Invasive species

As a biological invasion ( colloquially introduction ) is called the spread of a species in an area where they are not native. The term is used in particular with entrained by the human species, which change the traditional ecosystems significantly and lead to the displacement of other species. The introduced species is then called invasive species or Bioinvasoren; they form a subset of naturalized species or invasive species. In these, a distinction naturalized plants ( neophytes ), fungi ( Neomyceten ) and animals ( invasive species ). Biological invasions are subject of research in invasion biology, a side branch of biology.

• 3.1 island ecosystems are particularly vulnerable
• 3.2 damage to the economy

• 4.1 Chile - Argentina: Changes in the flora as a result of the increased traffic between the two countries
• 4.2 Australia

General

Walks of living beings there are, since then tap new species habitats. These natural migrations go at a relatively slow pace vonstatten and come there to their limits, where the species natural spread barriers such as water bodies, mountains, ice, desert or the like can not overcome on their own.

These natural limits can be overcome by species under certain conditions. For example, can be achieved and settled or the obstacle be overcome via an appropriate host using a driftwood an island. Take place without the influence of people this biological invasions.

For all natural hiking is the speed and quantity with which the type used in the new area, so slowly that the resident species to adapt to the immigrants. If a resident species in the same ecological niche occupied as the immigrants, it often succeeds to push back the invading type again or the original species may in turn open up new habitats.

From man-made introductions usually have a completely different dimension. So are the possibilities that arise from the modern navigation or air traffic immense. The regularity with which a route is flown or driven to export and thus the probability of the same species in a particular place, is much higher than the probability of reach with, for example, representatives of the same species to a driftwood on the same island. Also incomparable is the quantity change with today's goods and people to the place. In addition, the velocity at which the often enormous distances are set, not be compared with that of a living being.

It is striking that there are very different definitions of the concept of biological invasion in the literature. The various proposals differ mainly in the questions 1) whether people need to be involved in the process of range extension or whether natural, " self-employed " immigrations are invasions and 2) whether a type which they caused by the damage in the new area can be characterized as invasive or whether immigrant species that cause no damage are invasive. From a scientific perspective, a definition might look like this (after Heger 2004): A biological invasions are all man-made or naturally induced processes of range extension referred to in which a propagation barrier has been overcome. As propagation barrier is understood to be an area that can only be with a probability that tends to zero, overcome by the type under consideration. The area in which the species passes after overcoming barriers was previously already ecologically suitable for them. The species is ecologically alien there, because they did not occur in the new area for an evolutionarily relevant time.

Invasive species are those who wildlebend occur in an area that is outside their previous area. In this case, the occurrence of the species must have been prevented by a propagation barrier in the area, not by the local conditions of the new area. Invasive species are alien species that spread in the new area. It does not matter to what extent and how quickly this happens propagation, also is irrelevant whether it is a culturally or economically, to be designated as a negative influence on the local biological communities is exercised or not.

Pathways

With the advance of globalization and the acceleration of society also have the ways in which an immigrant can achieve a new habitat, changed. Especially due to globalization the routes from one place to another can be overcome faster and more frequently. Since 1990, international trade has risen by 50%. With each flight of an airliner, with each container on a container ship, with every tourist and every package can be triggered theoretically bioinvasion. Through globalization, natural barriers such as water, mountains or deserts for invasive species have become surmountable.

In general, one must distinguish between an accidental introduction and the intended introduction.

Intentional introduction

Today, still often alien species are intentionally introduced into new habitats. Most of the introduced species to benefit the people directly or indirectly. Many of the proposed introductions are made short-sighted and ill-considered. It is seldom considered what may be incurred for damage if the person loses control of the introduced species. Often the reason for this but simply lies in the ignorance of the people.

Plants are often introduced as ornamental or useful plants; their introduction pathways are systematized in the Hemerochorie. It often happens that the plants grow wild and colonize off the gardens and agricultural land. The same is true for animals: Many domestic animals pose a major threat to native species dar. particularly predators can cause enormous damage very quickly. In addition, the animals run wild common and can thus build up a population that draws even more extensive damage. For example, are often stocking fish in a big risk if they can establish themselves. Many species of animals have escaped from fur farms throughout history and have been able to establish.

Another possible form of the proposed introduction is the aquarium or terrarium. Often, fish, reptiles or other animals are exposed to when they are too big for the aquarium or terrarium. Most tropical species can not survive in our latitudes, but especially sub-tropical species become established in part to warm waste water industry. Especially in forestry organisms are often introduced for pest control. Often, these organisms provide not only for the pest but also for other animals a threat, sometimes eats the organism is not the pest itself. Especially after the pest has been successfully controlled are the invasive species often a serious threat dar. But disease control alien species are introduced, for example, fish in the fight against mosquitoes that transmit malaria. But they often destroyed some other aquatic insects and other small creatures. And finally, many organisms are introduced for research purposes. In part, this is also a wildness and a bioinvasion.

Unintentional introduction

Unintentional introductions are much more common than intentional introductions. Especially with the global transports of the global economy organisms are dragged back and forth across the globe. Relatively easy is it to counteract the spread of larger animals. Plants are particularly abducted as seeds, which can be difficult to control due to the size. Particularly difficult is the control and prevention of small invertebrates, insects, multi - and single-celled organisms and viruses.

Organisms are often distributed as insects or plants. They then often lead to pest outbreaks in the forestry and agriculture. Also on or in cut flowers, fruit and vegetables alien species are introduced again and again. Sometimes invasive species with plant products or plant and cultivation substrates are common.

A further possibility of accidental introduction is with domestic and farm animals. Many domestic animals carry pathogens on or in them, but are immune or vaccinated, which is why the disease did not break out with them. Then infest related unprotected species and can quickly cause epidemics.

In transport packaging, there are also organisms. Especially in packaging wood pests are common. But many other small organisms are overlooked in packaging, such as arachnids, insects or rodents.

Even with the means of transport even many invasive species can be deported. Are particularly serious case planes because they cover enormous distances, and boats which particularly aquatic organisms in ballast water in foreign waters. In ballast water to survive many small organisms, especially plankton. Larger organisms survive the long periods by feeding on smaller organisms. Plankton often forms spores or other shapes, so that it can survive without food. Of the surviving organisms can survive only a few permanently in the new waters in the rule, since most temperature, food, and the salt content of the water does not suit you. As a countermeasure, the exchange of ballast water on the high seas is recommended, but it is binding only on the Great Lakes of the United States. Moreover, it is not possible for any sea and it is also very efficient, since the technology is not designed for a full exchange. With sailboats probably some mussel species were common ( see below).

Two independent studies from University of California at Davis * came to the conclusion that invasive plants spread better along paved roads than in the wild. Invasive grasses ( brome, knapweed ) now have more than 500,000 square kilometers of the American West conquered. One kilometer away from the streets invasive plants can no longer spread according to this study already. This revealed by the researchers, for example, that roads and trails should be avoided entirely in natural parks. This would not only serve the preservation of the protected area, but also the preservation of cultural landscapes, as the control of invasive plants was linked to skyrocketing costs for farmers.

Temporal context

Invasive species accompany humans for a long time. Previously, the rate was, however, still much lower and also the distances covered can not compare with those of today you.

Today well traceable and momentous bioinvasions took place especially in the discovery and colonization of America, Australia, New Zealand and several smaller islands. Their effects are still visible. The artificial eradication of invasive species is largely impossible.

Particularly striking are the damage caused by invasive species in Australia and New Zealand: There was originally no predators and otherwise, the animal and plant world very different from that in Eurasia or America. The largest predator in Australia was the thylacine, which was wiped out by about 1900. The marsupials and many small mammals are found only in Australia or New Zealand. They were extremely endangered by the new arrivals and feral rabbits, rats, cats, dogs and foxes. Where was not a robber before, there were suddenly several predators and strong competitors for food. Especially the rabbits proliferated explosively. A danger also, this represents for horse and rider, as the horse very often occur in the buildings of the rabbit and it can easily break a leg, which usually takes two and a fall after the death of the horse itself. In New Zealand, there are now about 1570 invasive species over native species in 1790.

On the Galapagos Islands make feral goats and pigs the only slowly proliferating giant tortoises food dispute. On the Galápagos island of Pinta lived until June 24, 2012 Lonesome George the last individual of the originally least 15 and today only eleven giant tortoise subspecies. In Hawaii, about two-thirds of the plants have been introduced. There are a total of 861 Hawaii 956 invaders and native species.

Conditions for bioinvasions

Not every type that is introduced can establish themselves permanently or spread explosively. It often takes years or even decades to become a stable population. Absence of natural predators or other factors ( eg climatic ) that can regulate the population, then the invasive species to a serious threat to the biodiversity of the habitat are. Basically must predict an entrained kind of the nature of the habitat and climate. They also need appropriate food and for a working population of several individuals are necessary. This can be a few hundred or even thousands, but often reach only a few individuals of different gender. In an extreme case of introduction of tree snake on Guam has been genetically proven that all snakes are descended from a single fertilized snake. Why is it the new species at all possible to build a stable population? Generally one can say that the native species often are not able to compete with the new species sufficient.

Many successful invaders have a faster generation than the resident species. Once a healthy population base has built up, they begin to multiply. Often this creates an enormous population density, do not arrive to their competition with the native species to their slower propagation. The resources are also scarce and the populations of the native species are weakened even more. Many invasive species have another important property: they are generalists. This also accelerates the rate of increase compared to the often more specialized native species that are more dependent on specific resources such as appropriate food, matching base, enough water or lots of light.

Moreover, almost always lack the natural enemies of the invasive type, which they can propagate freely, while the resident species is constantly threatened by a natural enemy, and so the population remains in a balance to existing resources. Furthermore, there is often no diseases in the new habitat, which can damage the invasive species, while native species are regularly affected and weakened by new diseases. Particularly serious occurs disproportion -days, when the population of the native type is haunted by a stronger epidemic. Then it is possible that the population of breaks down within a few weeks or months.

Another major threat to native species represent new pathogens that are introduced with the invaders. The invaders are often immune to it, but in the native species, the new pathogens can mean the scenario described above with the complete disappearance of the population. All this is enhanced and accelerated by the increasing pollution and destruction of habitats, making the native species are further weakened. Often, immigrants are also better adapted to the changed circumstances than the native species. Therefore, the damage is multiplied by these factors.

Bioinvasions cause many damages, from both an environmental and economic perspective. It is believed that the most irreversible damage caused by bioinvasions, about as high as those which are caused by the destruction of natural habitats, these two phenomena are increasingly integrating and amplified by global warming.

In addition to the threat to biodiversity through the displacement and extinction of native species and the ecosystem is affected as a whole: The elimination of the extinct species, the ecological balance often gets out of kilter. This is then often followed by a kind of chain reaction: Other specialized species also suffer and die from. Particularly serious is the situation when a keystone species disappears, to which a large part of the other species is directly or indirectly dependent. Although most invasive species cause damage, it can also happen that the new species to be complementary to the ecosystem, without this adversely impairing. Most of these species are particularly specialized and occupy a previously unoccupied niche.

Island ecosystems are particularly vulnerable

Since there are generally lacking large land predators, live on many islands species, which are very vulnerable to hunting and predators, such as flightless birds and animals that have lost the instinct to run, so are very tame. Therefore entrained rats ( Pacific rat (Rattus exulans ) by the Polynesians, brown rat (Rattus norvegicus) by Europeans ) There are several types of hunting have been eradicated and dogs.

Damage to the economy

The economic damage that can cause the invasive species is not to be underestimated. In comparison to the environmental damage can be negligible, but the economic damage. Often it is only possible to raise money and other resources for the fight against invasive species when it also benefits the economy, at least indirectly.

Particularly high damage cause invasive species in forestry, agriculture and fisheries. In Germany, a study was published, which alone twenty invasive species have caused damage of 167 million euros in 2002. Alone, hogweed causes 12.3 million euros costs and by the horse chestnut leaf miner costs the equivalent of about 19.2 million euros. The cost of agriculture and forestry in the United States according to Pimentel et al. (2000) estimated at about 138 billion U.S. dollars annually. These figures are intended to show only about how serious the problem of increasingly invasive species is worldwide and that measures, however, are important.

Case Studies

Chile - Argentina: Changes in the flora as a result of the increased traffic between the two countries

Trade between Chile and Argentina runs mainly by road. Since 2000, the transport volume has more than tripled. Originally the Andes formed a natural barrier between the two countries, but increasingly disappearing due to the increasing traffic. Nearly 300 of the 875 alien species are each only in Chile and Argentina, as well as over 300 in both countries. The most dangerous species for Argentina, the UFZ researchers classified a yellow Bartsie ( Parentucellia viscosa ), which was originally native to the Mediterranean. Within 48 years, it has already spread to 10 provinces of Chile. The Mediterranean blackberry (Rubus ulmifolius ), the wine - rose (Rosa rubiginosa ) or the silver wattle (Acacia dealbata ) have already established themselves in the countries. Good chance of stopping the invasion consist for example in Striped broom ( Cytisus striatus ), since this is not yet widespread.

Australia

The cane toad is spreading since 1936 from northeastern Australia over the continent.

Measures against invasive species

According to the Species Survival Commission (SSC ) of the IUCN following seven goals to be pursued: