Food waste is a bigger problem than previously believed and will get worse as developing nations become more affluent, according to a study by Dutch researchers.

The study, published in the journal Plos One, says that food waste amounts to twice the amount previously estimated and constitutes up to a third of all food available for human consumption.

The researchers found a correlation between food waste and wealth, with waste increasing as a nation or region begins to become prosperous, then tapering off. They called this the “affluence elasticity of food waste.” The tipping point was identified at $6.70 per day per capita; once that average is reached, consumers rapidly begin wasting food.

Food waste also present a sustainability problem due to the squandering of agricultural resources. This is a major source of greenhouse gas; a United Nations panel estimates that 3.3 billion tons of carbon dioxide are expended to produce food that never gets eaten.

The Dutch study recommended that governments, especially in emerging nations, educate consumers to alter consumption patterns and choose sustainable options as much as possible.