Because of the harsh winters in the Northern Hemisphere, there have always been seasonal variations in the number of bees, with significant reduction of individuals during the coldest season of the year.
Besides this climatic factor, in the course of the twentieth century, many situations were observed in which there were sudden reductions in the number of bee nests.
In general, these events were analyzed in a timely fashion, without being characterized as an irreversible trend.
However, in the last ten years, we have seen a number of instances in countries in Europe and North America that resulted in drastic decreases in the number of hives, especially among those used in a crop pollination migratory system.
This phenomenon has been referred to by the scientific community as CCD – Colony Collapse Disorder.
