Rusty patched bumblebee on the verge of extinction: How will this impact our lives?

Just 20 years ago, the rusty patched bumblebee (Bombus affinis) was a common sight, so ordinary that it went almost unnoticed as it moved from flower to flower, collecting nectar and pollen throughout eastern North America and the upper Midwest.

But it's now balancing precariously on the brink of extinction and has become the first-ever bumblebee in the United States to be listed as endangered.

The US Fish and Wildlife Service listed the rusty patched bumblebee as endangered under the Endangered Species Act last year in January. Endangered species are animals and plants that are in danger of becoming extinct. The rusty patched bumblebee has declined by 87 per cent in the last 20 years and is likely to be present in only 0.1 per cent of its historical range.

Rusty patched bumblebee - Appearance and range

Rusty patched bumblebees live in colonies that include a single queen and female workers. The colony produces males and new queens in late summer.

Queens are the largest bees in the colony, and workers are the smallest. All rusty patched bumblebees have entirely black heads, but only workers and males have a rusty reddish patch centrally located on the back.

Historically, bumblebee was broadly distributed across the eastern United States and Upper Midwest, from Maine in the US and southern Quebec and Ontario in Canada, south to the northeast corner of Georgia, reaching west to the eastern edges of North and South Dakota.

Its range included 28 states, the District of Columbia and two provinces in Canada. Since 2000, this bumblebee has been reported from only 13 states and Canadian provinces; Illinois, Indiana, Iowa, Maine, Maryland, Massachusetts, Minnesota, North Carolina, Ohio, Pennsylvania, Tennessee, Virginia, Wisconsin, and Ontario.

Bumblebees as pollinators

1. Bumblebees such as the rusty patched are important pollinators of plants and wildflowers that provide food and habitat for other wildlife. They are also the chief pollinator of many economically important crops.

2. Bumblebees are able to fly in cooler temperatures and lower light levels than many other bees, such as honey bees, making them excellent pollinators for crops like tomatoes, peppers, and cranberries.

3. Even where crops can be self-pollinated, the plant produces more and bigger fruits when pollinated by bumblebees.

4. Bumblebees specialize in an unusual form of pollination known as 'buzz pollination' or 'sonication,' where the bee hangs from the flower and vibrates its flight muscles rapidly, which shakes loose pollen that is held tightly by the flower.

5. The bee then goes on to fertilise the next flower she visits. For some unknown reason, honeybees are unable to do this.

6. Blueberries, tomatoes, aubergines, and kiwis are just some examples of the many plant species that require this form of pollination.

Why is the rusty patched bumblebee declining?

1. Habitat loss and degradation

Most of prairies and grasslands of the Upper Midwest and Northeast have been converted to monoculture farms or developed areas, such as cities and roads. Grasslands that remain tend to be small and isolated.

2. Intensive farming

Increases in farm size and technology advances improved the operating efficiency of farms but have led to practices that harm bumblebees, including increased use of pesticides, loss of crop diversity which results in flowering crops being available for only a short time, loss of hedgerows and the flowers that grew there, and loss of legume pastures.

3. Disease

Pathogens and parasites may pose a threat to rusty patched bumblebees, although their prevalence and effects in North American bumblebees are not well understood.

4. Pesticides

The rusty patched bumblebee may be vulnerable to pesticides used across its range. Pesticides are used widely on farms and in cities and have both lethal and sublethal toxic effects.

Bumblebees can absorb toxins directly through their exoskeleton and through contaminated nectar and pollen. Rusty patched bumblebees nest in the ground and may be susceptible to pesticides that persist in agricultural soils, lawns, and turf.

5. Global climate change

Climate changes that may harm bumblebees include increased temperature and precipitation extremes, increased drought, early snowmelt, and late frost events.

These changes may lead to more exposure or susceptibility to disease, fewer flowering plants, fewer places for queens to hibernate and nest, less time for foraging due to high temperatures, and asynchronous flowering plant and bumblebee spring emergence.

Why are rusty patch bumblebees important?

Bumblebees are the most important insect pollinators of a variety of crops like cranberries, blueberries, and tomatoes.

In the United States and globally, native bees are responsible for most pollination of plants that require insect pollination to produce fruits, seeds, and nuts.

According to the UN's Food and Agriculture Organization, 90 per cent of the world's food supply comes from about 100 crop species and 71 of those crops (especially fruits and vegetables) rely on bees for pollination.

In the US, bee activities generate 15 billion USD a year, according to the World Wildlife Fund. This also includes domesticated bees such as honeybees.

New observations since last year

After a year of new observations for the rusty patched bumblebee, the core range of the species continues to grow. The number of individual bees sighted is also up from previous years.

The higher number of observations is likely a factor of increased survey effort and awareness, but could also be a sign of a good production year for the bumblebee colonies.

So far in 2018, there have been more than 300 individual rusty patched bumblebees reported, and many locations are documenting four to 12 individuals observed at a time.

Read | Are bees capable of ending the human race?