temperature-decreasing in abundance in naturally warm summer nests and warm growth chambers. We also report the discovery of a member of the Candidate Phlya Radiation (Phylum: Gracilibacteria), a suspected epibiont, found in low abundance within the guts of this ant species.

Urbanization hampers biological control of insect pests: A global meta-analysis.

Biological control is a major ecosystem service provided by pest natural enemies, even in densely populated areas where the use of pesticides poses severe risks to human and environmental health. However, the impact of urbanization on this service and the abundance patterns of relevant functional groups of arthropods (herbivores, predators, and parasitoids) remain contested. Here, we synthesize current evidence through three hierarchical meta-analyses and show that advancing urbanization leads to outbreaks of sap-feeding insects, declining numbers of predators with low dispersal abilities, and weakened overall biological pest control delivered by arthropods. Our results suggest that sedentary predators may have the potential to effectively regulate sap-feeders, that are one of the most important pests in urban environments. A well-connected network of structurally diverse and rich green spaces with less intensive management practices is needed to promote natural plant protection in urban landscapes and sustainable cities.

Gardening can relieve human stress and boost nature connection during the COVID-19 pandemic.

The COVID-19 pandemic has severely disrupted social life. Gardens and yards have seemingly risen as a lifeline during the pandemic. Here, we investigated the relationship between people and gardening during the COVID-19 pandemic and what factors influenced the ability of people to garden. We examined survey responses (n = 3,743) from gardeners who reported how the pandemic had affected personal motivations to garden and their use of their gardens, alongside pandemic-related challenges, such as food access during the first wave of COVID-19 (May-Aug 2020). The results show that for the respondents, gardening was overwhelmingly important for nature connection, individual stress release, outdoor physical activity and food provision. The importance of food provision and economic security were also important for those facing greater hardships from the pandemic. While the literature on gardening has long shown the multiple benefits of gardening, we report on these benefits during a global pandemic. More research is needed to capture variations in public sentiment and practice - including those who do little gardening, have less access to land, and reside in low-income communities particularly in the global south. Nevertheless, we argue that gardening can be a public health strategy, readily accessible to boost societal resilience to disturbances.

Where birds felt louder: The garden as a refuge during COVID-19.

During the COVID-19 pandemic, many countries experienced something of a boom in interest in gardening. Gardens have long been considered as refuges into which we retreat to escape various struggles and challenges. In this study we examine the characteristics and functions of the garden as a refuge during the period of increased garden interest associated with the COVID-19 pandemic. Analysis of qualitative results about garden experiences from 3,743 survey respondents revealed intertwining garden and emotional geographies. Utilising non-representational and therapeutic landscape theories, we found multifarious and heightened experiences of non-material aspects of gardens; that is, the sensory and emotional aspects. People experienced, for example, a sense of joy, beauty, and reassurance, a greater attunement to the natural world and an increased sense of nature connection than they had at other times: birds felt louder. These heightened sensory and emotional experiences had therapeutic benefits, across age and geographical spectrums, during these difficult times. This research improves our understandings of the positive potential of non-material aspects of gardens in the creation of therapeutic landscapes in and beyond COVID-19.

Fascination and Joy: Emotions Predict Urban Gardeners' Pro-Pollinator Behaviour.

The conservation of pollinators requires social understanding to catalyse restoration action. Citizen science (CS) is discussed as a way to promote interest and action for pollinating insects. Yet, the drivers behind pro-pollinator behaviour are largely unclear, especially in urban areas. To better understand public engagement in pollinator conservation, we studied urban community gardeners' identity, nature-relatedness, emotions, and attitudes toward pollinators and their intentions to get involved in pro-pollinator behaviour in their gardening practice. We surveyed community gardeners in Berlin and Munich, Germany, some of which were participating in a citizen science project. In this scientific study, we created four different sets of generalized linear models to analyse how the gardeners' pro-pollinator behaviour intentions and behaviour were explained by socio-psychological factors. The responses of 111 gardeners revealed that gardeners that were fascinated by pollinators, held positive attitudes and felt joy about seeing pollinators reported intentions to protect or support pollinators, suggesting that fascination and joy can be harnessed for research and conservation on pollinators. Similarly, joy about seeing pollinators predicted participation in the CS project. We believe that CS may represent a pathway through which urban residents may become key actors in conservation projects within their nearby greenspaces.

Confronting the Modern Gordian Knot of Urban Beekeeping.

With insect population declines, cities are important habitats for wild pollinators. Urban beekeeping is an increasingly popular activity, yet honeybees present important risks to wild insect pollinators in cities. We argue for new, scientifically evidenced urban pollinator strategies to simultaneously enhance the benefits of urban beekeeping while protecting wild pollinators.

Natural enemy-herbivore networks along local management and landscape gradients in urban agroecosystems.

Ecological networks can provide insight into how biodiversity loss and changes in species interactions impact the delivery of ecosystem services. In agroecosystems that vary in management practices, quantifying changes in ecological network structure across gradients of local and landscape composition can inform both the ecology and function of productive agroecosystems. In this study, we examined natural-enemy-herbivore co-occurrence networks associated with Brassica oleracea (cole crops), a common crop in urban agricultural systems. Specifically, we investigated how local management characteristics of urban community gardens and the landscape composition around them affect (1) the abundance of B. oleracea herbivores and their natural enemies, (2) the natural-enemy : herbivore ratio, and (3) natural-enemy-herbivore co-occurrence network metrics. We sampled herbivores and natural enemies in B. oleracea plants in 24 vegetable gardens in the California, USA central coast region. We also collected information on garden characteristics and land-use cover of the surrounding landscape (2 km radius). We found that increased floral richness and B. oleracea abundance were associated with increased parasitoid abundance, non-aphid herbivore abundance, and increased network vulnerability; increased vegetation complexity suppressed parasitoid abundance, but still boosted network vulnerability. High agricultural land-use cover in the landscape surrounding urban gardens was associated with lower predator, parasitoid, and non-aphid herbivore abundance, lower natural-enemy : herbivore ratios, lower interaction richness, and higher trophic complementarity. While we did not directly measure pest control, higher interaction richness, higher vulnerability, and lower trophic complementarity are associated with higher pest control services in other agroecosystems. Thus, if gardens function similarly to other agroecosystems, our results indicate that increasing vegetation complexity, including trees, shrubs, and plant richness, especially within gardens located in intensively farmed landscapes, could potentially enhance the biodiversity and abundance of natural enemies, supporting ecological networks associated with higher pest control services.

Socio-ecological connectivity differs in magnitude and direction across urban landscapes.

Connectivity of social-ecological systems promotes resilience across urban landscapes. Community gardens are social-ecological systems that support food production, social interactions, and biodiversity conservation. We investigate how these hubs of ecosystem services facilitate socio-ecological connectivity and service flows as a network across complex urban landscapes. In three US cities (Baltimore, Chicago, New York City), we use community garden networks as a model system to demonstrate how biophysical and social features of urban landscapes control the pattern and magnitude of ecosystem service flows through these systems. We show that community gardens within a city are connected through biological and social mechanisms, and connectivity levels and spatial arrangement differ across cities. We found that biophysical connectivity was higher than social connectivity in one case study, while they were nearly equal in the other two. This higher social connectivity can be attributed to clustered distributions of gardens within neighborhoods (network modularity), which promotes neighborhood-scale connectivity hotspots, but produces landscape-scale connectivity coldspots. The particular patterns illustrate how urban form and social amenities largely shape ecosystem service flows among garden networks. Such socio-ecological analyses can be applied to enhance and stabilize landscape connectedness to improve life and resilience in cities.

Towards better species identification processes between scientists and community participants.

Urban gardens are a model system for understanding the intersection between biodiversity conservation and citizen science. They contain high plant diversity that contributes to urban flora. However, this diversity is challenging to document due to site access and complex plant taxonomy with hybrids and cultivars. Community research participation provides a tool to measure plant diversity and distribution by engaging gardeners who are most familiar with their plants to report on their garden's species richness using citizen science. Yet there is little empirical exploration of plant identification consistency between citizen scientists and scientific researchers. This could lead to reporting differences (e.g., missing species, multiple reporting of the same species) due to spatial and temporal effects, different perspectives and knowledge systems, and cultural context. We leverage a scientific survey of garden plants and a questionnaire asking gardeners to report on the species in their gardens to perform an opportunistic comparison of gardener and researcher reported plant diversity in community gardens. The comparison shows that gardeners interpret instructions to report plants quite variably, with some reporting all species (including herbaceous weeds) and crop varieties, while others reporting only their main crop species. Scientist on the other hand seek clarity in terms of species and variety and report all species located in the plot, including the small weed species that are overlooked by some gardeners. Consistency could be improved if researchers are more specific about their reporting expectations when asking community members to participate in data collection. We use this case study to communicate that paired citizen scientist-researcher data collection and dialogue between groups is necessary to improve methods for conducting consistent and collaborative assessments of biological diversity.

Local and Landscape Effects to Biological Controls in Urban Agriculture-A Review.

Urban agriculture is widely practiced throughout the world. Urban agriculture practitioners have diverse motivations and circumstances, but one problem is ubiquitous across all regions: insect pests. Many urban farmers and gardeners either choose to, or are required to forego, the use of chemical controls for pest outbreaks because of costs, overspray in populated areas, public health, and environmental concerns. An alternative form of pest control is conservation biological control (CBC)-a form of ecological pest management-that can reduce the severity of pest outbreaks and crop damage. Urban farmers relying on CBC often assume that diversification practices similar to those used in rural farms may reduce insect pest populations and increase populations of beneficial insects, yet these management practices may be inappropriate for applications in fragmented urban environments. In this review, we assess urban CBC research and provide a synthesis for urban agriculture practitioners. Our findings indicate that local and landscape factors differentially affect insect pests and beneficial arthropods across the reviewed studies, and we identify several on-farm practices that can be implemented to increase biological control in urban agriculture.

Local and Landscape Drivers of Carabid Activity, Species Richness, and Traits in Urban Gardens in Coastal California.

Urban ecosystems, as mosaics of residential, industrial, commercial, and agricultural land, present challenges for species survival due to impervious surface, degradation, fragmentation, and modification of natural habitat, pollution, and introduced species. Some urban habitats, such as community gardens, support biodiversity and promote ecosystem services. In gardens, local factors (e.g., vegetation, groundcover) and landscape surroundings (e.g., agriculture, built or impervious cover) may influence species abundance, richness, and functional traits that are present. We examined which local and landscape factors within 19 community gardens in the California central coast influence ground beetle (Carabidae) activity density, species richness, functional group richness, and functional traits-body size, wing morphology, and dispersal ability. Gardens with higher crop richness and that are surrounded by agricultural land had greater carabid activity density, while species and functional group richness did not respond to any local or landscape factor. Gardens with more leaf litter had lower carabid activity, and gardens with more leaf litter tended to have more larger carabids. Changes in local (floral abundance, ground cover) and landscape (urban land cover) factors also influenced the distribution of individuals with certain wing morphology and body size traits. Thus, both local and landscape factors influence the taxonomic and functional traits of carabid communities, with potential implications for pest control services that are provided by carabids.

Temperature variability influences urban garden plant richness and gardener water use behavior, but not planting decisions.

Urban environments are being subject to increasing temperatures due to the combined effects of global climate change and urban heat. These increased temperatures, coupled with human planting preferences and green space management practices, influence how urban plants grow and survive. Urban community gardens are an increasingly popular land use, and a green space type that is influenced by unique climate-human behavior interactions. Despite ongoing rapid temperature changes in cities, it is unknown how gardeners are adapting to these changes, and to what extent changes influence planting decisions and patterns of urban plant diversity. In this study, we monitored the variation in daily air temperatures and measured plant species richness at the garden and garden plot scale in 11 community gardens in Melbourne, Australia. We surveyed >180 gardeners to better understand the relationships between temperature variation, garden plant species diversity, and gardener management practices. We found that garden scale temperature variability is driven by regional context, and temperatures are more stable in landscapes with higher impervious surface cover. Gardeners agreed that climatic/temperature changes are influencing their watering behavior, but not their plant selection. Instead plant selection is being driven by desired food production. Yet, when comparing two bioregions, temperature did have a measurable relationship with garden plant composition in the region with more temperature variation. Temperature variability negatively related to plant species richness within garden plots, providing evidence that plant survival is related to climate at this scale in such regions. Although gardeners may be able to water more in response to regional climate changes, gardeners are unlikely to be able to completely control the effects of temperature on plant survival in more variable conditions. This suggests the inner city with more stable temperatures (albeit potentially hotter for longer due to heat island) may accommodate more species diverse gardens.

Soil management is key to maintaining soil moisture in urban gardens facing changing climatic conditions.

Urban gardens are vital green spaces, providing food for residents and space for engaged citizenry and community development. In California, climate change conditions (heat and drought) are becoming more extreme, threatening the resilience of urban gardens. Water use restrictions limit the timing and amount of water that gardeners can access, exacerbating these climate challenges for urban food production. Together with volunteer gardeners, we examined how ambient temperature, water use, vegetation, ground cover, and soil management affect rates of soil moisture gain and loss in urban gardens for a six-week period in the summer of 2017, during the hottest part of the growing season. We found that plot-level management of soils is essential for creating urban garden plots that maintain stable levels of water within garden soils. Although plots with better soil quality (i.e. water holding capacity) experienced slower rates of soil moisture gain after a watering event, they also experienced slower rates of soil moisture loss after the event, leading to soils with more stable, less fluctuating moisture profiles over time. This may benefit gardeners because under extreme climates (such as heat and drought) and water use restrictions, maintaining more stable soils for their plants means that the soils will retain water over a longer period after each watering event. Overall, such results highlight that better soil management that improves soil quality measures such as water holding capacity are potential solutions for maintaining soil moisture and reducing water use under changing climate conditions.