Around the world, the populations of bees, butterflies and other insects that promote plant growth are crashing, a threat not only to biodiversity but also to the global food supply. A study last year from a group associated with the United Nations warned that an increasing number of species that aid the growth of hundreds of billions of dollars’ worth of food each year face extinction.

“Obviously, it’s sad that anything has to get on the endangered list, but this really provides a great opportunity,” said Dennis vanEngelsdorp of the University of Maryland, a bee expert who applauded the government’s decision. “When you’re talking about saving the bumblebees, what you’re really talking about is saving the community.”

The kinds of measures that could protect the rusty-patched bumblebee could help many other pollinators, as well, by restoring habitats and food sources and restricting the use of pesticides — especially nicotine-based insecticides that have been linked to the decline in bee species. Such measures are especially important with native bumblebees, Dr. vanEngelsdorp noted, as opposed to honeybees, which are maintained in large colonies and trucked around the country for commercial pollination.

The service is reviewing three other species of bees to determine whether they ought to be listed as endangered as well: Franklin’s bumblebee, the western bumblebee and the yellow-banded bumblebee.

When a species is listed as endangered, the Fish and Wildlife Service is required to design a recovery plan, which is often carried out by other agencies, nongovernmental organizations, universities and tribes. Other federal agencies have to check that their actions will not hurt an endangered species or its habitat, particularly when it comes to land use planning.

Bumblebees are particularly effective pollinators because, though they seem to prefer native flowers, they will pollinate pretty much anything and can fly in lower temperatures and lower light conditions than many other insects. They also use the technique of “buzz pollination,” in which they grab the pollen-producing part of the flower in their jaws and vibrate their wings, shaking the pollen loose, a process that seems to benefit plants like tomatoes, peppers and cranberries, according to the Fish and Wildlife Service.