Bees much prefer clearcut land over forest canopy areas

Research conducted by Oregon State University has revealed that native bee populations in the Oregon Coast Range are flourishing in clearcut areas within a few years of timber harvest, only to experience a drastic decline as the forest canopy closes. This study contributes to the understanding of forest management’s potential role in conserving crucial pollinator groups.

The study, led by graduate student Rachel Zitomer and Jim Rivers, an animal ecologist in the OSU College of Forestry, was published in Ecological Applications. 

“The research demonstrates that Douglas-fir plantations develop diverse communities of wild bees shortly after harvest,” said Rivers.  He added that promoting open conditions and enhancing floral resources in the initial years following harvest are likely to encourage bee diversity in intensively managed forest landscapes.

Despite growing concern over how human activity may be driving global declines in pollinator species, the impacts of land management practices on wild bees outside of agricultural systems remain largely unknown. The scientists emphasize the need to close this knowledge gap, as bees play a vital role in pollinating many of the flowering plants that make up ecosystems and support food webs.

To conduct their research, the team examined native bee communities in 60 Douglas-fir stands of varying ages across a time frame representative of a typical 40-year harvest rotation during the spring and summer of 2018 and 2019. They discovered that both the total number of bees and the number of different bee species dropped significantly with stand age, with an average decline of 61% and 48%, respectively, for each five-year increment after harvest.

Zitomer explained the significance of these findings: “Our results are important for forest managers because they indicate that bees do use intensively harvested stands, and that the window for bee conservation measures is restricted to a relatively short time period.” 

She also highlighted that their research is among the first attempts to quantify how native bee communities change over time after a dominant forest disturbance in the Oregon Coast Range.

Bees are essential pollinators for nearly 90% of the Earth’s flowering plants, including many food crops, and contribute to insect and plant biodiversity. 

Native insect pollinators, primarily bees, are estimated to provide over $3 billion per year in commercial pollination services in the United States. Oregon is home to more than 600 species of native bees, with almost a quarter of them found in recently harvested forests.

Rivers emphasized the importance of understanding bees’ habitat requirements and their response to human activity for effective conservation measures. “Wild bees are the top pollinators in most temperate regions, and widespread declines have prompted worries about food security as well as ecosystem function.”

The experts suggest that moderately reducing herbicide applications in the initial years after harvest could enhance pollinator species richness, sometimes without compromising revenue potential. 

Zitomer described this approach as a win-win for timber production and biodiversity conservation. The researchers also recommend including bee-pollinated plant species in seed mixes used for revegetation along roadsides and at log landings, to ensure maximum bee presence after timber harvesting.

Importance of bees to the ecosystem

Bees are essential to Earth’s ecosystems due to their role as pollinators. Pollination is the process of transferring pollen from the male reproductive structures (anthers) of a flower to the female reproductive structures (stigma) of another flower, enabling fertilization and the production of seeds and fruits. Bees play a crucial role in this process as they collect nectar and pollen from flowers to feed themselves and their offspring. In doing so, they inadvertently transfer pollen between flowers, leading to successful pollination.

Here are a few reasons why bees are so important to Earth’s ecosystems:

1. Biodiversity and food web support: Bees help maintain biodiversity by pollinating a wide variety of flowering plants, which in turn provide habitat and food for other organisms. This contributes to complex and stable ecosystems that support a multitude of species.
2. Agricultural productivity: Bees pollinate many of the food crops that humans consume, such as fruits, vegetables, and nuts. In fact, it is estimated that about one-third of the food we eat depends on pollination by bees and other insects. Without bees, agricultural yields would decline, leading to higher food prices and reduced food availability.
3. Food source for other species: Bees produce honey, which is not only consumed by humans but also serves as a food source for various other species, including birds and insects.
4. Ecosystem services: Bees provide valuable ecosystem services, such as improving air quality and soil health, by promoting plant growth and diversity. These ecosystem services are critical for sustaining both natural and human-modified environments.
5. Economic impact: The pollination services provided by bees are estimated to be worth billions of dollars annually. By pollinating plants that provide food, fibers, and other resources, bees contribute significantly to global economies.

In summary, bees play a critical role in maintaining Earth’s ecosystems by supporting plant reproduction, promoting biodiversity, and ensuring food security for humans and other species. Their decline, due to habitat loss, pesticide exposure, and other factors, poses a significant threat to global ecosystems and human well-being. Consequently, it is crucial to protect and conserve bee populations to maintain the balance of Earth’s ecosystems.

This study was funded by the U.S. Department of Agriculture and Food Research Initiative and a National Science Foundation Graduate Research Fellowship. Other researchers involved included Matthew Betts of the OSU College of Forestry, Andrew Moldenke of the OSU College of Agricultural Sciences, Sara Galbraith of Colorado State University, and Robert Progar of the U.S. Forest Service.

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