農地投資：カリフォルニア州における農作物の栽培面積の変化が、どのように水使用量を減らし、かつ付加価値を高めたのか？

ウェイイー・ツァン、Ph.D.
シニア・アグリカルチュラル・エコノミスト

キース・バルター
マネージング・ディレクター、エコノミック・リサーチ

【日本語抄訳】

・2007年から2020年の間に、カリフォルニア州の上位20種類の作物の栽培面積は8％減少しましたが、ナッツ類の栽培面積は拡大し、中でもアーモンドは拡大した面積の過半を占めて最大でした。

・一方で、栽培面積の減少はアルファルファや干し草など水使用量が多い飼料作物に集中しましたが、これは、カリフォルニア州の酪農・畜産業の競争力低下によるものでした。また、アーモンドやピスタチオと比較しても1エーカー当たりの収益が低水準でした。

・ナッツ類は飼料作物よりも栽培のための水使用量が少なくて済むため、作物の転換が州全体の水使用量の減少に寄与しています。これには、ナッツ農園における効率的な灌漑システムの導入が増加したことも関係しています。さらに、ナッツ農園はより多くの雇用を生み出しており、農地の生産性向上による収益改善にとどまらず、地域経済のエンパワーメントにもつながっています。干ばつに対して市場は短期的にセンシティブになりますが、昨年の豊作により現在の在庫水準は高く、アーモンド需要への対応が可能と考えます。生産性が高い新品種への植え替えや、水が安定した土地への移動など、既に始まっていたいくつかのトレンドが加速するものと見込まれます。

・今後、水の規制強化や気候変動による水不足が続けば、カリフォルニア州の農業は更なる試練を迎えるかもしれませんが、これまでに発揮してきた適応力やイノベーションの導入により、新たな障害も克服することが期待されます。

【英語全文】

How California's crop acreage shifts result in reduced water use while adding value

California’s tree nut sector is expanding relative to other crops, and its impact on statewide water use is increasing the competitive position and economic resilience of the state’s farm economy.

The reoccurrence of drought conditions in California in 2021 has focused attention on almond producers as a major user of the state’s agricultural water resource. The rapid expansion in the state’s almond acreage over the past two decades and the significant water demands of tree nut production compared with other crop types have raised questions around the role of almond production in California’s overall farm economy and the durability and sustainability of the state’s almond industry. At the same time, the rollout of the California Sustainable Groundwater Management Act will place additional future regulatory constraints on the availability of water for California’s agricultural sector.

Total acreage dedicated to the production of top agricultural crops in California decreased

Total acreage dedicated to top 20 agricultural crops in California 2007–2020 (000 acres)

Between 2007 and 2020, total bearing acreage for the top 20 crops in California experienced a 464,300-acre (–8%) decline. Diving into the details of acreage shifts during the past 14 years, seven of the top 20 crops, including tree nuts (e.g., almonds, pistachios, and walnuts), grapes, and tangerines, added 1.15 million bearing acres during this period. Combined production of almonds, pistachios, and walnuts increased by 1.03 million acres, with almonds leading all other crops in acreage gains, adding 610,000 additional bearing acres and accounting for 53% of all crop acreage increases from 2007 to 2020. 

Tree nuts and fruits replaced acreage previously used for feed crops and hay crops in California

Major crop acreage changes in California, 2007–2020 (000 acres)

Source: USDA NASS, as of September 2021.

Acreage loss is concentrated in water-intensive row crops

Over the same period, 13 California crops lost bearing acreage, for a net decline of 1.62 million acres. Losses in acreage were heavily concentrated in water-intensive feed crops, such as alfalfa, hay, and silage corn, which are often double and triple cropped each year. Alfalfa acreage experienced the most pronounced single-crop decline, falling by 515,000 acres and accounting for over a third of all crop acreage decrease. Row crops, such as corn, wheat, and cotton, experienced combined losses of nearly one million acres, representing 59% of the total net acreage decline over the 14-year period. California cotton acreage also decreased by 60% between 2007 and 2020. The losses in feed crops reflect the declining competitive position of California’s dairy and livestock producers versus other regions. California’s dairy and beef production has been in decline, while dairy production in Wisconsin, Idaho, and Texas has grown, and cattle production in Nebraska, Kansas, and Iowa has increased. The losses experienced by cotton, wheat, and corn were also significant and occurred in highly competitive markets characterized by tight margins and a wide range of supply regions. 

Cattle and dairy industries experienced decline, 2007–2020

California’s calf (1,000 slaughter heads) and milk production share in the U.S. (%)

Economics drives acreage shift

The acreage shift among crops in California during the past 14 years reflects economic decisions made by farmers in the state. The degree to which the acreage of various crops expanded in California was positively correlated with each crop’s economic value as measured by total average revenue per acre. Corn and alfalfa, which yielded the lowest economic value per acre for the period 2007 to 2020, also experienced the steepest acreage reduction. During the same period, almonds, pistachios, and walnuts were the top three crops in acreage expansion and registered strong positive per-acre revenue. Some tree fruits, which experienced better per-acre revenues than tree nuts, still faced other market challenges, such as stagnant per capita consumption growth (e.g., peaches and nectarines) or competition from imports (e.g., lemons), and achieved only negligible acreage increases. The robust expansion of tree nut production reflects California’s competitive position in global production. The state’s favorable growing conditions for tree nuts have allowed California to capture a dominant share of global almond production (80%), a major share of pistachio production (47%), and a lesser, but still significant, position for walnut production (28%). In addition, global demand for tree nuts has been trending steadily higher over the past two decades as consumers recognize tree nuts as healthy diet options. In comparison, other fruit crops with higher total revenue per acre than tree nuts face more fierce competition globally, as the United States accounts for just 12% and 3% of global lemon/lime and peach/nectarine production, respectively.

Acreage shifts translate into economic value

The relationship between total revenue and area shift 

Almonds and pistachios use less water per acre compared with alfalfa and rice 

Source: “Jobs per drop irrigating California crops,” UC Davis Center for Watershed Sciences, April 28, 2015. 

California irrigation water usage declines despite higher tree nut acreage 

Source: Tree nut-bearing acreage data is from USDA NASS, as of September 2021; irrigation water data is from "Water Use Data for California," U.S. Geological Service Water Resources, as of September 2021. Tree nut-bearing acres include almonds, pistachios, and walnuts. Total irrigation water use includes withdrawals of self-supplied fresh and saline groundwater and self-supplied withdrawals of fresh and saline surface water. 

Conversion to tree nuts yields irrigation efficiency and reduced water demand, along with economic benefits

In addition to improving the per-acre income of California farmland, the shift in acreage from alfalfa and other feed and row crops to tree nuts has been positive for the state’s water use profile, as nut crops generally use less water than feed crops. The most water-intensive crop per acre in California is alfalfa, averaging five acre-feet per acre, followed by rice, which consumes 4.6 acre-feet per acre; alfalfa and rice accounted for nearly eight million acre-feet of water use in total. In comparison, almonds and pistachios are estimated to use 3.5 acre-feet per acre. In its totality, the increase of tree nut production, especially almond and pistachio acreage expansion, hasn’t been positively correlated with irrigation water consumption in California. While historical comparisons of irrigation water usage and tree nut acreage in California reflect limited historical data, point data on irrigation water use is available for the years 2005, 2010, and 2015. Based on this information, California irrigation water use decreased from over 24 billion gallons/day in 2005 to 19 billion gallons/day in 2015, a 22% decline, despite an expansion in the state’s total bearing acreage of tree nuts of over half a million acres (63% increase). This decline in irrigated water usage reflects both the relatively lower water demands of the tree nuts compared with alfalfa and rice and the improved water use efficiency achieved in the irrigation of tree nut orchards. For example, surface irrigation area for all crops in California decreased 26% from 2005 to 2015, while acreage applying micro-irrigation systems, such as sprinklers and drippers, increased 35% during the same period. The higher returns associated with almond production have allowed for the deployment of advanced water technology and management to optimize irrigation water use.

Increase in micro-irrigation system helps reduce irrigation water usage

Total irrigation amount (mil gal/day) and land area by irrigation system 2005–2015 (1,000 acres)

Source: "Water Use Data for California," U.S. Geological Service Water Resources,  https://waterdata.usgs.gov/ca/nwis/water_use, as of September 2021. The total irrigation water use includes withdrawals of self-supplied fresh and saline groundwater and self-supplied withdrawals of fresh and saline surface water. 

More crops and more jobs per drop

In addition to increasing economic productivity and easing pressure on the state’s agricultural water resources, the turnover of acreage from feed and row crops to tree nuts has opened job opportunities in rural communities. According to data collected by the UC Davis Center for Watershed Sciences in 2015, almond and pistachio crops were responsible for over 5,700 more jobs, or 39% more than alfalfa and row crops combined, while using 36% less water. In terms of efficient value creation by water, less than one job was created per thousand acre-feet of net water applied in alfalfa production, while production of almonds and pistachios generated nearly five jobs with the same amount of water applied. We believe investing in tree nuts goes beyond the financial returns captured by increased farmland productivity and extends to empowering rural communities.

Almonds and pistachios use less water and create more jobs than alfalfa and row crops

Source: "Jobs per drop irrigating California crops," UC Davis Center for Watershed Sciences, April 28, 2015. The net water use is volume consumed by crops, which is the water applied minus runoffs and ground seepage.

Over the past two decades, California agriculture has experienced a paradigm shift, moving from production of feed crops, such as hay and alfalfa, to tree nut production. The shift, driven by changing market conditions and on-the-ground economic decisions, has improved farmland productivity, advanced rural economic development, and reduced demand on increasingly scarce water resources. Tighter water regulation and increasingly scarce water availability due to climate change will likely present the state's farm sector with additional challenges in the future. To meet these challenges, California will need to draw on historical resilience and adaptive innovation to overcome financial and natural obstacles.

Increasing emphasis on sustainable agricultural management practices and continued capital investments in research and development should allow California’s farm segment to continue to make environmentally sustainable positive contributions to the state’s economy and to its overall social fabric.

Editor’s note: Much of this material originally appeared on Global AgInvesting, December 6, 2021.