The loss of natural land isn't just a problem for the Amazon or the rainforests of Southeast Asia. The United States is losing its forests, grasslands, wetlands, and deserts at a truly startling pace.

Between 2001 and 2017, some 97, 124 square kilometers of natural land-around the size of Indiana- were destroyed in the US to make way for roads, industry, farms, and other signs of human civilization. That's equal to a football field-sized piece of land being lost every 30 seconds. Some of the most serious losses have been experienced in the South and Midwest, where human development took over 47 percent and 59 percent of all land area, respectively, in the 16 years studied.

These findings come from a report published by The Center for American Progress.

Using available satellite data and open- source databases, they calculated the rate of loss of natural lands and its relationship to oil and gas extraction(开采), road construction, urban development, agriculture, and other human- related activities. If national trends continue, a South Dakota- sized expanse of forests, wetlands, and wild places in the continental United States will disappear by 2050.

Now only 12 percent of the country's land area has been conserved as national parks, wilderness areas, national monuments, or other protected areas, while 26 percent of ocean are a is safeguarded from oil and gas extraction. According to this report, it's now time to extend this level of protection even further.

Keeping in line with present scientific recommendations, they conclude that the US should aim to protect at least 30 percent of lands and oceans in a natural state by 2030.

However, it isn't all about desperation. The authors conclude on a remarkably optimistic note (well, relatively optimistic for an environmental report, at least)."The United States is entering new times when it will rely more than ever on the integrity (完整) and stability of the natural world to provide economic boom, safeguard the health of communities, and weather (平安渡过) the effects of a changing climate," they write.

Every summer, the calls of thousands of swamp sparrows can be heard across North America's wetlands. These little brown birds know only a few songs, but they know them very well. In fact, their musical set list probably hasn't changed much for centuries.

Like humans, baby swamp sparrows learn to communicate by copying adults. From a young age, they learn to copy, or mimic, songs sung by their elders. "Swamp sparrows very rarely make mistakes when they learn their songs," says biologist Robert Lachlan. In fact, their mimicry is so accurate that the music changes little between generations.

Just like children, the sparrows don't remember every song they hear. Lachlan says. "They don't just learn songs at random; they pick up commoner songs rather than rarer songs." In other words, they learn songs they hear most often. It's an example of a strategy that scientists call conformist bias. Until recently, this learning ability was thought to be special only to humans.

Between 2008 and 2009, Lachlan's research team recorded the calls of 615 male swamp sparrows across the northeastern United States. The researchers used computer software to break each song into a collection of notes, or syllables. They then measured the differences between the tunes.

The research revealed that only 2 percent of male sparrows sang a different song from the standard tune. The combination of accurate mimicry and conformist bias allows the birds to create traditions that last for centuries. "With those two ingredients together, you end up with traditions that are really stable," says Lachlan. "The song-types that you hear in the marshes（湿地）of North America today may well have been there 1,000 years ago." Lachlan's study is also among the first to measure the longevity of song traditions within a bird species.

The findings are really exciting, says scientist Andrew Farnsworth. He hopes that future research will evolve from these studies. For example, scientists may be able to identify how other animals are able to preserve their cultural traditions. "Seeing the potential for it in other organisms is super cool," says Farnsworth.

Holding the large and heavy "brick" cellphone he's credited with inventing 50 years ago, Martin Cooper talks about the future.

Little did he know when he made the first call on a New York City street from a heavy Motorola prototype(原型) that our world would come to be encapsulated on a sleek glass sheath where we search, connect, like and buy.

Cooper says he is an optimist. He believes that advances in mobile technology will continue to transform lives but he is worried about risks smartphones pose to privacy and young people.

"My most negative opinion is we don't have any privacy anymore because everything about us is now recorded someplace and accessible to somebody who has enough intense desire to get it," the 94-year-old said in an interview in Barcelona at MWC, the Mobile World Congress, the world's biggest wireless trade show, where he was getting a lifetime award.

Cooper sees a dark side to the advances, including the risk to children. One idea, he said, is to have "various Internets intended for different audiences."

Cooper made the first public call from a handheld portable telephone on a Manhattan street on April 3,1973, using a prototype device his team at Motorola had started designing just five months earlier.

Cooper used the Dyna-TAC phone to famously call his opponent at Bell Labs, owned by AT&T. It was literally the world's first brick phone, weighing 2.5 pounds and measuring 11 inches.

Cooper spent the best part of the next decade working to bring a commercial version of the device to market.

The call helped kick-start the cellphone revolution (革命).

Cooper said he's "not crazy" about the shape of modern smartphones. He thinks they will develop so that they'll be "distributed on your body," possibly as sensors "measuring your health at all times."

Batteries, he said, might be replaced by human energy. The body makes energy from food, he argues, so it could possibly also power a phone. Instead of holding the phone in the hand, for example, the device could be placed under the skin.