UN-SDG 2: Zero Hunger

Our Double-Edged Nitrogen Sword Nitrogen exists as a profound duality in Earth’s systems. Its inert atmospheric form ($N_2$) constitutes the most abundant gas surrounding the planet, serving as an invisible backdrop to existence. When converted into reactive forms through fixation processes, nitrogen transforms into a fundamental building block for proteins and DNA, becoming the engine of agricultural productivity that sustains billions of people. ...

Historical Evolution of Water Security Understanding The understanding of water security has evolved significantly over time, particularly in conjunction with the growing awareness of climate change. Historically, water management often focused on ensuring supply for specific sectors like agriculture or urban consumption, often through large-scale infrastructure projects such as dams and irrigation systems1. However, the late 20th and early 21st centuries saw a broadening of the concept of “water security” to encompass not just quantity but also quality, ecosystem health, and the equitable distribution of water resources23. ...

A Planetary Problem with a Social Toll Ocean acidification, driven by anthropogenic carbon dioxide emissions, represents a critical planetary boundary within Kate Raworth’s Doughnut Economics framework, directly linking climate change impacts to marine ecosystem health and human food security. As atmospheric CO₂ levels have risen from pre-industrial concentrations of 280 µatm to current levels exceeding 414 µatm, the ocean’s absorption of this excess carbon has fundamentally altered seawater chemistry1. This process has decreased ocean pH by approximately 0.1 units since the Industrial Revolution, with projections indicating further declines to pH 7.8 by 2100 and potentially as low as 7.45 by 23002. The concept of fish adaptation to ocean acidification sits at the intersection of planetary health and social foundations, as marine fisheries provide essential protein sources for over 3 billion people globally while supporting the livelihoods of millions in coastal communities. ...

Ecological Impacts of Nitrogen and Phosphorus Runoff Eutrophication and Aquatic Dead Zones Excess nitrogen and phosphorus from fertilizers enter waterways through surface runoff and leaching, triggering eutrophication—a process where algal blooms deplete dissolved oxygen, creating hypoxic “dead zones” incapable of supporting marine life12. The scale of this crisis is particularly evident in the Gulf of Mexico, where a massive 6,334-square-mile dead zone persists due to Midwestern agricultural runoff. This environmental catastrophe has decimated local fishing industries, reducing shrimp catches by 40% and destabilizing coastal economies that have relied on these waters for generations34. ...

To truly understand the complexities of ocean acidification, it’s essential to delve into its underlying chemical mechanisms. When seawater absorbs atmospheric CO2, a gas that is being emitted at alarming rates due to human activities, it triggers a cascade of chemical reactions that ultimately increase hydrogen ion concentration and subsequently lower the water’s pH, making it more acidic.12 This intricate chemical process simultaneously reduces carbonate ion availability, a critical building block. This reduction proves particularly devastating for shell-building organisms such as oysters, clams, and mussels, which rely on these carbonate ions for survival and the development of their protective shells.34 ...