The complex causes of worldwide bee declines

Over the past two decades, bee declines worldwide have drawn international attention. Managed honey bee (Apis mellifera) colonies decreased by 25% over 20 years in Europe and 59% over 58 years in North America, and many bumble bee populations in Europe and North America have gone locally extinct, resulting in dramatic range contractions. It is important to note that not all bees in all places are declining. Some populations are actually growing, and there are many more for which data are insuffi