The forum backs a group called the Tropical Forest Alliance 2020, which brings together household names like Mars, Nestlé and Walmart alongside more than 100 other corporations, nonprofits and governments. It was founded to help an industry trade group, the Consumer Goods Forum, meet a commitment its members made 10 years ago to stop using ingredients that contribute to deforestation by 2020.

But most of the retail and manufacturing giants that make up the alliance have been unable to fully achieve the goal. “I don’t think a single one can say they’ve met their commitments 100 percent,” said Justin Adams, executive director of the Tropical Forest Alliance 2020.

Since the pledge was made a decade ago, at least 50 million hectares of forest, or 123.5 million acres — an area twice the size of the United Kingdom — have been destroyed for commodities, according to an analysis by Greenpeace International.

Nestlé, which makes Cheerios, Kit Kat bars and Haagen-Dazs ice cream, says over 90 percent of its key agricultural commodities will be “deforestation-free” by the end of 2020. Mars, best known for its chocolate bars but also responsible for many other products, says commitments for cocoa, beef and soy will be met by 2025 and, for palm oil, by the end of this year.

Kellogg’s, the company behind Pringles chips and Crunchy Nut cereal, said that “like others, we will fall short of the deforestation goal.” While Walmart is “on track” to meet the goal in its own-brand products that use paper and palm oil, a spokeswoman said “soy and beef chains are more opaque and complex,” impeding “transparency and progress.” Other multinationals, like Mondelez, PepsiCo and Unilever did not respond to requests for figures or declined to supply them.

“I don’t think anybody, when they were making these commitments, envisaged it was going to be anything like as hard,” Mr. Adams added.