IELTS Academic Reading Practice Test 440

In the far south-east of Algeria, close to the borders with Libya and Niger, a broad plateau of sandstone rises out of the Sahara. Tassili n'Ajjer takes its name from a Tuareg word for a plateau and from a local Tuareg people, and it is a harsh landscape of eroded pillars, arches and deep, shaded gorges. Rain falls rarely and unpredictably, and for most of the year the plateau is almost waterless. Yet the rocks carry one of the largest collections of prehistoric art anywhere in the world, and the animals painted on them tell of a time when this desert was green.

The images were produced over an immense span of time. The earliest engravings are generally thought to be considerably older than the paintings, while the youngest images may be no more than two thousand years old. In total the plateau is said to hold more than fifteen thousand paintings and engravings, although no complete count exists and new finds are still reported. They are scattered across rock shelters, cliff faces and fallen boulders, many of them in places that are difficult to reach, and a few have been noticed by herders sheltering from the midday heat.

European knowledge of the art dates from the colonial period, when French officers serving in the Sahara were shown painted shelters by their local guides in the 1930s. The French researcher Henri Lhote led expeditions in the 1950s that copied hundreds of images, in some cases by tracing them onto paper held against the rock, and his books and films brought Tassili to international attention. Lhote divided the art into styles and periods, naming them after the subjects most often shown: the Round Head period, the Cattle period, the Horse period and the Camel period.

His chronology has not survived intact. Lhote proposed dates for the Round Head paintings, but later researchers have suggested both earlier and later ones, and the question is far from settled. The sequence he identified, running from hunter-gatherers to cattle herders, then horsemen and finally camel nomads, is still broadly accepted. Precise dating remains difficult, because the pigments themselves cannot be tested reliably and the deposits rarely contain organic material of the kind that laboratories can measure.

What makes the art so valuable is not only its quantity but its subject matter. The earliest images show animals of the savanna — giraffes, elephants, rhinoceroses, lions and crocodiles — together with human figures wearing masks and elaborate headdresses. In the Cattle period, herds dominate: long-horned cattle are shown being driven, milked and guarded in camps, while the people are depicted carrying bows and clubs and living in round huts. Later come horses, some of them drawing chariots, and after them camels, which appear in scenes of trade and travel across the desert.

The sequence is a record of climate change as much as of human culture. Giraffes and crocodiles cannot survive in the Sahara of today, and their presence implies permanent water and grassland. Sediments from former lakes in the region confirm that the desert was far wetter between roughly eleven thousand and five thousand years ago, a period that researchers call the African Humid Period. As the rains shifted southwards, the lakes shrank, the grassland gave way to scrub and eventually to sand, and the artists recorded the transformation.

The painters made their colours from minerals found close at hand: red and yellow ochres, white kaolin and black charcoal or soot, ground and mixed with a liquid to form a paste. Analysis of samples has identified a range of ingredients, but the binding medium is still disputed. Many images are remarkably well preserved, protected by the dry air and by a thin, hard skin that forms on exposed sandstone; others have faded to faint outlines or have flaked away altogether. The white of the kaolin has in places turned grey and the reds have darkened, so the original appearance of a panel can only be guessed at.

Conservation is now the principal concern. Water running down cliff faces during rare storms loosens the surface of the rock, and wind-blown sand slowly wears it away. Graffiti and the theft of loose decorated stones have damaged some sites, and the growth of adventure tourism, although strictly controlled, brings people and vehicles into fragile areas. Algerian archaeologists have recorded and photographed vulnerable panels, but guarding thousands of scattered shelters is beyond the resources available.

Protection has been attempted at several levels. The plateau was made a national park in the early 1970s, and in 1982 it was inscribed on the UNESCO World Heritage List in recognition of both its rock art and its unusual geology. The listing brought international experts and funding, and it also brought a steady trickle of visitors, nearly all of whom arrive through the oasis town of Djanet at the edge of the plateau.

Much remains unknown. Only a fraction of the decorated shelters has been studied in detail, and the identity of the artists, the languages they spoke and the ceremonies the images served are matters for argument rather than fact. Nor is it clear why some shelters were decorated and others nearby were left bare.

A seed is a plant in waiting: an embryo with a store of food and a protective coat. Because the parent plant cannot move, the seed must do the travelling, and the reason is competition. A seedling that germinates directly beneath its parent will share light, water and minerals with a much larger rival. Yet most journeys are short: the great majority of seeds come to rest within a few metres of the plant that produced them.

The simplest way to travel is by air. Wind-dispersed seeds are small and light, and many are built to fall slowly. The dandelion's seed carries a bristly parachute, the pappus. In 2018 a team of mathematicians and engineers reported that the hairs of the pappus generate a stable ring of swirling air, a vortex, just above the seed, and that this, rather than simple drag, explains why the seed descends so gently. The fruit of a maple, by contrast, consists of a seed enclosed in a single wing, and it spins like a helicopter blade as it falls. Wind dispersal works best in open country, where nothing interrupts the flow of air.

Water carries seeds as well as air. The coconut is the best-known example, and its thick, fibrous husk is buoyant and waterproof. A nut that has drifted for weeks or even months can still germinate when it is washed ashore. Mangroves take a different approach: their seedlings begin to grow while they are still attached to the parent tree. When such a seedling drops, it floats upright, and it adjusts its buoyancy so that it moves with the tide before lodging in mud. Rivers and floods carry the seeds of many floodplain species downstream and scatter them over the land when the water retreats.

Animals are the most important agents of all, and they carry seeds in two quite different ways. Some seeds attach themselves to fur or feathers, using hooks, barbs or a sticky coating; the burdock, whose hooked spines gave inventors the idea for the fastening material Velcro, is the classic case. Others are swallowed, and this route takes them much further.

Fleshy fruits are an advertisement to birds and mammals, which digest the pulp and pass the seeds in their droppings. The seed's coat protects it from the acid in a bird's stomach, and the journey often softens that coat in a way that makes germination more likely, a process known as scarification. Some seeds will not sprout at all until they have made such a journey, which gives the plant a further reason to offer fruit.

A third route depends on forgetfulness. Jays, squirrels and nutcrackers collect nuts and acorns and bury them in small stores for the winter. A bird may carry a single acorn several kilometres before hiding it, and although most stores are later recovered, some are not, and a proportion of those produce seedlings. In parts of Europe and North America this habit has allowed oaks and pines to spread across the landscape faster than they could have done unaided.

Ants are unlikely-looking dispersers, but in many shrublands they are essential. The seeds of these plants bear a fatty appendage called an elaiosome, which ants find irresistible. Workers drag the seed into the nest, eat the appendage and leave the seed itself in an underground chamber or on a refuse heap, where the soil is rich in nutrients. The seed is thus buried, hidden from animals that would eat it and supplied with fertiliser, and the young plant may appear several metres from its parent.

A few plants rely on an explosion. The pods of gorse and broom split open with a sharp twist, and the ripe fruit of the squirting cucumber detaches itself and fires a jet of liquid and seeds across the ground. Impatiens, familiar as the busy lizzie of garden centres, has pods that burst at the lightest touch. Such mechanisms throw seeds only a short distance, typically a metre or two, so they are often combined with something else: an ant may carry the seed further, or a passing animal may tread it into the ground.

These mechanisms are reasonably well understood. What is much less certain is how far seeds travel in practice, and how often one of them crosses a distance that matters. Ecologists therefore describe dispersal statistically, as a distribution in which the great majority of seeds land close to the parent and a tiny minority go far. Evidence comes mostly from the genes of plants themselves, since populations on remote islands often turn out to be close relatives of mainland species.

The animals that do the work are disappearing. Hunting and habitat loss have removed many of the large birds and mammals that once swallowed and scattered the fruits of tropical forests, and the trees with the largest seeds are the ones most affected, because no smaller animal can swallow them. Conservationists speak of the empty forest: a wood that still has its trees but has lost the creatures that kept it renewing itself.

For a plant, then, dispersal is a lottery with long odds. A seed may be superbly engineered for flight, for floating or for hitching a ride, and still end up in the stomach of a beetle or on bare rock.

In March 2017 the Whanganui River in New Zealand was declared a legal person by an Act of Parliament. In principle the river can now sue and be sued, hold property and enter into contracts, as a company can. It is represented by two guardians, one appointed by the Māori group that has lived along its banks for centuries and one by the government. A year earlier the Constitutional Court of Colombia had recognised the Atrato River as a subject of rights. The question is whether any of this makes a river cleaner.

Environmental law has generally treated rivers as property or as a resource to be allocated. A river cannot complain, so a case must be brought by a person or organisation that can show it has been harmed. Damage to a river is usually gradual, spread across many sources and felt most by people who are poor and poorly organised. By the time the harm is obvious, the pollution is in the sediment. Giving a river legal personality is an attempt to solve this problem of standing: it creates an entity whose interests a guardian can defend in court.

The New Zealand arrangement is widely misunderstood. The legislation was not primarily an environmental measure. It was, in essence, the settlement of a long dispute under the Treaty of Waitangi, concluded after decades of negotiation. For the iwi concerned, the river is an ancestor, not a resource. The Act provides for a strategy document, a fund and the two guardians, and it stops short of transferring ownership of the water to anyone.

Other jurisdictions have moved faster and less carefully. In 2017 a state high court in India declared two of the country's great rivers, together with their tributaries, to be living entities with the rights of a person. Within months the Supreme Court suspended the order, after the state government argued that it had no idea how the ruling would work in practice: who exactly would represent the rivers, what would happen to existing dams and irrigation schemes, and who would pay for the claims? The two rivers remain legally as they were.

This exposes the central difficulty. A right is only as good as the institution that enforces it. Someone must be appointed to speak for the river, and there is no guarantee that a guardian chosen by a government will represent everyone who depends on the water: farmers, fishers, boatmen and the people who live downstream all have different interests. If disputes are settled in court, they are settled slowly and expensively, and judges must weigh questions of hydrology and ecology for which they are not trained.

Sceptics also point out that legal personality is a fiction, and fictions can be hollow. A company is a legal person, and the consequences of that invention have been enormous, but nobody supposes that incorporation has made firms considerate of anything but profit. Granting a river the capacity to hold rights, without also writing down what those rights are, may generate litigation without cleaner water. A right to flow, or a right not to be polluted, has to be defined before it can be defended.

Supporters reply that this misses the point. The value of personhood, they argue, lies less in the verdicts it produces than in the way it changes the terms of a debate. Once a river is a subject rather than an object, an official who proposes a dam must justify the proposal in a different language, and the assumption that water is simply there to be used is no longer automatic. Recognition of this kind is not merely symbolic: it supplies a framework in which decisions can be challenged.

Not every reform need take this form. Ecuador's constitution, rewritten in 2008, grants rights to nature directly, without appointing guardians for particular places, and applying those provisions in court has proved difficult. Elsewhere the same ends have been pursued by giving environmental organisations the right to sue, by imposing statutory duties on regulators, and by setting up catchment boards on which competing users sit. Each approach distributes power differently, and none of them is a substitute for a clear limit on what may be discharged into a river.

My own view is cautiously favourable. The movement deserves support, not because personhood is a magic solution, but because it corrects an assumption so deep that it is rarely noticed: that a river is a thing, and that only people can be wronged. Two conditions matter, however. The guardian must be genuinely independent of the government of the day and properly funded, and the rights must be spelled out in rules that a regulator can apply. Where personhood grows out of a long relationship between a community and a river, as in New Zealand, it is far more likely to last than where it is handed down in a single judgment.

Rivers cannot feel, vote or complain, and it would be sentimental to pretend otherwise. Yet the law has always invented persons when it needed them, and extending the device to a river is a modest correction to a system that has treated the natural world as inert.