One Observatory Circle is the lesser-known official residence that has housed every vice president since 1974.

National Honey Bee Day 2019 marks just over two years after some unexpected guests moved into the official address, courtesy of second lady Karen Pence. Pence's spokeswoman told INSIDER the second lady would not participate in this article.

Pence has touted the environmental benefits of successful beehives before. See how the buzzy creatures have made the vice president's residence their home.

Welcome to Number One Observatory Circle, the vice president's residence located a 15-minute drive from the White House in D.C.

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Read more: Inside Number One Observatory Circle, the often overlooked but stunning vice president's residence where the Pences live

Sitting on roughly 13 acres, the grounds have ample room to house many flowering plants and the bees to pollinate them.

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In June 2017, Pence announced the arrival of the hives, which would house approximately 20,000 bees.

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Preston Keres/USDA

Source: USDA

Pence said it "was important for us to do what we could" to support bees. "All types of pollinators, such as bees, butterflies, birds and bats, are critical to providing our nation's food, fiber, fuel and medicine," she said.

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Preston Keres/USDA

Source: USDA

She previously kept bees at the Indiana governor's residence, unveiling a hive there in 2014.

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Michael Conroy/AP

Source: The Associated Press

"One of the reasons that we wanted to bring a beehive to the vice president's residence was because we wanted to help our bee population and we do have colony collapse disorder," Pence told CNN.

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Alex Brandon/AP

Source: CNN

Colony collapse disorder is one of the biggest threats facing bees today. It's what happens when worker bees leave the hive, and the queen is left with too few bees to keep the hive thriving. Habitat destruction, pesticide poisoning, and diseases affecting bees are all contributing to CCD.

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Alex Brandon/AP

Source: EPA

Honeybee populations have been on a decline, facing threats from parasites, pesticides, habitat loss, and climate change. In the 1940s, there were an estimated 6 million honeybee hives in the US, compared to 2.5 million today.

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Rick Bowmer/AP

Source: USDA

"Our beekeepers have been losing colonies for many years," Pence said. "This presents a serious challenge to our ability to produce many of the agricultural products that we enjoy today."

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US Department of Agriculture

Source: USDA

The bees at the residence are housed in triple-deep "Langstroth" beehives, which are made up of stacked, wooden boxes with frames inside that the bees can build honeycomb on and the beekeepers can easily remove.

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Alex Brandon/AP

Sources: USDA , Bee Built

Pence said the tens of thousands of bees would provide the added benefit of pollinating the residence's vegetable and flower gardens.

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Preston Keres/USDA

Bees help pollinate a third of the crops Americans eat, including almonds, apples, avocados, and blueberries.

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Preston Keres/USDA

Source: American Beekeeping Federation

US Department of Agriculture Secretary Sonny Perdue and his wife Mary joined Pence to unveil the beehives. According to the USDA, 90 crops benefit from bee pollination, adding at least $15 billion a year through increased yields and production.

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Preston Keres/USDA

Source: USDA

"Our honeybee population has been losing ground at an alarming rate," Perdue said. "The problem represents a diverse mix of challenges requiring a wide range of solutions. And at USDA we are leading the way in research to help out our pollinator friends."

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Preston Keres/USDA

Source: USDA

At the time, Perdue touted the agency's "significant research" on the topic. But in July 2019, the USDA stopped collecting data for its annual Honey Bee Colonies report, citing cost cuts.

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Preston Keres/USDA

Sources: CNN , EcoWatch

In her capacity as second lady, Pence has also visited bee research labs and invited school groups to see the hives at the residence.

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Preston Keres/USDA

Meanwhile, the bees are buzzing away on the grounds of the residence, showing just how important the pollinators are to the country.

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SEE ALSO: Inside Number One Observatory Circle, the often overlooked but stunning vice president's residence where the Pences live