Many bumblebee populations have drastically declined in recent years. In some regions, they have completely disappeared. While the exact cause of the decline remains a mystery, scientists believe that habitat destruction, pesticides, invasive species, climate change and diseases spread through commercial bumblebee operations are all to blame. When these factors combine, they become even deadlier. The decline of North American bumblebees is part of a larger global pollinator crisis that threatens food production for humans and countless species of wildlife.