Skillful 3E Level 2 R&W Scientific American Lesson


INTEGRATED SKILLS You will read a text about tree species and analyze a graph. You will then hear a short podcast related to the topic. There are some questions to help you with language and the main ideas. Finally, you will summarize the points in both texts. A CLOSE READING Read the Scientific American text about tree species and look at the graph. Choose the correct options to complete the sentences. 1 The researchers believe that science has discovered / hasn’t yet discovered 9,200 tree species. 2 Over two fifths of all known tree species are in North / South America. GLOSSARY identify (v) to recognize something and know what it is draw on sth (v) make use of something (e.g., data, expertise) extrapolate (v) to predict based on known data preponderance (n) how many of something there are lump sth together (v) classify two or more things in the same category, even though they’re different 3 Oceania has only around one / three thousand of the tree species which haven’t been discovered yet. 4 The researchers based their calculations on the number of known but rare / common but unknown tree species in the databases. 5 Both Liang and Silman agree that there are probably more / fewer unknown species than the study’s estimate. B READING ANALYSIS Discuss the questions with a partner. 1 What does Jingjing Liang suggest we should do to learn more about tree species? 2 What does Miles Silman think will help us to learn more?

To arrive at their estimate of 9,200 still unknown trees, the researchers extrapolated from the number of rare trees already in the databases. They used this strategy because most unknown trees on the Earth are likely to be rare species, found in limited numbers in small geographical areas, says study co-author and Purdue University quantitative forest ecologist Jingjing Liang. The team’s result is “a rather conservative estimate,” Liang says, because scientists know less about the preponderance of rare trees in places such as the Amazon—where unexplored spots could host pockets

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 yet to be discovered. Most of these species are likely in the tropics, according to new research, which was published in Proceedings of the National Academy of Sciences USA . Though trees are hard to miss, they are also hard to quantify. They are not even always easy to identify. “Their crowns are hundreds of feet up; they’re in between other things; they look like similar [species],” says Miles Silman, a conservation biologist at Wake Forest University, who was not involved in the new study. The new research drew on two huge data sets: One, the Global Forest Biodiversity Initiative, records every species found in extensively documented forest plots around the globe. The other, TREECHANGE, compiles sightings of individual species. The study’s authors used these databases to calculate that there are approximately 64,100 known tree species on the planet—up from previous estimates of around 60,000. South America has the highest tree biodiversity, representing 43% of species, the team found; followed by Eurasia, with 22%; Africa, with 16%; North America, with 15%; and Oceania, with 11%.

C CLOSE LISTENING 3 Listen to a podcast about how forests are changing. Use the words below to complete the summary. fuel habitat personal storage temperature windstorms 1 Four things that trees do for us: they give us paper and ; they clean the air; they store carbon; they provide . 2 Six factors that cause large, old trees to die faster than before: rising air , wildfire, drought, pathogens, , and deforestation. 3 Three reasons why old trees are important: carbon , biodiversity, aesthetic and reasons. D LISTENING ANALYSIS Discuss the questions with a partner. 1 Why does Nate McDowell expect more continued loss of big, old trees? 2 Why are forests becoming younger and shorter? E INTEGRATED WRITING Work with a partner. Summarize the points made in the podcast and explain how it relates to the ideas about tree species in the reading text and graph. Write between 150 and 225 words for your answer.

of unusual species found nowhere else. “If we can focus the resources, the forest inventory expertise, and money, on those rainforests in the Amazon and Borneo, then we would be able to estimate it with higher confidence.” Silman says the study result is likely an underestimate. Tree species often get lumped together based on appearance, he adds, so new genetic analysis techniques will likely lead to the discovery of even more biodiversity.

Estimated Tree Species per Continent Estimated Tree Species per Continent


North America


Observed tree species

Species yet to be documented


South America



8,000 12,000 16,000 20,000 24,000 28,000 32,000




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