The concept of exotic species is being more present in the press due to some famous cases like apple snails, monk parakeets, American minks, pond sliders and red swamp crayfishes in Spain. Here we will focus on defining the concept of exotic and invasive species and what we can do to avoid their presence.
EXOTIC SPECIES AND INVASIVE SPECIES: DIFFERENT CONCEPTS
An exotic species, known also as introduced, alien, non-native or non-indigenous species, is that foreign species that have been introduced in a zone out of its natural distribution. This introduction usually happens for human causes, either voluntarily or involuntarily. The opposite concept is indigenous species.
It is necessary not confusing the first concept with the concept invasive species. A species is invasive when, being exotic or indigenous, the increase of its population supposes an environmental problem, so put in danger the rest of the species present in the specific zone. Despite most of the invasive species are exotic, there are also some cases in which can be indigenous. To give an example, if in a forest disappears the main predator of a particular species, this can increase the number of individuals, so it can become an invasive species.
The concept of exotic and invasive species are different, but most invasive species are exotic (Picture from Swapsushias).
It’s advisable to highlight that the establishment of exotic species in a specific zone is not easy, so the ecosystems have some filters that have to be exceeded. The first barrier that have to be exceeded is the geographical separation between the origin and the arrival point. Then, it can just establish if it has the ability of surviving in the new habitat and of reproducing. Finally, the species would be able to spread and, in this way, it is an exotic species that can become invasive.
IMPACT OF EXOTIC SPECIES
The presence of exotic species, by itself, not necessarily represent a problem. Imagine a field of potatoes or corn, which come form America and don’t suppose an environmental problem by themselves. In most of the cases, the problem is when they become invasive species, which represent a worldwide problem, especially in islands and archipelagos, for the impact that they suppose:
Alteration and degradation of habitat.
Biodiversity loss.
They can suppose a health problem.
They can suppose a negative impact on economy, for the negative effect on natural resources and on tourism.
NUMBERS IN SPAIN
According to the Spanish Catalogue of Invasive Exotic Species, inside the Spanish territory there are 13 invasive exotic species of algae, 75 of plants, 14 of non-arthropod invertebrates, 26 of arthropods, 19 of fishes, 4 of amphibians, 4 of reptiles, 17 of birds and 15 of mammals.
Zebra mussel (Dreissena polymorpha) is one of the many invasive exotic species present in Spain (Picture from El mon d’en Cotildu).
WHAT CAN I DO?
Acquisition of pets:
To acquire pets in specialised shops to guarantee the legal and healthy security.
Don’t abandon or free exotic species in the nature.
Don’t acquire invasive species.
In the garden:
Plant indigenous species.
Never throw ornamental plants, aquarium plants or pieces of exotic plants in humid zones or rivers.
Travelling:
Don’t transport animals, plants or seeds without declaring them from a country to another.
Clean the soles of your boots and your equipment before doing hiking in a new zone.
Fishing:
Don’t transport water from a place to another.
Don’t use exotic bait.
REFERENCES
Notes of the subject Marine Reserve of the Master in Oceanography and Marine Environmental Management (University of Barcelona)
Since a few years ago, we have heard about the climate change. Nowadays, it is already evident and also a concern. This not only affects to us, the humans, but to all kind of life. It has been talked enough about the global warming, but perhaps, what happens to the vegetation has not been much diffused. There are many things affected by climate change and vegetation is also one of them. In addition, the changes in this also affect us. But, what are these changes? how can the vegetation regulate them? And how we can help to mitigate them through plants?
CHANGES ON PLANTS
Biomes distribution
In general, due to climate change, an increase of precipitations in some parts of the world are expected, while in others a decrease is awaited. A global temperature increment is also denoted. This leads to an alteration in the location of the biomes, large units of vegetation (e.g.: savannas, tropical forests, tundras, etc.).
Biome triangle classified by latitude, altitude and humidity (Author: Peter Halasaz).
On the other hand, there is an upward trend in the distribution of species in the high latitudes and a detriment in the lower latitudes. This has serious associated problems; the change in the species distribution affects their conservation and genetic diversity. Consequently, the marginal populations in lower latitudes, which have been considered very important for the long-term conservation of genetic diversity and due their evolutionary potential, are threatened by this diversity loss. And conversely, the populations in high latitudes would be affected by the arrival of other competing species that could displace those already present, being as invasive.
Species distribution
Within the scenario of climate change, species have some ability to adjust their distribution and to adapt to this.
But, what type of species may be responding more quickly to this change? It appears that those with a faster life cycle and a higher dispersion capacity will be showing more adaptability and a better response. This could lead to a loss of some plants with slower rates.
The Purple milk Thistle (Galactites tomentosa) is a plant with a fast life cycle and high distribution capacity (Author: Ghislain118).
One factor that facilitates adjustment in the distribution is the presence of wildlife corridors: these are parts of the geographical area that enable connectivity and movement of species from one population to another. They are important because they prevent that some species can remain isolated and because they can also allow the movement to new regions.
Another factor is the altitudinal gradient, which provides shelter for many species, facilitates the presence of wildlife corridors and permits redistribution of species along altitude. Therefore, in those territories where there is greater altitudinal range, the conservation is favored.
In short, the ability of species to cope with climate changedepends on the plant characteristics and the territory attributes. And, conversely, the species vulnerability to climate change occurs when the speed to displace their distribution or adapt their lives is less than the climate change velocity.
At internal level
Climate change also affects the plant as an organism, as it causes changes in their metabolism and phenology (periodic or seasonal rhythms of the plant).
One of the effects that pushes the climate change is the carbon dioxide (CO2) concentration increase in the atmosphere. This could produce a fertilization phenomenon of vegetation. Due the CO2 increase in the atmosphere it also increases the uptake by plants, thus increasing the photosynthesis and allowing greater assimilation. But, this is not all advantages, because for this an important water loss occurs due that the stomata (structures that allow gas exchange and transpiration) remain open long time to incorporate CO2. So, there are opposing effects and fertilization will depend on the plant itself, but the local climate will also determine this process. Many studies have shown that various plants react differently to the CO2 increase, since the compound affects various physiological processes and therefore there are not unique responses. Then, we find a factor that alters the plant metabolism and we cannot predict what will be the effects. Furthermore, this fertilizer effect is limited by the nutrients amount and without them production slows.
On the other hand, we must not forget that climate change also alters the weather and that this affects the vegetation growth and its phenology. This can have even an impact on a global scale; for example, could produce an imbalance in the production of cultivated plants for food.
PLANTS AS CLIMATE REGULATORS
Although one cannot speak of plants as regulators of global climate, it is clear that there is a relationship between climate and vegetation. However, this relationship is somewhat complicated because the vegetation has both effects of cooling and heating the weather.
The vegetation decreases the albedo; dark colours absorb more solar radiation and, in consequence, less sunlight is reflected outward. And besides, as the plants surface is usually rough, the absorption is increased. Consequently, if there is more vegetation, local temperature (transmitted heat) intensifies.
But, on the other hand, by increasing vegetation there is more evapotranspiration (set of water evaporation from a surface and transpiration through the plant). So, the heat is spent on passing the liquid water to gas, leading to a cooling effect. In addition, evapotranspiration also helps increase local rainfall.
Therefore, it is an ambiguous process and in certain environments the cooling effect outweighs, while in others the heating effect has more relevance.
MITIGATION
Nowadays, there are several proposals to reduce climate change, but, in which way can the plants cooperate?
Plant communities can act as a sinks, carbon reservoirs, because through CO2 assimilation, they help to offset carbon emissions. Proper management of agricultural and forest ecosystems can stimulate capture and storage of carbon. On the other hand, if deforestation were reduced and protection of natural habitats and forests increased, emissions would be diminished and this would stimulate the sink effect. Still, there is a risk that these carbon sinks may become emission sources; for example, due to fire.
Finally, we must introduce biofuels: these, unlike fossil fuels (e.g. petroleum), are renewable resources, since they are cultivated plants for use as fuels. Although they fail to remove CO2 from the atmosphere or reduce carbon emissions, they get to avoid this increase in the atmosphere. For this reason, they may not become a strict mitigation measure, but they can keep neutral balance of uptake and release. The problem is that they can lead to side effects on social and environmental level, such as increased prices for other crops or stimulate deforestation to establish these biofuel crops, what should not happen.
Sugarcane crop (Saccharum officinarum) in Brazil to produce biofuel (Author: Mariordo).
REFERENCES
Notes of Plant Physiology, Science of the Biosphere and Analysis of vegetation, Degree of Environmental Biology, UAB
Hample & R. J. Petit. 2005. Conserving biodiversity under climate change: the rear edge matters. Ecology letters 8 (5): 461-467.
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