The world’s forests may hold more secrets than previously thought: a new global estimate of tree biodiversity suggests that there are about 9,200 tree species remaining undocumented. Most are likely in the tropics, according to the new research.

The new research drew on the efforts of hundreds of contributors, who have categorized trees in two huge data sets: One, the Global Forest Biodiversity Initiative, records every species found in extensively documented forest plots worldwide. The other, TREECHANGE, puts together sightings of individual species. Together they suggest there are approximately 64,100 recorded tree species on the planet — up from previous estimates of around 60,000.

The researchers reached their estimate of an additional 9,200 yet undocumented species on the basis of the number of rare ones already in the databases. Most unknown species are likely to be defined as rare, found in limited numbers in small geographical areas, says the quantitative forest ecologist Jingjing Liang. The team’s result is “a rather conservative estimate,” Liang says, “because scientists know less about the preponderance of uncommon trees in places such as the Amazon, where out-of-the-way spots could host pockets of unusual species found nowhere else.” “If we can focus the resources on those rain forests in the Amazon,” Liang adds, “then we would be able to estimate it with higher confidence.”

Silman, a conservation biologist, who was not involved in the new study agrees that the study result is likely an underestimate. His and his colleagues’ local surveys suggest there are at least 3,000 and possibly more than 6,000 unknown tree species in the Amazon basin alone. Tree species often get grouped together based on appearance, he notes, so new genetic analysis techniques will likely lead to the discovery of even more biodiversity. Sliman wonders how many species will go extinct before scientists describe them. “How many are already known to native peoples in the Amazon — or were known to peoples or cultures who have themselves been made extinct through colonization, disease, or absorption? How many “species” already have dried samples sitting in a cabinet?” he says.

Searching for the new species will inform not only conservation but the basic evolutionary science of how and why species diversify and die out, Silman says. “Just the fact that there are thousands of species of something as common as trees out there that are still left to be discovered,” he adds, “I find pretty inspirational.”

Cold weather during winter months may keep many people from leaving home and running in the open air. However, a new study shows that the drop in temperature is a good reason to run. In fact, researchers say, running in cold weather helps improve one’s performance.

Many people say running in the winter can be difficult because of low temperatures and bitter winds. Yet many runners might find it easier than running in hot weather. That could be because lower temperatures reduce stress on the body. When you run in cold weather, your heart rate and the body’s dehydration (脱水) levels are lower than in warmer conditions. The body needs less water on a cold day than in warm weather.

This information comes from sports scientists at St. Mary’s University in San Antonio, Texas. John Brewer is a professor of applied sport science at St. Mary’s. For this study, he and other researchers put a group of people into a room they called an “environmental chamber”. The researchers then recreated summer and winter weather conditions in the room, under which the test subjects (接受试验者) were asked to run 10 kilometers. Brewer says he and his team recorded biological measurements of the runners.

“We’ve got a group of subjects into the environmental chamber, we’ve changed the conditions to replicate the summer or winter and we’ve got them to run 10 kilometers under both of those conditions and taken various measurements on each runner while they’ve been completing their 10 kilometers.”

Brewer says every movement runners make produces heat. He explains that one way in which we lose heat is by sweating. The body loses heat through droplets of sweat. He says the body also loses heat by transporting blood to the surface of the skin.

Earthworms were the beginning of a childhood dream for Jane Goodall. Her mother told a story of going to Goodall’s room when she was one and a half years old.

“She’d found I’d taken a whole handful of earthworms to bed with me,” Goodall said, “and instead of getting mad, she said very quietly, ‘They’ll die if you leave them here, they need dirt.’ So together we took them back into the garden.”

“I never went to university after school because we couldn’t afford it,” she said. Since college was impossible, she got a secretarial job with Louis Leakey, the famed biologist.

It was in the Serengeti plains that Leakey realized Goodall was capable of much more than a secretary. “He just saw that I was very passionate about being out in the wilderness and animals and that I was a good observer,” Goodall said. “Most important of all, he could see I had patience and that I knew how to behave out in the bush even though I hadn’t grown up there.”

Leakey sent Goodall to Tanzania to observe chimpanzees (黑猩猩) in the wild in hopes that their behavior could help explain his research on early humans. Goodall was met with challenges when she faced the chimpanzees. “My first encounters with the chimpanzees were disastrous because they ran away immediately at the sight of me,” Goodall said.

Goodall was surprised by the chimps’love for one another and the bonds between families. She also was surprised when she witnessed one chimpanzee removing the leaves from a small branch and using it as a tool to catch ants.

“At that time, we were defined as the only tool—making creature on the planet,” Goodall said. Goodall sent a telegram to Leakey, who famously replied, “Scientists are faced with two alternatives: Either accept chimpanzees as man, by definition, or else redefine man.” “There is no sharp line dividing us from the rest of the animal kingdom,” Goodall said. “It’s a very blurry (模糊的)line, and it teaches us so clearly that we are not separate from the rest of the animal kingdom, but part of it.”

At 86 years old, Goodall still is educating, discovering and working to bridge the gap between man and chimpanzee.