Environmental squirrels situation

Unfortunately since 20 years ago there is a great threaten brought to red squirrels ("sciurus vulgaris) by the grey ones. The incoming of grey squirrels which had place during the fifties by diplomatic personnel from US to UK created a cruel struggle between native British-European and the greater American-Caledonian ones (which are called in scientific Latin "Sciuri carolinensi"), which are capable of creating letal viruses for the reds, and to desroy much more trees too. We may also add that grey squirrels are dangerous for the health of trees in which they are inhabitants. There is also a huge intolerance that affects a red squirrels to American nutes.