The world wastes more than $750 billion worth of food every year — 1.6 billion tons of food left in farm fields, sent to landfills, or otherwise scattered across the countryside, plus another seven million tons of fishery discards at sea. That waste has gotten a lot of attention lately, mostly in terms of human hunger.

Hardly anyone talks about what all that food waste is doing to wildlife. But a growing body of evidence suggests that our casual attitude about waste may be reshaping the way the natural world functions across much of the planet, inadvertently subsidizing some opportunistic predators and thus contributing to the decline of other species, including some that are threatened or endangered.

A new study in the journal Biological Conservation looks, for instance, at California’s Monterey Bay, where the threatened steelhead trout population has declined by 80 to 90 percent over the past century. Efforts to restore the species along the Pacific Coast have focused on major initiatives like the recent demolition of a dam that had blocked access to critical steelhead breeding grounds on the Carmel River, which empties into Monterey Bay.

But a team of co-authors led by Ann-Marie Osterback, a marine ecologist at the University of California-Santa Cruz, suspects that garbage and fishery discards might also play an underrated part in the problem. The hypothesis is that local food wastes inadvertently subsidize Western gulls in the Monterrey Bay area, and these gulls in turn prey on the juvenile steelhead trout.

The dramatic decline in steelhead numbers would normally mean that fish-eating birds around Monterey Bay would have to move down the food chain to survive. That’s what’s happened to Brandt’s cormorants and marbled murrelets, and their populations have declined as a result.

But according to Osterback, the number of gulls have doubled or quadrupled in different parts of the bay just since the 1980s — thanks to a steady diet of landfill garbage and fishery discards. Osterback and her co-authors found that each individual gull now eats less steelhead than in the past, but the combination of a greatly increased gull population and a severely reduced run of steelhead trout adds up to a dramatic rise in predation pressure. She estimates that the gulls may eat up to 30 percent of juvenile steelhead en route to the sea.