Hat is the main idea of this paragraph?

Scientists do not fully understand CCD (colony collapse disorder). They know that CCD puts the world's honeybee population at risk, which, as a result, puts the health of agricultural crops at risk. Scientists first observed CCD in North America in late 2006. They have been working hard to discover its root cause, whether a pathogen, a parasite, an environmental toxin, or, as crazy as it may sound, cell phone transmissions.