【推荐2】The Great Barrier Reef has seen its third mass bleaching (大规模白化) event in five years. For the first time, all three sections of the Australian reef have been badly affected. The damage happened in February when the area was exposed to the hottest month of water temperatures on record.

Surveys conducted by Terry Hughes at James Cook University in Australia and his team during March made it known that 25 percent of the reef had been badly bleached and 35 percent bleached to some degree. The northern, central and southern sections of the reef were all hit.

Terrible bleaching also struck in 1998, 2002, 2016 and 2017, but was limited to one or two sections. This is the first time that all three sections have experienced terrible bleaching at exactly the same time, says Hughes. “It’s heartbreaking.”

Some of the damaged corals（珊瑚）will survive, including more heat-resistant（耐热的） species. But many others were probably “literally cooked” at the peak of the heatwave in early 2020, says Hughes. Others will die more slowly from stress over the next few months, he adds. Hughes has serious concern about the southern reef, which was mostly unaffected in former bleaching events and hasn’t developed the same heat resistance as other parts.

The 2016 and 2017 events killed about half the coral on the reef. It usually takes a decade for even fast-growing corals to recover, meaning the latest damage will seriously weaken the reef’s ability to recover, says Hughes. The high frequency of mass bleaching in recent years has been driven by climate change, which results from human activity and is steadily raising ocean temperatures. The only way to deal with the problem is to immediately reduce the release of greenhouse gases, says Hughes.

【推荐3】It’s a popular belief that a fish's memory lasts for only seven seconds. It may seem sad to think that they don’t remember what they’ve eaten or where they’ve been, and they don't identify you or any of their friends- every moment in their life would be like seeing the world for the first time.

But don’t be so quick to feel sorry for them. A new study has found that fish have a much better memory than we used to think. In fact, certain species of fish can even remember events from as long as 12 days ago. In the study, researchers from Mac Ewan University in Canada trained a kind of fish called African cichlids to go to a certain area of their tank to get food. They then waited for 12 days before putting them back in the tank again. Researchers used computer software to monitor the fish’s movements. They found that after such a long break the fish still went to the same place where they first got food. This suggested that they could remember their past experiences.

In fact, scientists had been thinking for a long time that African cichlids might have a good memory. An earlier study showed that they behaved aggressively (挑衅地) in front of certain fish, perhaps because they remembered their past “fights”. But until the latest findings, there was no clear evidence.

Just as a good memory can make our lives easier, it also plays an important part when a fish is trying to survive in the wild. “If fish are able to remember that a certain area contains safe food, they will be able to go back to that area without putting their lives at risks,” lead researcher Trevor Hamiton told Live Science.

For a long time, fish were placed far below chimpanzees, dolphins and mice on the list of smart animals. But this study has given scientists a new understanding of their intelligence.

【推荐1】When Ariel Cordova-Rojas rode her bike to Jamaica Bay Wildlife Refuge in Queens, New York, last November, she planned to go hiking and bird-watching. A mile into her walk, she found a female mute swan (疣鼻天鹅) near the water’s edge. Cordova-Rojas, 30, who had worked at the Wild Bird Fund rehabilitation centre in Manhattan, knew that mute swans can be angry and ready to attack. But as she approached this one, it didn’t move.

She was certain that the bird needed medical attention. Cordova-Rojas put her jacket over the bird’s head to keep it calm, carefully picked it up, and held it in her arms. And then a thought struck her: What do I do now?

Her best hope was the rehab (康复) centre, but that was across the East River and clear on the other side of town. How was she going to transport a 17-pound swan on her bike all that way? Luckily, some strangers driving by offered her, her bike, and the swan a lift to a nearby subway station.

On the subway, no one seemed particularly frightened by the feathered passenger. One guy, says Cordova-Rojas, was “sitting right in front of me on his phone. I don’t know if he noticed there was a swan in front of him.”

Cordova-Rojas called the rehab centre on the road, and Tristan Higgin-botham, an animal-care manager, picked her up at the subway station and drove the bird, the bike, and the rescuer to the centre. There, staff members determined that the swan might have lead poisoning (中毒), caused by taking weights used on fishing lines.

The staff got the swan back up on her feet. Sadly, even with all that care, the swan got a serious infection (感染). Two months after Cordova-Rojas came to her rescue, she passed away.

【推荐3】It's easy to understand why early humans domesticated dogs as their new best friends. Domesticated dogs can guard against fierce animals and provide warmth during cold nights. But those benefits only come following domestication. Despite more than a century of study, scientists have struggled to understand what it was that caused the domestication process in the first place.

A new theory given by Maria Lahtinen, a senior researcher, might be able to explain this puzzle. She made this theory when studying the diet of late Pleistocene hunter gatherers in Arctic and sub-Arctic Eurasia. At that time, around 20,000 to 15,000 years ago, the world was in the coldest period of the last ice age.

In cold environments then, as today, humans tended to gain the majority of their food from animals. Nutritional deficiencies came from the absence of fat and carbohydrates, not necessary protein. Indeed, if humans eat too much meat, they can develop protein poisoning and even die. “Because we humans are not fully adapted to a diet that is carnivorous, we simply cannot digest protein very well,” Lahtinen says.

During that time, animals that humans killed for food would have been struggling to live, barely having fat and composed mostly of lean muscle. Using previously published early fossil records, Lahtinen and her colleagues calculated that the animals killed by people in the Arctic and sub-Arctic during this time would have provided much more protein than they could have safely consumed.

Under the tough circumstances of the Arctic and sub-Arctic ice age winter, sharing excess meat with dogs would have cost people nothing. The descendants of wolves that took advantage of such handouts would have become more gentle toward humans over time, and they likely went on to become the first domesticated dogs.

【推荐2】Recently, a new kind of tourism has sprung (出现) up in China. Called “special forces (特种兵) style tourism”, this new kind of tourism is mainly about visiting many places of interest in a short period, most often on weekends. Most of these visitors are college students.

Yu Yinghua, a college student in Shanghai, is one of them. The 22-year-old started the “special forces style tourism” in March after she was attracted by such experiences of some travel bloggers. “After staying a long time at school, I’m hungry to take trips in my spare time,” said Yu, “Now it’s time! Spring has come and we can go out to enjoy the beautiful natural scenery.”

Most of her trips were inspired by understanding from her daily life, such as a place mentioned in a chat with friends. “But making a plan spot in the city, she was able to find a lot of information and learn more about these sites. That would help her save time when traveling on-site and enjoy the sites better.”

Unlike Yu who traveled in nearby cities, Chen Junjun, a doctoral student in Shanghai likes to travel far to get rid of academic stress. In April, the 24-year-old took a two-day trip to Xi’an, Shaanxi province. During her trip, she visited all the scenic sites in the city. “With many academic responsibilities, such a trip can bring color to my life.” said Chen.

Even so, the 24-year-old added that such tourism is not suitable for everyone. Chen said that it’s labor-consuming (耗费体力的) as visitors have to visit as many sites as possible in a short period. To some degree such trips are not as flexible (灵活的) as days-long trips in which you can change your plan as you like. “Thus, a great deal of energy and a calm mind are needed for this kind of tourism,” said Chen.