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Urban vertical farming — the practice of growing crops in stacked layers inside controlled indoor environments — has attracted significant investment in recent years. Proponents argue that vertical farms can produce food year-round regardless of weather conditions, use up to 95% less water than conventional agriculture through hydroponic or aeroponic systems, and eliminate the need for pesticides entirely. Some vertical farms have achieved yields per square metre that are 100 times greater than those of traditional outdoor fields.

Critics, however, point out that vertical farming faces substantial economic and environmental challenges. The energy costs of artificial lighting... are considerable, and in regions where electricity is generated from fossil fuels, the carbon footprint of vertical farms can exceed that of conventional agriculture. A 2021 analysis found that leafy greens grown in vertical farms in the United Kingdom had a carbon footprint approximately 6.5 times higher than those grown in heated greenhouses in Spain and transported by road.

Despite these challenges, vertical farming is considered particularly promising for certain crops and contexts. Leafy greens, herbs, and microgreens — which have short growing cycles and high market value — are the most economically viable crops for vertical production. Urban areas with limited agricultural land, regions with extreme climates, and countries with food security concerns are considered the most suitable locations for vertical farm deployment.

The long-term viability of vertical farming will depend on technological progress, particularly in the development of more energy-efficient LED lighting systems. Advances in LED technology have already reduced energy consumption by approximately 40% over the past decade, and further improvements are anticipated.

The relationship between social media use and mental health has become one of the most intensely studied topics in contemporary psychology. A growing body of research suggests that heavy social media use is associated with increased rates of anxiety, depression, and loneliness, particularly among adolescents and young adults. However, the nature of this relationship is complex and contested: some researchers argue that social media is a direct cause of mental health problems, while others contend that individuals with pre-existing mental health difficulties are more likely to use social media heavily — a phenomenon known as reverse causation.

Longitudinal studies — which track the same individuals over time — have provided some of the most compelling evidence for a causal link between social media use and mental health outcomes. A large-scale study conducted in the United Kingdom, which followed over 10,000 adolescents for several years, found that girls who used social media for more than five hours per day were significantly more likely to report symptoms of depression than those who used it for less than one hour. The association was weaker and less consistent for boys.

The mechanisms by which social media may affect mental health are thought to include social comparison and cyberbullying. Social media platforms present a curated version of other people's lives, which can lead users to feel that their own lives are inadequate by comparison. Cyberbullying, which affects an estimated 15–35% of young people in high-income countries, has been consistently linked to depression, anxiety, and in severe cases, self-harm.

Not all research points to negative effects. Some studies have found that social media can provide valuable social support for individuals who are isolated or marginalised. The key variable appears to be the type of social media use: passive consumption of content — scrolling without interacting — is more strongly associated with negative outcomes than active, communicative use such as messaging friends or participating in interest-based communities.

Rewilding — the large-scale restoration of ecosystems to a more natural state — has emerged as one of the most ambitious and controversial approaches to conservation in recent decades. Unlike traditional conservation, which typically focuses on protecting existing habitats and species, rewilding aims to restore ecological processes and allow nature to manage itself with minimal human intervention. Key strategies include the reintroduction of apex predators, the removal of artificial barriers such as fences and dams, and the cessation of intensive land management practices.

The reintroduction of wolves to Yellowstone National Park in the United States in 1995 is frequently cited as a landmark example of rewilding's potential. Following their reintroduction, wolf predation reduced the size and altered the behaviour of elk herds, allowing vegetation in riparian areas to recover. This in turn stabilised riverbanks, reduced erosion, and created habitat for beavers, birds, and fish — a cascade of ecological effects described as a 'trophic cascade'. However, some ecologists have questioned the extent to which these changes can be attributed solely to wolf reintroduction, arguing that other factors such as drought and human hunting also played significant roles.

In Europe, rewilding projects have faced particular challenges due to the continent's high population density and long history of intensive land use. The reintroduction of large predators such as wolves and lynx has generated significant opposition from farming communities, who fear livestock losses. Proponents of rewilding argue that compensation schemes and non-lethal deterrents can adequately address these concerns, but critics contend that the economic and social costs of coexisting with large predators are consistently underestimated.

Despite these controversies, rewilding has gained considerable momentum in recent years. The European Union's Biodiversity Strategy for 2030 includes a commitment to restore at least 30% of degraded ecosystems across the continent. Supporters argue that rewilding offers a cost-effective approach to addressing both biodiversity loss and climate change, as restored ecosystems can sequester significant quantities of carbon.