【推荐1】Grizzly bears, which may grow to about 2.5 m long and weigh over 400 kg, occupy a conflicted corner of the American psyche — we revere (敬畏) them even as they give us frightening dreams. Ask the tourists from around the world that flood into Yellowstone National Park what they most hope to see, and their answer is often the same: a grizzly bear.

“Grizzly bears are re-occupying large areas of their former range,” says bear biologist Chris Servheen. As grizzly bears expand their range into places where they haven’t been seen in a century or more, they’re increasingly being sighted by humans.

The western half of the US was full of grizzlies when Europeans came, with a rough number of 50,000 or more living alongside Native Americans. By the early 1970s, after centuries of cruel and continuous hunting by settlers, 600 to 800 grizzlies remained on a mere 2 percent of their former range in the Northern Rockies. In 1975, grizzlies were listed under the Endangered Species Act.

Today, there are about 2,000 or more grizzly bears in the US. Their recovery has been so successful that the US Fish and Wildlife Service has twice attempted to delist grizzlies, which would loosen legal protections and allow them to be hunted. Both efforts were overturned due to lawsuits from conservation groups. For now, grizzlies remain listed.

Obviously, if precautions (预防) aren’t taken, grizzlies can become troublesome, sometimes killing farm animals or walking through yards in search of food. If people remove food and attractants from their yards and campsites, grizzlies will typically pass by without trouble. Putting electric fencing around chicken houses and other farm animal quarters is also highly effective at getting grizzlies away. “Our hope is to have a clean, attractant-free place where bears can pass through without learning bad habits,” says James Jonkel, longtime biologist who manages bears in and around Missoula.

【推荐2】100-year-old Alfred Larson has been through a lot in his lifetime, but one thing that keeps him going is bluebirds.

When Alfred retired in 1978, he wanted to find a hobby or something to do that would keep him busy and provide him with a sense of purpose. When he read a National Geographic article about crafting wooden nest boxes for bluebirds to help improve their populations, he decided to give it a try. Alfred explained that he started building nest boxes on his ranch (大牧场) using left-over pieces of wood.

More than four decades later, Alfred is still going strong and promoting bluebird conservation efforts. Alfred is now monitoring nearly 350 nest boxes on six different trails (小路) in Southwest Idaho. He said, “I settled on a simple design that was easy to build and easy to monitor. I kept adding more boxes on these trails, and these birds responded.” Alfred’s boxes give bluebirds a lot of help in survival. “Without his work, we can’t see so many bluebirds now,” said Pearman, the author of Mountain Bluebird Trail Monitoring Guide.

To celebrate his achievements, filmmaker Matthew Podolsky worked with Alfred for weeks to create a 30-minute documentary—Bluebird Man. The film explores how everything led him to the work he does today and his efforts in bluebird protection. “I remember the first trip I took to the bluebird trail with Alfred, and I was very surprised by the speed with which he moved from box to box,” said Podolsky. “He was hiking across difficult and uneven terrain (地形). I often struggled to keep up with him. Sometimes we’d check more than 100 boxes and be driving home in the dark.”

The impact he’s had on the populations of bluebirds in North America will continue.

【推荐3】Bee protection is a big issue these days in America, with people planting native pollinator gardens, setting up bee houses, and taking part in scientific activities to monitor local bee populations. And this is for good reason—in North America, a quarter of native bee species are at risk of extinction. Bees pollinate 35 percent of our global food supply and many of the wild plants our ecosystems depend on.

No Mow May, a movement that began in the UK, is now rapidly spreading throughout the US. Its popularity lies in its being simple: Just give bees a help during the crucial springtime by removing a chore from your list and letting your lawn grow for the month of May. This lets “lawn flowers” such as dandelions grow at a time when bee food is rare.

Dandelions, despite being pretty and useful, are non-native. Then why do we promote a movement that encourages their growth? Here’s the basic answer don’t let “perfect” be the enemy of “good”. Sure, it’d be great to turn your entire neighborhood into a bee kingdom of native plants, but that can take lots of time and money.

While dandelions have become the poster child for No Mow May, other plants-including native species — may also appear in your lawn. “Besides dandelions, there are many other plants that are going to be there,” says Dr. Claudio Gratton at the University of Wisconsin-Madison.

In Massachusetts, scientists found 63 species of plants in lawns, 30 percent of which were native to the state. Most of the Americans probably loved dandelions as children but have tended to hate them as adults because of American lawn culture, which allows no flowers. “No Mow May forces us to think about our relationship with nature. We should reflect on the way we have made nature suit our needs, and realize flowers play really important roles,” says Dr. Claudio Gratton.

【推荐2】Few dishes taste better than a juicy cut of beef. One survey in 2014 found that steak was Americans’ favorite food. Unfortunately, by cooking so many cows, humans are cooking themselves, too.

The influence of food on greenhouse-gas (GHG) emissions (排放) can slip under the radar. In a survey in Britain last year, the share of answerers saying that “producing plants and meat on farms” was a “significant contributor” to climate change was the lowest among ten listed activities. Yet two papers published this year in Nature Food find that food, especially beef, creates more GHGS than previously thought.

This March researchers from the European Commission and the UN’s Food and Agriculture Office released a study estimating that the global food system was responsible for 34% of GHG in 2015. The paper assigns the full impact of deforestation to the agriculture that results from it;includes emissions after food is sold(such as from waste and cooking);and counts non-food crops like cotton. But even when the authors took away emissions from sources like transport and packaging, they still found that agriculture generated 24% of GHGS.

Another recent paper, by Xiaoming Xu of the University of Illinois and eight co-authors, allocates (分配) this impact among 171 crops and 16 animal products. It finds that animal-based foods account for 57% of agricultural GHGS, versus 29% for food from plants. Beef and cow’s milk alone made up 34%. Combined with the earlier study’s results, this implies that cattle produce 12% of GHG emissions.

Relative to other food sources, beef is uniquely carbon-intensive. Because cattle emit methane (甲烷) and need large grasslands that are often created by cutting more forests, they produce seven times as many GHGS per calorie of meat as pigs do. This makes beef a bigger share among foods than coal is among sources of electricity.

The simplest way to cut beef output is for people to eat other animals instead, or become vegetarians. But convincing people to give up their burgers is a tall order.

Fortunately, lab-grown meats are moving from Petri dishes (培养皿) to high-end restaurants. Doing without beef from live cattle is hard to imagine, but the same was true of coal 100 years ago. Lab-grown meat could play an essential role in slowing a climate disaster.