Globally, we throw out about 1.3 billion tons of food a year, or a third of all the food that we grow.

That’s important for at least two reasons. The less the world wastes, the easier it will be to meet the food needs of the global population in coming years. Second, cutting back on waste could go a long way to reducing greenhouse gas emissions.

How do we manage to waste so much?

Food waste is a glaring measure of inequality. In poor countries, most of the food waste is on the farm or on its way to market. In South Asia, for instance, half of all the cauliflower that’s grown is lost because there’s not enough refrigeration, according to Rosa Rolle, an expert on food waste and loss at the United Nations Food and Agriculture Organization. Tomatoes get squished if they are packed into big sacks. In Southeast Asia, lettuce spoils on the way from farms to city supermarkets. Very little food in poor countries is thrown out by consumers. It’s too precious.

But in wealthy countries, especially in the United States and Canada, around 40 percent of wasted food is thrown out by consumers.