雅思阅读 10: Cities Beneath the Canopy（树冠下的城市）

改编自 LiDAR 考古研究 / Science & Nature（2024-2026）。雅思阅读 Section 3 难度，约 1050 词。 素材来源：https://m.economictimes.com/us/news/a-lost-civilization-under-the-rainforest-lidar-is-rewriting-amazon-history/articleshow/128943501.cms

Reading Passage

A. For nearly a century, the Amazon rainforest was described by archaeologists as a pristine wilderness — a vast, untouched green expanse in which only small, mobile bands of hunter-gatherers could survive. The region's thin, nutrient-poor soils and dense canopy were held to preclude the rise of agriculture, towns or social hierarchy. That consensus, already under pressure from scattered archaeological finds, has collapsed almost entirely in the space of a decade, overwhelmed by evidence from an unlikely source: airborne laser scanning. Known as LiDAR (Light Detection and Ranging), the technology fires millions of laser pulses from aircraft, measures the time they take to return, and constructs a three-dimensional map of the ground beneath the trees. In the Amazon, that map has revealed what centuries of foot survey could not: vast networks of planned settlements, raised roads, water-management systems and agricultural earthworks hidden beneath the canopy. The revolution is only a decade old. The first major Amazonian LiDAR surveys date to the early 2010s, and they were undertaken not by archaeologists but by mining and energy companies mapping terrain; it was only later that researchers realised the data already in commercial archives contained, in effect, an aerial survey of the entire forest floor.

B. The technology itself is elegant. Most laser pulses reflect off leaves and branches and never reach the forest floor; those that do return to the aircraft reveal the shape of the terrain beneath. Specialised software then strips away the vegetation, producing a "bare-earth" model in which subtle mounds, ditches and geometric platforms become visible. The method has transformed tropical archaeology because it can survey hundreds of square kilometres in days, replacing painstaking ground surveys that would take years and often missed structures entirely beneath dense canopy. In the Llanos de Moxos region of northeastern Bolivia, LiDAR surveys published in Nature in 2022 identified two exceptionally large sites belonging to the Casarabe culture, which flourished between AD 500 and 1400. The larger covered more than 300 hectares, with elevated platforms, monumental architecture and pyramidal structures linked by raised causeways stretching several kilometres across seasonally flooded plains. The resolution achieved by airborne LiDAR is such that platforms barely a metre high — invisible on the ground, where the canopy shuts out all sideways view — stand out as clear geometric shapes. A single flight can cover an area that would take a ground survey team years to walk, and it does so without the months of preliminary clearing that traditional digs demand. The authors described the sites as low-density urban centres integrated into a regional network rather than isolated villages.

C. A second major survey, published in Science in 2024, focused on Ecuador's Upano Valley and uncovered more than 6,000 earthen platforms arranged in organised clusters, connected by a grid of straight roads extending across the landscape. Occupied continuously for over a thousand years beginning around 500 BC, these settlements indicate populations that likely reached into the tens of thousands. The scale of construction implies coordinated labour, social hierarchy and long-term planning — precisely the features that the old "pristine wilderness" model insisted were absent. Archaeologist Stéphen Rostain, who has worked in the Upano Valley for decades, noted that LiDAR allowed researchers to see how previously scattered mounds and plazas formed an integrated urban system: roads linked ceremonial centres, farmland and residential zones in a deliberate spatial logic that no amount of walking through the forest could have discerned. The Upano settlements were already known to archaeologists from surface survey, but for decades they looked like a scatter of unrelated mounds. LiDAR did not create the sites; it connected them, showing that what had appeared isolated was in fact a planned landscape whose scale no single field season could have reconstructed.

D. The discoveries extend beyond individual cities. LiDAR has documented thousands of geometric earthworks across the Amazon basin — circular enclosures, rectangular platforms and linear roads intersecting at precise angles — as well as raised agricultural fields and canal systems. Equally important is the recognition of terra preta, or "dark earth": anthropogenic soils enriched with charcoal, organic waste and bone fragments that remain fertile centuries after their creation. The existence of terra preta demonstrates that ancient Amazonians did not merely occupy the rainforest but actively improved its soils, permitting sustained agriculture in regions once dismissed as agriculturally marginal. Together, these findings paint a picture of a landscape that was comprehensively engineered — forests managed for useful species, rivers modified with canals, fields raised above seasonal floods — rather than a wilderness encountered by accident. Terra preta is also among the most fertile soils in the Amazon, and its distribution maps have become, in effect, maps of ancient settlement. Where the dark earth is deep, people once lived; where it is absent, the landscape may have been used only lightly. No modern agricultural technique has yet matched its sustained fertility.

E. The implications for the history of the Americas are profound. If significant portions of the Amazon were densely settled, managed landscapes before European contact, then the post-contact epidemics that devastated Indigenous populations — often blamed on virgin-soil diseases sweeping through empty wildernesses — may have collapsed societies that were in fact complex, populous and economically sophisticated. That revision is uncomfortable for narratives that cast the pre-Columbian Amazon as an untouched paradise, and equally so for those that cite it as evidence that large-scale civilisation was impossible in tropical forests. LiDAR surveys are continuing, and researchers estimate that thousands of additional sites remain buried beneath the canopy. What once appeared to be endless primeval forest is now understood as a palimpsest of human construction — and the reading has only just begun. That revision reaches deep into environmental history. The post-contact depopulation of the Amazon, once described as a tragedy visited upon a nearly empty land, now looks like a catastrophe that erased dense, engineered societies whose environmental legacy survived only as soil, banks and faint outlines beneath the trees. The rainforest the first Europeans entered was not, it seems, the rainforest that had existed a century earlier — and certainly not the rainforest of the popular imagination.

Questions 1-4

Choose the correct heading for paragraphs B, C, D and E from the list of headings below.

List of Headings i. The engineering of soils and landscapes beyond the cities ii. How laser scanning reveals what foot survey could not iii. The destruction of Amazonian cities by Spanish conquistadors iv. A valley in Ecuador reveals an integrated urban grid v. Why the Amazonian soil is naturally fertile vi. What these findings mean for pre-Columbian history vii. The financial cost of LiDAR surveys

1. Paragraph B: ____
2. Paragraph C: ____
3. Paragraph D: ____
4. Paragraph E: ____

Questions 5-8

Choose the correct letter, A, B, C or D.

5. What is the advantage of LiDAR over traditional archaeological survey? A. It can date artefacts with greater precision. B. It can reveal structures hidden beneath forest canopy over large areas. C. It requires no aircraft or specialised equipment. D. It works equally well in dense urban environments.

6. What did the Casarabe sites in Bolivia demonstrate? A. They were isolated farming villages with no connection to one another. B. They were low-density urban centres linked by causeways. C. They were built after European contact in the seventeenth century. D. They contained no monumental architecture.

7. What is terra preta? A. A type of tropical hardwood used for construction. B. A naturally fertile soil found in undisturbed rainforest. C. Human-enriched soil that remains productive over centuries. D. A mineral used in ancient road construction.

8. The article suggests that post-contact epidemics may have A. had no effect on Amazonian populations. B. collapsed complex societies rather than empty wildernesses. C. spread from Europe to Asia via the Amazon. D. been caused by Amazonian pathogens.

Questions 9-13

Do the following statements agree with the claims of the writer?

Write:

• TRUE if the statement agrees with the information
• FALSE if the statement contradicts the information
• NOT GIVEN if there is no information on this

9. The old "pristine wilderness" view was supported by early twentieth-century scholarship.
10. LiDAR was first used by archaeologists in the 1980s.
11. The Upano Valley settlements were occupied for more than a millennium.
12. Terra preta forms naturally in undisturbed Amazonian soils.
13. All Amazonian archaeological sites have now been surveyed.

Questions 14-15

Complete the summary below using NO MORE THAN TWO WORDS from the passage.

LiDAR produces a (14) __________ model by stripping away vegetation to reveal the ground surface. The discovery of (15) __________ shows that ancient Amazonians actively improved the soil rather than merely farming it.

答案与解析

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