Urban greenery and climate change: Remorini speaks
In the increasingly urban context of our lives, the presence of green spaces plays a crucial role in the quality of our existence.
The Order of Agronomists and Forestry Doctors of Arezzo, in collaboration with the Professional College of Agricultural Experts of Siena, Arezzo and Florence and with the national trade association of psychologists presented, in mid-September, the seminar entitled:
Urban Green: are you sure it’s only GREEN?
Green is not just a color: the biological, psychological and social effects of living in areas with a high density of urban nature.
What is meant by Urban Green? How is urban greenery classified? How does climate change affect urban greenery? How much urban greenery per inhabitant?
With Professor Remorini, from the Department of Agricultural Sciences of the University of Pisa, we open the series of articles dedicated to the conference: Urban Green: are you sure it is only Green? A simple approach to understand yet full of complexity and knowledge of the topic.
Remorini speaks
First a fact: in 2007 it happened that the people who live in the city exceeded those who live outside the city. In 2021 it was 60% and it is estimated that this value will grow further.
A second fact to start from is that after 2000 we began to talk about ecosystem services as those multiple benefits provided by ecosystems to mankind.
What are the benefits of urban greenery?
Among the physical benefits, probably one of the most important is the improvement of the microclimate. In our cities we are witnessing the heat island phenomenon: built = higher temperatures green = lower temperatures
The contribution of greenery, and of trees in particular, to the mitigation of the heat island is primarily due to the transpiration of water from the leaves which, passing from the liquid to the gaseous state, absorbs heat from the environment, cooling the air.
Furthermore, the direct shading of trees on buildings allows the temperature of the latter to be reduced by up to 10-15 °C.
Then it is known that the presence of greenery improves air quality because plants absorb not only CO2 but also particulates and heavy metals.
Does it matter how the tree is managed?
However, the absorption of CO2 depends greatly on how the tree is cultivated and managed and on the pedoclimatic conditions in which it lives.
Among the economic benefits there is the increase in value for apartments located near parks or green spaces and the lower expense for heating and air conditioning linked to the mitigation of heat in the presence of plants.
The recreational and social functions of greenery bring leisure and aggregation for people and animals which therefore bring us physical and psychological benefits
And how does urban greenery influence the field of health?
There are dozens of studies by doctors regarding the contribution that the use of greenery, and sometimes even just the sight of greenery, provides to many human physiological parameters and to the treatment of many pathologies.
The designer of Central Park, Olmstead in 1800, already invited the population to frequent the park to improve their lives.
The conservation of biodiversity and the importance of ecological corridors along the edges of crops are another advantage.
Environmental education of children sensitizes them to the cultivation of curiosity and therefore respect towards nature.
The resilient city
What is resilience? It is the ability of a material to resist dynamic stress without breaking.
The resilient city resists climate change. For example, in Paris the current mayor has opened school gardens to the population, implementing services and replacing asphalt with permeable materials and transforming unused car parks into small gardens (they had previously strengthened public services making cars less desirable).
You can learn more about the situation in Paris in the article “An Agronomist in Paris”.
The example of Rotterdam
In Rotterdam they decided to focus the green evolution on the GREEN use of roofs. Having many roofs at their disposal, one square kilometer in the center alone, they have developed four types, greenery, recovery of meteorological water, social spaces and solar panels. You can also go from one to the other at altitude.
Barcellona
In Barcelona, a city that has the problem of water bombs, they have decided to use already tested Rain Garden systems, that water drainage system that absorbs excess water in the city by channeling it into large tanks that allow it to be reused in a second moment.
They have experimented with these underground drainage systems in some pilot areas and given the excellent results they have made their implementation mandatory in road redevelopments
Furthermore, they decided that biodiversity needed to be preserved and inserted plants in every available space that allowed the presence of useful insects after a study in collaboration with the University.
How did the citizens react?
It is interesting to note that the population, not informed of these decisions, protested this different management, thinking they would forget to cut the lawn. The municipality therefore decided to activate an information campaign that would explain to citizens why.
When choosing new plants planted, or when replacing those that have been removed, you must be careful about the “exotic/allochthonous” plants (in the sense of non-native) that are inserted. In fact, these must not be invasive.
The use of exotic (but never invasive!) plants can however be a strategy to use in some cases as these can adapt better than many native plants to the changed conditions caused by climate change
If you want to check that there is no prohibited species in your garden you can consult the following link:
List of invasive plants banned in the European Union
Arezzo itself, as a consequence of these reasonings, is trying to draw up a list of alien plants to evaluate their presence.
Greenwashing
Some newspapers write that to cure the world from climate change, 1000 billion trees should be planted.
By making a simple calculation of the space necessary to grow such a quantity of trees, so that they can carry out the task we ask of them, it highlights that almost 70% of the emerged land would be needed!
According to other studies, doubling the existing spaces dedicated to planting would solve the problem. Well it wouldn’t even be enough to triple them.
These theories therefore seem, more than anything else, to be a phenomenon of Greenwashing, that is, the method that sends house dust under the carpet and not into the dustbin.
The problem is more complicated and mainly concerns stopping using oil
Let’s look at the image:
It shows how the same plant in an urban and rural environment has a different development and a different life expectancy due to the stress and limited development to which it is subjected. Care must therefore be taken to create the best conditions in which the plant can develop.
It is better to spend 100 euros on a tree and 200 on the planting site, rather than the opposite
If you want to know the courses at the University of Pisa you can go here
the Mondo del Giardino advice
The change in mentality is what we aspire to: starting from the addition of green spaces we will live better and travel more by bicycle and public transport. By living better, we will have more aware children who will become politicians who will change things. We will act like water that digs the stone not because of its strength but because of its constancy.
Now on horseback! Work awaits us! Our new wonderful outdoor space is about to be born!
GOOD WORK and … if you have any questions please write to info@mondodelgiardino.com
Image sources: thanks to Prof. Remorini for the slides and Pixabay with in particular in order of photos corvin for the social media image, Chil Vera and VĂN HỒNG PHÚC BÙI for the cover, JudaM, Wolfgang Eckert and Pexels for the trio .