Bees are important agents for cross pollination. Many plants are dependent on a particular kind of bees for their reproduction. For orchids and clovers, it is the bumble bee.
The widespread use of insecticides in agriculture has the unwelcome side effect of killing the bees that help to maintain crop production. When bee population has declined drastically, it may even be necessary for farmers to rent bees from bee keepers to pollinate their crops.
Such is the economic and environmental importance of bees. Can you imagine a world without bees?