Physical water retention and availability

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).

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).

In 2018, the City of Detroit implemented a drainage charge to help cover the costs of capturing, conveying, pumping, treating, and safely returning combined sewage to the Detroit and Rouge Rivers (1). The charge is calculated based on each parcel’s impact on the sewer system, particularly by measuring impervious acreage (1). Since then, this fee has posed significant challenges for one group in particular: Detroit’s houses of worship (2). Churches, with their large roofs and parking lots, face higher monthly drainage charges, creating financial strain for many faith leaders (2).
To support these institutions, Sacred Grounds has been providing grants, labor, and design assistance to install projects that reduce water bills and drainage fees (2). Sacred Grounds collaborates with the National Wildlife Federation, Friends of the Rouge, and Sierra Club of Michigan to implement these projects through the city’s green credit program (2). A recent initiative involved installing four rain gardens located on the perimeter of St. Suzanne Our Lady Gate of Heaven Church (3). These bioretention gardens, funded by several private and public actors and led by Detroit Future City, diverts water from 20 large downspouts, redirecting an estimated 500,000 gallons of runoff annually away from the municipal sewer system (3, 4).
In addition to managing water, the gardens foster a thriving habitat for pollinators and adds beauty to the area (3). St. Suzanne’s commitment to environmental education includes engaging over 130 youth and adults in training programs that build pathways to STEAM careers and opportunities where local residents are often underrepresented (4). The church also features an innovative, eco-friendly outdoor classroom developed by students, further supporting their sustainability mission (4).

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).

Arizona is experiencing an unprecedented drought, now nearing 15 years and surpassing the most severe drought in over 110 years of recorded history (1). For Phoenix residents, accustomed to extreme heat and minimal rainfall, rising temperatures are bringing new health risks (3). Diminished rainfall not only leads to water scarcity but also raises temperatures, as the sun’s energy, instead of being absorbed to evaporate moisture, intensifies the heat on the ground (2). In 2023 alone, extreme heat claimed at least 147 lives, with Arizona seeing the majority of these fatalities. By early August, over 100 heat-related deaths had been reported in the state (2).
In response to these challenges, the Watershed Management Group (WMG) has collaborated with Arizona State University’s Sustainability Teachers’ Academies to develop a program that maximizes the desert’s limited rainfall to build community resilience (3). Their Schoolyard Water Education Program brings educational services to Phoenix schools, focusing on designing and installing rain gardens as part of outdoor learning initiatives (3). This hands-on approach transforms schoolyards into interactive laboratories where students learn the principles of sustainability through direct engagement with their surroundings (3).
A project at Clarendon Elementary School in Phoenix involved constructing a rain garden with native plants and wood chip mulch to help retain moisture (3). These gardens offer students a living classroom, where they can observe seasonal changes in native plant life, distinguish beneficial species from invasive weeds, and track rainfall to measure the garden’s water intake from rooftops and direct rain (3). Beyond the academic learning, rain gardens provide cooler, safer spaces for students to gather, fostering a lasting connection with nature and a deeper understanding of sustainable water practices (3).

This project aims to increase water retention capacity in the landscape around urban areas and promote biodiversity by restoring wetlands and natural streams in the forested areas on the island of Hisingen in northern Gothenburg. Many wetlands and streams in the area have been drained or otherwise affected by human activity, reducing biodiversity, increasing the risk of floods and droughts and causing greenhouse gas emissions from peatland. The goals of the project are to reduce the risk of floods downstream, reduce the effects of dry periods, increase groundwater infiltration and benefit species living in and around wetlands and streams in the forest [Ref. 1-3]. The Swedish Anglers Association has initiated the project in cooperation with the City of Gothenburg and the environmental engineering company Miljöteknik I Väst AB [Ref 1]. The project's first stage is a continuation of an earlier project to make an inventory of wetlands and their status [Ref 1, 2]. For the second part, 6,9 ha of wetlands and streams on land owned by the city were restored [Ref. 1, 3]. The project will lead to further efforts in wetland restoration around Gothenburg [Ref. 2, 4].

The "Ventanilla Wetlands" Regional Conservation Area (ACR) is an area of 275.45 hectares protected and administered by the Regional Management of Natural Resources and Environmental Management of the Regional Government of Callao (1, 2). It was established on December 20, 2006, by Supreme Decree No. 074-2006-AG, to conserve a representative sample of the coastal wetlands of the Subtropical Pacific Desert (2). With an ecosystem shaped by various hydrological and ecological processes, the "Ventanilla Wetlands" ACR is home to 126 bird species and 27 native plant species, making it an ideal area for ecotourism, recreational, educational, scientific, and cultural activities, thanks to its landscapes and biodiversity (2). However, the Ventanilla Wetlands face several challenges due to urban growth, water pollution, waste, traffic and plane overflights from the National Police and Navy, leading to a decline in bird populations due to noise exposure (5).
This area is fed by the hydrological system of the Chillón River, by surface waters from the Sedapal oxidation ponds, and by water seepage from nearby human settlements and populations adjacent to the wetland. The Ventanilla Wetlands are also influenced by the marine system, especially in the northwest zone. This gives the ACR area lagoon-like characteristics, meaning that its waters are slightly brackish despite being separated from the sea. The internal hydrological system supports the growth of species such as cattails, bulrushes, and reeds. In total, there are 27 native plant species, which serve the function of filtering and purifying the wetland's water. Additionally, the flora provides protection and food for various fauna species, particularly birds, with 126 species recorded, including resident and migratory birds from the Andes, local areas, and the Northern and Southern Hemispheres. Moreover, this protected natural area is home to five reptile species, including endemic species from Lima that are endangered (3).

The Torre Sevilla is a commercial building complex with extensive green roofs. The green roofs cover 11000 or 12000 m2 (different sources report different numbers) and aim to contribute to thermal isolation and energy efficiency of the building, improve air quality and provide an urban green space for relaxation and recreation [Ref. 1-3]. The green roofs include a mosaic of different vegetation types and about 60 mostly native plant species. There is a rainwater recovery system that allows the gardens to be irrigated in a sustainable way [Ref. 1-3, 6]. The building finished construction in 2017 and the gardens were initially not available to the public. In 2023, the owner applied for a permit to host events in the gardens, which will allow the public to visit on occasion [Ref. 1, 3-5].

The City of Mobile has developed and implemented a Storm Water Management Program (SWMP) as required by the regulations of the Environmental Protection Agency (Ref 1). Flooding is a significant issue in Mobile, occurring frequently throughout the town (Ref 3). The SWMP aims to protect water quality and prevent harmful pollutants in stormwater runoff from entering the Municipal Separate Storm Sewer System (MS4) area (Ref 1). Stormwater runoff refers to rainfall that does not seep into the ground but instead flows over yards, streets, parking lots, and buildings, eventually entering the storm sewer system, which directs it into creeks, rivers, bays, and the Gulf of Mexico (Ref 1). Stormwater can collect pollutants such as trash, debris, sediment, heavy metals, oils, and hazardous household materials. Additionally, development increases impervious surfaces, leading to more stormwater runoff (Ref 2).

Perch Creek is one of the many meanders that drain into Dog River (Ref 2), located just west of Mobile Bay (Ref 3). These areas include sensitive, tidally influenced marshes and flats where the brackish water of the Bay meets fresh waters (Ref 1). The Perch Creek Nature Trail & Preserve project aims to protect 96 acres on Perch Creek (Ref 3). It is part of efforts to revitalise Mobile’s coastal community and improve the water quality of the city's urban river (Ref 2), following the devastation of the BP oil disaster in 2010.
The project focuses on two main aspects: creating a low-impact recreational destination to spark economic redevelopment, and preserving Mobile’s coastal wetlands (Ref 1).
The conservation aspect involves wetland acquisition, marsh restoration, and invasive species management, improving water quality in both waterbodies (Ref 1). The area, rich in wildlife, requires habitat protection, including for migrating birds, foxes, alligators, manatees, and bald eagles (Ref 1). Brackish marshes on the property serve as nurseries for fish, while forested areas provide natural corridors for wildlife (Ref 3). The wetlands also play a role in flood control, acting as natural sponges to absorb rising tides and cleanse stormwater runoff before it reaches Mobile Bay (Ref 1). Additionally, they store stormwater, helping mitigate flooding as storms intensify (Ref 3).
The recreational aspect includes developing nature-based recreation, such as nature trails and kayak launches, as well as expanding public access to natural resources (Ref 3). In 2018, the Perch Creek section was added to the Alabama Coastal Birding Trail, with educational signage for kayakers (Ref 1).
This comprehensive project preserves vital habitats and flood-absorbing wetlands, while providing outdoor recreation opportunities and supporting the coastal community's recovery (Ref 2). It combines high-quality water resources, wildlife connectivity, scenic beauty, and outdoor recreation (Ref 3).