Detroit’s midnight sun: How Canadian greenhouses could endanger Detroit River migratory birds

Courtesy feature photo taken over Grosse Pointe Park on Nov. 20, 2020. The drone pilot wishes to remain anonymous.

This past fall, Rachel Weinstein-Bacal was walking along the Detroit River with her husband and another couple when they noticed a yellowish-orange glow to the southwest. 

“We actually had to check the time to be like, ‘Wait, is that the sunset?” she said.

What they were actually witnessing was the light from a massive conglomeration of greenhouses about 40 miles away, in the area around Leamington and Kingsville, Ontario. Depending on the night, the lights used to grow tomatoes and cannabis broadcast a spectral glow across much of Metro Detroit. 

Bill Barlage, president of the East English Village neighborhood association, told Planet Detroit that residents are continually asking about the lights. “Everyone lost their mind over the purple-blue glow of the stadium,” he said, comparing it to controversial lighting at Ford Field several years ago. “This is 10 times that size.”

The southern lights — which seem to glow red some nights and yellow others — have attracted a fair amount of attention. The Windsor Star reports that Kingsville residents are seeking to regulate both light and the heavy marijuana odors coming from greenhouses, but light pollution from greenhouses could be affecting ecosystems as well, particularly the millions of migrating birds that move along the Detroit River and through Canada’s Point Pelee National Park every spring and fall. 

And Michigan could soon see more of this light pollution, with increasingly inexpensive LED lights enabling cheaper production of vegetables and legal cannabis in greenhouses.

Light + birds = trouble

At the confluence of the Atlantic and Mississippi flyways, the Detroit River and Point Pelee are an ecologically significant area for large numbers of migratory birds whose populations have declined by more than a quarter in the past 50 years. The Detroit River is recognized as an Urban Bird Treaty City, which involves protecting habitat and reducing hazards. Point Pelee provides crucial habitat as well as a strategic take-off and landing spot for birds making the journey across Lake Erie.

Light pollution has come into focus as a major threat to migratory birds everywhere, with one significant study examining the impact of the New York City’s 9-11 “Tribute in Light,” which uses eighty-eight 7,000 watt xenon light bulbs to project columns of light four miles into the sky. Volunteers and researchers have been monitoring the installation to count and identify the birds that were drawn into the lights. Between 2010 and 2016 they found that 1.1 million birds had been affected, most of them songbirds. However, when the lights for the 9-11 memorial were turned off for even 20 to 30 minutes, the birds quickly dispersed, showing that even small interventions can have a significant impact.  

“Birds use the light from the moon and the stars to navigate during migration,” explained Ava Landgraff, research coordinator for Detroit Audubon. “When there’s a super bright light coming from another area, that’s extremely disorienting to them and they will go towards that light, kind of like a moth goes towards a small light.” 

Another recent study identified Chicago as the most dangerous city in the country for birds as a result of light pollution. “The windows are what kills them, the light is what brings them into danger,” said Douglass Stotz, a senior conservation ecologist at the Field Museum’s Keller Science Action Center. Researchers estimate that as many as one billion birds die each year in the U.S. as a result of window collisions. 

“It seems like folks are starting to gravitate towards this as a potentially serious issue for migratory birds,” Kyle Horton, from Colorado State University’s Aeroecology Lab who co-authored the Chicago study, said of the threat from greenhouses. Horton said that while bright lights from buildings can cause collisions, more often they simply force birds into sub-optimal conditions like concrete-covered downtowns or acres of glass and plastic where food is scarce. Birds may circle around the bright lights until they exhaust themselves.

Landgraff suggested that light pollution could be disrupting insect life cycles as well, reducing their numbers and subsequently limiting the amount of food available for migrating birds. Recent research backs up this concern, showing that light pollution is combining with other factors like habitat loss and pesticide use to impact insect populations. 

“It can affect insects in pretty much every imaginable part of their lives,” Brett Seymoure of Washington University in St. Louis said in a report on the issue.

A growing problem

The most critical time periods for migrating birds and related species are likely to be between March 15 and May 30 for spring migration and from Aug. 15 to Oct. 31 for fall migration. And these are also important periods for utilizing supplemental light to grow things like tomatoes and cannabis, according to Erik Runkle, a Michigan State University researcher who specializes in greenhouse production. He said that these crops are essentially grown year-round, using supplemental light in every season except mid-summer. 

The greenhouse industry around Leamington has become one of the largest hubs for production in North America, Runkle said. There are currently around 2,890 acres of greenhouses in operation there with another 120 acres under construction. Legal marijuana has helped fuel this boom, but so have lower prices for LED lighting, which make growing in greenhouses cheaper and provide economic benefits like allowing farms to employ workers all year. Yet, what’s happening in Canada could serve as a warning to Michigan where more greenhouses are going up, albeit not at the same rapid clip as the developments around Leamington.  

Map of Leamington, Ontario in relation to Detroit and the Detroit River

“It’s much cheaper to install curtains or blackout systems when you build a greenhouse than it is to try to go into a facility that’s already been built and try to figure out how you’re going to install it,” Runkle said. He has written that the Netherlands — where there is a large horticultural sector — has implemented regulations to keep as much 95 to 98% of the light from escaping greenhouses. Still, this is much easier to do with new greenhouse construction because the trapped heat and humidity can cause problems in structures that have been designed without adequate ventilation.

Canadian growers are complaining of exactly these problems as municipalities like Leamington move to regulate light and odors coming from greenhouses, saying that blackout curtains make the structures overly hot. And yet, these may be the only actionable solution to this problem, Runkle said. Although researchers like Horton can predict bird migration with a high degree of accuracy, asking growers to turn off their lights for a period of time could prove to be an unworkable solution. Every day without additional lighting could lead to reduced yields and potentially cause growers to lose their contracts with purchasers.

The biggest questions now are if and when Canada will implement new regulations, and perhaps why people didn’t see this coming. Weinstein-Bacal said, “It’s strange to me that there wasn’t more of a concerted effort to begin with to make sure that that wouldn’t happen.” 

For now, she and other Detroiters will have to make their peace with lights that she said look like “’something out of Ghostbusters’” and hope that the birds can still find their way past them.