Nicole Mortillaro for CBC News:  The legalization of cannabis in Canada last October created a new type of agricultural industry. Some estimate cannabis could be worth $6.5 billion in retail sales alone. That's good news if you're a grower.

But, as with any new industry, there's a learning curve. And this one involves lights.

Growing cannabis is no easy task. The plants have different stages and require precise lighting cycles, with the largest area in greenhouses reserved for plants requiring 12 hours of sunlight and 12 hours of darkness. At one stage of growth, a plant might thrive best with 18 hours of light.

This image shows lights from a local cannabis greenhouse in Leamington, Ont. Light pollution plagues cities, but with cannabis greenhouses it's encroaching into rural areas, and some are concerned. (Courtesy Wally Simpson)

If the sun doesn't provide adequate light, cultivators use artificial lights. These lights can be on at night, and the result — particularly for large greenhouse facilities — is a brightly lit night sky, commonly referred to as light pollution.

Light pollution plagues cities, but this time it's encroaching into rural areas, and some are concerned. For example, there have been complaints in Kingsville, Ont., Leamington, Pelham, and Langley, B.C.

The consequences of light pollution go beyond just not being able to see the stars. It can have serious ecological consequences, and studies suggest that it has adverse health effects on humans.  Full Article: