Are alien species always dangerous to local species?
Invasive / Exotic Species I intentionally wrote the two terms for the same phenomenon in the title, since the attribution is aliens less violent and threatening, since in my opinion the attitude towards the various new species in our environment should be according to the level of threat and danger and not a simple and inclusive negative attitude .
Invasive species are defined by zoologists and botanists as species that were not known in a given geographic area and appeared there recently: such appearance can be through human importation, migration and natural spread or both factors combined. Another concept is Organisms that are not in their place that have arrived in an ecosystem, settled and established themselves in it, these can be: mammals, birds, insects, plants or bacteria, the risk of the introduction of a new species Stranger to the environment is expressed in injury In existing species, the composition of the environment has changed, a violation of the equilibrium that has developed over the years of evolution.
In the wider world it is accepted that a foreign species is a species that arrived in a new place from the nineteenth century onwards. Of course, this is an arbitrary determination adapted to the needs and skills of the determiners, in our country the count begins later, from the beginning of the twentieth century, also based on convenience and knowledge calculations. The process of species invasion into new habitats is natural and occurs over many generations, But when humans are involved in the process with the help of means of transportation and mobility, the process takes place in a short time, a short time that does not allow the natural environment to balance, and then the invasion could be an environmental disaster. There are researchers in various branches of science who estimate that invasive species that have reached their destination with the help of humans cause eighty percent of the damage to diversity The species, more
from any other factor.
There are many examples of invasions, some of which have caused such disasters: in our country, the nutria Myocastor coypus is known, which was brought with the intention of raising fur animals, as well as in an attempt to lower the level of the reeds in fish ponds. walls of the mikvah and destroys the vegetation of the banks.
Blue acacia Acacia saligna was imported to Israel in order to stabilize migrating sands: today the acacia is a nuisance that appears in all areas of the country and is difficult to exterminate. The lantana Lantana camara was imported from Australia to wide areas on all continents, here the lantana covered orchards and pastures, in the wider world it is considered a noxious weed that is difficult to exterminate.
Ganga Maina - the maina was imported to wide areas of the world and also to Israel with the aim of reducing insect populations in agriculture. Some of the insects were indeed eaten, but local birds were harmed with them and the species was declared an enemy, to what extent this declaration is valid for our country is still unclear,
The better known harmful invasive species are those that have been introduced to the islands. In Australia, the English imported rabbits and foxes for the purposes of hunting sports. The rabbits that bred without a natural enemy are a threat to the pastures, the foxes prey on all the small marsupials. The damage to nature and man is great.
Recently, the Australians have been "attacked" by thousands of Bufo marinus cane toads that were brought to treat a harmful insect in the sugar cane fields. The toads multiplied without a natural enemy, occupying large areas and eating everything in their path: lizards , bird eggs, beneficial insects, in addition to poisonous toads they cause the death of predators, raptors, snakes and alligators that try to eat the unfamiliar creature The disaster is the "successful" attempt of the English to populate Lake Victoria with the "Princess of the Nile" Oreochromis niloticus. The lake that provided a livelihood for many fishermen lost eighty percent of the three hundred species of fish that were in it and became unisex and monochromatic.
Into the same environment came two species of plants from Syria: (Nymphaea odorata, Salvinia nymphaea, and watercress, and both of them, without someone to eat them, clog water bodies and cause the killing of animals in lakes and rivers.
In Ethiopia lives the rarest canine in the world: Canis simensis) the Ethiopian wolf. Due to the intrusion of flocks of sheep into its grazing areas, the shepherd dogs mate with the unique wolf and cause the species to disappear. The problem of interbreeding wild animals with domestic animals exists all over the world when The bearers of the flag are cats and dogs that have "gotten wild", these are paired with their fellows wild cats and wolves and cause them to disappear.
In the Mediterranean, an algae called Caulerpa taxifolia is spreading. Algae grows on the bottom and on its way destroys every other plant. Algae "escaped" from the aquarium in Monaco several years ago and today covers thousands of square kilometers.
One of the more studied invasions is the Lespes invasion, after Lespes built the Suez Canal, since the opening of the canal there has been a two-way movement between two bodies of water that were previously far away. Since the Indian Ocean is richer and less known, it is convenient for researchers to test the new species in the Mediterranean Sea, and there are many such. One species is even known, famous and well-known on our shores: the wandering filamentous jellyfish from the Rhopilema family that stings many in the summer season, arrived from the Red Sea, its damage is bad. As for the influence of other species, there is still no information. The seaways have become invasion routes: different species are transported in the water that ships fill for balance, in every port, before loading or unloading, water is pumped into the balance cells on a ship or They are emptied, an activity that causes dozens of species to be imported from region to region, this is how a small mollusk, the zebra mussel Dreissena polymorpha, was imported into the waters of the lakes in the USA, which today clogs water pumping facilities and causes damages in the millions .
An oyster fisherman in Tasmania was eliminated following the arrival of a starfish from the North Pacific Ocean. A jellyfish imported in the balance water of ships to the Black Sea eliminated the zooplankton that is the food base for fish and thus caused the elimination of the anchovy fishing industry.
There are species that have different effects in different regions:
Eucalyptuses are becoming the most accepted fuel in Africa because of their fast growth rate, in many countries the Australian eucalyptuses are used to produce medicines in perfumes and perfumes, in many areas the casuarina from Australia is planted as an ornamental tree and wind breakers, the pepperoni from Dram Known as a common ornamental tree, both the casuarina and the papelon have been declared in the USA as invasive species that must be destroyed, this is because of their damage to stream banks and vegetation locally.
Man is responsible for spreading the two harmful invasive species that can cause more problems for the environment in general and the human race in particular. These are the various mosquito species and the rat species, until they were spread by humans in the world, the two species "divided" the world between them into areas of distribution, and each species caused unique problems, today since the eighteenth century almost all kinds of mosquitoes and all kinds of rats are common almost everywhere and thus all the problems all over the world
And so the list of invasive species continues to several hundred whose negative impact on the environment and economy is well-known and recognized, and several thousand whose impact is still unknown.
After all this, it is worthwhile for the conservationists and environmentalists to check, investigate, consider and refine the data before declaring an all-out war on the alien species, the natural environment changes and nature adjusts itself to the data and reaches an equilibrium, the question is whether the equilibrium fits our requirements and does not harm the continuity of human existence in the natural balance, since the definition of invasive species is our definition, according to data we have, data about the past, not necessarily data based on future possibilities, also If these are not to our liking.
Are the dingoes in Australia harmful? Or fill the gap with a super predator? Is the American squirrel that repels its European friend really harmful? The various species that penetrated the Mediterranean Sea through the Suez Canal during the Hessapian invasion, are they all harmful and harmful? The species in Israel harms and thins out bird species, are the parrot species the same? ?
When in Eilat they declare a war of extermination against a species like the Indian crow, it is worth remembering that until its appearance there was a plague of pigeons in the city and the rats of the crows keep them at a low level, so what is better? The low chance that someone will hurt a mead protecting his chicks, or the pigeons and rats bothering him?
And you should always remember: the invaders of the American continent about thirty thousand years ago destroyed the megafauna
And the new inhabitants, starting from the seventeenth century, persisted and continued to destroy the bison, the hunters of the north in today's Russia destroyed the mammoths (thousands of years ago), in our immediate surroundings groves and forests were destroyed until the nineteenth century, And our parents destroyed the sick lake, that is, every time there is an opportunity and a discussion about invasive species, it is important to remember and know that the most harmful invasive species is man.
Asaf
