Scientific American just published a really cool info-graphic documenting the loss of bee species in Illinois. Half as many species interactions as exited 200 years ago persist today, though new plants have arrived on the scene and some bees are visiting them. Tragically, numerous species have been lost locally.
Were the pollinator communities of yesterday similar to the ones we see today? Or have there been dramatic shifts in community structure that mirror the changes to the landscape made by humans? Are there any traits that make species more or less vulnerable to these changes? These are the questions a team of researchers set out to answer by examining entomological collections of bees from across the Northeastern US. This historic data can help determine whether native bee populations reflect the effects of over a century of development.
The researchers found that rare bee species declined over time, though many had to be excluded from analyses because they were not collected during the past decade. The trend was strongest for bumble bees, which experienced declines of 30% in the past 140 years. Only a few species exhibited recent steep declines, with more species showing long-term shifts in abundance. The researchers suggest these populations be monitored closely as slow declines could indicate impending collapse. Over the same period, non-native bee species increased 9-fold.
The most vulnerable species are those with limited diets (specialists), limited flight periods, and larger body sizes. Species found to increase were those in lower latitudes; the authors of the study posit they may be expanding their ranges in response to climate change. Interestingly, other characteristics that have been found to affect bee population structure in previous studies such as nest location (ground- versus twig-nesting) and sociality (solitary versus social) did not impact rates of decline.
It seems smaller bees that are active over longer seasons and visit a wide variety of flowers may be the winners, whereas big specialist bees may be the losers. Bumble bees are particularly vulnerable, which is worrisome because they are often keystone pollinators in natural systems, visiting a wide variety of plant species. In fact, one study that simulated the removal of pollinators from a system found that losing bumble bees had the most rapid and pronounced effects on the deterioration of plant diversity and abundance. Bumble bees are also able to buzz pollinate, and some plant species require this kind of pollination to reproduce. The message from this study is clear- some key bee species are declining and we need to figure out ways to conserve their populations to maintain healthy ecosystems.
Bartomeus et al. 2013. Historical changes in Northeastern US bee populations related to shared ecological traits. PNAS 110(12): 4656-4660.
Claire Kremen, my PI, just wrote an insightful piece that appears on the UC Berkeley Blog arguing why neonicotinoid pesticides should be better regulated by the EPA and the Farm Bill ought to be changed to better reflect agricultural practices that don’t disrupt bee biology (and are better for the soil, wildlife, and people too).
In other news, Oregon just permanently banned the neonicotinoid pesticides responsible for the thousands of bumble bee deaths this past summer. Will other states follow suite?
Like the bats swarmed from under the Congress street bridge at dusk, so too did the mellitologists congregate for the bounty of bee-related talks and posters at this year’s Entomological Society of America in Austin. Pollinator-related research covered a wide breath of topics, ranging from urban to agricultural landscapes, and evolutionary biology to landscape ecology. Such a diversity of subjects provided ample opportunities for cross-pollination.
This was particularly true of Monday’s pollinator-focused graduate student 10-minute paper competition, presided over by Teresa-Pitts Singer of the Logan Bee lab. Not only does it seem like are there more researchers than ever before, but the topics are becoming more interconnected, the techniques more sophisticated, and as a result, interpretations are more nuanced. In the midst of this diversity of bee-related subject matter, there were also many convergences upon central themes including the importance of floristic diversity across scales and need for additional research on native bee nesting.
Many of the speakers from the graduate session gathered to discuss the exciting techniques and case studies presented over lunch. Of course, we duly noted that one out of every three mouthfuls of tex-mex cuisine consumed relied on pollination from our humble study organisms. The table was a-buzz with lively discussions. At one point Shelly Wiggam-Ricketts, from Kansas State, rapped the table to get our attention: “In 5 years, we need to organize a symposium on all the amazing research we’ll have done examining native bee life history and conservation.” We all nodded in agreement.
With all the interesting work going on now, I wonder what will we be researching a few years from now? Will we have answered the key questions that hold our attention today? Will our findings alter pesticide use, or encourage homeowners to plant more pollinator-friendly gardens? Will farmers reduce field sizes, increase crop rotations and increase on-farm floristic diversity? What new insights will this group of motivated graduate students add to the field, and what new questions will they tackle? Time will only tell.
I was just at our neighborhood block party and met many people I didn’t know- but they knew me because they’d seen me out in my front yard tending my tiny pollinator garden. They commented on how beautiful it is, and one even asked if I could help her with her landscaping. It’s amazing how creating habitat for bees also serves as a way to connect with my local community.
Planting your own lovely pollinator garden is really satisfying and simple: A new study in the UK shows that planting your garden with pollinator-friendly flowering plants is easy and inexpensive. Plus some of the plants are common herbs that add to your culinary endeavors, including marjoram and lavender. Rosemary is another plant typical to urban landscaping that is highly attractive to bees. For the full story on BBC news, click here.
Last summer my husband and I planted native flowering plants along the “parking strip” in front of our house (the area between the side walk and the street). The area was just grass and weeds, which we pulled- then we turned the soil and amended it with gypsum (it has a lot of clay) and compost. To gather the plants, we went to the UC Botanic Garden sale, to the local California Native Plant Society Nursery, and to a neighborhood nursery, Westbrae. You can see the initial stages in the photo below. We enlisted a friend to help and got some nice pavers to make a walkway during a sale at a local hardware store.
A little over a year later we have a colorful array of sages (salvias), buckwheat, native grasses including blue fescue, yarrow, and california lilac (ceanothus). We also added some succulents, which are classic xeroscape plants, and some non-natives from other Mediterranean regions including lavender and New Zealand flax. The city of Albany has a program where they cost-share the price of planting trees in parking strips, so we had them plant a red bud (though sadly they would only let us plant the eastern variety, not the native western species). I’m also considering getting 2 more plants to put in this winter: milkweed, which is loved by bees and butterflies alike, and phacelia, a california native plant with purple or while flowers that stick up like a scorpion tail and are bumble bees absolute favorite.
If you want to encourage bee nesting, it’s important to leave bare soil. We decided not to mulch for weed suppression, though we do weed every 2 months or so. To fill in the spaces with bee-attractive blooms while leaving bare dirt, we collected a few poppy seeds from a nearby plant, and had dozens of poppies filling in the gaps this past spring and summer. We just bought a wildflower mix that we’ll sprinkle onto plot once the rains come- so next spring our front yard should be a pollinator paradise.
When it’s really hot out we water about once a week- but most of the CA natives are drought tolerant and low maintenance. After they establish, we shouldn’t have to water too much at all. The best time of year to plant is now- so the rains provide the moisture the plants need to put down their roots and thrive come spring.
For more ideas on plants that attract pollinators check out the Xerces Society book Attracting Native Pollinators and the informative urban bee website helpabee. The UC Agricultural Experiment Station just published a guide on plant selection in California as well. With this wealth of resources, it will be easy to make your garden a pollinator refuge.
The market near my home is sporting a massive pumpkin display in honor of the harvest season and the slew of upcoming holidays that incorporate gourds. The delicacies our festivities center around rely on native pollinators in order to swell to sometimes fantastic proportions. One species of native bee in particular, the squash bee (Peponapis purinosa), a specialist that only visits plants in the cucurbit family, including watermelon and pumpkin, is one of the critical players in our autumnal celebrations.
Squash bees, like 80% of all native bee species, builds it’s nests underground. It digs a tunnel with several lateral chambers off of it in which it lays it’s young. Most chambers are not too deep in the soil profile, ranging from 3 inches at the shallowest, to a few feet deep, with most around 5-10 inches. Squash bees prefer to nest near their source of pollen and nectar, which means that it nests within agricultural fields. Although the squash vines die out and get removed- the immature bees remain in their cells within the soil, waiting until next summer to emerge and find more squash blossoms. This means that any soil management can affect the young as they overwinter underground.
Katharina Ullman, a graduate student at UC Davis, has been looking at whether tilling negatively impacts squash bee pupating in agricultural fields. She experimentally added squash bees into flight cages and determined where they nested. She then disked and tilled up to 16 inches in the ground in half of these plots. The following summer (this year) she set up cages again to see whether the tilling affected the bees. She found that tilled plots had only half the number of emerging squash bees as untilled plots.
Most farmers disk every year, and till to the depth Katharina did every 3 years. This means they may be killing or disrupting up to half of the population of squash bees! No till or low till methods may help to protect bee larvae and pupae that overwinter in underground cells- helping to bolster pollinator populations year to year, and helping to maintain delicious food on our holiday tables.
Picture of a Squash Bee in a Squash Bloom from Discover Life
(This research was presented at an awesome UC Cooperative Extension Seminar that Katharina and Rachael Long coordinated in Davis last Friday. I learned a lot about neat research projects going on in the region, that I hope to write about in the future- but this seemed most relevant to this time of year)