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7
periurban green areas (i.e. their multifunctionality) and to the importance to make aware citizens
towards these services (figure 1).
Among ecosystem services particular emphasis is given to benefits provided by wooded areas in
terms of climate change and biodiversity conservation, thus consistent with the aim of these
Guidelines. In particular, at National scale (Italian), the Law n.10/2013 “Norme per lo sviluppo degli
spazi verdi urbani”
2 ,represents a fundamental normative reference for urban forestry interventions,
which realization has to improve the supply of ecosystem services.
An other important aspect is public awareness towards environmental, economic and social
benefits provided by forestry interventions. Also this aspects is taken into account in the Law 10/2013,
where the importance of encourage “
green culture
” is underlined (Art. 6). Public participation yet in
the planning phase of forestry interventions allows a greater guarantee of success, because citizens feel
involved and responsible for the result of the intervention
3 .Figure 1 -
Example of a multifunctional urban forestry intervention in a green area of Rome (Pratone delle
Valli)
1.1.1 Carbon sequestration
Vegetation needs CO
2
for photosynthesis, thus plants during growing store in the biomass large
quantity of carbon, acting like “carbon sink”. CO
2
absorption varies
depending on environmental
conditions (temperature, light availability, etc.), species and individual features (leaf surface, growing
rates, age, health condition, etc.). The capacity of store the atmospheric carbon, in the biomass or in
the soil organic matter, is crucial for climate change mitigation. In particular in urban environment,
vegetation contributes to climate change mitigation in two ways:
1.
absorption of CO
2
through stomata;
2.
CO
2
emissions reduction thanks to the energy saving deriving from the presence of trees. In
fact trees help in mitigating urban heat island and have an insulated and windbreak effect,
resulting in a reduction of energy consumptions due to a less use of air conditioning (in
summer) and of heating (in winter).
In urban areas it is important to consider the trees mortality, because in urban environment they are
exposed to many stresses (such as pollution). Therefore, it is important to select resistant species and
to replace death individuals in short time.
Moreover, energy saving due to the presence of trees in urban and periurban areas is a factor of
mayor effect in CO
2
emissions reduction respect to direct carbon storage and sequestration (Rosenfeld
et al., 199
8 4), especially in areas characterized by warm and dry summer (such as Mediterranean area,
in which Rome is located).
For example some estimates about CO
2
sequestration by urban trees are reported. The estimates are
obtained using specific models:
2
“Rules for urban green areas development” (G.U. n. 27 1st February 2013)
3
An example is the “Project 1000 trees” at Pratone delle Valli, Rome. For this forestry intervention, citizens were extensively involved
through a series of meetings during which the various project hypothesis were illustrated. Furthermore, citizens were actively involved in the
bedding out of some trees.
4
Rosenfeld, A.H., Akbarib, H., Romma, J.J., Pomerantz, M., 1998
. Cool communities: strategies for heat island mitigation and smog
reduction
. Energy and Building, 28: 51-62