森林变得更年轻也更矮

Forests are getting younger and shorter

刘立军 供稿

TRANSCRIPT

This is Scientific American's 60-second Science, I'm Annie Sneed.

They give us paper and fuel, as well as vital ecological services - like cleaning the air, storing carbon and providing habitat. We're talking about trees, of course. But changes in the environment largely caused by humans appear to be causing profound transformations in trees around the world.

In a new study, scientists reviewed global research on trends in tree birth, growth and death. They combined those data with an analysis of deforestation. And they found that worldwide, older trees are dying at a higher rate than in the past due to factors like rising air temperature, wildfires, drought and pathogens.

"Most of the drivers of that decrease in large, old trees are increasing themselves, such as temperature going up, droughts are more severe, wildfires, windstorms and deforestation are all - although variable across the globe - they're generally increasing. And so both the loss has already occurred, but we expect more continued loss of big, old trees."

Nate McDowell, an earth scientist at Pacific Northwest National Lab, who was one of the study's authors.

"So if we have an increasing rate of death, particularly of the larger, older trees, what's left are the younger trees. So that's why, on average, through the loss of bigger, older trees, our forests are becoming inherently younger and shorter."

This is a problem, because old trees are vitally important.

"For sure, the increase in death does limit the carbon storage of an ecosystem and can force the system to become a carbon source to the atmosphere. The second reason we care is from a biodiversity perspective: old growth trees tend to house a higher biodiversity than young forests do. And the third reason is aesthetic: As a society, we care about these trees. We have national parks named after these big trees. So there's a personal reason for people to care about this as well."

Thanks for listening for Scientific American's 60-second Science. I'm Annie Sneed.

VOCABULARY

1. pathogen n. a thing that causes disease 病原体

2. inherently adj. 固有地，内在地

3. aesthetic adj. concerned with beauty and art and the understanding of beautiful things 审美的；有审美观点的；美学的。The benefits of conservation are both financial and aesthetic. 保护自然环境在经济上和美化环境上都有好处。

QUESTIONS

Read the passage. Then listen to the news and fill in the blanks with the information (words, phrases or sentences) you hear.

This is Scientific American's 60-second Science, I'm Annie Sneed.

They give us paper and fuel, as well as vital (Q1) ______________ services - like cleaning the air, storing carbon and providing habitat. We're talking about trees, of course. But changes in the environment largely caused by (Q2) ____________________ appear to be causing profound transformations in trees around the world.

In a new study, scientists reviewed global research on trends in tree (Q3) ____________________. They combined those data with an analysis of deforestation. And they found that worldwide, older trees are dying at a higher rate than in the past due to factors like rising air temperature, wildfires, (Q4) ___________________ and pathogens.

"Most of the drivers of that decrease in large, old trees are increasing themselves, such as temperature going up, droughts are more severe, wildfires, windstorms and deforestation are all - although (Q5) _________________ across the globe - they're generally increasing. And so both the loss has already occurred, but we expect more continued loss of big, old trees."

Nate McDowell, an (Q6) _____________________ at Pacific Northwest National Lab, who was one of the study's authors.

"So if we have an increasing rate of death, particularly of the larger, older trees, what's left are the younger trees. So that's why, on average, through the loss of bigger, older trees, our forests are becoming inherently (Q7) _____________________."

This is a problem, because old trees are vitally important.

"For sure, the increase in death does limit the (Q8) ______________________ of an ecosystem and can force the system to become a carbon source to the atmosphere. The second reason we care is from a (Q9) __________________ perspective: old growth trees tend to house a higher biodiversity than young forests do. And the third reason is (Q10) ____________________: As a society, we care about these trees. We have national parks named after these big trees. So there's a personal reason for people to care about this as well."

Thanks for listening for Scientific American's 60-second Science. I'm Annie Sneed.

KEY

Read the passage. Then listen to the news and fill in the blanks with the information (words, phrases or sentences) you hear.

This is Scientific American's 60-second Science, I'm Annie Sneed.

They give us paper and fuel, as well as vital (Q1) ecological services - like cleaning the air, storing carbon and providing habitat. We're talking about trees, of course. But changes in the environment largely caused by (Q2) humans appear to be causing profound transformations in trees around the world.

In a new study, scientists reviewed global research on trends in tree (Q3) birth, growth and death. They combined those data with an analysis of deforestation. And they found that worldwide, older trees are dying at a higher rate than in the past due to factors like rising air temperature, wildfires, (Q4) drought and pathogens.

"Most of the drivers of that decrease in large, old trees are increasing themselves, such as temperature going up, droughts are more severe, wildfires, windstorms and deforestation are all - although (Q5) variable across the globe - they're generally increasing. And so both the loss has already occurred, but we expect more continued loss of big, old trees."

Nate McDowell, an (Q6) earth scientist at Pacific Northwest National Lab, who was one of the study's authors.

"So if we have an increasing rate of death, particularly of the larger, older trees, what's left are the younger trees. So that's why, on average, through the loss of bigger, older trees, our forests are becoming inherently (Q7) younger and shorter."

This is a problem, because old trees are vitally important.

"For sure, the increase in death does limit the (Q8) carbon storage of an ecosystem and can force the system to become a carbon source to the atmosphere. The second reason we care is from a (Q9) biodiversity perspective: old growth trees tend to house a higher biodiversity than young forests do. And the third reason is (Q10) aesthetic: As a society, we care about these trees. We have national parks named after these big trees. So there's a personal reason for people to care about this as well."

Thanks for listening for Scientific American's 60-second Science. I'm Annie Sneed.

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