IELTS Academic Reading Practice Test 30

A The seismograph, a device that records the ground motion largely produced by earthquakes, is widely regarded as among the most consequential scientific instruments to have emerged from the long human attempt to make sense of natural catastrophe. Although modern digital seismographs bear little physical resemblance to their earliest ancestors, the basic problem they address has not changed in nearly two thousand years: how to capture, in a stable and quantifiable form, vibrations that may last for only a few seconds and travel halfway around the planet.

B The first device known to have detected distant earthquakes is said to have been constructed in 132 CE by the Chinese polymath Zhang Heng. According to surviving accounts in the Book of the Later Han, Zhang's instrument took the form of a large bronze vessel decorated on the outside with eight dragons facing the cardinal and intercardinal directions. Each dragon held a small bronze ball in its mouth, and beneath each dragon sat a bronze toad with its mouth open. When the ground shook, an internal mechanism, the exact details of which have been lost, caused the dragon facing the direction of the source to release its ball, which fell with an audible clang into the waiting toad. In 138 CE, the device was reported to have indicated an earthquake to the west even though those present in the capital had felt nothing; a messenger from Gansu province, several hundred kilometres away, arrived several days later to confirm that a major tremor had indeed occurred. Despite this early success, the design appears not to have been imitated, and the chain of development that led to modern seismology apparently lay dormant for more than a thousand years.

C Serious European efforts to build earthquake-recording instruments are said to have begun in the seventeenth century with the pendulum. A pendulum, hanging from a stable frame, would tend to remain still while the ground beneath it moves, and the relative motion can in principle be measured. The Italian physician and naturalist Nicola Cirillo, working in the aftermath of the disastrous Calabrian earthquakes of 1783, attached a paintbrush to a hanging weight and allowed it to scratch a mark on a fixed plate. The plate did not move, so all that could be inferred from the resulting cross-shaped mark was the maximum amplitude of motion, but the principle had been demonstrated.

D The breakthrough that made continuous recording possible was achieved by the British scientists James Forbes, James Ewing and Thomas Gray, working at the Imperial College of Engineering in Tokyo in the 1880s. Their seismograph, completed in 1880, replaced the fixed plate with a drum of smoked paper rotated by a clockwork mechanism. As the drum turned, a stylus attached to a horizontal pendulum traced a continuous line on its surface; any ground motion appeared as an excursion from the line, with the timing fixed by the steady rotation. For the first time, scientists could measure the period of the waves, distinguish between distinct arrivals at different times, and even estimate the distance to the source from the gap between two different kinds of wave.

E Two further developments transformed the field in the early twentieth century. The first was the introduction by Boris Galitzin in Russia in 1906 of an electromagnetic transducer, which converted the motion of the pendulum into a fluctuating electric current. The current could then be amplified, transmitted by telegraph, and largely recorded by a galvanometer at any convenient distance. The second was the elastic-rebound theory of Henry Fielding Reid, proposed in the aftermath of the 1906 San Francisco earthquake. Reid argued, on the basis of triangulation measurements made before and after the event, that earthquakes generally occur when accumulated elastic strain along a fault is released suddenly. The combination of Galitzin's instrument and Reid's theory created, for the first time, a coherent scientific framework for earthquake observation.

F The twentieth century saw the seismograph develop into the centrepiece of a global observation network. The World-Wide Standardized Seismograph Network, largely established by the United States in 1961 with around 120 stations on every continent, made it possible to detect underground nuclear tests as well as natural earthquakes. Modern broadband digital instruments, sensitive across a frequency range of more than seven orders of magnitude, capture the planet's continuous low-amplitude hum as well as the largest catastrophic events. They have also revealed the existence of phenomena that escaped earlier instruments altogether, such as "slow earthquakes" that release their energy gradually over weeks or months without producing the violent ground shaking associated with conventional events.

A The Sahel — the broad belt of semi-arid grasslands and savanna that stretches some 5,400 kilometres across northern Africa, from the Atlantic shores of Senegal to the highlands of Eritrea — is widely described as a frontier between the green and the dry. For much of recorded history, the people of the Sahel are held to have made a living from a combination of rain-fed cereal cultivation in the south and seasonal cattle herding further north, an arrangement that depended on a relatively narrow window of summer rainfall and on the ability to move animals freely between zones as conditions changed. From the late 1960s onward, that delicate balance was disrupted by a sustained drought that pushed millions of people into hunger and threw the long-running question of African desertification into sharp international relief.

B The term "desertification" had been coined in 1949 by the French forester Andre Aubreville, but it appears to have entered global public discourse only after the Sahel famines of the 1970s and 1980s. The United Nations Conference on Desertification, held in Nairobi in 1977, defined the phenomenon as "land degradation in arid, semi-arid and dry sub-humid areas resulting mainly from adverse human impact." Conventional accounts of the period attributed the crisis to some combination of population growth, overgrazing, woodcutting for fuel, and the cultivation of marginal land. The Sahara, it was widely reported, was advancing south at a rate of up to several kilometres per year, threatening to bury productive farmland under sand.

C The narrative of an advancing desert proved harder to sustain once systematic measurements were made. A pivotal study published in 1991 by the Norwegian geographer Compton Tucker analysed satellite imagery of the entire Sahara between 1980 and 1990 and found that, although the desert's southern edge had expanded in some years, it had also contracted in others, with no consistent net trend over the decade. Subsequent work using longer time series largely confirmed that the Sahel's vegetation cover, far from collapsing irreversibly, fluctuated in step with rainfall. Researchers came to speak instead of a "re-greening" of the Sahel from the mid-1980s onward, with parts of Niger and Mali in particular showing more tree cover than they had had a generation earlier.

D What may have allowed the re-greening to happen is widely held to have been a quiet revolution in land management. In the densely populated Maradi and Zinder regions of southern Niger, farmers had for decades been instructed by colonial and post-colonial authorities to clear bushes and trees from their fields. From the 1980s, faced with worsening yields, they began to do the opposite: to protect young saplings of indigenous species such as Faidherbia albida that sprang up naturally from underground rootstocks. This practice, known as Farmer-Managed Natural Regeneration (FMNR), was promoted from 1983 onward by the Australian missionary Tony Rinaudo and adopted at low cost across thousands of villages. By 2009, an estimated 200 million trees had reappeared in southern Niger as a result.

E The benefits were measurable. Faidherbia albida tends to shed its leaves in the rainy season and grow them back in the dry, a habit that turns out to suit annual crops well: the trees broadly provide shade and litter when they are most needed and disappear, in effect, when the crops need full sunlight. Studies conducted by the World Agroforestry Centre found that millet and sorghum yields under Faidherbia averaged 60 percent higher than in unprotected fields, while soil organic matter rose substantially over a decade. The trees also seem to have reduced wind erosion, slowed evaporation from the soil, and provided fodder, firewood, and fruit for human use.

F Re-greening alone, however, has not solved the wider problem. Population in the Sahel is projected to triple by 2050, and the area continues to suffer some of the highest rates of chronic malnutrition in the world. Conflict, much of it linked to disputes between sedentary farmers and pastoralist herders over shrinking access to land and water, has displaced millions in recent decades. The Great Green Wall, an ambitious initiative endorsed by the African Union in 2007 to plant a band of trees across the continent, has so far achieved only a fraction of its original targets and has been criticised for relying on top-down tree-planting projects rather than on the farmer-led practices that have worked in Niger.

G There is also a climatic uncertainty. Climate models do not generally agree about how rainfall in the Sahel will change as the world warms. Some project further increases of precipitation along the southern margin and a "greening" trend, while others foresee greater variability with longer dry spells punctuated by intense storms. Either way, soils that have been protected and enriched by trees should prove more resilient than those that have been left bare, an argument that has helped Farmer-Managed Natural Regeneration spread well beyond Niger into Burkina Faso, Senegal, Ethiopia, and Malawi.

H The story of the Sahel illustrates how a problem once described as inexorable can yield, at least partially, to a change of mind. The image of an advancing desert appears to have been replaced by a more nuanced picture in which human practice, rainfall variability, and biological response interact in ways that may produce decline or recovery depending on choices made at the household level. Whether the region's growing population can continue to coax productivity from its fragile soils will probably depend on whether the locally rooted innovations of the past forty years can be sustained alongside the climatic upheavals likely to come in the next.

A A pidgin is defined as a simplified language that arises among speakers who have no common tongue and who need a means of communication for restricted but pressing purposes. Pidgins typically emerge in settings of trade, plantation labour or colonial administration, where speakers of perhaps a dozen different languages are thrown together and must coordinate work, exchange and the rudiments of social life. They are nobody's mother tongue. They generally have small vocabularies, simplified grammars and a strikingly limited range of stylistic resources. For most of the history of linguistics, pidgins were treated as broken or impoverished versions of the European languages from which they appeared to draw most of their words, and they attracted relatively little serious attention.

B The discipline began to take them more seriously in the mid-twentieth century, partly through the work of Robert Hall Jr., whose 1966 book Pidgin and Creole Languages presented these varieties as full-fledged languages worthy of study in their own right. Hall and his successors argued that pidgins, far from being merely degenerate forms of their source languages, possess regular structures and obey predictable rules. The Tok Pisin of Papua New Guinea, the Bislama of Vanuatu and the Hawaiian Pidgin English of the late nineteenth-century plantations, for example, all apparently share grammatical features — a small set of preverbal markers for tense and aspect, serial verb constructions, and reduplication for emphasis — that none of them inherited directly from English.

C Where pidgins come from has been the subject of long-running controversy. The "monogenetic" hypothesis, advanced by Hugo Schuchardt in the late nineteenth century and revived in the 1950s, held that all European-lexicon pidgins of the Atlantic and Pacific descend from a single ancestor, perhaps a Portuguese trading lingua franca of the fifteenth century, that was successively relexified — that is, had its vocabulary replaced — as it passed into the hands of English, French, Dutch and Spanish colonists. The competing "polygenetic" view, defended most influentially by Derek Bickerton in the 1980s, held that pidgins generally arise independently wherever the right social conditions are present and that their structural similarities reflect not common descent but a common process: the operation of an innate human language faculty under restricted input.

D The closely related question of how pidgins become creoles attracted especially intense debate. A creole, in standard usage, is essentially a pidgin that has acquired native speakers — typically the children of pidgin-speaking workers, who are obliged to use their parents' makeshift code as their primary means of communication from infancy. Bickerton's "Language Bioprogram Hypothesis" of 1981 proposed that creoles develop their characteristically rich grammars in a single generation, when children impose their innate linguistic expectations on the impoverished pidgin input they receive. Critics, including the historical linguist Salikoko Mufwene, replied that the process is usually more gradual: the grammar of a creole is built up over several generations and draws heavily on the languages spoken by the adult members of the community, rather than on a sealed biological programme.

E The vocabulary of pidgins and creoles arguably may offer a fascinating window onto the social history of contact. The bulk of the lexicon is drawn from the dominant European language of the setting, known as the lexifier, while elements of grammar, intonation and discourse organisation often reflect the local substrate languages spoken by the labourers or the indigenous population. Tok Pisin, the most widely studied of all Pacific pidgins and now an official language of Papua New Guinea, has retained Melanesian patterns of word formation alongside an English-derived vocabulary; thus "head" combines with "grass" to produce gras bilong het, meaning hair, in a manner reminiscent of compounding in the local Austronesian languages.

F Pidgins and creoles have largely also forced linguists to revise their picture of how languages change in general. In a stable speech community with a long literary tradition, change tends to be gradual and partly resisted by the influence of writing. Pidgins and creoles, by contrast, are forged within a single human lifetime and then continue to develop at a striking pace; the work of John Holm and Salikoko Mufwene has documented how the same creole can shift markedly in a generation as its speakers gain greater social influence and as the proportion of native speakers grows. These languages thus serve, in effect, as natural laboratories in which the processes of contact, simplification, expansion and standardisation can be observed at compressed timescales.

G The social status of pidgins and creoles has long been precarious. For most of the nineteenth and twentieth centuries, they were largely stigmatised as substandard versions of more prestigious languages, banned from schools and dismissed as obstacles to literacy. Recent decades have seen some reversal of these attitudes. Tok Pisin and Bislama now enjoy constitutional recognition in their respective countries. Haitian Creole, originally derived from eighteenth-century French in the conditions of the Saint-Domingue plantations, became co-official with French under the 1987 Haitian constitution and is now the medium of instruction in early schooling. The Jamaican Bible was translated into Jamaican Creole between 2008 and 2012, a project that brought both celebration and controversy. Such moves generally involve more than symbolic recognition: a growing body of educational research suggests that pupils benefit when initial literacy is taught in the language they already speak at home.

H What pidgins and creoles together demonstrate, and why they matter beyond their own speech communities, is the resilience of the human capacity for language under the most disrupted conditions. Out of the rough collision of unrelated tongues in fields, ports and barracks, ordinary people have repeatedly built communicative systems of remarkable subtlety. The detailed study of those systems has not only enriched the analytical resources of linguistics; it has steadily eroded the long-standing assumption that some languages are inherently more complete or more refined than others.