As the main body of urban ecosystems, urban forests have changed the cold appearance of urban steel and concrete, fulfilling the strong desire of urban people to get close to nature. Allowing forests to enter cities and allowing cities to embrace forests has become a new concept for enhancing urban image and competitiveness and improving the quality of life of urban residents. Developing urban forests and achieving an upgrade from greenery to ecology is a new issue and trend in current urban construction. Urban forest construction has been officially included in the national forestry development strategy. Vigorously developing urban forests, fully exerting the irreplaceable role of forests in regulating climate, purifying air, conserving water sources, purifying water quality, maintaining soil and water, reducing noise, and beautifying the environment, continuously improving the living environment of cities, and promoting the construction of harmonious cities.
1. Forests can effectively alleviate the greenhouse effect. Due to the extensive use of petrochemical fuels by modern humans, the concentration of greenhouse gases such as carbon dioxide and methane in the atmosphere continues to rise, causing the greenhouse effect on Earth. On average, every hectare of forest can absorb 20-40 tons of carbon dioxide per year while releasing 15-30 tons of oxygen.
2. Forests can effectively curb land desertification and sandstorms. Large-scale afforestation and forest cultivation can not only effectively control and reduce wind-sand hazards, prevent the expansion of land desertification, reduce the frequency of sandstorms, and improve human living conditions but also transform deserts into oases, expanding human living space.
3. Forests can effectively conserve water sources and prevent soil erosion. Due to their vast canopy, thick layers of dead branches and fallen leaves, and well-developed root systems, forests play a good role in storing water, retaining soil, and reducing surface erosion.
4. Forests are also natural experts in disinfection, sterilization, and noise reduction. Many types of tree leaves secrete volatile substances that can kill bacteria, fungi, and protozoa. Some refer to these substances as leaf bactericides. According to urban surveys, the number of bacteria in the air in bustling city areas and streets is more than seven times higher than in green areas. One of the reasons is that certain trees in green areas can secrete powerful bactericides. Many tree species also emit various bactericidal substances during their growth, such as lemon oil, cinnamon oil, and geranium oil, killing some pathogenic bacteria.
5. Forests can effectively protect biodiversity. Among the approximately 5 million to 30 million species on Earth, more than half reside and reproduce in forests.
6. Forests can effectively purify the air. Forests are beauticians and guardians of the urban environment. They are not only huge carbon absorbers and oxygen producers but also fuzzy dust collectors and detoxifiers, as well as doctors and sanitizers for urban atmospheres and waters. Where there are forests, there is water; planting forests creates water. In regions with water shortages and severely polluted water quality, forests serve as water's protector and sanitizer.
7. Forests also have the function of reducing noise. Noise poses great harm to humans. Abroad, noise is called a new type of poison, and some call it a slow-killing weapon. Living in a noisy environment for a long time may cause noise-induced deafness, arrhythmia, elevated blood pressure, coronary heart disease, and arteriosclerosis. Dense foliage has strong sound-absorbing properties; therefore, greening and afforestation have become one of the measures for urban noise prevention. As the role of forests in reducing noise becomes increasingly recognized, design standards for constructing noise-reducing forest belts have emerged in urban greening.
Since the 1980s, building forest cities has increasingly become the goal of urban construction in China. Having large areas of forest in cities undoubtedly becomes an advantageous condition and important marker for constructing green ecological cities. Vigorously carrying out forest city construction and effectively increasing forest coverage is an important direction for urban development in China in the new century. The ecological construction and economic development of forest cities are constrained by economic balance and ecological balance, which drive the ecological and economic development of forest cities. Forest cities aim to achieve maximum economic and ecological benefits, i.e., the greatest possible ecological and economic benefits, which is the purpose of urban forest construction.
The primary role of large forest patches lies in enhancing and improving biodiversity and tourism and leisure activities. However, regarding the environmental impact range, it is quite limited. This model should be developed in limited areas rather than comprehensively rolled out. At this stage, developing a forest network model is more reliable and effective, and it does not exclude the development of large forest patches. The existing forest network can also serve as the foundation for future large forest patches.