【推荐1】It may sound strange, but cutting down a real tree for Christmas is actually greener than going with the artificial kind, one scientist says.

“It is a little confusing to people,” said Clint Springer, a biologist at Saint Joseph’s University in Philadelphia. Because of concerns over deforestation（砍伐森林）around the world, many people naturally worry that buying a real tree might contribute to that problem. But most Christmas trees for sale these days are grown not in the forest but on tree farms for the purpose of being cut.

Moreover, from the viewpoint of greenhouse gases, real trees are “the obvious choice”. Live trees actively release oxygen as they grow, and meanwhile remove carbon dioxide from the atmosphere. After they have been cut and Christmas is over, they’re usually cut into smaller pieces for mulch（覆盖物）. As mulch, the bits of trees very slowly release carbon dioxide back into the atmosphere. So in the end, a real Christmas tree is carbon neutral, putting the same amount of carbon dioxide back into the air as it took out (although much more slowly).

The tree farms that grow the trees also replant after the trees are cut. Artificial trees, on the other hand, don’t come out even in the carbon balance. Petroleum（石油）is used to make the plastics in artificial trees and lots of carbon dioxide-creating energy is required to make and transport them. Because these trees just end up in the places where waste is buried under the ground after use, “those greenhouse gases are lost forever,” Springer said.

【推荐2】Healthy See, Healthy Do

Visit the grocery store on an empty stomach, and you will probably come home with a few things you did not plan to buy. But hunger is not the only cause of additional purchases.     1     And it may make or break some healthy eating habits.

The checkout area is a particular hotspot for junk food. Studies have found that the products most commonly found there are sugary and salty snacks.     2     A 2012 study in the Netherlands found that hospital workers were more likely to give up junk food for healthy snacks when the latter were more readily available on canteen shelves, for example. In 2014 Norwegian and Icelandic researchers also found that replacing unhealthy foods with healthy ones in the checkout area significantly increased last-minute sales of healthier foods.

    3     It has been working with more than 1,000 store owners to encourage them to order and promote nutritious foods. “We know that the stores are full of cues meant to encourage consumption,” says Tamar Adjoian, a research scientist at the department, “Making healthy foods more convenient or attractive can lead to increased sales of those products.”

Adjoian and her colleagues wondered if such findings would apply to their city’s crowded urban checkout areas, so they selected three Bronx supermarkets for their own study. They replaced candies and cookies with fruits and nuts near the checkout counter.     4    

Of the more than 2,100 shoppers they observed, just 4 percent bought something from the checkout areas. Among those who did, however, customers in the healthy lines purchased nutritious foods more than twice as often as those in the standard lines.     5     The findings were reported in September in the Journal of Nutrition Education and Behavior.

The potential influence may seem small, but Adjoian believes that creating more checkout lines would open customers’ eyes to nutritious, lower-calorie foods. Health department officials are now exploring ways to expand healthy options at checkout counters throughout New York City.