While use of public spacelinked in particular to increasingly hot summers, is intensifying and numerous events take place there throughout the year, the English garden and the Bastions park are subject to a ever-increasing pressure. This occupation generates impacts on tree heritage. However, in order to last over time and promote the services it provides us, it must be protected.
Two studies to attest to the condition of the trees and the quality of the soil
The Green Spaces Service (SEVE) has mandated between September 2022 and February 2023 two studies to attest to the condition of the trees and the soil quality. “The conclusions made it possible to adopt an action plan to establish a new balance And respectful cohabitation between the different occupants of the place, whether trees or citizens. We now have precise studies which will allow us to follow the evolution of these spaces in order to adapt the measures according to needs. It is necessary toact today so as not to have to close these parks tomorrow,” underlines Alfonso Gomez, Administrative Advisor in charge of the environment.
Soil analysis
Soil analysis focused on their compactness and the useful depth for trees. The results revealed a great heterogeneitywith variable qualities, due to the constitution of the soils which result from backfilling and successive rearrangements by man.
Tree expertise
L’tree expertise focused on 417 trees at Bastions And 163 trees in the English Gardenof which were analyzed
- measurements,
- L’physiological state (vigor of the tree, prospects for maintenance and development),
- L’mechanical condition (defects likely to cause all or part of the tree to fall).
Study results
At the English Garden, the condition of the trees is described as “declining”
At English Gardenthe analysis is based on significant physiological problemswith around thirty trees in mediocre to poor condition, or one tree in five. The overall condition of the trees is described as “declining”.
Uncertainties at the Bastions
To Strongholdsthe trees are in better condition but strong uncertainties remain in the mechanical condition of 6% of the trees.
Recommended interventions
The studies recommend interventions on 50 trees at the English Garden and 110 at the Bastions For extend their lifespan And secure the premises. The types of interventions will vary depending on the case – pruning, additional examination, guying, felling or laying of mulch (branch shavings or coarse organic mulch).
Multiple causes of dieback
No direct correspondence between the two subjects of analysis emerged, which can be explained by a great heterogeneity of soils and the multifactorial nature of the causes of dieback.
Among these, the lower quality of reworked soilswith a water storage less efficient. However, the climate change is already leading to a change in the distribution of annual precipitation. Furthermore, the ancient trees have reduced coping skills to changes, especially when they are rapid.
Regular repair of lawns and the desire to grass a maximum of surfaces also causes a loss of organic matter restitution.
To finish, theincreased use of parks leads to a number of injuries to the trees. If event organizers increasingly integrate the recommendations, their multiplicity causes more pressure and damage. Rolling marks at the base of trees, leading to compaction or even waterproofing of the soil, are regularly observed.
Installation of protections for 15 priority zones
Based on the recommendations of the studies, the Green Spaces Department of the City of Geneva (SEVE) has set up a action plan to achieve a better balance between protection of tree heritageTHE rescue of dying trees and the legitimate need of the population to dispose of the premises.
Long-lasting protections will be installed quickly around 15 priority areas (9 zones for 33 trees in the English Garden and 6 zones for 23 trees in the Bastions). Under the crown of these trees, the laying of mulch will allow limit water evaporation and give back more life on the groundthus stimulating root development and growth. These protected areas will be moved periodically, depending on the condition of the trees.
Tree protection plan required during demonstrations
From now on, it will also be required of organizers of events that they provide a detailed tree protection planwhich must be validated by the SEVE. Trees subject to pressure linked to vehicle or public traffic must be individually protected, using suitable barriers, to avoid trampling, storage of equipment or damage to the surroundings of the tree.
Medium-term avenues for reflection
Moreover, in the medium term, several avenues for reflection must be carried out. The iinstallation of certain infrastructures during major events could be adjusted and certain sectors be entirely preserved. A reasoned occupancy plan for the City’s parks must be developed in order to achieve a better distribution of events.
The relevance of a systematic soil monitoring will be studied for major events.
Finally, it will be a matter of maintaining reasonable pressure on the parks, particularly in limiting new authorizations for demonstrations and their duration.
As a reminder, the two studies had been launched at the following the fall of a 180-year-old pine in perfect health in Bastionslast May, due to heavy rainfall following a period of drought, coupled with poor soil condition. The neighboring cedar, heavily impacted by the incident, had to be felled.
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