Science: Pollinators

close-ups of three bees: the first bee is black and yellow, the middle bee is blue, and the third bee is black and yellow
Three bees native to California: digger bee (Anthophora urbana), Hoplitis fulgida, and Crotch bumble bee (Bombus crotchii) (Photos of A. urbana and B. crotchii courtesy of Brooke Goggins. Photo of H. fulgida courtesy of US Geological Survey Bee Inventory and Monitoring Lab)

Importance of Pollinators

Pollinators assist in plant reproduction by helping to move pollen within or between flowers. By aiding in this essential ecological mechanism of pollination, pollinators play a crucial role in supporting biodiversity. Plants serve as the foundations of our ecosystems, and over 80% of flowering plants require pollination services. Pollinators act as keystone species that help hold ecosystems together, by supporting plant reproduction and plant diversity.

In addition to being vital to biodiversity, pollinators support many benefits that humans receive from healthy ecosystems (i.e., ecosystem services), the most notable being food security. Pollinators pollinate the flowering plants that provide us with fruits, vegetables, and nuts. Over 1200 types of crops require the help of pollinators, with pollinators contributing $217 billion to the global economy. In California alone, pollinator-dependent crops are worth $11.7 billion.

Pollinator Biodiversity

ruby-throated hummingbird flying next to a pink flower
Ruby-throated hummingbird (Archilochus colubris)

Worldwide, around 350,00 different animal species are pollinators. While bees might be the most well-known, other insects like butterflies, flies, moths, beetles, and wasps provide pollination services too. In addition, birds, bats, other small mammals, and even lizards can act as pollinators. 

Why is it important to have so many different pollinators? Many plant-pollinator relationships feature a level of redundancy, meaning that some pollinators may visit a variety of flowering plants and certain plants may be pollinated by a range of pollinators. Pollinator diversity allows for this redundancy, providing some insurance in case certain pollinator species are absent in some years. link opens in new windowA study by Winfree et al. (2018) has even shown that high pollinator diversity may be key to successful crop pollination across a landscape. Additionally, pollinator diversity is important because some plants and pollinators have co-evolved to have morphological, behavioral, or phenological traits that make them dependent on each other. Consequently, some plants may need certain types of pollinators for successful pollination.

When it comes to native bee biodiversity, California is a global hotspot with about 1600 native bee species. Pinnacles National Park in Central California has one of the highest densities of native bee species in the U.S. and potentially in the world. One of the benefits to native pollinators is that they are adapted to local ecosystems, and therefore making use of their pollination services may require less management and maintenance.

Threats to Pollinators

white butterfly feeding on yellow flowers
Becker's white butterfly (Pontia beckerii) (Photo courtesy of Dave Feliz, CDFW)

Evidence points to a general reduction in pollinator diversity and abundance across multiple spatial scales worldwide. In North America, the non-native honey bee Apis mellifera, as well as some, hummingbird, butterfly, and bat species, are in decline. About 25% of bumble bee species are threatened in North America. In California, the western population of monarch butterflies has experienced a 90% reduction since the 1980s.

Habitat loss is one of the major threats to pollinators. Pesticide use, disease, parasites, and non-native species also pose risks to pollinators. Climate change can amplify the effects that these stressors have on pollinators, while also potentially shifting the ranges of plant species and the timing of flowering.

How Can We Help Pollinators?

wooden bench in a garden, surrounded by purple, yellow, pink, and red flowers
Pollinator garden (Photo courtesy of Jeff Silva (link opens in new windowCC BY 2.0) via link opens in new windowFlickr)

Since habitat loss is one of the greatest threats to pollinators, habitat protection and restoration are important to supporting pollinator populations. In addition to protecting and restoring large tracts of undeveloped habitat, habitat protection and restoration can include planting hedge rows on farms, link opens in new windowcultivating pollinator habitat in home gardens, and urban greening efforts. Furthermore, creating pollinator habitat along roadsides would help increase connectivity between patches of habitat and along migratory routes.

Pesticides contribute to declines in pollinator populations, even when pollinators are not the targeted pests. The practice of link opens in new windowintegrated pest management can help protect pollinator health. Rather than rely solely on pesticides, integrated pest management focuses on long-term pest prevention through management of the ecosystem with the goal of removing only the target organisms.

There are many opportunities to get involved in citizen sciences efforts that are building baseline datasets so that researchers can track where pollinators are found and keep track of population health of pollinators. A number of citizen science smartphone apps and online databases exist:

California Department of Fish and Wildlife's Efforts to Help Pollinators

The mission of California Department of Fish and Wildlife (CDFW) is to manage California’s diverse fish, wildlife, and plant resources, and the habitats upon which they depend, for their ecological values and for their use and enjoyment by the public. In managing wildlife resources and habitat, many efforts underway at CDFW lead to improved conditions for pollinators. Below are some examples of CDFW’s involvement in projects directly focused on pollinator conservation.

Western Monarch Butterfly

orange and black butterfly feeding on a purple flower
Monarch butterfly (Danaus plexippus plexippus) (Photo courtesy of Lisa Cox, US Fish and Wildlife Service)

CDFW is a member of the link opens in new windowWestern Association of Fish and Wildlife Agencies’ (WAFWA) Western Monarch Working Group and led development of a link opens in new windowWestern Monarch Conservation Plan adopted by WAFWA in 2019, which establishes goals for population size and habitat conservation, strategies, and actions for monarch butterflies overwintering along the California coast and breeding throughout the western US. (For more information, see the CDFW Monarch Butterfly web page.)

The western monarch population has declined about 98 percent since the late 1980s, when the population was estimated at 4.5 million. In the winter of 2018, the overwintering population of western monarchs declined 86% from the previous year, with fewer than 30,000 counted at overwintering sites. Primary threats to monarchs include loss and degradation of overwintering habitat, loss of breeding habitat (including loss of native milkweed), pesticide exposure, and climate change. Models of monarch and milkweed habitat suitability show that California, the Central Valley in particular, is a key area in the western monarch’s range. Therefore, restoring habitat in the Central Valley and other regions of California is an important step in monarch conservation.

In response to this need, a link opens in new windowMonarch Butterfly and Pollinator Rescue Program within the Wildlife Conservation Board was established by passage of Assembly Bill 2421 and signed into law in 2018, for the purpose of recovering and sustaining populations of monarch butterflies and other pollinators. A Central Valley Monarch Habitat Enhancement Project, developed under this program, will restore over 500 acres of native plant habitat for monarch butterflies and other pollinators on CDFW and partner lands in the Sacramento and San Joaquin Valleys and San Diego County. The project, funded by the Wildlife Conservation Board and carried out in partnership with CDFW, River Partners, Environmental Defense Fund, the Xerces Society, and others, will employ site-specific restoration methods on various properties, including Oroville Wildlife Area (WA) in Butte County, North Grasslands WA in Merced County, Dos Rios Ranch in Stanislaus County, Panorama Vista Preserve in Kern County, Rancho Jamul Ecological Reserve (ER) in San Diego County, Upper Butte Basin WA in Glenn County, Yolo Bypass WA in Yolo County, and Feather River WA (Abbot Lake) in Sutter County.

These restored habitats will benefit monarch butterflies by providing milkweed, the host plant for monarch larvae, as well as a variety of nectar-rich plants attractive to adult monarchs. Nectar plants available in early spring and late fall may be especially important for supporting monarchs during their migration. These nectar-rich plants, in addition to milkweed, provide floral resources for other pollinators, including native bees. The restoration sites will be designed and monitored to meet restoration objectives to produce high quality habitat and valuable monitoring data to contribute to the existing body of knowledge regarding monarch butterfly and pollinator habitat needs in three important regions of California.

Bumble Bees

close-up of bumble bee face
Western bumble bee (Bombus occidentalis occidentalis) (Photo courtesy of US Geological Survey Bee Inventory and Monitoring Lab)

In 2019, the California Fish and Game Commission (Commission) designated the Crotch bumble bee (Bombus crotchii), western bumble bee (Bombus occidentalis occidentalis), Suckley cuckoo bumble bee (Bombus suckleyi), and Franklin bumble bee (Bombus franklini) as link opens in new windowcandidate species under the California Endangered Species Act (CESA). The Commission’s action designating these four species as candidate species triggered CDFW’s process for conducting a status review intended to inform the Commission’s decision on whether listing the species is warranted. In an effort to provide California’s agricultural industry with information to help protect these species from potential adverse impacts, CDFW partnered with California Department of Food and Agriculture and California Department of Pesticide Regulation to compile available resources including link opens in new windowguidance on pesticide use, habitat management options, funding opportunities, and general regulatory information (PDF).


flying bat approaching cactus flowers
Lesser long-nosed bat (Leptonycteris yerbabuenae) (Photo courtesy of Merlin D. Tuttle, Bat Conservation International)

Although most of California’s 25 bat species are insectivorous, two species the lesser long-nosed bat (Leptonycteris yerbabuenae) and Mexican long-tongued bat (Choeronycteris mexicana) primarily forage on nectar and pollen. These species serve as important pollinators of agaves and large cacti in southwestern North America. CDFW is engaged with partners from other states, federal agencies, and non-governmental organizations to monitor bat populations through the North American Bat Monitoring Program (NABat). NABat partners use a variety of techniques including acoustic monitoring and roost counts to assess distribution and trends of bat populations in Canada, the US, and Mexico. White-nose syndrome is a disease caused by the fungus Pseudogymnoascus destructans and has killed over six million bats in the eastern US. CDFW leads the California White-Nose Syndrome Steering Committee, which is a multi-agency scientific research group that has been monitoring the syndrome across the US since 2009. In 2019, CDFW and US Fish and Wildlife Service announced that surveillance results suggest that the fungus was present in California. CDFW continues to work with US Fish and Wildlife Service, as well as other partners, to carry out surveillance for the fungus and the disease and research where bats hibernate. CDFW is also working to complete the California Bat Conservation Plan, which is an in-depth assessment of the conservation threats and best management practices for all of California’s bats, including the pollinator species.  The Conservation Plan should be finalized by 2021.

Additional Resources on Pollinators