IELTS Academic Reading Practice Test 10

Agriculture is both a contributor to and a victim of climate change. The sector accounts for approximately 10 to 12 percent of global greenhouse gas emissions, primarily through methane from livestock, nitrous oxide from fertilised soils, and carbon dioxide from land-use changes. Simultaneously, agriculture is among the economic sectors most vulnerable to changing climate conditions, as crop yields, water availability, pest pressures, and growing seasons are all directly influenced by temperature and precipitation patterns.

The effects of climate change on crop production vary significantly by region and crop type. Moderate warming of 1 to 2 degrees Celsius may benefit agriculture in higher latitudes by extending growing seasons and opening new areas to cultivation. Russia, Canada, and Scandinavia could see substantial increases in agricultural productivity. However, in tropical and subtropical regions, where many of the world's poorest and most food-insecure populations are concentrated, even modest temperature increases are projected to reduce yields of staple crops including maize, rice, and wheat by 5 to 15 percent per degree of warming.

Water scarcity is projected to become the most critical climate-related constraint on agriculture. The Intergovernmental Panel on Climate Change (IPCC) estimates that by 2050, the area of land subject to increasing drought will more than double, while water availability from glacial melt and snowpack will decline in regions that currently depend on these sources for irrigation. The Indo-Gangetic Plain, which produces food for approximately 1.5 billion people across India, Pakistan, and Bangladesh, is particularly vulnerable, as Himalayan glaciers that feed its river systems are retreating at accelerating rates.

Adaptation strategies range from incremental adjustments to transformative changes. Crop breeding programmes are developing heat-tolerant and drought-resistant varieties, with CRISPR gene-editing technology accelerating the process. Conservation agriculture, which minimises soil disturbance and maintains permanent soil cover, improves moisture retention and carbon sequestration. Diversification of farming systems, including agroforestry and integrated crop-livestock management, builds resilience by reducing dependence on any single crop or income source. Climate-smart irrigation technologies, such as drip irrigation and deficit irrigation scheduling, can reduce water use by 30 to 50 percent compared to traditional flood irrigation.

The relationship between climate policy and food security presents difficult trade-offs. Biofuel mandates, intended to reduce fossil fuel emissions, can compete with food production for land and water resources. Carbon pricing may increase the cost of fertilisers and transportation, raising food prices. Conversely, payments for ecosystem services could provide farmers with income for practices such as carbon sequestration and watershed protection. Navigating these trade-offs requires integrated policy frameworks that consider food security, climate mitigation, and rural livelihoods simultaneously.

The deep ocean floor, once thought to be a barren wasteland, harbours extraordinary ecosystems centred around hydrothermal vents. Discovered in 1977 near the Galapagos Islands, these vents release superheated, mineral-rich water at temperatures exceeding 400 degrees Celsius. Remarkably, dense communities of organisms thrive in these extreme environments, sustained not by photosynthesis but by chemosynthesis, a process in which bacteria oxidise hydrogen sulphide and other chemicals to produce energy. Giant tube worms reaching 2 metres in length, ghostly white crabs, and dense clusters of mussels form ecosystems entirely independent of sunlight.

The discovery of hydrothermal vent ecosystems fundamentally challenged assumptions about the requirements for life. If organisms could thrive in such extreme conditions on Earth, the possibility of life existing in similar environments elsewhere in the solar system became more plausible. Jupiter's moon Europa and Saturn's moon Enceladus both possess subsurface oceans that may harbour hydrothermal activity. The deep-sea vents also represent potential sources of valuable minerals, including copper, zinc, gold, and rare earth elements, attracting interest from deep-sea mining companies, though extraction poses significant risks to these fragile ecosystems.

Research on vent organisms has yielded practical applications, including heat-resistant enzymes used in molecular biology (the Taq polymerase used in PCR was originally isolated from a thermophilic bacterium). Pharmaceutical companies are investigating bioactive compounds from vent organisms for potential drug development. However, the remoteness and harsh conditions of the deep sea mean that vast areas remain unexplored, and scientists estimate that fewer than 5 percent of hydrothermal vents have been studied in detail.

The question of whether human behaviour is primarily shaped by genetic inheritance or environmental influences has been debated for centuries. Modern behavioural genetics has largely moved beyond this dichotomy, recognising that genes and environment interact in complex ways. Twin studies, comparing identical twins (who share 100% of their DNA) with fraternal twins (who share approximately 50%), have provided evidence that genetic factors contribute significantly to individual differences in personality, intelligence, and mental health, typically accounting for 40 to 60 percent of the variation observed in these traits.

Genome-wide association studies (GWAS) have identified hundreds of specific genetic variants associated with behavioural traits, each typically contributing only a tiny fraction of the overall effect. Educational attainment, for example, has been linked to over 1,200 genetic variants, yet even collectively these explain only about 12 to 16 percent of the variation between individuals. This finding underscores the polygenicity of behavioural traits and highlights the substantial role of environmental factors, including prenatal conditions, parenting, education, socioeconomic status, and random developmental processes.

Epigenetics has added another layer of complexity by demonstrating that environmental experiences can modify gene expression without altering the DNA sequence itself. Studies of individuals who experienced famine during the Dutch Hunger Winter of 1944-45 revealed that prenatal exposure to malnutrition produced epigenetic changes detectable decades later, associated with increased rates of obesity and cardiovascular disease. Such findings suggest that the boundary between 'nature' and 'nurture' is far more permeable than previously imagined, with environmental influences literally shaping how genes are expressed.