Case Studies
Main Groups of Pollinators and some species We Defend


The honeybee comes immediately to most people's minds when they hear the word "bee." However, the honeybee's life cycle, capacity to make honey, and extreme degree of sociality and accompanying behaviors are not traits of the typical bee. Most native bees — besides bumblebees — live solitary lifestyles in holes in trees and loose soil, without a colony or hive. Honeybees, on the other hand, live in large colonies of about 10,000 individuals with specific castes. They're easily transported, making them ideal for modern industrial agriculture — and this does not accommodate native pollinators, which require a continual diversity of flowers and nesting sites. Added to all this is the simple fact that honeybees aren't native to the United States and can compete with native pollinators for resources.

Many people know that honeybees are suffering. Land use, chemical use and climate change weaken the health of individuals and populations of bees, making them more susceptible to infestations of mites and what has come to be called "colony collapse disorder." In the case of social bees, like honeybees and bumblebees, this decline in health limits their ability to fend off diseases and parasites, which some bee biologists hypothesize may be spread in beekeepers' queen-rearing facilities and mass-storage areas. Native bee populations are susceptible to the same threats of human activity that impact honeybee health.

There are more than 20,000 species of bees described in this world, with more than 4,000 of them native to North America and more than 1,200 in California. Many bees are small, seemingly nondescript and frequently mistaken for a small fly. The health status of most populations of these bee species are largely unknown, since limited research funding is typically awarded to honeybee studies. However, most conservation professionals agree that native pollinator species are at an immense risk of regional extirpation and even extinction. The greatest immediate threats to native bees are the use of toxic chemicals in agriculture, land management and industry, as well as the modification and fragmentation of natural landscapes, which reduces the floral resources and nest availability provided by intact wild landscapes with native plant diversity.

Science has shown conclusively that native bees are not only important pollinators of wild plants and crops in their own right, but they can also increase the efficiency of honeybees. There exists an amazing diversity of life histories and ecological adaptations in bees, such that generalizing them is a challenge. See photographic examples of the diversity of native bees from the USGS Bee Inventory Lab.

Bumblebees: There are 46 described species of bumblebees north of Mexico in the Americas. Bumblebees live in colonies of about 500 individuals, which are commonly found in abandoned burrows or cavities of ground-nesting vertebrates, like gophers and groundhogs, reminding us again that a messy garden is a pollinator friendly one (see our Gardening Guide). Some bumblebees are disappearing at astonishing rates. Fifteen years ago, one of the most common bumblebees in the western United States was the western bumblebee (Bombus occidentalis). But today the occasional sighting of this bee west of the Rockies is a newsworthy event.

Bumblebees' big, fuzzy bodies make them very effective pollinators, and amongst the most easily recognized and well-loved of bee groups. The flowers of some plants, like tomatoes and blueberries, need to be shaken up through vibration using what's referred to as "buzz pollination" in order to release their pollen. at the vibration the bees use is roughly the same frequency of a middle C musical note; bumblebees do this kind of pollination by grabbing a flower and vibrating their wing muscles without flapping their wings.

Some bumble species of conservation concern are:

  • The western bumblebee (Bombus occidentalis), which was once very common in the western United States and western Canada. While this bee can still be found in the northern and eastern parts of its historic range, its once-common populations, found from southern British Columbia to central California, have nearly disappeared. This bumblebee is an excellent pollinator of greenhouse tomatoes and cranberries, and it has been commercially reared to pollinate these crops. Before its regional disappearance, it was an important pollinator of alfalfa, avocado, apples, cherries, blackberries and blueberries.
  • The Franklin's bumblebee (Bombus franklini) is actually feared extinct and, most recently, known only from southern Oregon and northern California between the Coast and Sierra-Cascade ranges. With the most restricted range of any known bumblebee, its entire historic distribution can be covered by an oval of about 190 miles north to south and 70 miles east to west. Populations of Franklin's bumblebee have declined precipitously since 1998, and despite efforts by biologists to locate a population, the last confirmed sighting was in 2006.
  • The rusty-patched bumblebee (Bombus affinis) is an eastern bee once commonly distributed throughout its wide range, but it has hardly been seen since the early 2000s. A confirmed Virginia sighting of a single worker in 2014 was the first sighting in five years. The rusty-patched bumblebee was an excellent historic pollinator of countless wildflowers, in addition to cranberries, plum, apple, alfalfa, onion seed and other food crops.


Solitary Bees: Most bees live solitary lifecycles, as opposed to honeybees and bumblebees, which have social lives; they also exhibit a clear overlap of female generations, as well as colonies (of about 10,000 and 500, respectively, on average) — hence their description as social bees). Bees with solitary lifecycles lack clearly delineated social castes, like queens and workers, and often live independently or in small groups. Most species of bees live "solitary" lives, frequently nesting in loose soil or in the narrow cavities bored by beetles in dead trees or the hollow stems of dead herbaceous plants. Learn more about North America's bees on our Native Bee Factsheet.

Monarch butterflies, once a familiar sight throughout America, are plummeting toward extinction due to landscape-scale threats from pesticides; development; global climate change; and a lack of its required host plant, milkweed. The heart of the monarch's range is the midwestern Corn Belt, where most of the world's monarchs are born on milkweed plants growing in agricultural fields. Because of the ubiquitous spraying of the herbicide Roundup on corn and soy that have been genetically modified to resist herbicides, the monarch is in serious trouble in the core of its range, where milkweed is disappearing.

To fight this threat the Center petitioned the secretary of the Interior and the U.S. Fish and Wildlife Service in August 2014 to list the species as "threatened" under the Endangered Species Act. Read a factsheet about the petition.

Biologists observed the Bay checkerspot's population plunge early on, which earned the butterfly a federal Endangered Species Act listing in 1987. But this sensitive species and its native host plants are no match for human development and nonnative plant invasions. Since the Fish and Wildlife service failed to designate critical habitat for the species after its listing, the Center filed suit and ultimately won more than 23,000 acres of habitat protections for the butterfly. Unfortunately, the agency slashed that protected habitat by 23 percent in August 2008, ignoring the conclusions of its own federal recovery plan, as well as the threat of climate change, which reduces food availability for the butterfly's larvae.

Like all butterflies, the Bay checkerspot is extremely vulnerable to pesticides, which contaminate its host plants and poison its larvae. The Center has released the comprehensive report, Poisoning Our Imperiled Wildlife, which details the risks posed by pesticides to the checkerspot and other endangered wildlife in California's San Francisco Bay Area.

As far back as the 1920s, it was clear to naturalists that the Hermes copper butterfly was being threatened by Southern California's urban sprawl. Much more recently, ignoring a listing petition submitted by the Center in 2004 — and a 2005 Center lawsuit — the Service announced in 2006 that it would continue to deny the butterfly federal protection. After the Center took the agency to court again in 2009, it promised to reconsider federal protection for the Hermes copper — but in 2011 the Service again denied it protection, merely placing it on the candidate list.

Other native pollinators the Center has directly advocated for:

Bay checkerspot butterflyHermes copper butterfly Hine's emerald dragonflyIsland marble butterflyMiami blue butterflyMonarch butterflyQuino checkerspot butterflySacramento Mountains checkerspot butterflySand Mountain blue butterflySmith's blue butterflyThorne's hairstreak butterfly


Bumblebee photo courtesy Flickr/Smudge 9000; honeybee photo courtesy Flickr/Rakib Hasan Sumon; rusty-patched bumblebee courtesyFlickr/Dan Mullen; Bay checkerspot courtesy USFWS