Article fromA&B 06 | 2022 issue
If we want to improve the quality of life, reduce city operating costs and adapt to anthropogenic climate change, it is necessary to revise the approach and view greenery and water as critical infrastructure.
Anthropogenic climate change in our latitude means, in addition to rising temperatures, more frequent and more intense heavy rainfall and worsening droughts. And yet, the lack and excess of rainwater are already exposing our cities to many inconveniences. Surface sealing and scarcity of greenery result in flash urban floods, paralyzing city life after rainfall. Conventional stormwater drainage systems do not solve the problem - they are costly and often become overloaded. Relatively clean rainwater, once it flows over the surface of the city, becomes polluted. Its introduction into rivers causes a sudden, unnatural increase in flow and pollution that often exceeds the adaptive capacity of river ecosystems. Their condition, already bad due to regulation and intensive "maintenance" operations consisting of mowing vegetation and cleaning the bottom, deteriorates further. On the other hand, a consequence of the city's drainage is the drying of its spaces. An unfavorable microclimate is created, increasing the likelihood of asthma, allergies and respiratory diseases and exposing city residents to many health problems during increasingly prolonged and frequent heat waves. Lack of water also limits the growth of vegetation, which forms the basis of urban adaptation to climate change by strengthening and restoring blue-green infrastructure (BZI).
Urban blue-green infrastructure is all forms of greenery and ecosystems that are aquatic (rivers, lakes or small dam reservoirs) and water-dependent (such as wetlands, which are already very rare in our cities, but extremely important). However, in planning a city, or individual developments, it is not enough to ensure the presence of open water elements and green areas or to maintain a minimum proportion of biologically active land. It is equally important to maintain a high quality of BZI so that it provides urban residents with benefits - ecosystem services - including services related to urban adaptation to climate change. The international CICES classification described ninety-eight ecosystem services provided by healthy ecosystems. They make up the improvement of ecological security and the quality of human life and health, as well as the reduction of costs associated with it, with urban management, especially under conditions of increasing climate extremes. Therefore, the most important thing in adaptation is to ensure high quality BZI, that is, the presence of water in the urban space, high biodiversity and connectivity of the natural system.
Access to water is crucial to the functioning of urban greenery, especially now, with increasing heat and droughts, the demand of plants for water is increasing. If we don't want to "water the city from the tap," and after all, drinking water supplies may be limited in the future as well, the approach to rainwater needs to change. Do not treat them as a threat, but as a valuable resource. Their excess during heavy rainfall should be retained at the site of the rainfall, and then used locally in times of drought. Large, collective solutions of a hydro-engineering nature will not work here, but dispersed measures that are close to natural solutions. This type of approach is now called nature-based solutions (NBS, nature-based solutions). Stormwater retention in line with NBS implies a number of complementary solutions adapted to urban spaces. These include, among others, the maintenance or restoration of varied landforms (depressions, basins, flow paths and space for temporary water retention); in more peripheral and greened parts of the city, larger dry polders, basins andabsorption wells or ponds that intercept water from the roof; in housing estates and single-family developments, rain gardens; and in parts of strictly built-up areas, permeable materials in traffic routes, lowered strings of street greenery, green roofs and loosening of buildings.
In adapting cities to climate change, green areas with high biodiversity, inspired by natural ecosystems, are of the greatest value. Single trees, especially surrounded by sealed surfaces or planted in pots, or a short-clipped lawn are of little value here. They won't significantly reduce intense surface runoff or effectively lower temperatures in hot weather. They are also less resistant to climatic extremes and more costly and time-consuming to maintain than natural natural systems. Following the principle of nature-based solutions, greenery clusters with the highest possible biodiversity (many species), layered structure (e.g. trees + shrubs + perennials + grasses) and consisting of native species or even reproducing natural plant communities will do better in adaptation. Already replacing a lawn with a flower meadow can significantly improve the biodiversity of both plants (dozens of species) and animals (several hundred species of insects, arachnids and small vertebrates). There is also an increase in rainwater retention, including from adjacent areas - the expanded root system supports seepage, groundwater, soil structure and purification, and retains water for the dry season; the microclimate and aesthetics of the site are improved; the meadow does not require fertilization, herbicides and pesticides, has fewer requirements for watering and regular mowing, which reduces maintenance costs.
Any natural area functions better if it is connected to other natural areas. At the planning level, a network form that uses a system of green areas and urban aquatic ecosystems as the basis for a functional, economic and logical organization of the city's space is ideal (e.g., the blue-green network in Lodz). Connected systems have greater resilience to extremes, adaptability, biodiversity and ability to provide ecosystem services.
Effective and low-cost adaptation is adaptation using solutions based on nature and blue-green infrastructure as critical infrastructure, i.e. infrastructure that impacts multiple social and economic aspects and is necessary for minimal functioning of cities under climate change. To enable it to function, distributed and flexible management of precipitation and support for biodiversity are key. At the same time, it should be emphasized that adaptation is only an ad hoc and time-limited measure. The key action in the face of the climate crisis is immediate decarbonization aimed at achieving climate neutrality in the shortest possible time, by 2050 at the latest.
Many of the solutions described above have been applied in the project: LIFE_RADOMKLIMA-PL (LIFE14 CCA/EN/000101) www.life.radom.pl.
