IELTS Academic Reading Practice Test 4

A Few animals have been as quietly fundamental to the human food economy as the bee. The European honeybee, Apis mellifera, has been an indispensable partner to human agriculture for thousands of years, accompanying settled farming wherever it has spread. Beyond producing honey and wax, the species pollinates approximately one-third of the global food supply, including the great majority of fruits, nuts, and oil-bearing crops. Without that work, agricultural economists generally argue, the variety and affordability of the modern diet would contract. Its decline over the past two decades, therefore, is, according to many entomologists, a matter of more than sentimental concern. In the winter of 2006-7, American commercial beekeepers reported losing roughly 30 percent of their hives — three times the historic norm — and similar losses began to be recorded across Europe and parts of Asia. The pattern persisted in subsequent years and prompted what has been described as a major international scientific response.

B The phenomenon was named Colony Collapse Disorder (CCD), and its defining symptom was strikingly peculiar: apparently healthy worker bees would simply abandon a functioning hive, leaving behind a queen, brood, and stored food. Researchers initially struggled to identify a single cause, and the dominant view today is that CCD results from the interaction of several stresses rather than any one pathogen. Parasitic mites of the genus Varroa, viral infections, the spread of the gut parasite Nosema ceranae, and exposure to a class of insecticides known as neonicotinoids have all reportedly been implicated. Field studies have shown that no single factor accounts for collapse in every case, and the most widely accepted modern view is that combinations of two or more stresses, applied to colonies already weakened by poor nutrition or long-distance transport, exceed what an otherwise resilient hive can tolerate.

C Neonicotinoids attracted particularly intense scrutiny because of their unusual mode of action. Unlike older insecticides that act on contact, neonicotinoids are absorbed systemically by treated plants, appearing in pollen and nectar at low but biologically active concentrations. Foraging bees are thus exposed to the chemical not by accidental drift but by the routine collection of the very resources on which the colony depends. Studies published between 2012 and 2018, including a major field trial in three European countries by researchers at the Centre for Ecology and Hydrology, demonstrated measurable harm to honeybee colonies even at exposures that fell within regulatory limits. Effects included impaired navigation, reduced overwintering survival, and lower queen production. The European Union restricted three major neonicotinoids in outdoor crop use in 2018, although critics argue that effective replacements have yet to be developed, and that substitute chemistries may carry their own, as-yet poorly understood, ecological costs.

D Varroa destructor, a parasitic mite originally adapted to the Asian honeybee, has spread worldwide since the late twentieth century and is widely regarded as the single most damaging pest of Apis mellifera. The mite feeds on the fat body of bees and transmits at least eighteen viral diseases, including the particularly destructive Deformed Wing Virus. Once infestation passes a threshold of typically a few percent of adult bees carrying mites, colony collapse over the following winter is widely considered probable. Conventional miticides have proven only partially effective and have selected for resistant Varroa populations in many regions, leaving beekeepers in a chemical arms race with an evolving parasite. Recent research at Washington State University has explored selective breeding of honeybees that display hygienic behaviour — detecting and removing mite-infested brood — as what many regard as a more sustainable long-term strategy.

E Climate change has, in many ecologists' view, added a further layer of complexity. Warmer winters generally disrupt the bees' overwintering cycle, while shifts in flowering times can produce mismatches between when colonies need food and when flowers are available. Drought reduces nectar yields and pushes beekeepers to move colonies longer distances in search of forage — a stressful experience for bees and a key vector for spreading disease between regions.

F Despite the alarming headlines, commercial beekeeping has, on the whole, proved unexpectedly resilient. Total managed honeybee colonies worldwide have continued to grow as beekeepers replace lost hives, even as per-colony productivity has fallen. The picture is darker for wild and feral honeybees, which lack human management, and for the more than 20,000 species of non-honeybee bees that play vital roles in pollination. Many bumblebee species, in particular, have suffered precipitous declines, and several are now classified as endangered. Conservation focused exclusively on the European honeybee, scientists warn, risks distracting from the broader collapse of pollinator diversity. A more comprehensive response, in many ecologists' view, would combine reduced pesticide use, restored habitat at landscape scale, and active monitoring of wild bee populations.

A The phrase Silk Road conjures images of a single great highway running across Asia, traversed by camels laden with the namesake fabric. The reality, on the whole, was more complex and more interesting. The term was coined only in 1877 by the German geographer Ferdinand von Richthofen, more than a thousand years after the network it described had reached its peak. What von Richthofen called Seidenstrasse — and what historians now usually render as Silk Roads in the plural — was, in many historians' view, in fact a shifting web of overland and maritime trade routes connecting the empires of East Asia, the Middle East, and the Mediterranean from roughly 130 BCE to the mid-fifteenth century. The singular form of the name has, according to many recent scholars, obscured both the geographical complexity and the political fragmentation of the system it purports to describe.

B The conventional starting point is the embassy sent by the Han dynasty emissary Zhang Qian to the western regions in the second century BCE, which is widely said to have opened sustained Chinese diplomatic and commercial contact with the kingdoms of Central Asia. By the first century CE, regular caravan traffic was carrying Chinese silk to the Parthian Empire, where it was traded onwards to Roman markets. Roman demand for silk became so substantial that it drew complaints from Roman moralists, who feared that gold flowing east in payment for luxury textiles was draining the empire's reserves. The senator and historian Tacitus, among others, is said to have regarded the appetite for Eastern luxuries as evidence of moral decline, although such complaints did not measurably reduce consumption among those who could afford the cloth.

C Silk was the most famous commodity but far from the only one. Eastbound caravans typically brought woollens, glass, and silver from the Mediterranean and Iranian world. Spices, gemstones, and cotton textiles travelled from India. Tea, paper, gunpowder, and porcelain moved westward from China in successive centuries. Equally important, in many scholars' view, were the intangible goods: technologies such as paper-making and printing diffused along the same routes, as did religious and philosophical traditions. Buddhism reached China from India along the Silk Roads; Nestorian Christianity reached Tang-dynasty China; and Islam is widely said to have spread eastward into Central Asia and western China from the seventh century onwards. The transfer of ideas and disciplines proved as consequential as the transfer of goods, reshaping intellectual life across an enormous span of Eurasia.

D Cities along the routes flourished as commercial and cultural hubs. Samarkand, Bukhara, and Merv in Central Asia, Dunhuang at the western edge of China, and Palmyra in Syria all owed much of their prosperity to long-distance trade. These cities were multilingual and religiously plural, hosting communities of merchants from across Eurasia, and contemporary travellers often remarked on their cosmopolitan character. Caravanserais — fortified inns spaced approximately a day's camel journey apart — provided shelter, water, and protection for travellers, and the chain of such inns enabled small merchants to undertake otherwise impossible journeys. The political instability of any single empire mattered less than might be expected, because the network as a whole rerouted around troubled regions; merchants followed the path of least resistance, and the system was, in many historians' view, structurally more robust than any individual state along it.

E Maritime routes complemented the overland ones throughout the period and eventually surpassed them in importance. From at least the first century CE, ships using the seasonal monsoon winds carried goods between Roman Egypt, India, and beyond. By the eighth and ninth centuries, Arab and Persian traders dominated the Indian Ocean, and Chinese ships reached as far west as the Persian Gulf and East Africa during the Tang and Song dynasties. The famous early-fifteenth-century voyages of the Ming admiral Zheng He, with fleets of hundreds of ships and tens of thousands of sailors, represented a final apex of state-sponsored Chinese maritime trade before imperial policy turned inward. The reach of these voyages, which extended at least as far as the East African coast, demonstrated that Chinese maritime capacity at the time was on a scale unmatched by any contemporary European power.

F The overland Silk Roads declined steadily after the fifteenth century. The fragmentation of the Mongol Empire — which had briefly unified an enormous portion of the route in the thirteenth and fourteenth centuries — removed a key facilitator of long-distance travel. The Ottoman conquest of Constantinople in 1453 disrupted the western terminus, and the European discovery of direct sea routes to Asia is widely said to have rendered the overland passage commercially obsolete. The Silk Roads, in many writers' view, thus did not so much end as gradually become irrelevant, supplanted by an entirely different global trade architecture organised around European maritime empires.

A Plastic in the ocean is a problem visible to anyone who walks a beach. Less visible but increasingly understood, in many oceanographers' view, is the secondary problem of microplastics — plastic particles smaller than five millimetres in diameter. Microplastics typically arise either through the fragmentation of larger plastic items under the influence of sunlight and wave action, or as primary particles deliberately manufactured at small scale for use in cosmetics, abrasive cleaners, and industrial processes. By the early twenty-first century, oceanographers had begun to document the accumulation of these particles in every major ocean, including in remote polar waters and at depths exceeding ten kilometres.

B The first systematic surveys of microplastic concentration were carried out by the Sea Education Association in the North Atlantic between 1986 and 2008. The researchers found that the average number of plastic fragments in surface seawater had not increased over the period, despite production and disposal of plastic having risen dramatically. This counterintuitive result has been the subject of considerable debate. Possible explanations generally include settlement of particles to the deep ocean, ingestion by marine organisms, and biological colonisation that may increase particle density and accelerate sinking. None of these mechanisms is, in researchers' view, mutually exclusive, and the consensus has shifted toward viewing the surface ocean as one compartment within a larger system in which microplastics are progressively redistributed rather than retained.

C Once in the marine environment, microplastics typically interact with biota at every trophic level. Filter-feeding organisms including mussels, oysters, and many zooplankton species reportedly ingest microplastics indiscriminately along with food. Fish, seabirds, and marine mammals generally accumulate them through their diet. A 2019 review estimated that an average European seafood consumer eats around 11,000 microplastic particles annually, though the long-term health consequences, according to many researchers, generally remain a subject of active research. Comparable estimates for drinking water, table salt, and inhaled airborne particles have added to the total dietary exposure attributed to plastic-derived contaminants.

D Of particular concern, in many toxicologists' view, is the role of microplastics as carriers of chemical contaminants. Polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and the chemical additives manufactured into plastics themselves — including bisphenol A and phthalate plasticisers — can adsorb to or leach from microplastic particles. Laboratory studies have demonstrated that organisms ingesting contaminant-laden microplastics absorb the chemicals into their tissues, although the contribution of microplastics to overall contaminant exposure relative to other pathways remains debated. Some toxicologists argue that, while microplastics are a real exposure pathway, the relative magnitude of harm depends on local pollution context and on the precise chemistry of the particles involved.

E Regulation has lagged behind the science, but recent years have seen the first concrete responses. The United States Microbead-Free Waters Act of 2015 prohibited the manufacture of rinse-off cosmetics containing intentionally added microbeads, and the United Kingdom, France, Canada, and Sweden have introduced similar measures. The European Union's REACH chemicals regulation was amended in 2023 to phase out a much wider range of intentionally added microplastics over an eight-year timetable. Critics argue, however, that primary microbeads generally account for a small fraction of total ocean microplastic input, with the larger share coming from fragmentation of macroplastic litter and from synthetic textile fibres released during laundering. The implication, according to many analysts, is that microbead bans are necessary but plainly insufficient to address the scale of the contamination problem.

F Mitigating the textile-fibre pathway has attracted growing attention. Standard washing machine cycles typically release substantial quantities of polyester and acrylic fibres into wastewater systems, where they often pass through filtration and into rivers and oceans. France became the first country in the world in 2023 to mandate the installation of microfibre filters on all new domestic washing machines from 2025, and several manufacturers have begun marketing add-on filtration devices for existing machines. Industry observers generally expect the French requirement to set a regulatory template that other jurisdictions may adapt.

G The scale and persistence of marine microplastic contamination has prompted broader reflection on plastic itself. Annual global plastic production stood at approximately 1.5 million tonnes in 1950 but is forecast to reach 600 million tonnes by 2050 on current trajectories. Although recycling rates have improved in some economies, the overwhelming majority of plastic produced is said to end its useful life in landfills, incinerators, or the environment. Researchers and policymakers increasingly argue that reduction in primary plastic use, rather than improved end-of-life management, is, in many writers' view, the only intervention adequate to the scale of the problem.