12-11-2015
Invasive species are organisms originating from other areas of the world that cause environmental and/or economic problems. The most harmful for the Serra de Collserola Natural Park is the ailanthus.
The Serra de Collserola Natural Park is the great
jewel of biodiversity that our municipality enjoys. However, it is not exempt from conservation problems. One of the most important are invasive species. This incidence is not exclusive to it, but it is accentuated by the fact that it is surrounded by the most densely populated area in the country.
Invasive species are organisms foreign to our regions and that for various reasons settle in our ecosystems. These are plants, animals, fungi or microorganisms that
compete with our species ,
contaminate them genetically ,
disrupt the functioning of the
ecosystems that host them,
cause diseases or
damage our
economic interests .
Without a doubt, it is
invasive plants that have the greatest impact on the Park and
gardening is one of the main
sources of introduction of invasive plants .
The maintenance of the city's biodiversity is included in the
Green Plan of the City of Barcelona 2020. One of the sections of
this plan contemplates the application of control measures for
invasive exotic
flora . For this reason, the council commissioned a study on
plant species with invasive potential , which should be the areas in which these species should not be planted to minimize the impact on Collserola, the Llobregat Delta and the Besòs River and what should be the alternative species for each specific purpose.
One species of tree
stands out as an invasive species,
the ailanthus (
Ailanthus altissima ). This tree is of Chinese origin and was used to plant it in the streets due to its rusticity. Like most invasive plant species, it begins its colonization in degraded areas. Thus, we find it on the edges of roads and cleared slopes. It has good
characteristics to become invasive :
very fast growth , 2 meters per year to surpass other plants and achieve full exposure to the sun;
great reproductive potential , 30,000 seeds per kg of female tree;
great dispersal capacity , seeds carried by the wind and with the ability to float;
it expels a poisonous substance to other plants through the roots, bark and leaves to eliminate competition;
adaptation to live in
many types of environments , it withstands acidity, salinity, drought, many atmospheric pollutants such as sulfur dioxide or ozone and even mercury;
regrowth of roots after being cut, even if the aerial part is dead due to intense frost; or its roots can pierce sewer pipes to get water. With these characteristics, the fight against it is not easy at all.
The successful treatment that has been used in Collserola consists of
making a one-centimeter hole and
injecting a mixture of
two herbicides at the base of the tree. It is a tremendously expensive system, as it must be done individually. From 2004 to 2014, action was taken on 25,000 specimens, and since April of this year on 19,000, thanks to the interest of the current council. As unfortunately happens with other well-established invasive species, its
eradication seems
impossible and the only
hope is to
control it and
prevent its expansion .
Citizen collaboration is very important. An example is the
Mas Sauró Neighbors Association . Neighbors
report where they find
feet of this species .
Related news:
An invasive Chinese tree endangers the Collserola park . El Periódico Barcelona 4/11/15
