“We found that biodiversity plays a key role in the stability of ecosystems over time,” said Natalie Lemansky, the study’s lead author and a postdoctoral researcher in the Rutgers School of Environmental and Biological Sciences (SEBS) Department of Ecology, Evolution and Natural Resources. “You actually need more bee species to have stable pollination services throughout the growing season and years.”
The research team focused on different bee populations on dozens of farms in New Jersey, Pennsylvania and California and found that not only did pollination require many more bee species than expected throughout the bloom, but even more over several years. .
The researchers said they observed different bee species pollinating the same type of plant at different times of the year. They also found that different bee species were dominant pollinators of similar plants in different years. Because of the natural fluctuations in bee populations, the researchers said all bee species present were needed to maintain a minimum pollination threshold in lean years.
“This study demonstrates that abundance [of a species] matters, but the diversity of bees matters even more,” said Michelle Elekonich, associate director of the Division of Biological Sciences at the National Science Foundation, which funded the study. “It’s not the same bees that are abundant at any given time, and variety is necessary to achieve balance during the growing season — and year after year.”
Lemanski said the study provides justification for a long-standing concept ecologists call the “insurance hypothesis.” The idea is that ecosystems probably benefit when nature “diversifies the portfolio” by supporting multiple species of a plant or animal class, rather than relying on a single dominant species.
“We found that two to three times more bee species were needed to achieve the target level of crop pollination during the growing season compared to a single date,” Lemanski said. “Also, twice as many species were needed for pollination in six years compared to one year.”
The researchers based their analysis on their own extensive observations of bee visits to flowers and measurements of the number of pollen grains on individual flowers over weeks and months during a given calendar year and then over several years. With the permission of farmers, they collected data from 16 blueberry farms in South Jersey, 25 watermelon farms in central Jersey and eastern Pennsylvania, and 36 watermelon farms in northern California.
“Over many years, the magnitude of the increase in required species was remarkably consistent across cropping systems when looking at the same time period,” Lemanski said. “Furthermore, the fact that the relationship between time scale and number of species required did not level off suggests that even longer time series spanning multiple seasons may still reinforce the need for biodiversity to ensure a reliable ecosystem service.”
Source: The Nordic Page