Invasive Plants in Portugal
Portugal is a country of lush natural beauty, with a unique diversity of ecosystems that harbor an impressive variety of flora and fauna. However, this wealth is threatened by the presence of certain species, which pose a significant challenge to biodiversity and local ecosystems.
Various plants, animals, and other organisms originate from other territories, having been accidentally included in Portuguese lands or even deliberately imported due to their socio-economic, aesthetic, and environmental benefits.
These species, called exotics, are characterized by not being native to the region in question. Due to their sometimes erratic behavior, these "foreign" plants are also known as invasive.
In this article, we present the reasons why an exotic plant is considered invasive, as well as the Portuguese reality on this topic.
Can Invasive Species be a problem?
As previously mentioned, invasive exotic species are organisms that have been introduced to a new environment, often by human action and have the ability to spread rapidly and cause significant damage to native ecosystems.
Invasive species disrupt the balanced coexistence with other plants.
Although sometimes they are brought to the territory due to their potential advantages, they can affect the indigenous species of that ecosystem. These species can compete with local species for resources such as food and space, prey on them, or alter the environment in ways that harm their survival.
Their rapid growth patterns, extensive expansion, and intrusion into cultivated areas are three of the reasons that make an exotic species invasive.
In Portugal
Portugal is not immune to the problem of invasive exotic species. Due to its geographical location and intense maritime and commercial traffic, the country is vulnerable to the introduction of non-native organisms. Additionally, climate change and increased tourism have contributed to the increased introduction and spread of these invasive species.
In mainland Portugal, over the past two centuries, there has been a notable increase in the number of exotic species. Nowadays, this number has reached around 670 species, which is about 18% of the total native flora. As for the Madeira and Azores archipelagos, this value is also very high.
Regarding Madeira and adjacent islands, 430 exotic species have been identified, accounting for 43% of the current flora. In the Azores, this value is even higher, with 60% of exotic plantations - a total of over 1000 species.
Invasive Species in Portugal
In Portugal, invasive plant species are regulated by specific legislation. Decree-Law no. 92/2019 lists 197 species within all identified whose presence is prohibited in national territory, including the Madeira and Azores archipelagos.
The ICNF - the Institute for Nature Conservation and Forests - is responsible for the application of this Decree-Law, in addition to its administrative, technical-scientific, and oversight duties.
In our country, the cultivation or ornamental use of prohibited invasive plants is not allowed. The transportation of seeds or other elements of these is also forbidden to prevent their reproduction.
Of the 197 mentioned above, the Institute for Nature Conservation and Forests recognizes several invasive arboreal species (trees and shrubs) that have managed to naturalize, meaning they are well-adapted and with high natural reproduction.
From the total list, these are just some of the invasive exotic species that currently represent a threat to ecosystems in Portugal:
- Acacia (Acacia) - all Acacia species cause significant damage. Their risk level is always above 16, reaching up to 31 in some varieties;
- Giant reed (Arundo donax) - a large perennial herb that threatens native biodiversity. Its risk level is 14;
- Water hyacinth (Eichhornia crassipes) - this floating aquatic plant is one of the most dangerous for Portuguese territories, with a risk of 30;
- Ice plant (Carpobrotus edulis) - this is a creeping perennial subshrub whose risk level in Portugal is still under evaluation, despite its increasingly extensive presence.
The introduction and spread of these species have caused significant damage to native biodiversity and the ecosystem services that these environments provide.
Given the dispersion of these and other exotic species, various projects have been promoted to reduce their appearance and recover the Portuguese autochthonous forest.
Conclusion
The problem of invasive exotic species is a global concern, and Portugal is no exception.
It is crucial that measures be taken to prevent the introduction of new invasive species and control those that are already established. This requires a coordinated and collaborative approach among governments, non-governmental organizations, scientists, and the general public.
Only through joint efforts can we protect our ecosystems and ensure a sustainable future for future generations.