REPORT
Invasive species are gaining ground
Published on October 21st, 2015
Climate change is one of the most serious threats to biodiversity. Although there is much talk of fauna, the flora is also being severely affected, and some plant species are even expected to disappear. Portugal is no different, especially when it comes to biological invasions.
The coastline of our country is facing the “invasion” by plant species that are gradually gaining ground to native species. These species, rightly called invasive, are being benefited by climate change, in particular by changes in standard temperature and humidity patterns.
“Right now, the outlook is very serious, especially in the coastal region. In many areas, native, autochthone vegetation is being completely replaced. The competition is being won by non-native species”, says Paulo Alves of the Predictive Ecology (PRECOL) group at the CIBIO-INBIO - Research Centre in Biodiversity and Genetic Resources.
Acacias are examples of well-known invasive species, whose aggressive behaviour particularly in forest areas altered by fires and degradation, is quite evident. The most worrying exotic tree species (neophytes) of the genus Acacia are the silver wattle (Acacia dealbata), the long-leaved wattle (Acacia longifolia) and the Australian blackwood (Acacia melanoxylon).
But climate change is also affecting the flora of the mountains. In the countryside, temperature increase puts the survival of endemic species at risk in certain mountainous areas, where a reduction in available area where some indigenous plants have their ecological niche is already being witnessed.
“Mountain areas are ‘islands’ with a colder climate in the middle of warmer areas. These 'islands' are very interesting for biodiversity, allowing our flora to have many endemic species, many species characteristic of these environments. The increase in temperature can lead some to lose their habitat conditions”, warns the researcher.
Rare native species such as the Armeria humilis, a plant that grows on top of the Serra do Gerês, and Festuca henriquesii, which grows on top of the Serra da Estrela are at risk.
Proliferation of invasive species at sight
If the current situation is not favourable, predictions based on climate change scenarios and land use, are not encouraging. “With climate change scenarios, we expect that invasive species will start, on the one hand, to expand into the countryside, using corridors of seed dispersal, such as roads and rivers, and on the other hand, rising in altitude, and occupying the inland areas”, predicts Joana Vicente of the CIBIO.
In fact, the construction of road infrastructures favours some invasive species such as acacias and pampas grasses. It happened, for example, on the A25, where silver wattles began to emerge and proliferate.
Joana Vicente, who is a member of the PRECOL and BIOCHANGE groups has also analysed the impacts of invasive species such as the acacia and the needle bush (Hakea sericea), a kind of thorny bush in protected areas and ecosystem services. In general, these species produce large amounts of seeds, whose germination is stimulated by fire, giving a rapid establishment of dense populations that prevent regeneration of native vegetation.
According to the researcher, the main impacts of biological invasions are, thus, the occupation of native species habitats, and the decline in forest production because invasive species cannot be used or monetised for commercial purposes, and must be destroyed.
Moreover, invasive species act upon the regulation of water, causing the soil to become more permeable. “The water table does not have the regulation capacity it could have if native vegetation existed, such as oaks”, notes the expert in biological invasions.
It is true, however, that not all impacts are negative. It is known that if there is an invasion by tree species, even though they are invasive in an area that would normally be occupied by shrub species, carbon sequestration will increase. Another “good” example is the hottentot-fig, used to stabilise dunes.
Currently, the researcher and her colleagues are also working in the area of Socioecology, seeking to understand how the ecological impact is perceived by society. At the same time, they are assessing whether the invasion by Acacia is irreversible for forest certification of eucalyptus and analysing the relationship between the invasion by acacias and the fire in oak forests in the Peneda-Gerês National Park.
Climate and land use: a synergy
In terms of flora, the measures to be taken to adapt to climate change will depend heavily on soil use and management practices.
According to Joana Vicente, “changes in climate and in land use act synergistically. There are species strongly determined by the climate but there are species that are quite determined by soil occupation and management. In these cases, it is possible to make landscapes more resilient to climate change. When soils are occupied and managed, invasive species cannot enter or flourish. When soils are abandoned or when there are areas with eucalyptus but without management, the invasion is impressive.”
In addition to actions to combat and eradicate invasive species, Joana Vicente and Paulo Alves also recommend the management of forest areas using preventive and adaptive strategies supported by evaluation and monitoring systems.
“Right now, the outlook is very serious, especially in the coastal region. In many areas, native, autochthone vegetation is being completely replaced. The competition is being won by non-native species”, says Paulo Alves of the Predictive Ecology (PRECOL) group at the CIBIO-INBIO - Research Centre in Biodiversity and Genetic Resources.
Acacias are examples of well-known invasive species, whose aggressive behaviour particularly in forest areas altered by fires and degradation, is quite evident. The most worrying exotic tree species (neophytes) of the genus Acacia are the silver wattle (Acacia dealbata), the long-leaved wattle (Acacia longifolia) and the Australian blackwood (Acacia melanoxylon).
But climate change is also affecting the flora of the mountains. In the countryside, temperature increase puts the survival of endemic species at risk in certain mountainous areas, where a reduction in available area where some indigenous plants have their ecological niche is already being witnessed.
“Mountain areas are ‘islands’ with a colder climate in the middle of warmer areas. These 'islands' are very interesting for biodiversity, allowing our flora to have many endemic species, many species characteristic of these environments. The increase in temperature can lead some to lose their habitat conditions”, warns the researcher.
Rare native species such as the Armeria humilis, a plant that grows on top of the Serra do Gerês, and Festuca henriquesii, which grows on top of the Serra da Estrela are at risk.
Proliferation of invasive species at sight
If the current situation is not favourable, predictions based on climate change scenarios and land use, are not encouraging. “With climate change scenarios, we expect that invasive species will start, on the one hand, to expand into the countryside, using corridors of seed dispersal, such as roads and rivers, and on the other hand, rising in altitude, and occupying the inland areas”, predicts Joana Vicente of the CIBIO.
In fact, the construction of road infrastructures favours some invasive species such as acacias and pampas grasses. It happened, for example, on the A25, where silver wattles began to emerge and proliferate.
Joana Vicente, who is a member of the PRECOL and BIOCHANGE groups has also analysed the impacts of invasive species such as the acacia and the needle bush (Hakea sericea), a kind of thorny bush in protected areas and ecosystem services. In general, these species produce large amounts of seeds, whose germination is stimulated by fire, giving a rapid establishment of dense populations that prevent regeneration of native vegetation.
According to the researcher, the main impacts of biological invasions are, thus, the occupation of native species habitats, and the decline in forest production because invasive species cannot be used or monetised for commercial purposes, and must be destroyed.
Moreover, invasive species act upon the regulation of water, causing the soil to become more permeable. “The water table does not have the regulation capacity it could have if native vegetation existed, such as oaks”, notes the expert in biological invasions.
It is true, however, that not all impacts are negative. It is known that if there is an invasion by tree species, even though they are invasive in an area that would normally be occupied by shrub species, carbon sequestration will increase. Another “good” example is the hottentot-fig, used to stabilise dunes.
Currently, the researcher and her colleagues are also working in the area of Socioecology, seeking to understand how the ecological impact is perceived by society. At the same time, they are assessing whether the invasion by Acacia is irreversible for forest certification of eucalyptus and analysing the relationship between the invasion by acacias and the fire in oak forests in the Peneda-Gerês National Park.
Climate and land use: a synergy
In terms of flora, the measures to be taken to adapt to climate change will depend heavily on soil use and management practices.
According to Joana Vicente, “changes in climate and in land use act synergistically. There are species strongly determined by the climate but there are species that are quite determined by soil occupation and management. In these cases, it is possible to make landscapes more resilient to climate change. When soils are occupied and managed, invasive species cannot enter or flourish. When soils are abandoned or when there are areas with eucalyptus but without management, the invasion is impressive.”
In addition to actions to combat and eradicate invasive species, Joana Vicente and Paulo Alves also recommend the management of forest areas using preventive and adaptive strategies supported by evaluation and monitoring systems.
By: Cláudia Azevedo