Can crops help fight global warming?

Reflective crops studied for possible role as climate change fighters

The Albedo Effect. A great title for a mediocre action thriller, likely starring Keanu Reaves.


Albedo is actually a scientific term, representing the amount of solar energy that reflects off the earth.


Different types of land cover, trees, cropland and asphalt reflect different amounts of solar energy.


When it comes to crops, canola is an albedo superstar during its flowering period.


“Anybody that has driven by a canola field in full flower will (think), ‘I wish I had my sunglasses on,’ ” said Brian McConkey, an Agriculture Canada scientist in Swift Current, Sask., who specializes in the interaction between agriculture and the environment.


The amount of solar energy a crop reflects is more important than simply forcing someone to don sunglasses. 


If crops reflect more radiation it keeps the earth cooler and could, potentially, be a valuable tool to combat global warming.


“When you’re talking the Canadian Prairies, 35 million hectares (86 million acres), if you can make that more reflective, that would have an effect on the world’s climate,” McConkey said, following his presentation at the Agricultural Institute of Canada conference, held in late April in Winnipeg.


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Scientists at the University of Bristol in England have studied the potential of bio-engineering crops so they reflect more light. A 2009 paper, published in Current Biology, reported that plants with waxy coatings on their leaves reflect more sunlight. 


However, scientists estimated that increasing the albedo of plants by 20 percent would cool the planet by only 0.11 C. The seasonal benefits could be much larger in certain geographies.


“The mid-latitudes of North America and Eurasia could cool by as much as 1 C in June, July and August,” the report said.


McConkey said plant scientists haven’t really thought about the albedo of broad acreage crops, but selecting for traits that increase reflection, perhaps hairy leaves, could have multiple benefits.


Besides cooling the planet during the summer months, it could protect crops from hotter temperatures in the future


“One of the biggest concerns is it going to get too warm, for some of these crops, to keep cool, especially (during) the reproduction stage,” McConkey said.


Satellite observations show that canola does reflect more radiation than other crops, mostly because of the yellow flowers during bloom period and partly because of the crop canopy.


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“One of the purposes of the flower is to keep the reproductive parts (of the plant) cool,” McConkey said. “Anything with (visible) flowers tends to be cooler…. Wheat seems to be particularly not reflective, compared to other crops.”


The concept of crops reflecting solar energy becomes more intriguing if Canadian farmers are compensated for the ecological services.


“At $50 a tonne CO2 equivalent, some of these (practices become more appealing),” McConkey said.


Research reported in Scientific American suggests that planting gardens on roofs or painting roofs white could increase albedo in cities and help fight global warming.


But McConkey said cities are tiny, in geographic size, compared to hundreds of millions of acres of cropland. Altering the albedo from cropland offers more environmental benefits than painting roofs white.


Other scientists are more skeptical. Making crops more reflective could cut into photosynthesis.


“Increasing shininess will reduce (crop) production, full stop,” Colin Prentice, a University of Bristol scientist who didn’t participate in the study, told nature.com. “We really do not need anything that reduces primary production.”


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Ray Desjardins, an Agriculture Canada researcher in Ottawa, plans to write a scientific paper on the topic this summer.