2 billion more mouths to feed

He and four fellow investigators will try to lay the groundwork for answering one huge question: Where might the world's food come from in 2050, when the world's population is a couple billion people larger and water is scarcer?

They propose to stitch together various satellite images to map the extent and location of croplands worldwide, what is growing, how it's irrigated (or fed with rain) and the amount of crops grown per year.

"The idea of this project is to look at the entire world, look at croplands and where they are growing," Thenkabail said.

Thenkabail plans to hire a doctoral student at Northern Arizona University and two more local researchers as part of the $3.5 million project.

Formerly a civil, water and agriculture engineer who has mapped drought in Africa and water use worldwide, Thenkabail thinks water availability is going to become a limiting factor.

"To grow more food, you need more water," he said.

Water, land and food supplies are of international concern for some of these reasons, Thenkabail outlines:

-- About 90 percent of all water used worldwide goes to irrigate crops. Those water supplies are forecast to decline in some places due to climate change and warmer temperatures.

-- World population could grow from 7 billion in 2011 to 9 billion by 2043, the United Nations projects.

-- Developing countries have built a demand for food with greater variety and more nutritional content.

-- The land required to grow enough food to satisfy these desires and larger population, worldwide, would be roughly equal to another United States in area.

-- Use of pesticides, herbicides, yield-maximizing farming techniques and fertilizer has likely already maximized the amount of food that can be grown per acre, and in some cases may have made the land less fertile.

This research might ultimately be used to look at how much food each country has for its own population and how much is going from, say, Brazil to Germany in sugarcane turned to ethanol, or from Africa to the United States.

It could answer questions like "Who is using which water where, and what land where, for whom?" Thenkabail said.

He envisions policymakers asking how many units of food can be grown on a plot of land with as little water as possible, somewhat like fuel efficiency in automobiles.