What are invasive plants? – Residing in Portugal

What are invasive plants?  – Residing in Portugal

Simply put, invasive plants are those that, being alien, are fully adapted to local conditions and, due to their great ability to reproduce and spread, cause negative environmental and economic impacts. But not all alien/exotic species are potentially invasive.

Ecologically, invasive species are responsible for changing the natural dynamics that occur anywhere. They compete with native species for space, water and nutrients and inhibit their growth.

They end up reducing biodiversity and changing the physical and chemical structure of the soil. Also, since nature operates in a larger interconnected system, it not only affects plants and animals, but modifies the functioning of the ecosystem itself, its habitats and landscapes.

Their presence and spread primarily affects natural systems, but also has social and economic consequences. These species can be a source of new parasites and diseases, and some of them can invade agricultural areas, forests or fishing areas, greatly harming these activities and affecting food production.

Pampas grass – JLPC images – Wikipedia

Species with high water needs reduce the availability of groundwater, affecting the supply of this increasingly scarce resource and, finally, changing the aesthetic and cultural value of the landscape. Many invasive plants from Australia are highly flammable, e.g Eucalyptus gum and Acacia species, which form a false monoculture.

Many invasive species were first introduced as ornamental plants in parks and gardens. For this reason, their presence seems natural, we accept their aggressive nature, and we even use them in gardens. However, we should not be fooled into this way of thinking.

gall wasp (Trichilogaster acaciaelongifoliae) It is a natural (biological) control of acacia and is a specific method that can only affect the target species – in this case, the invasive Acacia longifolia A species that is closely related.

It is active in the Algarve region and trees bearing the balls should not be cut down as they help disperse control. It should be noted that the gall wasp is a very specific organism and has been subjected to scientific experiments here in Portugal. There are currently nine species of acacia on the invasive list.

Balls on acacia
Balls on acacia

In Portugal, many species that today behave as invasive were introduced in the past with the aim of preventing erosion (e.g. Chorao das Praias, Acacia de Espejas), stabilizing slopes (e.g. Mimosa), and using trees. Wood (eg. Mimosa, Australia), tanning bark (Black Acacia), hedges (eg. Hakias), fodder (eg. Lagustim vermelho) or simply ornamental (pampas grass). Apart from these deliberate introductions, other cases occurred accidentally, but with equally serious consequences.

In the case of some of the more common species, please do not plant them, and if you already have them, dispose of them properly. In some cases, culling is not enough, and it is necessary to resort to other techniques to prevent reproduction (crushing, burning, etc.). There is more on the informative website below, in English and Portuguese.

Water hyacinth

pampas grass (Cortaderia is crying) is a common gas seen along road edges. It is a perennial herb that can exceed 4 meters in height and 3 meters in diameter. The flat leaves have a well-developed edge and can reach almost 2 meters in length. The flowers are known as columns. Each column can produce thousands of seeds per reproductive cycle.

This species also reproduces vegetatively, as it has the ability to regenerate after cutting or fire and to root from parts of the root in contact with the soil. Even if you don’t find seedlings on your land, they will invade nearby sites.

There are also many species of invasive aquatic plants. water hyacinth (Ecornia crassips) Removal is very expensive and clogs waterways and rivers. Invasive aquatic plants are often introduced, so it is very important to be vigilant and report these and other species you see spreading.

Become a citizen scientist and help map invasive plants in BioDiversity4All (iNaturalist).

For more information, see INVASORAS.PT platform

With many thanks to www.invasoras.pt

By Rosie Biddle
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