Water-intensive crops are agricultural products that require significant water during cultivation. They are a major part of global food systems, providing sustenance and economic value. However, their substantial water demands raise concerns about environmental impact and water resource management. Understanding these crops is increasingly important as global populations grow and water resources face pressure.
Defining Water Intensive Crops
A crop is considered “water intensive” based on its physiological water needs, growth duration, and typical climate. Plants require water throughout all growth stages, from seeding to harvest. Evapotranspiration rates, measuring water lost from soil and plant surfaces, are a key factor in determining a crop’s water demand. Crops in arid or semi-arid regions often rely heavily on irrigation, increasing their water intensity.
Common water-intensive crops include rice, cotton, sugarcane, and alfalfa. Rice, a staple for over half the world, can require 2,500 to 5,000 liters of water per kilogram. Cotton uses an average of 22,500 liters per kilogram in India. Sugarcane needs 1,500 to 3,000 liters per kilogram, and almonds have a global average water footprint of about 12 liters per single almond.
The water footprint quantifies the total freshwater consumed during a crop’s production. This metric includes three components: “blue water” from rivers, lakes, and aquifers for irrigation; “green water” from rainwater absorbed by plants; and “grey water,” the volume needed to dilute agricultural runoff pollutants. It is expressed in liters per kilogram or cubic meters per ton. For instance, global average water footprints range from about 200 cubic meters per ton for sugar crops to around 9,000 cubic meters per ton for nuts.
Environmental and Resource Impact
Cultivating water-intensive crops has significant environmental and resource implications, especially for freshwater sources. Agriculture accounts for about 70% of global freshwater withdrawals, mainly for irrigation. This extensive use depletes sources like aquifers, rivers, and lakes. Over 25% of the world’s population and 40% of global agricultural production rely on unsustainable groundwater extraction. In countries like India and China, over-extraction has led to declining water tables, reducing future water access.
Over-irrigation contributes to land degradation, including soil salinization and desertification. Irrigation water contains dissolved salts that accumulate in the soil as water evaporates or is absorbed by plants. This accumulation, especially with poor drainage, leads to high salt content, making it difficult for plants to absorb water and potentially reducing crop yields. Salinity reduces yields on about 30% of irrigated land in the United States and 50% worldwide.
The energy for irrigation also impacts the environment. Pumping water, particularly from groundwater, is energy-intensive and often relies on fossil fuels. Globally, irrigation systems consume about 1,896 petajoules of energy annually, contributing around 216 million metric tons of CO2 emissions, or about 15% of agricultural emissions. Groundwater pumping accounts for 89% of this total energy consumption.
Driving Factors Behind Water Intensive Agriculture
Global consumer demand significantly drives the cultivation of water-intensive crops. Staples like rice, wheat, and corn are fundamental to global calorie intake, with over half the world relying on rice. The growing world population, projected to reach 9.8 billion by 2050, continuously increases demand for agricultural products, straining water resources. Higher incomes and urbanization also boost consumption of livestock products, which are water-intensive due to the water needed for feed crops.
Economic incentives also encourage farmers to cultivate these crops on a large scale. Water-intensive crops often yield higher-value products, making them attractive. For example, in Australia, sugarcane was worth $1.33 billion in 2022, and almonds generated $800 million. Subsidies and market values can encourage farmers to continue growing these crops, even in water-stressed regions.
Historical agricultural practices and trade policies also shape water-intensive farming. Traditional flood irrigation methods are highly inefficient, wasting water through evaporation and runoff. Some regions’ climates are suitable for these crops, leading to widespread cultivation even with limited water. For example, alfalfa, a high-water-use crop, is grown in desert regions where water scarcity is an issue.
Towards More Sustainable Water Practices
Technological advancements are transforming agricultural water management, offering ways to reduce crop water footprints. Precision irrigation systems, like drip and sprinkler systems, deliver water directly to plant root zones, minimizing evaporation and runoff. These systems, often integrated with sensors and GPS, can reduce water usage by up to 50% compared to traditional methods. Variable Rate Irrigation (VRI) systems further enhance efficiency by adjusting water application rates based on real-time data on soil type, topography, and crop needs.
Agricultural best practices also contribute to water conservation. Developing drought-resistant crop varieties, such as sorghum, millet, and sweet potatoes, allows for food production in water-scarce conditions by requiring less water. Crop rotation and improving soil health are effective strategies; healthy soil with increased organic matter improves water infiltration and holds more water for plants. Practices like cover cropping and mulching protect the soil surface, reducing evaporation and erosion.
Policy interventions promote sustainable water use. Water pricing mechanisms can incentivize more efficient water use by making farmers aware of the resource’s value. Regulations, such as Saudi Arabia banning alfalfa cultivation due to high water demands, can steer agricultural practices away from water-intensive options. Government subsidies and programs also encourage farmers to adopt efficient irrigation and other water-saving practices.
Consumer choices also influence demand for water-intensive crops. Shifting towards plant-based diets can significantly reduce an individual’s water footprint, as animal products generally have a higher water footprint. Supporting local farmers who use sustainable practices and choosing water-efficient foods like wheat or barley also reduces the overall water footprint. Increasing consumer awareness through informative campaigns and eco-labeling can empower individuals to make sustainable dietary decisions.