Bees and other pollinators are responsible for one of every three bites of food we eat, but 40 percent of all pollinating species are on the brink of extinction, according to a new report.

Friends of the Earth evaluated the country's biggest food retailers to determine how much organic produce they offer, and to what extent they support protecting pollinators and pesticide reduction.

Of the top 20 food retailers, 17 received an "F" in its analysis.

Tiffany Finck-Haynes, a Food Futures campaigner with the group, says demand for organic produce has experienced double-digit growth, but grocers aren't keeping up.

"A lot of the major food retailers have started to increase their organic offerings," she acknowledges. "But few of them have really adopted clear goals or metrics to continue to significantly increase their organic food offerings in the future."

Finck-Haynes says retailers aren't letting their customers know where they stand. On the grocers' websites, 11 of the 20 rated in the report don't provide basic information about their policies regarding organic food, pollinators and/or pesticides.

She advises that retailers increase organic offerings by 15 percent in the next decade, and put together a public plan that shows how they're trying to protect pollinators in the supply chain.

"There's a lot that retailers could do, by adopting creative programs with their supply chain to help farmers grow their organic offerings, and then be able to sell that in their stores," she adds.

While demand for organic food is skyrocketing, Finck-Haynes points out that less than one percent of total U.S. farmland is in organic production.

"Without bees and other pollinators, our supermarket shelves would be pretty bare and empty," she says. "And they're an indicator species, so they're really telling us that their decline is most likely resulting in a larger decline that we're seeing for the rest of the species in our ecosystem."

The report says bees contribute an estimated $20 billion to the U.S. economy, and $217 billion to the global economy.