FunNature & AnimalEcosystem services of urban parks and gardens

Ecosystem services of urban parks and gardens

Some cities have abundant green areas, from small groves with trees, and landscaped flower beds, to large parks and gardens that give color and life to the city. Others, however, suffer from a serious lack of such areas. Against those who think that parks are the lungs of cities, in the sense that they increase the available oxygen, and that its lack makes the air rarefied; The reality is that the amount of oxygen that trees provide is not that much, rather it is almost insignificant compared to the oxygen that is already in the atmosphere.

However, green areas have many other virtues of great value to the population. Among them, one particularly important: the parks are islands of biodiversity .

The urban ecosystem, although relatively simple compared to wild ecosystems, is still rich and biodiverse, although it is also threatened by effects of anthropic origin, such as climate change or invasive species —very frequent and particularly harmful in these highly disturbed environments. —. In addition, parks, especially when they are made up of native plants, have the effect of raising social awareness : they bring fragments of nature closer to the inhabitants of large cities, and help them understand the need to preserve biodiversity.

But in addition to the obvious benefits in ecological terms, urban parks provide direct benefits to people’s lives.

Effects on environmental pollution

Long ago it was thought that urban parks had the function of purifying the air of cities. In fact, more recent studies show that this decrease in atmospheric pollutants is less than expected, especially in small-sized parks.

What has been observed is that the presence of plants and trees in cities alters the way in which these pollutants are dispersed, reducing the entry from peripheral roads into the interior of cities, and greatly limiting the concentration in the interior of these parks. So, although the parks do not significantly reduce air pollution, the tendency of people to walk through landscaped areas does help the inhabitants to be less in contact with that pollution .

One type of pollution that is significantly attenuated by the presence of parks and gardens is noise pollution ; the vegetation absorbs much of the noise of the city, so that the interior of a park is, in the end, a calm island of silence in a sea of noise.

soften the temperature

The trees cast shade. This is not only a cause of their physical and opaque existence, as in animals, but a consequence of their own metabolism. After all, they feed on sunlight to carry out photosynthesis. Trees orient their leaves so that they catch as much light as possible, and thus cast as much shade as possible. That is, they cast shadow much more effectively than other living things.

Also, plants evaporate water through their leaves, in a process called evapotranspiration . Water is a substance with a high specific heat, which requires a large amount of energy to evaporate. That’s why blowing on a wet finger cools it more than blowing on a dry finger—evaporating water draws heat from the skin—and it’s also why we sweat when it’s hot. In other words, this evapotranspiration from plants, by mere physical effect, lowers the ambient temperature.

Sunlight heats the air, warms the ground, and the ground in turn returns more heat to the air. In the middle of summer, where there are no trees and only black asphalt, air temperatures can rise above what is humanly tolerable, and those of the ground, in some places, rise to such values that they melt the rubber of the shoes when stepped on. The presence of trees, due to the combined effect of shade and evapotranspiration , lowers air and ground temperatures, with a cold island effect that, in the case of large parks, extends beyond the limits of the park.

Some studies recommend that, in areas of extreme heat —which in a scenario of global change, will be increasingly abundant—, open spaces be designed with less than 50% paved area, and with at least 30% covered by vegetation, even if it is tall, such as trees, which allow more space below. In the event of extreme heat waves, if you go outside, the option of going to a park will always be better than staying in an area without vegetation.

reducing stress

Breathing purer air than that found between buildings and enjoying an area with attenuated noise and more tolerable temperatures help the population to relax. Studies show a positive relationship between the presence and use of urban parks and gardens and the state of health and mood perceived by the population . This ability of natural elements to function as “calming areas” is particularly beneficial in urban areas where stress is an all too common aspect of daily life.

Other studies relate the presence of parks and gardens with greater integration and social cohesion, thanks to the effect they have as an element of socialization; people walking their dogs chatting with each other, young people who meet in the shade of a large tree, or old people and children sitting on a bench, in the shade of the poplars, watching the ducks swim in the pond, are scenes more than usual in urban parks.

Parks and gardens, in this sense, act as promoters of social ties , help people to relax and even reduce levels of incivility, aggression and violence.

Parks and gardens, in general, satisfy many needs, both social and psychological . The presence of parks and gardens in cities, and the possibility of access for the urban population provides great advantages that cushion, even minimally, the serious and multiple pernicious effects of living in the big city.

Reference:

Chang, C.-R. et al. 2014. Effects of urban parks on the local urban thermal environment. Urban Forestry & Urban Greening, 13(4), 672-681. DOI: 10.1016/j.ufug.2014.08.001

Chiesura, A. 2004. The role of urban parks for the sustainable city. Landscape and Urban Planning, 68(1), 129-138. DOI: 10.1016/j.landurbplan.2003.08.003

Kuo, F. E. et al. 2001. Environment and Crime in the Inner City: Does Vegetation Reduce Crime? Environment and Behavior, 33(3), 343-367. DOI: 10.1177/0013916501333002

Tashakor, S. et al. 2021. Temporal variability of noise pollution attenuation by vegetation in urban parks. Environmental Science and Pollution Research, 28(18), 23143-23151. DOI: 10.1007/s11356-021-12355-5

Xing, Y. et al. 2019. Role of vegetation in deposition and dispersion of air pollution in urban parks. Atmospheric Environment, 201, 73-83. DOI: 10.1016/j.atmosenv.2018.12.027

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