A regional nuclear conflict would compromise global food security

A limited nuclear war between India and Pakistan could ignite fires large enough to emit more than 5 Tg of soot into the stratosphere. Climate model simulations have shown severe resulting climate perturbations with declines in global mean temperature by 1.8 °C and precipitation by 8%, for at least 5 y. Here we evaluate impacts for the global food system. Six harmonized state-of-the-art crop models show that global caloric production from maize, wheat, rice, and soybean falls by 13 (±1)%, 11 (±8)%, 3 (±5)%, and 17 (±2)% over 5 y. Total single-year losses of 12 (±4)% quadruple the largest observed historical anomaly and exceed impacts caused by historic droughts and volcanic eruptions. Colder temperatures drive losses more than changes in precipitation and solar radiation, leading to strongest impacts in temperate regions poleward of 30°N, including the United States, Europe, and China for 10 to 15 y. Integrated food trade network analyses show that domestic reserves and global trade can largely buffer the production anomaly in the first year. Persistent multiyear losses, however, would constrain domestic food availability and propagate to the Global South, especially to food-insecure countries. By year 5, maize and wheat availability would decrease by 13% globally and by more than 20% in 71 countries with a cumulative population of 1.3 billion people. In view of increasing instability in South Asia, this study shows that a regional conflict using <1% of the worldwide nuclear arsenal could have adverse consequences for global food security unmatched in modern history

Towards a revised planetary boundary for consumptive freshwater use: role of environmental flow requirements

We review the conceptual and quantitative foundation of the recently suggested ‘planetary boundary’ for freshwater (PB-Water; i.e. tolerable human ‘blue’ water consumption), and propose ways forward to refine and reassess it. As a key element of such a revision we suggest a bottom-up quantification of local water availabilities taking account of environmental flow requirements. An analysis that respects these requirements in a spatially explicit manner suggests a PB-Water of ~2800 km3 yr-1 (the average of an uncertainty range of 1100–4500 km3 yr-1). This is notably lower than the earlier suggestion based on a simpler top-down analysis (4000 km3 yr-1, the lower value of a range of 4000–6000 km3 yr-1). The new estimate remains provisional, pending further refinement by in-depth analyses of local water accessibility and constraints up-scaled to the global domain, including study of cascading impacts on Earth system properties. With a current blue water consumption of >1700 km3 yr-1, PB-Water is being approached rapidly. Thus, design opportunities to remain within PB-Water are imperative. We argue that their quantification requires analysis of tradeoffs with other planetary boundaries such as those for land use and climate change

Deriving root zone storage capacity from Earth observation

Water ManagementCivil Engineering and Geoscience