Which factors make up a species habitat?
Neobiota: How New Species Change Ecosystems
As of August 2016, 37 animal and plant species have been considered undesirable in the European Union that come from areas outside Europe. Because they displace native species and thus threaten European biodiversity, the European Commission wants to prevent them from establishing themselves in Europe or from spreading further.
Animal and plant species that settle outside their natural range repeatedly attract attention and media reports. It's all about very different species, from raccoons to Asian tiger mosquitoes. Often there are phrases in reports that emphasize dangers, for example "fight against invaders" or "mass spread". The Federal Agency for Nature Conservation also rates the introduction of species into regions outside their natural range as one of the most important threats to biological diversity.
What are "invasive species"?
Species that have found their way into a new range through the influence of humans are referred to as alien. Species that naturally occur in a certain area are referred to as indigenous or as indigenous or autochthonous.
From the point of view of nature conservation, alien species are called invasive if they have negative effects on other species or biotopes in their new environment. The regulations of the European Union explicitly refer only to invasive alien species, because most alien species do not pose a nature conservation problem.
Sometimes the term "invasive" is used, for example in biology, in contrast to the view of nature conservation, only to describe rapid spreading processes without direct reference to negative effects. This different use of the same term can quickly lead to misunderstandings when an alien species is referred to as invasive without specifying the exact circumstances. In nature conservation, the term "expansive" is generally used to distinguish "invasive" from describing rapid spread.
Invasive species can cause conservation problems in a number of ways. For example, they can become competitors of native species and displace them, as they, like them, require habitat and resources. They can also transmit diseases that native species often have no resistance to, or change the gene pool of native species by crossing them.
In addition, invasive species can cause economic problems. This includes, for example, damage caused by alien pests to crops. The effort to contain alien species also generates costs.
In addition, they can be a problem for human health. For example, touching the giant hogweed from the Caucasus in connection with daylight can lead to painful wheals and blisters in humans. It is particularly problematic when children use the strong, hollow stems as a blowpipe or telescope while playing.
The history of "species migration"
The distribution areas of animal and plant species are constantly changing. Species can also colonize new areas naturally. This usually takes place over the long term or step by step.
The anthropogenic spread - that means: the spread caused by humans - overcomes natural spread barriers as well as long distances within a very short time. Half of the alien plant species established in the wild in Germany were intentionally introduced. About 30 percent came to Germany as ornamental plants, about 20 percent as useful plants. Some alien species play an important role in our diet today: the best known are potatoes, corn and tomatoes. These species are grown on agricultural land or in gardens. Feral occurrences in the wild are not known.
Humans have been influencing the composition of the species in their environment for a long time. Since the beginning of agriculture in the Neolithic Age, humans in Central Europe have brought alien species to new environments. However, only a few species can establish themselves permanently in their new environment. Usually this is only possible for species that come from regions with similar climatic conditions.
The transport by humans is partly intentional, partly unintentional. For example, crops are deliberately introduced into new regions and grown there. Sometimes they are then intentionally introduced into the wild or they spontaneously grow wild. Species unintentionally find their way to new regions, for example with the cargo of trucks and airplanes or in the ballast water of ships. In this case one speaks of the "introduction" of the species.
The introduction and introduction of species into a new ecosystem is therefore closely related to trade and transport. Therefore, experts use the year Christopher Columbus discovered America to classify introduced species. Species that entered a new range before 1492 are called archaeobiota. Species introduced after 1492 are called neobiota. The following terms are often used to distinguish the three main groups of species (animals, plants, fungi): archaeo- / neozoa, archaeo- / neophytes, archaeo- / neomycetes.
The Federal Agency for Nature Conservation has created an overview to differentiate the terms for the species population (link to overview in PDF format):
Source: Federal Agency for Nature Conservation, link to the overview in PDF format
How alien species establish themselves
Most of the alien vertebrates were intentionally introduced into Germany, including for fishing and hunting. Most alien invertebrates such as insects or mussels found their way into their new environment unintentionally, for example in flower pots or in the ballast water of ships.
It is estimated that only ten percent of 1,000 alien species can establish themselves permanently. Again only ten percent of these species have undesirable effects and are therefore considered invasive species. However, some alien species have characteristics that can give them an advantage over domestic competition. These include, for example, rapid reproduction, strong vigor or the ability to spread over a great distance.
However, it is not yet possible to predict with certainty which species will spread in which new areas and become invasive there.
What problems do alien species cause?
Most of the alien species are not a problem from the point of view of nature conservation. Some are even perceived as "enrichment"; These are mainly non-native wild herbs that were brought in hundreds of years ago and are now witnesses of old farming culture. This is true at least for Central Europe. Because the region is a geographical passageway that has been used and managed by people for a long time.
In isolated areas - for example on islands - invasive species pose a greater threat to biodiversity than in Central Europe. Because there the species are particularly well coordinated and can therefore easily be disturbed in their equilibrium. Also, due to the spatial restrictions of islands, there are often only few or no retreat options for the native species, which moreover often only occur on a single island. This can be seen, for example, in Hawaii, where the biomass of the alien plants already exceeds that of the native ones. Ten percent of the native species have already been displaced by the new species and become extinct there.
There are around 1,000 alien plants in Germany, 400 of which have become established. The Federal Agency for Nature Conservation describes 40 of these species as invasive. There are 1,100 alien animal species, of which around 260 species are considered "established".
However, the risk of invasive species will increase due to climate change. Because the warming of the climate enables an increased spread of alien species, especially the many heat-loving ornamental plants from gardens and urban greenery.
Worldwide, invasive species are considered to be the second greatest threat to biological diversity, surpassed only by the danger of destroying natural habitats.
A direct consequence of the spread of invasive species is that the new species compete with native species. They can displace other species because they also take up habitat and resources. One example is the knotweed, which mainly grows on the banks of rivers and streams, but also on fallow land in residential areas. It grows so strong and dense that it largely displaces other plants. For example, its roots can damage bank reinforcements.
Invasive species can also endanger native species as predators. For example, the invasive muskrat threatens the stocks of the native river mussel. As a predator, the North American raccoon not only endangers many breeding birds and amphibians, but also eats the endangered European pond turtle and digs up their eggs.
Invasive species may change the gene pool. They can interbreed with native species. This leads to a loss of individual genes and thus genetic diversity. There is a gradual change in the species, in which finally the native species is more or less replaced by so-called hybrid forms. One example is the crossing of the European white-headed duck with the North American black-headed duck.
Diseases and parasites can also be transmitted through invasive species. For example, the invasive American crayfish carry an infectious disease that is fatal to native crayfish species. The American crayfish themselves are immune to this. The roundworm introduced with raccoons is also dangerous for humans.
Alien species can change entire ecosystems, for example the nutrient content of soils. The invasive black locust grows on semi-arid lawns and enriches the soil with nitrogen there. This favors the growth of plants that normally grow less well there and which in turn displace species that are typical of semi-arid grasslands.
What is the correct way to deal with invasive species?
Various legal regulations at European and national level as well as international treaties form the framework for dealing with invasive species. The international agreement on biological diversity (CBD) stipulates that the prevention, control and combating of invasive species are the goal of nature conservation.
The Regulation on the Prevention and Management of Invasive Alien Species has been in force within the European Union since January 1, 2015. At the heart of the regulation is a list of alien invasive species that are relevant to nature conservation across the EU. It is also known as the "Union List". The first list of 37 species was published in July 2016 and came into force in August 2016.
The ordinance specifies how these species should be dealt with in the future. The measures include prevention (e.g. prohibition of possession, marketing and release), early detection and immediate disposal in areas where the respective species has not yet been able to establish itself in the wild. It also includes the management of species that are already widespread in order to at least minimize the negative effects. In the future, further invasive species are to be added to the Union list.
In addition, there are regulations on alien species in national laws such as the Federal Nature Conservation Act, the Federal Species Protection Ordinance or the Plant Protection Act.
"Accept or Exterminate?"
Most of the alien species occurring in Germany have integrated into the local ecosystems without any discernible adverse ecological effects. Therefore, according to the Federal Agency for Nature Conservation, they can be accepted as part of these systems. This is especially true for the archaeobiota that have been established for centuries.
According to the Federal Agency for Nature Conservation, many problematic alien species can no longer be eradicated because they have already spread widely. Therefore, they should only be combated in justified individual cases, as the EU regulation on invasive species provides for these cases. Possible reasons for control include, for example, that rare or endangered species or habitats are threatened or that human health is endangered. What speaks against interventions is that they are usually associated with a great deal of effort and that a cost-benefit analysis should be carried out. In addition, the control measures can also cause damage.
In addition to elimination, dealing with invasive species is primarily about prevention and early detection. Most of the alien species are carelessly introduced into a new environment. On the other hand, private individuals can make an important contribution by, for example, disposing of garden waste of invasive species or invasive aquarium plants in the organic waste bin instead of illegally in the wild. In agriculture and forestry, native species should be used whenever possible. The spread of seeds or parts of plants from alien species should be prevented as far as possible.
An essential basis for the protection of biological diversity is well-functioning environmental monitoring, which also includes the populations of alien species. Effective early detection of new invasive species is particularly important. It is important to act quickly here to prevent it from becoming established and from spreading. Experience shows that the containment of dangers from invasive species becomes more and more difficult and expensive the longer the spread is not stopped.
Federal Agency for Nature Conservation: Alien Species (Overview)
Federal Agency for Nature Conservation: Neobiota information portal
EU Commission: Information brochure and list of 37 invasive species (brochure: see link to PDF file)
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