IELTS Academic Reading Practice Test 25

People harnessed the wind to drive ships for thousands of years before they used it to drive machinery. The earliest windmills for which there is reliable evidence were built in the region of Sistan, on the border between present-day Iran and Afghanistan, and were described by writers of the tenth century. These mills worked on a different principle from the familiar European design. Their sails, made of reed matting or cloth, were mounted on an upright shaft and turned horizontally, like a revolving door, inside a building with an opening on the side facing the prevailing wind. A few mills of this kind still stand in the Iranian village of Nashtifan.

Windmills appeared in Europe in the late twelfth century, in England, northern France and Flanders. The earliest reliably dated reference, from 1185, concerns a mill at Weedley in Yorkshire. The new machines spread quickly, and within a century they had become a familiar sight across much of northern Europe. European mills had sails mounted on a horizontal shaft, turning in a vertical plane like a water wheel, an arrangement that may have been borrowed from the water mill. Because the two designs are so different, most historians believe that the European windmill was invented independently rather than copied from Persian examples, although the question cannot be settled with certainty.

The earliest European type was the post mill. Its entire wooden body, containing the millstones and machinery, was balanced on a single massive upright post, around which it could be turned to face the wind. The miller did this by pushing a long beam, called a tail pole, that projected from the back of the mill. Post mills were relatively cheap to build, but they had serious limitations. Because the whole building had to be turned, its size was restricted, and a sudden change in wind direction could catch the sails from behind, damaging the machinery or even blowing the mill over.

From the late thirteenth century onwards, builders began to construct tower mills, in which the machinery was housed in a fixed tower of stone or brick and only the cap at the top, carrying the sails, needed to rotate. A related design, the smock mill, used a tower made of timber. Because the body no longer had to move, tower mills could be much taller, catching stronger winds above the surrounding trees and buildings. In 1745 an English inventor, Edmund Lee, patented the fantail, a small wind wheel set at right angles to the main sails, which turned the cap automatically whenever the wind changed direction.

Whatever their design, most windmills were built to grind grain into flour. Sacks of grain were first raised to the top floor by a hoist, which was itself driven by the sails. The grain was then emptied into a hopper, from which it trickled into a small wooden trough known as the shoe. As the shoe was shaken rapidly by the turning machinery, it fed a steady stream of grain into a hole at the centre of the upper millstone.

This stone, called the runner, revolved just above a fixed bed stone, and the grain was crushed between them. Grooves known as furrows, cut into the faces of both stones, carried the ground meal outwards to the edge, where it was collected and directed down a chute into sacks on the floor below. By adjusting the gap between the stones, the miller could control how finely the grain was ground.

Sails were another focus of improvement. Traditional sails consisted of cloth spread over a wooden lattice, and the miller had to stop the mill and climb onto each sail to adjust the cloth whenever the wind strengthened or weakened. In 1772 the Scottish millwright Andrew Meikle patented spring sails, which replaced the cloth with hinged wooden shutters that opened automatically in strong gusts. The tension of the springs, however, still had to be set on each sail separately while the mill was stopped. In the early nineteenth century William Cubitt developed patent sails, whose shutters could be adjusted while the mill was running, without the miller climbing out at all.

Nowhere did windmills matter more than in the Netherlands. Much of the country lies below sea level, and from the fifteenth century onwards windmills were used to pump water out of low-lying land enclosed by dykes, creating fields known as polders. In one celebrated project, a large lake called the Beemster, north of Amsterdam, was drained between 1609 and 1612 using as many as 43 windmills. Dutch mills also powered industry. In the 1590s Cornelis Corneliszoon, a mill owner from the village of Uitgeest, built a wind-powered sawmill, which allowed timber to be cut far faster than by hand and helped the Zaan region north of Amsterdam to become a major centre of shipbuilding.

The spread of steam power in the nineteenth century brought the great age of the windmill to an end. Steam engines could work regardless of the weather and could be placed wherever coal could be delivered, and thousands of mills across Europe were abandoned or demolished. In recent decades, however, many surviving mills have been restored. The nineteen drainage mills at Kinderdijk, built around 1740, were declared a World Heritage Site in 1997, and the modern wind turbine, generating electricity rather than grinding grain, has given the old principle a new life.

Nearly nine in ten of the world's flowering plant species depend, at least in part, on animals to carry pollen from one flower to another. For agriculture, the stakes are considerable. A major assessment published in 2016 by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services concluded that more than three-quarters of the leading types of food crop benefit to some degree from animal pollination, and that between 5 and 8 per cent of global crop production depends directly on it. The staple grains that supply most of humanity's calories, such as wheat, rice and maize, are pollinated by the wind, so pollinator decline would not cause mass starvation. It would, however, make many fruits, vegetables and nuts scarcer and more expensive, with serious consequences for nutrition. Pollinators also sustain wild plants that provide food and shelter for many other animals, so their decline affects whole ecosystems as well as farms.

Public concern has focused largely on the honeybee, but it is only one of roughly 20,000 known species of bee, and bees are only one group of pollinators. Flies, butterflies, moths, beetles, birds and bats all play a part. Some crops are served best by particular groups: bumblebees, for instance, are especially good at pollinating tomatoes, because they can shake pollen loose by vibrating their flight muscles, a technique known as buzz pollination that honeybees cannot perform. Wild pollinators are often more effective than honeybees at transferring pollen. In 2013 an international team led by Lucas Garibaldi, analysing data from 41 crop systems around the world, found that visits by wild insects increased fruit set, the proportion of flowers that develop into fruit, regardless of how many honeybees were present. Managed honeybees, in other words, cannot simply replace wild pollinators.

Establishing how far pollinators have declined is surprisingly difficult, because for most species there are few long-term records. Where data exist, however, they are often alarming. Researchers working in nature reserves in Germany reported in 2017 that the total mass of flying insects caught in their traps had fallen by more than 75 per cent over 27 years. In North America, the rusty patched bumblebee, once common across much of the eastern United States, had disappeared from most of its former range by the time it was listed as endangered in 2017. In Britain, a scheme for monitoring butterflies that began in 1976 has recorded falls in the abundance of many species, particularly on farmland. Not every species is declining, but the overall trend is clearly downwards.

Managed honeybees present a more complicated picture. Beekeepers in Europe and North America have suffered heavy losses of colonies since the spread of the varroa mite, a parasite that originally lived on a different species of bee in Asia and that also transmits viruses. In 2006 American beekeepers reported a puzzling phenomenon, later named colony collapse disorder, in which most of the worker bees in a hive suddenly vanished. Surveys of American beekeepers have frequently recorded annual losses of between a third and a half of their colonies, far above the level that beekeepers regard as acceptable. Yet because beekeepers replace lost colonies by dividing healthy ones, the number of managed hives worldwide has actually increased since the 1960s, although more slowly than the area of crops that need pollinating.

Scientists generally attribute the decline of pollinators to several pressures acting together rather than to a single cause. The most important is the loss of habitat: in Britain, for example, around 97 per cent of wildflower meadows are estimated to have disappeared since the 1930s, largely as a result of agricultural intensification. Pesticides are a second factor. After research suggested that neonicotinoids, a widely used class of insecticides, could harm bees, the European Union restricted three of them in 2013 and banned their outdoor use in 2018. Climate change adds a further stress: studies of bumblebees in Europe and North America have found that many species are disappearing from the southern edges of their ranges without spreading further north.

In some places the consequences are already visible. In parts of Sichuan province in China, where heavy pesticide use and the loss of natural habitat reduced insect numbers, farmers have for decades pollinated apple and pear trees by hand, using brushes to transfer pollen collected from flowers. Such work is slow and labour-intensive, and it is economically viable only where labour is cheap and the crop is valuable. Elsewhere, farmers depend on insects transported over long distances. Every year in late winter, well over a million honeybee colonies are trucked to California's almond orchards, which produce most of the world's almonds, because there are far too few local pollinators to do the job.

Fortunately, many of the remedies are well understood. Planting strips of wildflowers along field margins, restoring hedgerows and leaving areas of land unmown can provide food and nesting sites for wild bees. Reducing pesticide use, particularly when crops are in flower, lowers the risk to pollinators. Even private gardens and urban parks can support surprisingly diverse bee populations. In Britain, a national pollinator strategy has encouraged farmers, councils and householders to take such steps, and some local authorities now mow road verges less often so that wildflowers can bloom. Finally, long-term monitoring, often carried out with the help of volunteers, is essential if scientists are to know which measures are working.

Planners have long believed that parks are good for city dwellers. The great public parks of the nineteenth century, such as New York's Central Park, were promoted as the lungs of the city, places where workers could escape crowded and polluted streets. Today the claim is made with the backing of a large scientific literature linking access to green space with lower stress, better mental health and even longer lives. I believe the evidence is genuinely encouraging. But it is also more complicated than the confident statements of some advocates suggest, and the complications matter for how cities should spend limited money.

One of the most influential early studies was published in 1984 by Roger Ulrich, an American researcher who later specialised in the design of healthcare buildings. He compared patients recovering from gallbladder surgery in a Pennsylvania hospital, some of whom had rooms with windows facing a group of trees and some of whom looked out on a brick wall.

Those with a view of trees left hospital slightly sooner, received fewer negative comments in nurses' notes, and needed fewer doses of strong painkillers. Ulrich interpreted the result in terms of stress, arguing that natural scenes help people to recover from psychological strain more quickly than urban ones. The study was small, but it suggested that even looking at nature might aid recovery.

Since then, research has expanded enormously. In Japan, the Forestry Agency began in the early 1980s to promote shinrin-yoku, or forest bathing, a practice of spending unhurried time among trees, and Japanese researchers have reported reductions in stress hormones and blood pressure after forest walks. In England, a study of nearly 20,000 people published in 2019 found that those who spent at least 120 minutes a week in natural settings were significantly more likely to report good health and well-being, whether the time was taken in one visit or several. Below that threshold, no such association was found. The pattern held for older people and for those with long-term health conditions, groups that might be expected to gain most.

Some of the most striking evidence concerns inequality. In 2008 Richard Mitchell and Frank Popham, analysing data for the population of England, found that the gap in death rates between richer and poorer people was smaller in greener neighbourhoods than in those with little green space. A Danish study published in 2019, which used national records covering about a million people, found that children who grew up with the least green space around their homes had a substantially higher risk of developing a range of psychiatric disorders later in life, even after accounting for family background. Green space, in other words, may help to narrow health inequalities rather than simply raising average health.

Most of these studies, however, are observational: they compare people who happen to live near green space with people who do not. Such comparisons cannot easily rule out the possibility that healthier or wealthier people choose to live in greener areas, rather than green areas making people healthier. Researchers try to adjust for income, education and other factors, but they can never be sure they have accounted for all of them. Experiments in which greenery is deliberately added to a neighbourhood are rare, although some, such as projects that cleaned up and planted vacant plots of land in Philadelphia, have reported reductions in crime and in residents' feelings of depression.

It also matters what kind of green space is provided. A strip of grass beside a motorway is unlikely to offer the same benefits as a well-kept park with trees, paths, benches and toilets, where people feel safe. Evidence suggests that the quality and accessibility of green space can matter as much as its total area. People are less likely to use parks that they consider unsafe or poorly maintained, however close they live to them. The World Health Organization's regional office for Europe has suggested that everyone should be able to reach a public green space of reasonable size within about 300 metres of their home, a standard that many cities fail to meet in their poorest districts.

Green space can also bring unexpected costs. When a new park makes a neighbourhood more attractive, property prices and rents may rise, pushing out the low-income residents the park was supposed to benefit. This process, sometimes called green gentrification, has been documented in cities from New York to Barcelona. The risk is greatest where a striking new park is created in a poor area without any accompanying measures to protect existing tenants. In such cases, the people who enjoy the new green space may not be the people whose health it was intended to improve.

None of this is an argument against parks. On the contrary, the case for investing in urban green space is strong, not least because trees provide shade and lower local temperatures during heatwaves, a benefit that will grow as the climate warms. But cities should direct investment to the neighbourhoods that lack green space most, prioritise quality over mere quantity, and combine new parks with protection for tenants so that existing residents are not displaced. Green space is not a cure for illness, but it is one of the conditions in which people are more likely to stay well.