【推荐1】It seems hard to watch someone yawn (打哈欠) and not to yawn ourselves. Even reading about yawning can make you do it. Now, a new study has found why yawning has such a powerful force.

Yawning when others yawn, the study suggests, is a sign of pity and a form of social connection. Kids don’t develop this deeply rooted behavior until around age four, the study found. Kids with autism (自闭症) are less likely to catch yawns. In the most serious cases, they never do. Yawning might help doctors to see whether the children are developing rightly. The work could also lead to a better understanding of the ways that people communicate and connect.

“Emotional infection seems to be a born thing that connects us together,” said Molly Helt, a graduate student in psychology at the University of Connecticut. “Yawning may be part of that.” Inspiration for her study came when she tried to get her own autistic son to clear his ears on an airplane. She repeatedly yawned at him, hoping he would yawn back. He never did.

“The fact that autistic kids don’t do it might mean they’re really missing out on that emotional connection with people around them,” she said. “The biggest thing people try to figure out after birth is how we become humans and understand that humans have minds that are different from others’,” she added. “Autistic people never seem to understand that.”

Like infectious (有感染力的) laughter and crying, scientists have found that yawning is a shared experience that promotes social connection. Helt said it could fight stress after a period of being nervous and spread a feeling of calm through a group.

【推荐2】A new report said that different types of plants can release some chemical into the air to help other plants. These chemical warnings all have the same purpose — to spread information about one plant's disease or infestation so other plants can defend themselves. But exactly how plants receive and act on many of these signals is still mysterious.

In this week’s Proceedings of the National Academy of Sciences, researchers in Japan offered some explanations. They had identified one chemical message and traced it all the way from release to action.

The scientists looked at tomato plants infested by a common pest, the cutworm. The researchers studied leaves from exposed and unexposed plants. They found one compound showed up more often in the exposed plants. The substance is called Hex Vic. When the scientists fed Hex Vic to cutworms, it knocked down their survival rate by 17%. The scientists identified the source of Hex Vic, and sprayed it lightly over healthy plants. Those plants were then able to start producing the cutworm-killing Hex Vic. Researchers confirmed that uninfected plants have to build their own weapons to fight off bugs and disease. How do they know when to play defense? They are warned first by their friendly plant neighbors.

It is a complex tale, and it may be happening in more plant species than tomatoes. It may also be happening with more chemical signals that are still unknown to us. Further studies are needed to increase agricultural efficiency.

【推荐1】Balancing Forests and CO₂

Tree planting used to be regarded as an effective means of curbing (抑制) climate change. Perhaps it’s time for us to rethink this practice.

Trees pull carbon dioxide or CO₂ from the air. This effectively removes CO₂ from the atmosphere, making trees an important part of the fight against climate change. But trees only hold onto carbon dioxide as long as they’re alive. Once they die, trees decay (腐烂) and release that CO2 back into the atmosphere. This movement of carbon between forest and the atmosphere is called a carbon flux (碳通量), a natural process that happens as trees grow and eventually die.

Recent studies have found that trees around the world are growing faster than ever. Rising atmospheric CO2, mainly due to burning fossil (化石) fuels, is probably driving that rapid growth, said Roel Brienen, a forest ecologist at the University of Leeds, UK. High levels of this gas are boosting temperatures, which in turn speeds tree growth in those areas, he added.

The faster trees grow, the faster they store carbon. It seems like good news. However, it is known that fast-growing tree species, in general, live shorter lives than their slow-growing relatives.

In order to see whether the growth-lifespan trade-off (生长和寿命之间的权衡) is a universal phenomenon, Brienen and his colleagues analyzed over 210,000 individual tree ring records of 110 tree species from more than 70,000 sites worldwide. “By measuring tree rings’ widths one can tell how fast trees grew, while counting rings provides information on tree ages and allows making inferences about trees’ maximum lifespan,” Brienen explained.

They found that, in almost all habitats and all sites, faster-growing tree species died younger than slow-growing species, and even within a species, the trade-off between growth and lifespan held strong.

The team also created a computer program that modelled a forest and adjusted the growth of the trees in this model. Early on, it showed that “the forest could hold more carbon as the trees grew faster”, Brienen reported. But after 20 years, these trees started dying and losing this extra carbon again. “We must understand that the only solution to bring down CO₂ levels is to stop emitting (排放) it into the atmosphere,” said Brienen.

【推荐3】In a country where over 80% of residents live in public housing, a government commitment to sustainable urban design could have huge influence. And when it’s a tropical country like Singapore where convenience and air conditioning are a way of life, the impact could be greater still.

Promising 42,000 new homes across five residential districts, the eco-town of Tengah will be the 24th new settlement built by Singapore’s government since World War II. It is, however, the first with centralized cooling, automated trash collection and a car-free town center, with which environment lovers hope to offer a roadmap for reducing carbon emissions in the Southeast Asian city-state.

The development is named as “Forest Town” by officials, due to its abundant greenery and public gardens. Once home to brickmaking factories, and later used for military training, the 2.7-square-mile site has been reclaimed by a forest in recent years. A 328-foot-wide ecological “corridor” will be maintained through its center, providing safe passage to wildlife and connecting a water catchment area on one side to a nature reserve on the other.

The project has proven a new plan for urban planners supporting green design principles and “smart” technology, according to Chong Fook Loong, group director for research and planning at Singapore’s Housing and Development Board, the agency overseeing the country’s public housing. “Tengah is a new start,” he said in a video interview, explaining that roads and parking are being pushed beneath the town center. “We’re going for the ideal concept of separated traffic, with everything underground and then the ground level totally freed up for pedestrians — for people. So, it’s a very safe environment for all.”

“We want a town that allows walking and cycling in a very user-friendly manner,” he added, saying that cycling has “taken off” in Singapore in the “last three to five years especially”. The master plan will see the installation of electric vehicle charging stations.

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【推荐2】Laura Stone is the founder of Sydney by Kayak(皮划艇), a company that offers guided kayak tours of Sydney Harbour in Australia. Not only did their business increase during the COVID-19, but one of their tours is actually more popular than ever.

A few years ago, Laura was paddling in the harbour when she noticed trash floating in the water. For reference, the United Nations Environment Programme (UNEP) estimates that about 8 million tons of plastic end up in our ocean each year, causing big problems for wildlife and local plants. Laura was so shocked by the garbage in the water that she decided to dedicate a few paddles each week to trash cleanup. Incredibly, her clients were immediately on board with the idea, so Sydney by Kayak now leads four to five garbage-collecting tours every week!

At the start of the COVID-19, Laura thought her business would drop off as many others had. Instead, desperate for the purpose and a way to get outdoors, people flocked to her “Clean Up Kayak” tours. They now routinely take about 441 pounds of garbage out of the harbour each week! “We’ve been quite surprised, even through the COVID-19, we’ve been very busy,” Laura said, “Because they can’t travel, people are looking for something to do. That is not just good for them, but also good for the environment.”

Each tour begins with participants preparing for some working tools. Some people come back many times for the satisfaction of collecting trash from the harbour. Julie Greening, for example, has done about 10 tours so far and said, “Every little bit is worth it. We have 7 billion people on this planet. If everyone does a little, of course it’s going to help.”