potrero view

September 2008

Bees and Why We Need Them

By Mary Purpura and Silvano Purpura-Pontoniere

Bees are in crisis worldwide, and they’re not having an easy time on Potrero Hill either.  This is bad news, because bees are pollination workhorses. According to the United Stated Department of Agriculture, bees are responsible for 80 percent of insect-engendered pollination, with one-third of our diet coming directly or indirectly from insect-pollinated plants.  Many fruits, nuts, vegetables, legumes, and seed crops require pollination, and dairy products and eggs come from animals that rely, at least in part, on pollinated plants for their food source.

Bees don’t set out to help us by pollinating so many of the world’s plants.  Their pollinating activity is a byproduct of their food-gathering efforts.  Here’s how it works:  a bee flies to a flower to suck nectar out of the blossom. When it lands, it rests on part of the flower that contains pollen. Some pollen grains stick to the bee’s legs or abdomen. When she flies to the next flower to harvest more nectar, some pollen rubs off and sticks on to the flower, pollinating it.  The plant can now make seeds, propagating its further existence.

In 2005, about half of the country’s honey bees prematurely died or were dramatically weakened. By 2008, 70 percent of U.S. honey bees suffered an early death. The culprit appears to be Colony Collapse Disorder (CCD). Hives suffering from the disorder display a mysterious unfolding of events.  The colony transforms from a strong community with many healthy individuals to one with few or no survivors. Queen bees are often found with a few young adult bees, lots of baby bees, and more-than-sufficient food reserves. No dead adult bees are found in or around the colony, creating the effect of a bee ghost town.

No one knows what causes CCD, but scientists have a number of theories, including that the colonies are infested by previously unknown pathogens; pesticides or environmental chemicals are disorienting the bees, altering their all-important homing instinct, or damaging them physically; or a combination of factors, including disease or parasitic mites that could make it possible for opportunistic organisms to infest hives.

Many gardeners and beekeepers have introduced bee-friendly plants into their yards, or are nurturing one or two hives, as a way to address this global issue locally. At the Potrero Hill Community Garden on 20th and San Bruno streets, gardeners installed a couple of hives to aid in pollination. However, CCD wasn’t the only threat faced by the garden’s bees.  On at least three separate occasions, the hives have suffered severe vandal attacks.  In one instance, big rocks – weighing roughly 10 pounds each – were hurled at the hives; another time, the hive tops were removed, leaving  the bees vulnerable and exposed; and on a third occasion, a garden hose was inserted into one of the hives and turned on. The nature of the acts, as well as an eyewitness account of one of these strikes, have ruled out the possibility of a marauding raccoon or possum being responsible for the mischief; this is definitely the hand of man at work.

Local residents are upset about the senseless attacks on insects that are essential to our ecosystem.  “I live near the [Potrero Hill Community] garden, and for the first time my fruit trees have had fruit,” reported Cris Rys. “I...credit the bees at the garden for this.”

The Potrero Hill Community Garden at 20th and San Bruno has a long waiting list, but if you want to get on the list, email info@PotreroGarden.org with your contact information.  Anyone interested in community gardening can get started right away by adopting an available space on Potrero Hill in need of beautification or flower planting. You can use the same email address above to find out more about this option.

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