- Planting more reflective versions of crops could cool off the regional climate.
- Changing a plant's wax, hairiness or leaf arrangement can change it's reflectivity.
- About 11 percent of the global land surface is devoted to crops.
Increasing the reflectivity of crop plants by 20 percent could decrease temperatures in a given area by about one degree Celsius (1.8 degrees Fahrenheit), said Joy Singarayer of the University of Bristol, United Kingdom.
"It's quite immediate and it's quite safe because crops get planted every year," she said. "The idea is not to think about changing what crops you plant but rather to look within the variety of crops you might plant." This might mean choosing a more reflective variety of wheat, for example.
About 11 percent of the global land surface is devoted to crops, Singarayer said. Even planting all of the world's crops with more reflective varieties would not be enough to reduce climate change worldwide, but it could take the edge off of regional temperature increases as the climate warms.
"That's one degree you don't have to turn up the air conditioning," said John Shepherd of the University of Southampton who was not involved in the study. "You'd be clipping the extreme temperatures."
So far, the team has seen differences in reflectivity of up to 20 to 40 percent in some plant varieties.
Several things change the reflectivity of a crop, including the amount and composition of the wax on the leaf surface, and even how hairy the leaves are. The arrangement of the leaves in the canopy can also change how much sun is reflected.
Changing the wax can also change the plant's water retention, which could change crop yields, probably for the better, especially in arid regions, Singarayer said. Models suggest these changes could have a positive affect on regional water cycles, she added.
Genetic engineering could be used to improve reflectivity, but the team's intention is to start with conventional crop breeding to create more reflective crops.
"It's a very interesting idea and it's a very nice idea in many ways," Shepherd said. "It's using something that's there already."
The idea is similar to the proposal to reduce urban temperatures by making roofs white to reflect more sunlight.
"The disadvantage with white roofs is that there simply isn't enough area of them to make a difference," he said. "We have a much larger area of crops available. It's a question of what can be achieved, and if you can do that without damaging the productivity and water retention and all the other things that are important for crops."
"It's not going to make a big dent, but it could be a really affordable and non-threatening option," he added.
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