5.1 Urban ecosystems and habitats

Urban ecosystems are complex environments where nature and human activity intersect. These systems include parks, gardens, and even modified spaces like green roofs. They face unique challenges like habitat fragmentation and pollution, but also offer opportunities for biodiversity and ecosystem services.

Cities can enhance urban ecosystems through strategies like ecological restoration, sustainable design, and community engagement. Monitoring ecosystem health and implementing successful projects like New York's High Line or Singapore's Bishan-Ang Mo Kio Park demonstrate how urban areas can support thriving natural habitats.

Types of urban ecosystems

• Urban ecosystems are the ecological systems that exist within and around cities, including a diverse range of habitats and species adapted to the urban environment
• These ecosystems are shaped by the interaction between the built environment, human activities, and natural processes, creating unique challenges and opportunities for biodiversity and ecosystem services
• Examples of urban ecosystems include urban forests, wetlands, grasslands, and even highly modified habitats like green roofs and walls

Characteristics of urban habitats

• Urban habitats are characterized by high levels of human disturbance, fragmentation, and modification, leading to unique ecological conditions and challenges for species
• These habitats often have altered microclimates, with higher temperatures (urban heat island effect), reduced humidity, and increased air and noise pollution compared to surrounding rural areas
• Urban habitats also have altered soil conditions, with compacted soils, reduced organic matter, and the presence of anthropogenic materials like concrete and asphalt
• Despite these challenges, urban habitats can support a surprising diversity of species, including those adapted to the urban environment (synanthropic species) and those that benefit from human-provided resources (e.g., bird feeders, gardens)

Biodiversity in cities

Native vs introduced species

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• Urban biodiversity includes both native species that have adapted to the urban environment and introduced species that have been intentionally or unintentionally brought into cities by humans
• Native species are those that have evolved in the local ecosystem and play important roles in maintaining ecological processes and interactions
• Introduced species, also known as non-native or exotic species, are those that have been transported by humans beyond their natural range and can have both positive and negative impacts on urban ecosystems
• Some introduced species can become invasive, spreading rapidly and displacing native species, while others may provide important ecosystem services or have cultural value (e.g., ornamental plants)

Factors affecting urban biodiversity

• Urban biodiversity is influenced by a complex range of factors, including the size, age, and density of the city, the types of habitats present, and the management practices employed
• Habitat fragmentation and loss are major threats to urban biodiversity, as the expansion of the built environment reduces and isolates natural habitats, limiting species' ability to move and interact
• The urban heat island effect and other microclimatic changes can alter the suitability of urban habitats for different species, favoring those adapted to warmer, drier conditions
• Human activities, such as landscaping practices, pesticide use, and the presence of domestic pets, can also have significant impacts on urban biodiversity, both positive and negative
• Socioeconomic factors, such as income levels and cultural preferences, can shape the distribution and management of urban green spaces and biodiversity

Green infrastructure

Urban parks and green spaces

• Urban parks and green spaces are important components of green infrastructure, providing a range of ecosystem services and benefits for both biodiversity and human well-being
• These spaces can include a variety of habitats, such as forests, grasslands, wetlands, and gardens, and support a diverse range of species
• Urban parks and green spaces also provide opportunities for recreation, education, and social interaction, contributing to the physical and mental health of city residents
• The design and management of urban parks and green spaces can have a significant impact on their ecological value and the benefits they provide, with strategies like native plant landscaping and habitat restoration enhancing biodiversity and ecosystem services

Green roofs and walls

• Green roofs and walls are innovative forms of green infrastructure that integrate vegetation into the built environment, providing a range of ecological, economic, and social benefits
• Green roofs are vegetated roof coverings that can reduce building energy consumption, mitigate the urban heat island effect, and provide habitat for biodiversity
• Green walls, also known as living walls or vertical gardens, are structures that support the growth of vegetation on vertical surfaces, providing similar benefits to green roofs
• These green infrastructure elements can also improve air and water quality, reduce stormwater runoff, and enhance the aesthetic appeal of buildings and streetscapes
• The design and maintenance of green roofs and walls require specialized knowledge and techniques to ensure their long-term sustainability and effectiveness

Benefits of green infrastructure

• Green infrastructure provides a wide range of benefits for urban ecosystems and human well-being, addressing multiple sustainability challenges in cities
• Ecological benefits include habitat provision for biodiversity, improved air and water quality, and the mitigation of urban heat island effects and climate change impacts
• Economic benefits include reduced energy costs for buildings, increased property values, and the creation of green jobs in design, installation, and maintenance
• Social benefits include improved physical and mental health outcomes, increased opportunities for recreation and social interaction, and enhanced community resilience and cohesion
• Green infrastructure also contributes to the overall livability and attractiveness of cities, making them more desirable places to live, work, and visit

Urban wildlife

Common urban species

• Urban environments support a diverse range of wildlife species, including those adapted to the unique conditions of cities and those that benefit from human-provided resources
• Common urban bird species include pigeons, sparrows, starlings, and various species of gulls and raptors, which have adapted to nesting on buildings and foraging on human food waste
• Urban mammal species include squirrels, rats, mice, raccoons, and even larger species like coyotes and deer in some cities, which can thrive on the abundant food resources and shelter provided by human activities
• Insect species, such as bees, butterflies, and ants, play important roles in urban ecosystems as pollinators and decomposers, and can be supported by urban gardens and green spaces
• Urban aquatic habitats, such as rivers, streams, and ponds, can support a variety of fish, amphibians, and invertebrates, depending on water quality and habitat conditions

Human-wildlife interactions

• The close proximity of humans and wildlife in urban environments leads to a range of interactions, both positive and negative, that shape the dynamics of urban ecosystems
• Positive interactions include the aesthetic and educational value of observing wildlife, the ecosystem services provided by species like pollinators and seed dispersers, and the potential for wildlife-based tourism and recreation
• Negative interactions can include conflicts over space and resources, such as property damage caused by wildlife, the transmission of zoonotic diseases, and the impacts of human activities on wildlife health and behavior
• Human attitudes and perceptions towards urban wildlife vary widely, influenced by factors such as cultural background, personal experience, and knowledge of the species involved
• Effective management of human-wildlife interactions requires a combination of public education, stakeholder engagement, and evidence-based strategies that balance the needs of both humans and wildlife

Wildlife management strategies

• Urban wildlife management aims to maintain healthy and sustainable populations of wildlife species while minimizing conflicts with human activities and promoting positive human-wildlife interactions
• Habitat management is a key strategy, involving the protection, restoration, and creation of suitable habitats for urban wildlife, such as parks, green spaces, and wildlife corridors
• Population management strategies, such as reproductive control or relocation, may be used to address overabundant or problematic wildlife populations, but should be based on sound scientific evidence and consider animal welfare concerns
• Public education and outreach are essential for promoting coexistence with urban wildlife, raising awareness of the ecological value of these species and providing guidance on how to minimize conflicts
• Collaborative approaches, involving partnerships between local authorities, conservation organizations, and community groups, can help to develop and implement effective and socially acceptable wildlife management strategies

Ecosystem services in cities

Provisioning services

• Urban ecosystems can provide a range of provisioning services, which are the material benefits that people obtain from ecosystems, such as food, water, and raw materials
• Urban agriculture, including community gardens, rooftop farms, and vertical farming systems, can contribute to local food production and improve food security in cities
• Urban forests and green spaces can provide timber, wood fuel, and other forest products, as well as medicinal plants and herbs
• Urban water systems, such as rivers, lakes, and groundwater, can provide water for drinking, irrigation, and industrial uses, although the quality and availability of these resources may be limited by pollution and overexploitation

Regulating services

• Urban ecosystems also provide important regulating services, which are the benefits obtained from the regulation of ecosystem processes, such as climate regulation, air and water purification, and flood control
• Urban vegetation, particularly trees and green roofs, can help to mitigate the urban heat island effect by providing shade, evapotranspiration, and reflecting solar radiation, reducing the energy needed for cooling buildings
• Green infrastructure, such as parks, wetlands, and permeable pavements, can help to manage stormwater runoff, reducing the risk of flooding and improving water quality by filtering pollutants
• Urban ecosystems can also contribute to air purification by removing pollutants such as particulate matter, ozone, and nitrogen dioxide, although the effectiveness of this service depends on factors such as vegetation type and density

Cultural services

• Urban ecosystems provide a range of cultural services, which are the non-material benefits that people obtain from ecosystems, such as recreation, education, and spiritual enrichment
• Urban parks and green spaces offer opportunities for physical activity, relaxation, and social interaction, contributing to the physical and mental health of city residents
• Urban nature can also provide educational opportunities, such as nature-based learning programs for children and citizen science initiatives that engage the public in ecological monitoring and research
• Urban ecosystems can have significant aesthetic and cultural value, contributing to the sense of place and identity of cities and providing inspiration for art, literature, and other forms of cultural expression
• The cultural services provided by urban ecosystems are influenced by factors such as accessibility, safety, and the diversity of recreational and educational opportunities available

Challenges for urban ecosystems

Habitat fragmentation and loss

• Habitat fragmentation and loss are major challenges for urban ecosystems, as the expansion of the built environment reduces and isolates natural habitats, limiting species' ability to move and interact
• Urban development often results in the conversion of natural habitats, such as forests, wetlands, and grasslands, into buildings, roads, and other impervious surfaces, reducing the total area of available habitat
• The remaining habitat patches are often small, isolated, and degraded, lacking the size, connectivity, and quality needed to support viable populations of many species
• Habitat fragmentation can disrupt important ecological processes, such as pollination, seed dispersal, and nutrient cycling, and increase the vulnerability of species to stochastic events and genetic isolation
• Efforts to mitigate habitat fragmentation and loss in cities include the protection and restoration of existing habitats, the creation of green corridors and stepping stones to improve connectivity, and the integration of biodiversity considerations into urban planning and design

Pollution and environmental degradation

• Urban ecosystems are often exposed to high levels of pollution and environmental degradation, which can have significant impacts on the health and functioning of these systems
• Air pollution, including particulate matter, ozone, and nitrogen oxides, can have direct toxic effects on plants and animals, as well as indirect effects on ecosystem processes such as photosynthesis and nutrient cycling
• Water pollution, from sources such as sewage, industrial effluents, and stormwater runoff, can degrade aquatic habitats and harm aquatic species, as well as pose risks to human health through exposure to contaminated water and fish
• Soil pollution, from sources such as industrial activities, landfills, and the use of pesticides and fertilizers, can alter soil chemistry and microbial communities, affecting plant growth and ecosystem functioning
• Noise and light pollution can also have significant impacts on urban wildlife, disrupting communication, navigation, and reproductive behaviors, and altering the timing of biological events such as migration and flowering
• Strategies to address pollution and environmental degradation in cities include strengthening environmental regulations, promoting clean technologies and green infrastructure, and engaging citizens in pollution monitoring and reduction efforts

Climate change impacts

• Urban ecosystems are increasingly vulnerable to the impacts of climate change, which can exacerbate existing stresses and create new challenges for biodiversity and ecosystem services
• Rising temperatures and more frequent and intense heatwaves can increase the urban heat island effect, leading to higher energy demand for cooling, reduced air and water quality, and increased health risks for vulnerable populations
• Changes in precipitation patterns, including more frequent and severe droughts and floods, can alter the water balance of urban ecosystems, affecting the growth and survival of plants and the availability of water resources for human use
• Sea-level rise and coastal flooding can threaten low-lying urban areas, damaging infrastructure and ecosystems, and displacing human and wildlife populations
• Shifting climatic conditions can also alter the distribution and phenology of urban species, leading to mismatches between species' needs and resource availability, and facilitating the spread of invasive species and disease vectors
• Strategies to enhance the resilience of urban ecosystems to climate change include promoting green infrastructure and nature-based solutions, improving the energy efficiency of buildings and transportation systems, and developing adaptation plans that consider the needs of both human and ecological communities

Strategies for enhancing urban ecosystems

Ecological restoration and conservation

• Ecological restoration and conservation are key strategies for enhancing urban ecosystems, involving the protection, management, and rehabilitation of natural habitats and species
• Habitat restoration can involve a range of activities, such as removing invasive species, planting native vegetation, and restoring natural hydrological and soil conditions, to improve the ecological integrity and functionality of urban habitats
• Species conservation efforts can include monitoring and management of threatened and endangered species, as well as the reintroduction of extirpated species and the creation of artificial habitats, such as nest boxes and bat roosts
• Urban ecological networks, such as green belts, corridors, and stepping stones, can help to improve habitat connectivity and facilitate the movement of species across the urban landscape
• Engaging local communities and stakeholders in restoration and conservation efforts can help to build support for these initiatives, as well as provide opportunities for environmental education and stewardship

Sustainable urban design and planning

• Sustainable urban design and planning are essential for creating cities that support biodiversity and ecosystem services, while also meeting the needs of human communities
• Biophilic design principles, which integrate natural elements and processes into the built environment, can help to create buildings and public spaces that are more ecologically responsive and restorative for human well-being
• Green infrastructure planning, which considers the spatial distribution and connectivity of natural and semi-natural areas, can help to optimize the ecological and social benefits provided by urban ecosystems
• Sustainable transportation planning, which prioritizes walking, cycling, and public transit over private vehicle use, can reduce air pollution and greenhouse gas emissions, while also creating more space for green infrastructure and biodiversity
• Participatory planning processes, which engage local communities and stakeholders in the design and management of urban ecosystems, can help to ensure that these systems are socially and culturally relevant, as well as ecologically functional

Community engagement and stewardship

• Community engagement and stewardship are critical for the long-term success of efforts to enhance urban ecosystems, as they build social capital and a sense of ownership and responsibility for these systems
• Citizen science programs, which involve members of the public in ecological monitoring and research, can help to generate valuable data on urban biodiversity and ecosystem health, while also raising awareness and building scientific literacy
• Community gardening and urban agriculture initiatives can provide opportunities for people to engage with nature, produce fresh and healthy food, and build social connections and resilience
• Environmental education programs, such as nature-based learning in schools and community workshops, can help to foster a sense of connection to and appreciation for urban ecosystems, as well as provide skills and knowledge for sustainable living
• Stewardship networks, which bring together diverse stakeholders to collaborate on the management and advocacy for urban ecosystems, can help to coordinate efforts and leverage resources for greater impact

Monitoring and assessment

Indicators of ecosystem health

• Monitoring and assessment are essential for understanding the status and trends of urban ecosystems, and for evaluating the effectiveness of management interventions and policies
• Indicators of ecosystem health are measurable attributes that provide information on the structure, function, and composition of urban ecosystems, and can be used to track changes over time and space
• Biodiversity indicators, such as species richness, abundance, and distribution, can provide insights into the diversity and resilience of urban ecosystems, as well as the impacts of human activities and environmental stressors
• Ecosystem service indicators, such as carbon sequestration, water infiltration, and air quality, can help to quantify the benefits provided by urban ecosystems to human well-being, and inform decision-making on land use and management
• Socio-ecological indicators, such as green space accessibility, environmental justice, and community engagement, can help to assess the social and cultural dimensions of urban ecosystems, and ensure that the benefits and costs of these systems are equitably distributed

Citizen science and monitoring programs

• Citizen science and community-based monitoring programs can play a valuable role in the monitoring and assessment of urban ecosystems, by engaging the public in data collection and analysis
• These programs can help to fill data gaps and provide fine-scale, locally relevant information on urban biodiversity and ecosystem health, which may be difficult or costly to obtain through traditional scientific methods
• Citizen science programs can also help to build scientific literacy and environmental awareness among participants, and foster a sense of stewardship and connection to urban nature
• Examples of citizen science programs in urban ecosystems include bird counts, butterfly monitoring, water quality testing, and tree inventories, which can be conducted by individuals or groups with varying levels of expertise and resources
• To ensure the quality and usefulness of citizen science data, it is important to provide clear protocols and training for participants, as well as mechanisms for data validation and integration with other monitoring efforts

Case studies and best practices

Successful urban ecosystem projects

• Case studies of successful urban ecosystem projects can provide valuable insights and inspiration for practitioners and policymakers working to enhance biodiversity and ecosystem services in cities
• The High Line in New York City is an example of a successful urban ecological restoration project, which transformed an abandoned elevated railway into a linear park and greenway, supporting a diverse range of native plant and animal species
• The Bishan-Ang Mo Kio Park in Singapore is an example of a successful green infrastructure project, which restored a concrete drainage channel into a naturalized river and wetland system, providing flood control, water quality, and recreational benefits
• The City of Melbourne's Urban Forest Strategy is an example of a successful urban forestry initiative, which aims to increase tree canopy cover and diversity in the city, while also engaging the community in the stewardship and appreciation of urban trees
• The London Wetland Centre