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Bees aren't the only pollinators under threat.

Bees aren't the only pollinators under threat.

Monarch butterfly populations have shrunk by about 59 per cent, according to a recent survey of butterfly populations in Mexico.

Scientists cite two main causes: extreme climate fluctuations and widespread loss of the milkweed plant, an important food source, which is being wiped out by herbicides used in soy and corn farming in the US.