Security Movie Ending

[Kerby Kolpack]

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Water and food security are intrinsically linked as irrigated agriculture contributes around 40% of global food production on 20% of cultivated land1. At the same time, water use in agriculture accounts for around 70% of global freshwater withdrawals, of which 40% is used for animal feed production2. An estimated 42% of irrigation water is sourced from groundwater (GW)3, and China, India, Iran, Pakistan and the USA are the globally largest GW users in terms of volume. Development of GW for irrigation offers many advantages, including proximity to users, lower investment requirements4, individual control, higher water productivity, often better water quality compared with surface sources and lower seasonal variation in availability5. Moreover, GW development is accelerating in sub-Saharan Africa as a result of cheaper technologies, including the increased availability of affordable solar-powered pumps6,7.

As climate change renders rainfed agriculture less viable and disrupts surface water (SW) availability for irrigation, GW is increasingly being favoured as the primary source of irrigation for agriculture24. Moreover, climate change also directly affects the quantity and quality of GW recharge through changes in precipitation, temperature and sea-level rise25 and indirectly affects water use26. As such, GW resources are affected by climate change through both increased extraction levels for irrigation and other uses and lower recharge. Recent assessments conducted to quantify the extent of GW depletion at regional to global scales27,28 demonstrate the large-scale changes in GW storages across hotspot regions of the world. Our analysis of changes in GW recharge due to climate change further highlights these issues (Supplementary Fig. 1). Even in areas where recharge is expected to increase with climate change, such as in northwestern India29, the increase is unlikely to compensate for anthropogenic extraction in the short to medium term30.

We first estimate the effects on food security from eliminating GW overdraft under climate change by 2050. Climate change affects GW recharge levels34 through both changes in precipitation, temperatures and extreme events and changes in the demand for GW as SW flows decline or become less reliable. We then analyse a series of agricultural, water and nutrition policy levers that can reduce or offset the adverse food security impacts from more sustainable GW management. These include public investments in agricultural research and development (R&D); more effective use of precipitation (green water) through mulching, terracing, conservation agriculture and other means (ERM); and reduced meat consumption in high-income countries (HICs) (RMC). Details of scenario assumptions and settings are presented in Methods.

No GWC is the baseline without GW conservation, while GWC ensures that GW withdrawals are equal to net recharge rates. Both are simulated under climate change, averaging results from three climate change scenarios: GFDL, HadGEM and IPSL with RCP 8.5. Calculated using the IMPACT-IWSM.

Halting GW depletion reduces agricultural production, increases food prices and results in a larger number of people at risk of hunger. As rice and wheat globally account for the largest applications of irrigation water, and most irrigated wheat is grown in Asia, production declines are largest for these two crops, at 1.8% and 1.5%, respectively. This is followed by declines in production of maize (1.0%) and sugarcane (0.6%). Across all agricultural commodities, production declines by 0.73%, and across all animal and plant-based foods, it declines by 0.66%. In terms of most affected regions, wheat, rice and maize production decline most in LMICs while HICs make up for some of the production shortfalls of wheat and sugarcane in response to higher prices for these commodities (Supplementary Fig. 2a). In terms of country-level impacts, in India wheat and sugar production are affected most, while in China rice production drops most sharply. Neither country can make up for these declines through increased production of other crops or elsewhere in their countries (Supplementary Fig. 2b).

Changes in GW access also affect global trade regimes, with net trade in rice increasing globally by 10.8% and trade in sugar by 3.5% to compensate for production shortfalls. At the same time, global net trade in wheat is projected to contract by 3.3% because of reduced exports from the South Asia region (Supplementary Table 3). Given thin agricultural commodity markets, limited stocks and the time it takes for production systems to adjust, small declines in global food production can lead to large changes in global food prices. We observe this in the case of rice and wheat, where prices increase by 7.4% and 6.7%, respectively, and on average, prices for all cereals increase by 5.2%.

Higher food prices impact the poor the most, as their share of household expenditures on food is higher. Lower food production and associated higher food prices because of GWC make food less affordable to poorer populations, with subsequent increases in the severity of undernourishment, disproportionately affecting LMICs (Fig. 2). This translates to approximately 24 million more undernourished people in LMICs, including 5.2 million more undernourished people in China and 2.6 million more undernourished people in India. The global increase in the number of people at risk of hunger would be around 26 million higher with GWC, above the 520.6 million people at risk of hunger in the No GWC baseline. With GWC, by 2050, the share of the population at risk of hunger would be 14% higher in India, 7% higher in the USA and 6% higher in China.

We implement three alternative policy scenarios to assess the potential of investments in food and water systems in reducing the adverse food insecurity impacts from GWC. The first scenario focuses on investment in agricultural R&D to increase yields of water-constrained irrigated crops through better seed technologies and associated agronomic practices. These include improvements in water use efficiency that can be achieved through improving transpiration efficiency of crops, by reducing the share of the harvested share in total biomass of crops through dwarf and semi-dwarf varieties and by reducing crop failure under climate extreme events in irrigated environments through drought-, heat-stress- and submergent-tolerant varieties, among others. These investments directly reduce the reliance on GW sources for agricultural production. The second scenario aims to reduce food security impacts from reduced GW pumping through improving the management of precipitation (ERM) through interventions such as conservation agriculture, mulching and terracing on both irrigated and rainfed areas. The third scenario reduces the propensity to consume meat products (RMC) in HICs through changing the elasticity of demand for these foods in these geographies. Reducing the consumption of meats reduces the demand for GW-fed animal feeds, such as maize. However, the resulting lower prices for meat products would also increase their affordability by poorer populations that currently cannot afford a healthy diet. The increased affordability of meat products from lower consumption levels in HICs might thus reduce or negate the benefits from reduced meat consumption in HICs. A fourth and final scenario combines the R&D and ERM scenarios to take advantage of their synergies, combining higher irrigated yields with more effective use of precipitation on agricultural lands (scenario details are presented in Supplementary Table 7). All these policy scenarios are simulated together with the GWC scenario and hereafter referred to with a + prefix.

By accelerating investments in irrigated crop yields (+R&D) by 4.5% over baseline investments (No GWC), wheat prices are only 3.0% instead of 6.7% higher with GWC, and on average, cereal prices are 1.2% higher and sugar prices are 0.8% higher. Prices for several other crops are slightly below the levels of the No GWC baseline. Results are somewhat similar for the +ERM scenario, where the least-cost approach calculated needed improvements of 4.5% over the projection horizon.

Under the +ERM scenario, rice prices are higher compared with the +R&D scenario as rice is mostly irrigated and benefits somewhat less from improved precipitation management. However, maize prices decline to levels below those of the +R&D scenario as maize is largely rainfed and more strongly benefits from better management of precipitation. In the +ERM scenario, cereal prices are 1.9% above those of the baseline.

The combined +R&D and +ERM scenario, which includes a 2% increase in irrigated yields and a 3% improvement in effective rainfall management, results in lower maize prices compared with the +R&D scenario and in lower rice and wheat prices compared with the +ERM scenario but cannot lower cereal prices to below the levels of the +R&D scenario. However, prices for sugar and oilseed crops are further reduced.

The +RMC scenario also lowers food prices compared with the GWC scenario, but price declines are very small, except for meat prices, which are 1.1% below baseline levels. Furthermore, prices of maize, the major irrigated livestock feed, are projected to be 2.5% higher than the baseline, which is a considerable but not major decline compared with maize prices under the GWC scenario.

Figure 4 presents the increase in the population at risk of hunger under the alternative policy scenarios compared with the No GWC baseline and compared with the results under the GWC scenario. Compared with the global increase in the population at risk of hunger of 5% under the GWC scenario, the increases are 0.9% under the +R&D scenario (Fig. 4a), 1.9% under the +ERM scenario (Fig. 4b) and 1.1% under the combined +R&D and +ERM scenario (Fig. 4c). The +R&D scenario is particularly beneficial for India and China, which are large GW irrigators and therefore particularly benefit from increased investments in seed technologies focused on improving water use efficiency. These investments help to retain food production levels in GW-fed Asian breadbasket regions, keeping food prices and the number of people at risk of hunger down. Benefits from investments in effective management of precipitation, however, are spread more broadly. While their ability to maintain production levels in China and India is comparatively limited, they still succeed in substantially reducing the risk of hunger. Under the +RMC scenario, however, the share of people at risk of hunger increases by 4.8%, which remains close to the 5.0% increase in the GWC scenario. Here the risk of hunger increases in the group of HICs by 15.9%, or 7.4 million people, compared with the No GWC baseline, while the increase in the risk of hunger in the group of LMICs is reduced to 3.7%, or 17.6 million people, compared with the GWC scenario increase of 5.0%. Despite a notable rise in the risk of hunger compared with the baseline, meat consumption experiences a marginal improvement of 2.1% in LMICs due to increased affordability. By contrast, HICs witness an 8.7% decline in consumption, while global consumption decreases by 0.96% compared with the baseline without GWC.

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