Hear the first real California rainfall of the season (recorded Feb 8, 2014):
You may have seen the pictures NASA scientists took on Jan 14, 2013 and 2014, showing the state of California’s drought. Most people immediately notice the difference in snow pack along the Sierras, but what hit me was how green California’s Central Valley was last year. That green represents ag fields, rangelands, and hills of the coast and mountains. It also represents germinating native wildflowers. We know that April showers bring May flowers, or if you live in California winter showers bring spring flowers, but what is the relationship between precipitation and bees? To find out the answer to this question check out the nice blog post that Hillary Sardiñas wrote. Her post focused on a study by Robert Minckleyet al. (2013). You can take a look at the abstract for the original paper here.
Almond bloom has arrived in California. This provides a beautiful site for those driving through the Central Valley, but for the honey bees it means it is time to get working, with almond bloom being the biggest crop pollination event of the year. While honey bees are important for almond pollination, a team of researchers led by Alexandra Klein wanted to investigate (i) whether wild insects contribute to almond pollination and (ii) how the amount of “free” pollination provided by these insects vary with surrounding land cover. To explore this they observed the visitors to almond flowers in 23 orchards in northern California that varied in their amount of surrounding natural habitat. They also recorded the fruit set in those orchards as the percent of flowers producing almonds (calculated from a sample of branches in each orchard).
The Klein et al. (2012) study found that the ground nesting bee Andrena cerasifolii (Cockerell), sweat bees (particularly Lasioglossum species) and the bumble bee Bombus vosnesenskii (Radoszkowski) were the main wild insect visitors to almond flowers in the northern Californian orchards where they conducted their observations. They also found that orchards with more surrounding natural habitat had more visits to almond flowers by wild bees AND a higher percent fruit set. One reason for this might be that wild bees are flying in from the surrounding natural habitat to collect pollen and nectar from the orchards during the almond bloom. This study showed that almond orchards can receive “free” pollination service from wild bees which can supplement honey bee pollination and improve fruit set. This highlights the importance of conserving the remaining natural habitat around almond orchards.
Recently, Kris from Tomten Farm in Colorado asked how to increase pollinator abundance and diversity on her farm. A paper by Jeroen Scheperet al.(2013) shows that one of the best ways to attract a lot of pollinators to your farm is to plant wildflowers and, if you want to get lots of different kinds of pollinators, plant diverse wildflower mixes. The researchers analyzed data from six European countries. In an effort to mitigate the negative effects of agricultural intensification the European Union established incentives for farmers to incorporate conservation measures into farm management plans. These conservation measures are known as agri-environmental schemes (AES). Some of these schemes are similar to cost-share programs in the United States offered by the Natural Resources Conservation Service.
The paper by Scheper et al. (2013) compared AES and conventionally managed fields using data collected from 121 paired fields. Specifically, they were interested in knowing whether wildflower plantings, conversion to organic production practices, or grassland establishment did the most for pollinators. They found that, in croplands, all of these practices benefited pollinators, but that wildflower plantings attracted the most pollinators (see Fig 2a in the paper). When they looked at wildflower plantings more carefully, they saw that the more different kinds of wildflowers you plant, the more bees you get! This is true both for bee abundance and bee diversity (see Fig 3a and b in the paper.) In a separate post we’ll talk about some of the other findings in this paper.
Questions researchers want to know now are: What is the best recipe for wildflower mixes that want to increase pollinator diversity? How does this recipe differ if the goal is to increase crop pollinating species? Do pollinators visiting farm wildflower strips pollinate crop plants as well? And, do farm wildflowers have the desired effect of increasing pollinator populations or simply attract and concentrate existing pollinators from the surrounding landscape?