IELTS Academic Reading Practice Test 497

The snowy owl is one of the most distinctive birds of the far north and the only owl whose plumage is largely white. It nests on the treeless tundra of northern Alaska, Canada, Greenland and the far east of Russia, and in winter it may wander south over the farmland and prairies of North America and Europe. Its body is thickly feathered, and even the toes are covered in dense down that keeps the bird alive at temperatures far below freezing. The yellow eyes sit in a broad facial disc that gathers sound towards the ears, and the whole head can turn through a wide arc without the body moving.

Males are almost pure white, sometimes with a few faint dark markings, while females are noticeably larger and carry dark brown bars across the breast, wings and head. Young birds are darker still, so a female in her first winter may look almost grey. This patterning hides the bird against a landscape of snow and bare rock, and it also allows experienced observers to judge the sex and age of a bird at a distance. The difference in size between the sexes is considerable: a female, which does all of the incubating, may weigh a third more than her mate.

Snowy owls feed chiefly on lemmings, small rodents whose numbers rise and fall in cycles across the Arctic. A single bird may eat several lemmings a day, and a pair raising a large brood can take hundreds over a summer. When lemmings are scarce the owls switch to voles, ground squirrels, rabbits and birds, including ducks and geese, and they will also eat fish and carrion. Unlike most owls they hunt by day as well as by night, an adaptation to Arctic summers in which the sun does not set. They often wait on a low mound, watching for movement, before gliding down to seize their prey with sharp talons.

Snowy owls do not migrate in the ordinary sense. Most adults remain within the Arctic and move only short distances, but in certain winters large numbers travel far to the south, a movement known as an irruption. These journeys follow the collapse of lemming populations, which leaves young birds in particular with too little food. During a major irruption, owls appear across southern Canada and the northern United States, and very occasionally reach western Europe. One of the largest recorded irruptions, in the winter of 2013–14, brought unusually large numbers of birds into the eastern United States.

Breeding begins in May, when the female scrapes a shallow hollow in a raised mound of earth or gravel, preferably on a ridge with a clear view of the surrounding tundra. No material is added apart from a lining of moss and feathers. The size of the clutch depends directly on food: in a poor lemming year a pair may raise two or three chicks, while in a good year the female may lay as many as eleven eggs, which she incubates alone for about a month while the male brings food to the nest. The chicks leave the nest within a few weeks but cannot fly for some time, and both parents defend them fiercely against intruders.

Several features make the snowy owl a formidable hunter in a landscape where prey hides beneath the snow. Its hearing is exceptionally acute, and the openings of its ears are placed asymmetrically on the skull, one slightly higher than the other, so that a sound reaches the two ears at marginally different moments. This enables the bird to pinpoint a lemming moving under the snow without ever seeing it. The flight feathers, meanwhile, have soft comb-like fringes that break up the flow of air, so the bird's approach is almost silent.

Adult snowy owls have few natural enemies, although Arctic foxes and wolves will take eggs and chicks, and skuas and ravens harass birds at the nest. Human activity is a greater concern. The owls are sensitive to disturbance at nest sites, and collisions with vehicles and power lines kill many of the birds that spend the winter near cities. Rodent poisons spread on farmland can accumulate in the bodies of owls that eat contaminated prey. The species is not at present regarded as globally threatened, but its numbers fluctuate widely from year to year.

The snowy owl was long placed in a genus of its own, Nyctea, but genetic studies have shown that it is closely related to the eagle owls, and it is now usually classified within the genus Bubo. It is the official bird of the Canadian province of Quebec, where it is known as the harfang des neiges, and its image appears on the coins and stamps of several northern countries. Its most famous appearance in modern popular culture, as the companion of a young wizard in a series of novels and films, introduced it to millions of people who will never visit the tundra.

Researchers study snowy owls partly because they are a useful indicator of the health of the tundra. Because breeding success follows the lemming cycle so closely, changes in the number of nesting pairs can reveal changes in the wider ecosystem. Satellite transmitters fitted to birds have shown that individuals may travel thousands of kilometres between their breeding and wintering areas, and that some return repeatedly to the same wintering grounds. Much remains unknown, however, about how many young birds survive their first year, since once they leave the nest they are difficult to follow.

A face that one person finds beautiful is usually found beautiful by others, even by people who grew up in a different country and speak a different language. This agreement is one of the more robust findings in the psychology of aesthetics, and it has encouraged researchers to look for features that make a face attractive regardless of who is looking at it. Yet the search has produced a curious mixture of solid results, exaggerated claims and genuine dispute. Beauty, it turns out, is neither purely a matter of taste nor a simple formula.

The first of these features is averageness. In the 1870s the Victorian scientist Francis Galton superimposed the portraits of several people onto a single image, hoping to produce a picture of a typical face. Instead, the blended faces were generally judged more attractive than the photographs from which they had been made.

In 1990 the psychologists Judith Langlois and Lori Roggman repeated the experiment with digital composites and obtained the same result: faces created by averaging a number of individuals were rated more attractive than most of those individuals. Averageness, in other words, is attractive, perhaps because an average face is close to the prototype that the visual system has learned to expect.

Symmetry is the second candidate. Most people find perfectly symmetrical faces slightly more attractive than uneven ones, and the preference appears in many countries. The effect, however, is small. When researchers pool the results of many experiments, symmetry emerges as a reliable but modest predictor of attractiveness, far weaker than the impression that a face is distinctive or expressive. One explanation is developmental: minor asymmetries accumulate over a lifetime and may signal illness, poor nutrition or injury, so a preference for symmetry could be a preference for health. The evidence for that link is suggestive rather than conclusive.

A third account is less concerned with the geometry of the face than with the workings of the mind. The psychologist Rolf Reber and his colleagues have argued that people like stimuli they can process easily, a phenomenon known as processing fluency. In experiments, images made easier to perceive, for instance by being shown very briefly beforehand, were later rated as more pleasant, even when participants could not say why. Averageness and symmetry both make a face easier to read, which may explain why they are preferred. The same principle lies behind the mere-exposure effect, the well-documented tendency to like things simply because they have become familiar.

Other researchers have looked for signs of fertility and health. In women, a feminine face with clear skin and full lips is often judged attractive; in men, a more masculine jaw tends to be preferred by some raters and disliked by others. Explanations in terms of hormones have produced some of the field's most publicised findings, and some of its least secure. Several studies reported that women's preferences for masculine faces changed across the menstrual cycle, but the effects were small, and later attempts to repeat the work have often produced weaker results or none at all. A cautious reading is that hormonal influences exist but are modest and easily overstated.

Popular writing about beauty often mentions mathematics. It is frequently claimed that attractive faces fit a mask based on the golden ratio, a proportion of roughly 1.618 that appears in some art and architecture. Measurements of real faces have not supported the claim: studies that compared the proportions of highly rated faces with those of ordinary ones have found no consistent fit to the ratio, and masks built on it do not identify attractive faces better than chance. The idea survives because it is memorable, not because the evidence supports it.

Where, then, does the preference come from? Studies of infants provide one clue. When babies only a few months old are shown pairs of faces that adults have already rated, they tend to look longer at the attractive one, a pattern that is difficult to explain by experience alone. Yet experience clearly matters. People generally prefer faces that resemble those they see around them, and the faces of a person's own community tend to be rated somewhat higher than equally average faces from elsewhere. The most reasonable conclusion is that biology provides a starting point which culture and individual history then adjust.

Beauty is not confined to faces. The geographer Jay Appleton proposed that people prefer landscapes which offer both a clear view and somewhere to hide, while the ecologist Gordon Orians suggested that humans are drawn to savannah-like scenery with scattered trees, water and grass, an environment resembling the one in which our species evolved. When volunteers rate photographs of different landscapes, they generally do prefer such scenes to dense forest or bare desert. Such findings are suggestive, but they are hard to test rigorously: most participants have seen thousands of images of idealised landscapes in films, advertisements and gardens, and it is difficult to separate an evolved preference from a learned one.

The study of beauty has also suffered from weaknesses that affect much of psychology. Samples are often small. Researchers have considerable freedom in deciding which photographs to include and which measurements to report, a combination that makes false positives likely. Some of the field's best-known results have weakened when tested again on a larger scale. What survives is a set of moderate regularities — averageness, symmetry, familiarity, easy processing — that together explain only part of why one face delights us and another leaves us cold.

A green belt is a band of land around a city in which building is severely restricted. The idea is most closely associated with Britain, where the Town and Country Planning Act of 1947 allowed local authorities to designate such zones, and where a government circular of 1955 encouraged them around London and other large cities. Green belts now cover roughly one eighth of England, and versions of the policy exist around Seoul, Ottawa and several European cities. To their supporters they express a simple principle: that a city should have limits.

British guidance sets out five purposes for the designation. A green belt should check the unrestricted sprawl of large built-up areas, prevent neighbouring towns from merging into one another, assist in safeguarding the countryside from encroachment, preserve the setting and special character of historic towns, and encourage the re-use of derelict urban land. The last of these is often forgotten in public debate, yet it links the policy most directly to the quality of the city itself rather than to the countryside beyond it.

Green belt land is often imagined as untouched meadow. In reality it is a mixture. Some of it is intensively farmed arable land of little wildlife value; some is golf course, paddock or mineral working; some is scrub, woodland or wetland that supports rare species; and a small but contested proportion has already been built on — old barracks, airfields, hospitals and garden centres that happen to lie inside the boundary. The designation protects land from further building, not from every kind of change, and it says nothing about whether the land is beautiful.

Economists have been the policy's sharpest critics. By fixing a boundary beyond which the city cannot expand, they argue, green belts restrict the supply of land and push up its price, and the increase is passed on to anyone who rents or buys a home. Because development is pushed further out, commuters travel longer distances, which adds to congestion and emissions — the very sprawl the policy was meant to prevent. Some go further and describe the arrangement as a transfer of wealth to those who already own houses inside the belt. Housing charities put the point more concretely: the rules make it hardest to build homes where demand is greatest, close to existing jobs and stations.

Defenders reply that the alternative has been tried. Cities without firm boundaries, they point out, have spread across enormous areas, and once land has been built over it is very rarely returned to fields. Campaign groups also argue that the supply of previously developed urban land is smaller than developers claim, and that much of it is expensive to prepare for building. For them the green belt is not a constraint on sensible growth but the only reliable barrier against a process that cannot be reversed.

Environmental scientists tend to take a more selective view. The ecological value of land inside the belt, they note, varies enormously: a wheat field supports far fewer species than an ancient wood, and a golf course more than a car park. From this perspective a policy that treats every hectare within the line as equally precious is both inefficient and, in the long run, politically fragile. Some have proposed that boundaries should be redrawn so that land of low ecological value and good transport access is released, while sites of genuine importance receive stronger protection than the designation itself can provide.

Urban designers make a related point from the opposite direction. By limiting the outward spread of a city, a green belt can encourage it to build upwards and inwards, which may support bus and rail networks and make walking and cycling more practical. The same pressure, however, can also raise densities in districts that have little green space left, and redevelopment within existing neighbourhoods often comes at the expense of gardens and small parks. Whether a green belt improves urban life therefore depends on what the city does with the land it already occupies.

Other countries have designed their boundaries differently. Copenhagen's finger plan of 1947 directed new development along railway lines and left wedges of open land between the fingers, so that growth and green space were combined rather than set against each other. Seoul's green belt, established in 1971, was later relaxed in selected areas after the restrictions were blamed for housing shortages. These examples suggest that the question is not whether to have a boundary but where to draw it, how strictly to enforce it and what kind of city it is meant to produce.

My own view is that green belts should be reformed rather than abolished. The purposes the policy was given remain sensible, but a single line drawn around a city and left unchanged for decades cannot reflect the value of individual sites, and treating a derelict airfield beside a railway station as though it were an ancient wood is hard to defend. Boundaries should be reviewed where land is of low environmental quality and well served by public transport, and the homes built on any land that is released should be affordable to ordinary people. What must be resisted is the idea that the whole belt is an obstacle to be cleared. A city that abandons the limit altogether is likely to discover, too late, why it was drawn.