在作物增长放缓的同时，地下水枯竭削弱了另一项长期支撑高产的基础。联合国于2026年1月的研究将情势描述为从「水危机」进入「水破产」：对降雨、河川与井水的取用超过其补注能力。约70%的全球含水层正处于长期下降，威胁到约一半的家庭用水与40%的灌溉供给。Saudi Arabia曾在1990年代初期因抽取沙漠地下水而短暂成为全球第六大小麦出口国，但其小麦产量其后下降近90%，呈现不可再生补注速度与政策诱因之间的结构性矛盾。压力亦扩散至人口更密集且资源更有限的地区：印度旁遮普邦（Punjab）部分地区地下水位每年下降近0.5公尺；为触及深层含水层而钻至超过70公尺（230英尺）的深井数量，从1980年代末约100,000口增加到今日约3,800,000口。依赖此水文体系供养9,300万人口的伊朗，也因水资源紧缩而出现迁都德黑兰等极端政策讨论，并伴随反复供水短缺与社会经济不安全感。
第三根支柱是贸易：自1960年代以来，阿根廷潘帕斯草原、巴西塞拉多与加拿大草原等地的剩余，特别是美国，长期为缺粮国家提供缓冲。仅美国在2024年对外净出口的玉米、稻米、小麦、植物油与糖所含的营养能量就约为2.66兆（2.66×10^12）膳食卡路里，约等于11.1拍焦（PJ；以1千卡≈4.184千焦换算），足以供养美国自身人口一年，并让如科威特等干旱国家以进口作物的方式取得「虚拟水」。但此一正和式分工正受到地缘政治与保护主义侵蚀：在Donald Trump主政下，美国农产品出口曾大体避开过去一年的关税混乱，但这种克制未必延续；俄罗斯在2022年入侵乌克兰后已尝试将粮油出口受阻作为杠杆，而在Gaza、Darfur等冲突地带，粮食贸易限制亦被用作政治手段。在更动荡且受气候冲击的世界中，将饥饿视为已被淘汰的政治胁迫工具，将是不切实际的假设。
Since 1900, the global population has risen to about five times its former level, yet humanity is better fed than at almost any point in history; that resilience has rested on three pillars: long-run gains in crop yields, dependable water systems, and trade that moves surplus from high‑productivity regions to deficit ones. All three are now under strain. For roughly six decades, farm output grew by more than 2% per year, but since 2020 it has slowed to 1.63%; total factor productivity, an efficiency measure, has averaged 0.76% over the past decade, a pace described as barely over one‑third of what is needed to feed 10 billion people in 2050. At the crop level, yield growth for the main cereals (corn, rice, wheat) and major vegetable oils has nearly flatlined over the past five years, and tropical staples such as cassava, yams, and plantain show prolonged stalls.
As yield momentum fades, groundwater depletion is weakening another foundation of modern agriculture. A United Nations study in January 2026 argues the world has moved from a “water crisis” to “water bankruptcy,” where withdrawals from rainfall, rivers, and wells exceed natural recharge. About 70% of aquifers are in long‑term decline, threatening systems that supply roughly half of household water and 40% of irrigation. Saudi Arabia illustrates the risk: after promoting desert groundwater extraction in the early 1990s, it briefly became the world’s sixth‑largest wheat exporter, but wheat output has since fallen by nearly 90% as ancient reserves ran down. Similar pressures are spreading to poorer, more populous areas: in parts of India’s Punjab, the water table is dropping by nearly 0.5 meters per year, and the count of wells drilled deeper than 70 meters (230 feet) surged from about 100,000 in the late 1980s to about 3.8 million today. Iran, which depends on stressed water supplies to feed 93 million people, now faces extreme policy proposals such as relocating Tehran amid rolling shortages and rising insecurity.
The third pillar is trade: since the 1960s, surplus from places such as Argentina, Brazil, Canada, and especially the US has buffered hungry countries. In 2024, US net exports of corn, rice, wheat, vegetable oil, and sugar contained about 2.66 trillion (2.66×10^12) dietary calories, about 11.1 petajoules (PJ; using 1 kcal ≈ 4.184 kJ), enough to feed America’s own population for a year and to let arid states import “virtual water” embodied in crops. Yet this optimistic model depends on political cooperation that may be fading: under US President Donald Trump, farm exports have mostly avoided the past year’s tariff chaos, but that restraint may not last; Russia has already tried to weaponize disrupted grain and oil exports after its 2022 invasion of Ukraine, and in places such as Gaza and Darfur, food trade restrictions have been used for political ends. In a more chaotic, climate‑ravaged world, it is naïve to assume starvation has been retired as a tool of coercion.