school energy&environment

Introduction of exotic species

Often a very important factor is neglected, which is the introduction of allochthonous species, i.e. species whose origin is in other geographic areas and that therefore have not adapted, through the long natural selection processes, to the new environment in which they are introduced. It has been calculated that approximately 20% of the cases of extinction of birds and mammals is due to the direct action of animals introduced by man. The reason for this extinction can be attributed to various causes: to competition for limited resources, to predation by the “new” species, to the diffusion of new diseases and to the damages that the species that have been introduced can cause to the natural vegetation, to the cultivations and to zootechnics. An example of the problem in Europe is seen in the introduction of the grey squirrel (Sciurus carolinensis) imported from North America, that is replacing the red European squirrels (Sciurus vulgaris). Also the red eared slider (Trachemis scripta elegans) was imported into Italy from the United States as a pet animal, but when people started to free them in the ponds (because they became too big) this triggered a competitive mechanism between the American slider and the European pond turtle (Emys orbicularis). Another problem that causes the loss of biodiversity is to be attributed to the introduction in the environment of genetically modified organisms (GMO) that are also known as transgenic organisms. A GMO is an organism, in whose chromosomes a foreign gene, taken from an organism of a different species, is inserted with genetic engineering techniques. In this way it is possible to create a new organism with particular desired characteristics: for example some organisms of the vegetable kingdom may become more resistant to herbicides or harmful insects; some livestock animals become more productive or more resistant to infections. With regard to the potential harmfulness of the GMO there is a violent debate between those who believe that the advantages for medicine and for society are greater than the possible effects on the environment, and those who state that too little is known to be able to use them, and that the environment will feel the effect of the genetic pollution of the natural species with numerous consequences: the involuntary transmission of resistance to herbicides in infesting plants, the evolution of more resistant parasites, the increased use of herbicides, the disappearance of species of insects and as a consequence the loss of biodiversity. Examples of GMO are to be found in two particular plants: maize and soya. In maize, resistance to harmful insects is obtained by introducing the Bt gene of the Bacillus thuringiensis bacterium. This bacterium, that lives in the soil, produces a protein that becomes toxic only in the insect’s intestine, and causes its death. The protein is not toxic for humans nor for other animals, in fact, before the invention of these sophisticated techniques in genetic engineering, it was used as a natural insecticide, particularly in Canada to protect the forests from insect attacks. This technology, for the maize plants, leads to a decrease in the harmful insects and contamination by bacteria, virus and fungi, that can produce mycotoxins that are carcinogenic. The above technique is applied to soya in order to make it more resistant to herbicides; in particular to glyphosate and glyphosinate, that are biodegradable herbicides that are harmless for man and animals, but can kill all the plants. In this way it is possible to eradicate all the infesting plants without the need for further treatments with products that are extremely harmful for man and the environment.