Maintenance and management of urban nature

The Mobile Tree Trail is a nature-based solutions (NBS) initiative aimed at preserving Mobile, Alabama’s urban forest while celebrating its cultural and ecological heritage (Ref 1, Ref 2). First established in the early 1990s by volunteers, the original trail featured 24 iconic trees, selected for their historical significance, environmental value, and beauty (Ref 1, Ref 2). Over the years, some trees were lost to development and storms, and the trail faded into obscurity (Ref 1, Ref 4).
From 2021, the Mobile Tree Commission, with support from The Nature Conservancy, is leading efforts to revive the trail (Ref 3, Ref 6). Activities include reviewing past entries, opening public nominations, and selecting new trees that best represent Mobile’s identity (Ref 3, Ref 4). The project emphasises inclusivity and public participation, welcoming volunteers and local input to shape a trail that evolves with the city (Ref 4, Ref 6).
Mobile faces environmental threats such as hurricanes, urban expansion, and loss of native tree cover (Ref 1, Ref 6). The revitalised trail helps address these challenges by promoting awareness, conserving old-growth specimens like the 300-year-old Duffie Oak, and maintaining vital green spaces (Ref 4, Ref 6).
The Mobile Tree Trail blends education, tourism, and conservation, enhancing urban resilience while telling the city’s story through its trees (Ref 3, Ref 6).

Bayou La Batre, also known as the seafood capital of Alabama, has been facing severe flooding problems, including the occurence of combined sewerage overflows. The Nature Conservancy has secured funding to install a green stormwater project in Bayou La Batre, adjacent to the library, sports fields and the community center. Alongside the aim of the green stormwater project to decrease flooding events in the community by infiltrating water, it also serves as an education and engagement project [1]

The Liberties is one of the most recognizable urban areas in Dublin and Ireland, strongly associated with old Dublin, working-class communities, and the brewing and distilling industries. While rich in history, cultural significance, and local stories, The Liberties faces numerous placemaking and quality-of-life challenges. The area continues to experience significant dereliction, a fragmented urban fabric, and a shortage of high-quality green spaces. For instance, tree coverage in The Liberties is sparse, with good-quality street trees only found in a few small areas, such as Gray St. and Reginald St., along the South Quays, Cornmarket, and near the fountain on James St. The area has approximately 1,200 trees, amounting to less than 5% canopy coverage.
In response to these challenges, Dublin City Council enacted The Liberties Greening Strategy in 2015. Building on the Liberties' Local Area Plan, this strategy aims to develop a network of new urban parks, improve access to heritage green spaces, and refurbish existing parks and play areas. It addresses multiple goals, including ecological connectivity, water management, flood risk reduction, air quality improvement, social cohesion, environmental education, and public health. This strategy is an initiative of the Parks and Landscape Services Division of Dublin City Council, in collaboration with the South Central Area Office and with input from Áit Urbanism + Landscape and Mary Tubridy & Associates.
Since its implementation in 2015, the strategy has resulted in the development of two new community parks, enhancements to several green spaces, and the greening of public spaces. It has also introduced measures to support food production in community gardens and allotments, revitalize ecosystems, strengthen water management, improve air quality, boost carbon sequestration through tree planting, divert water from the local sewer network, prevent flooding, and regulate heat. (1, 2, 3)

The likely impacts of climate change in South Dublin County include an increased risk of flooding, more frequent summer droughts, deteriorating air and water quality, and biodiversity loss (1). To address these climate challenges, the county developed the County Development Plan 2016-2022 as part of the South Dublin Climate Action Plan, aiming to establish a comprehensive legislative and policy framework for green infrastructure (GI) planning (1).
The plan outlines various objectives, including creating a coherent, integrated, and adaptable GI network across South Dublin County. One key initiative is the establishment of native mini woodlands throughout the city, designed to form strategic links and integrate the GI Strategy’s objectives into all relevant land-use plans and development across the county (1).
The purpose of these mini woodlands is to connect green spaces across the city (minimum size of 100 sq m), sequester carbon, and promote biodiversity in suitable locations, such as built-up areas, low-grade parkland, and other zoned areas deemed appropriate (1). Given the long time required for tree growth, the project employs the Miyawaki method, planting a high density of diverse native species to create mature forests up to ten times faster than traditional plantations (2). These forests are estimated to host 20 to 100 times more biodiversity and absorb carbon up to 40 times more effectively, without the use of chemicals or fertilizers; key factors include ground preparation, planting density, and species diversity (2).
In 2022, the project held a planting day for the mini woodlands initiative on Mill Lane, where 1,200 native trees and shrubs were planted with the help of volunteers from local schools, the community, a corporate group, and the Mayor of South Dublin, Councillor Emma Murphy (2).

The financial capital of Sri Lanka, Colombo, is the fastest-growing city in Sri Lanka, and as such, it is constantly changing. Most expansions in urban areas are taking place without proper planning, which can cause damage to existing pockets of forests, landscapes and green areas in and around the city (1). The environmental impacts of this rapid urbanisation include increased pollution, increased heat due to the expansion of roads/pavements, tall structures that block out light and wind and reduced biodiversity in fauna and flora (1).
To face these challenges, the Federation of Environmental Organisations (FEO) proposed a city-wide Tree Planting Campaign to create an Urban Forest Strategy in public and private lands in the greater Colombo area (1). The plan is to kick-start the program at the Borella Cemetery as it has a large land area available for planting, specifically 178062 sq meters (3). The project started to be implemented in July 2020 with the seasonal rains (1). This project aims to grow urban trees to help mitigate some of the negative impacts of unplanned and rapid urbanisation, thus making the city more resilient to these changes (1).
The trees that will be planted will be mostly native species and also exotic plants will be selected based on specific requirements (1, 3). It is also planned to have flowering plants and shrubs to encourage butterflies, bees and birds to interspace the trees (1). The new parking space near the Borella Cemetery will also be planted with deep root shading trees interspaced with flowering plants (1).
The project aimed to include a large number of stakeholders including the government, the private sector and the residents of Colombo (1). And they have also reached schools in Colombo and hope to involve environmental associations to further the cause (3).

The Mediterranean climate in Lisbon, already characterised by low precipitation, has been further exacerbated by climate change. The city faces challenges related to biodiversity loss, urban loneliness, and climate anxiety (1). To address these issues, Lisbon's urban development plans have prioritised the re-naturalisation of urban spaces and the integration of ecological networks. Urban nature is now a central component of the city's Master Plan (2012) and other strategic agendas (1).
It is being developed by the LISGREEN project, which aims to enhance ecological connectivity and mitigate the effects of urban heat islands in Lisbon. By establishing nature-based solutions, it aims to restore forests within the city (1, 2, 3). This project encompasses different strategies, such as the RENATURA pilot project. It is a collaboration with the NGO URBEM and involves active public participation in tree planting and forest maintenance. This initiative aims to educate the community about nature, promote well-being, and mitigate extreme climate events (1), through the creation of urban forests.
The main strategy is to create fast forests using the Miyawaki method, which involves dense planting of native trees, removal of invasive plants, and intensive initial care. This approach accelerates the growth of natural forests within a short period, using native species and reducing the need for watering (1)
The first fast forest was developed in Parque Casal Vistoso within Bela Vista Park, within the Eastern Green Corridor of Lisbon. The park is being underutilised because of the lack of shade (1). Thus, this initiative encouraged volunteers to participate in tree planting and forest maintenance activities (3). The NbS intervention began with a 300m² experimental plot near the Vale da Montanha pedestrian bridge and has since expanded to a new 1,500m² plot on the opposite side of the bridge (2). Over 500 volunteers joined the effort, planting more than 3,800 trees (1)

Lisbon is facing an increasing threat linked to climate change due to its geographical location and climate (6), which has had a negative impact on health and quality of life in the city (5). Its average annual precipitation is decreasing, although the city experiences more winter precipitation. This results in longer droughts and more seasonal flooding, which reduces water retention and soil conservation (6). Average temperatures are increasing by 14°C per year, with maximum temperatures up to 5°C higher (6).
As an adaptation measure to these challenges, the LIFE LUNGS project aims to increase Lisbon's resilience by implementing green infrastructure and promoting related ecosystem services (1, 3, 5, 6). Thus, it focuses on measures aimed at coping with temperature increase, mitigating the effects of heat waves and water scarcity, which are expected to become more frequent, being in line with the climate policies adopted by the municipality. The project runs from 2019/2020 to 2024/2025 (1, 5, 6). It aims to address cross-cutting issues such as climate, water and biodiversity (3). The project expects to work hand in hand with the City of Malaga, which has been developing projects aimed at adapting the city to climate change. It is expected to replicate the work in Malaga and post-project to 2 national territories, and 1 in the EU (4). It is also intended to transfer the project work to be implemented in private areas that are part of Lisbon's green infrastructure, and to disseminate and technically train municipalities of the Lisbon Metropolitan Area and other municipalities committed to climate change adaptation (4).

Sri Lanka, particularly its low-lying coastal areas, faces recurring flooding challenges exacerbated by climate change, coastal erosion, and urbanization (1). Wetlands have emerged as crucial ecosystems in mitigating these risks, acting as natural sponges during heavy rainfall and releasing water gradually as flood levels subside (1). Beyond flood control, wetlands play a vital role in environmental quality. Their biodiversity helps filter pollutants and chemicals from the air and water, creating a healthier environment for both humans and wildlife (1). In 2018, Colombo was designated as a Global Wetland City under the Ramsar Convention, becoming the first and only capital city to receive this recognition (1). Recognizing the significance of wetlands as nature-based solutions, international institutions have prioritized their conservation through financing programs (1), and the city has developed projects to raise awareness and involve its citizens in their protection (1). These efforts have resulted in the creation of four wetland parks in the city, that comparing to a wetland, the wetland parks have more human intervention. Thus, they are focused on different topics and activities (2): Diyasaru Park, Beddagana Wetland Park (managed by the Urban Development Authority), Kotte Rampart Wetland Park (managed by the Urban Development Authority), and the Gothatuwa Wetland Park (managed by the Sri Lanka Land Development Corporation) (2). Gothatuwa Park is the newest wetland park and it is located in the flood-prone Gothatuwa neighbourhood (1). Inaugurated in 2024, It has a recreational focus, with trails for cyclists and hikers, and together with the other wetland complex, this park is designed to make the wetlands a cornerstone of local people's lives (1). Currently, environmental education activities are carried out in the park, focusing on managing aquatic invasive plants, tree planting and solid waste collection (3).

The Thalangama wetlands are part of a network of wetland ecosystems around Colombo city that spread over 20 km2 and provide critical life support to the city. These ecosystems keep people safe from floods, cool the air, filter polluted water, provide food and medicines, and fight climate change (10). These wetlands have become an environmental protection area and a biodiversity hotspot in a rapidly urbanising environment, as they host an array of plants and animals, including the endangered fishing cat and otter (5, 10). In 2007, Thalangama Lake and its surroundings were declared an Environmental Protection Area (EPA) under the National Environmental Act (4, 5). This protected area covers approximately 118 hectares (4) and includes two man-made reservoirs: Thalangama Tank (11 ha) and Averihena Tank (3.2 ha), located just 300 meters apart (5). The area hosts floating and rooted plants, scrublands, and trees that provide habitat to up to 100 species of migratory, resident, and endemic birds throughout the year. In addition, the area supports 30 species of dragonflies, 12 species of reptiles, 10 species of mammals, and 15 species of freshwater fish (1, 4). Since the lakes and their surroundings were declared an EPA, only limited uses are permitted, such as traditional fishing and rice cultivation (4, 5). The lakes are also important for floodwater retention and have high scenic and aesthetic value, attracting many visitors, and scientific and educational activities (5, 13).
However, due to the area's rapid urbanisation, land values have increased significantly, leading to excessive landfilling and the reclamation of paddy lands for housing. This is compounded by the indiscriminate disposal of garbage and construction waste and the spread of invasive species (5). These challenges have also led to the engagement of surrounding communities in managing and maintaining it (11).

Sri Lanka faces multiple natural hazards, including tropical storms, flash floods, and landslides. As the country's urban population has grown, development projects have encroached on wetlands, compromising their natural flood protection, air and water purification, and carbon storage capabilities. Additionally, hilly regions are at risk of landslides, particularly during the monsoon season, posing significant threats to vulnerable communities (4).
To address these challenges, the World Bank and the Sri Lankan government collaborated on the Metro Colombo Urban Development Project. This initiative focused on nature-based solutions (NBS) as cost-effective and sustainable approaches to risk management (4). By strengthening natural processes and ecosystem services, the project aimed to mitigate hazards such as floods, erosion, and landslides (4). Technical assessments by the World Bank highlighted the importance of wetlands in flood protection, leading to efforts to protect and restore 20 square kilometres of freshwater lakes, wetlands, and swamps (1, 4).
The project supported the Sri Lankan government in reducing flooding in the Colombo Water Basin and enhanced local authorities' capacity to manage infrastructure and services. It prioritised metropolitan investments to mitigate the physical and socioeconomic impacts of flooding and aimed to build long-term capacity for urban management and local service delivery (6).