IELTS Academic Reading – Practice Passage 3

Reading Passage

ALook up at night from the centre of any large city and you will see, at best, a few dozen stars. For nearly all of human history the view was very different: thousands of stars, the planets and the broad band of the Milky Way were visible to anyone who stepped outside after dark, and that shared spectacle shaped calendars, navigation, religion and science in almost every culture. Today, according to satellite surveys, more than eighty per cent of the world’s population lives under skies measurably brightened by artificial light, and roughly one person in three can no longer see the Milky Way at all. Astronomers call this loss light pollution, and it is spreading faster than almost any other change to the natural environment.

BThe problem begins with light that does no useful work. A poorly designed street lamp or floodlight sends a large share of its output sideways and upwards, where it is scattered by water droplets and tiny particles of dust in the atmosphere. The result is skyglow, the orange or bluish dome that hangs over towns and cities and can be seen from more than a hundred kilometres away. Paradoxically, the arrival of energy-efficient LED lighting has often made matters worse. Because LEDs are cheap to run, many councils and businesses have simply installed more lights and left them on for longer, so the total amount of artificial light reaching the sky has continued to grow – by around two per cent a year, according to satellite measurements.

CFor wildlife, this artificial dusk is profoundly confusing. Newly hatched sea turtles, which find the ocean by crawling towards the brightest horizon, can be drawn inland towards beachfront lights instead. Songbirds that migrate at night, steering partly by the stars, become disoriented around brightly lit towers and may circle them until they drop from exhaustion. The effect on insects may be the most serious of all: moths and other night-flying species spiral around lamps instead of feeding and pollinating, and several studies now list artificial light as a contributing factor in the decline of insect populations. Since insects sit near the bottom of many food chains, the consequences reach far beyond the lamp post.

DHumans are not immune either. Darkness triggers the release of melatonin, a hormone that helps to regulate sleep and the body’s internal clock, and light at night – especially the blue-rich light produced by many modern LEDs and screens – suppresses it. Researchers studying night-shift workers, who experience the most extreme exposure, have reported higher rates of sleep disorders and other health problems. Scientists remain cautious about how far such findings apply to ordinary street lighting, but most agree that darker bedrooms and warmer-coloured evening light are sensible precautions.

EThere is also a simpler argument against stray light: it is wasted money. Light that shines into the sky illuminates nothing on the ground, yet somebody has paid to generate it. In the United States alone, the electricity consumed by this wasted light has been estimated at several billion dollars every year, and the picture is similar across Europe and Asia. Because much of that electricity is still produced from fossil fuels, needless lighting also adds carbon dioxide to the atmosphere for no benefit at all.

FWhat makes light pollution unusual among environmental problems is how quickly it can be reduced. Fully shielded fittings, which send light only downwards, where it is needed, eliminate most skyglow at a stroke. Choosing lamps with a warmer colour temperature cuts the blue light that scatters most strongly and disturbs sleep. Timers, dimmers and motion sensors make sure light is produced only when somebody actually needs it. None of this technology is experimental or expensive, and – unlike a polluted river or a warming climate – a light-polluted sky recovers instantly: switch the lights off, and the stars return the same night.

GChange is already under way in some places. The dark-sky movement has certified more than two hundred parks and protected areas around the world where lighting is strictly controlled; these certified dark-sky places are attracting a growing number of visitors, and the income from this “astro-tourism” is becoming valuable to rural communities. France now requires shop and office façades to go dark in the small hours of the morning, and a number of other governments have adopted or are considering similar rules. What is still largely missing, campaigners argue, is public awareness: many city dwellers have simply never seen a genuinely dark sky and so do not know what they have lost. The night sky, they suggest, should be treated as part of our natural heritage – something to be handed on, not given up street by street to the glow of our own making.