Greenery in the city: technologies and management models
A recent survey found Angers, Nantes and Limoges the three French cities with the most greenery as well as those dedicating the greatest resources for this purpose. In Italy, in the wake of positive results achieved abroad and shrinking financing due to the financial and economic crisis, differentiated maintenance is spreading in a number of municipalities. This means the adoption of a level of maintenance performed according to the type and function of the green area, the intensity of the use of the area and its location. A wide range of technologies are deployed, from mowers to leaf blowers
Increasing urban populations around the world and the uncontrolled expansion of cities has led to construction taking over rural lands and areas surrounding them and the loss of natural and partially natural farmland. The negative repercussions of this trend has resulted in recent years in the growth of attention paid by residents and municipalities to greenery in the urban environment. In Italy as well there is a heightened awareness that green areas make way for spaces for recreation, playgrounds and educational purposes which not only play social roles but improve the urban scene. In the meantime, these spaces provide numerous ecological benefits, from improving the climate to the reduction of pollution in the city environment.
Attention given to urban greenery in the countries of North Europe has a long tradition. This interest has also been great in France for some time. An interesting survey was recently conducted in this country on the maintenance of this heritage of greenery and initiatives for the promotion of an awareness of parks and gardens aimed at favoring biodiversity and for collecting and treating greenery residues. The top three most green cities in France turned out to be Angers, Nantes and Limoges. These in the leading category were distinguished by substantial investments in the creation and maintenance of green areas the allocation of 5% of their municipal budgets, which amounts to four times the national average, and areas accounting for 20% of the total of the territory of these municipalities. Angers led the way with 51 m2 of green area per resident. Nantes can vaunt as many as 100 hectares of park land and gardens, equal to 16% of the city’s territory, and invests € 98 per resident per year for them. This figure is only slightly less than the € 100 invested by the third ranked city with green areas which reach 10% of municipal territory.
In Italy, the National Statistics Institute, ISTAT, had reported that in 2013 public greens accounted for 2.7% of the land areas of provincial capitals. This means 577 million m2 turned over to greenery. Moreover, nearly 16% of these communities’ territories fit into the classification of Protected Natural Areas. Overall, these green areas cover more than 3.7 billion m2, equal to 18.2% of the territories of these provincial capitals. The major cities among them feature high green profiles, the metropolises of Rome and Naples in the south with Turin (Tab. 1) and Milan outstanding in the north.
Maintenance
In Italy, diversified maintenance is gaining ground in many municipalities following the positive results achieved abroad and also due to shrinking financial resources associated with the economic crisis. This maintenance involves the adoption of methods applied in relation to the type of green area, the intensity of its use and location. Three levels of maintenance can be named for the same city: intensive, normal and semi-natural. The first is deployed for areas of great ornamental value, including the road roundabouts giving access to the city. The floral attraction of these areas is maintained according to precise annual plantings, their lawns are mowed frequently, 12 to 15 mowings or more during the growth period, and cleaning operations are performed frequently or even daily. Normal maintenance is carried out on areas set aside for playgrounds, recreational purposes and neighborhood parks. Here mowing comes no more than ten times in the growing season and cleaning is done at planned intervals. Semi-natural maintainence features low intensity interventions in extensive peripheral areas not heavily frequented, in riverside parts and generally where the purpose is to preserve biotic features of the ecosystem. The grass is mowed no more than three times in the growing season, trees are pruned only when necessary and cleaning is done on a planned schedule.
Annual maintenance costs obviously differ according to the level of intensity carried out. These range from more than €10/m2 for high value ornamental greenery to figures of around €5/m2 for historic gardens and down to €1-2/m2 for playgrounds and recreation green areas and €0.50/m2 or even less for semi-natural maintenance.
In any case, in whatever form, maintenance is oriented towards not only financial sustainability but that of the environment. This means that treatments to defend against parasites are aimed at the reduction of chemical products through recourse to an integrated battle; efforts are made to avoid wasting water and to use clean water for irrigation; mowing grassy areas and road verges is performed with an eye on preserving biodiversity; the tendency is to recycle residues from mowed lawns and pruning for compost or chipping for the production of an energy source.
Machines and type of maintenance management
The machines for the maintenance of municipal green areas are the usual. In the lead are the various types of mowers – that is, reel push motor, ride-on mowers and tractor mounted mower – which differ according to the cutting apparatus, usually a horizontal blade. Also up front is machines for transport. Equipment for the maintenance of bushes and trees range from brushcutters to chainsaws and include elevated platforms and mounted or self-propelled chipping machines. The maintenance of areas on slopes and the banks of waterways involves the use of manual brushcutters and flail mowers on booms mounted on a tractor and cleaning operations the clearing leaves are performed mainly by leaf blowers. Unlike in other countries, in Italy public sector maintenance work is increasingly handed over to private concerns which must, however ensure established standards of quality operating under valid technical management, coordination and control. Outsourcing this service may be through giving the contract to the firm through a public tender or assigning maintenance to a farmer or a non-profit cooperative. In some cases a global service is brought in on a form of contract based on performance and the final results with considerable independence in operations.
A totally separate issue is the planned checking on the state of health and stability of the trees which make up the arboreal heritage of cities. This service is carried out through a specific method based on the careful observation of trees and the use of special, minimum invasive instruments which provide the information needed to evaluate their stability.
The purpose of outsourcing this maintenance service is to reduce investments in machinery and equipment and the cost of maintaining and managing the municipalities’ machinery inventory. The city of Turin, for example, uses mixed management combining, on a small scale, a specialized enterprise on contract and a non-profit cooperative to limit the city’s machinery inventory. (Tab. 2)
Maintenance and greenhouse gases
The use of machinery for the maintenance of a park involves the emission of greenhouse gases into the atmosphere but the balance between carbon sequestration and emissions is decidedly positive. This has been clearly demonstrated by Howard Wood, an ecologist specializing in landscape management, who conducted a study in England at the Romsey Wood War Memorial Park in Hampshire. The 2 hectare park contains a 1.5 ha lawn with 69 trees of various sizes as well as various types of hedges, shrubs and flowers. The data developed and reported by Wood, using a precise method for detecting the carbon footprint, shows that the park has a carbon pool of 778 tons of CO2 and that the annual sequestration comes to 8.2 tons against carbon emissions of 1.5 tons annually for a decidedly positive balance. On the side of CO2 maintenance emissions, 774 kg annually which account for 51% of total emissions, 575 kg or 38% of maintenance total are attributed to mowing and 66 kg or 4.3% to leaf sweeping. Transport and waste removal emissions come to 747 kg per year to account for the other 49% of all carbon emissions.
As regards carbon sequestration, it is pointed out that a natural pasture can sequester 1 to 3 tons per year whereas a quality lawn with good maintenance can sequester as much as 12 tons of CO2 in that period. An English lawn can reach sequestration of 4 tons/ha whereas the rate for trees can come to some 38 kg/tree/year. The study demonstrates the important role played by urban greenery in balancing the carbon footprint in a greatly frequently public park. The balance can become more positive with the selection of a grass seed with a high rate of CO2 sequestration and especially with the use, where possible, of electric maintenance equipment rather than gasoline or diesel powered machinery.
