Bees aren’t all alike. The tens of thousands of different bee species around the world need different habitat to do well. Getting unique species to take root in restored habitat is a whole other story. In a session at the Society for Ecological Restoration (SER) conference in Madison, Wisconsin, ecologists discussed how challenging it is to create habitat bees will use year after year, particularly in restored landscapes.
Places for Bees in Agricultural Areas
Claire Carvell, who is a researcher at the Center for Ecology and Hydrology in the UK, outlined how English bees have responded to habitat restoration projects. The situation for bees there is pretty dire. Some 75 percent of the UK is agricultural land. Some 97 percent of wildflower meadows, places bees love, are gone. As a result, “bees have significantly declined over the 20th century.”
The UK has more than 260 bee species, with some 26 species being social. There are 25 native bumblebees (2 have gone extinct). While there are still many types of bees, Carvell said bee diversity has decreased in more than half of the UK’s landscapes — by more than 50 percent since 1980.
To combat these trends, the UK government has initiated a program that pays subsidies for the “intensification of landscape quality.” Farmers must chose wildlife-friendly options to quality for those subsidies, which can total 280 pounds a year. One common outcome of this subsidy is natural strip of land left alone within farmland. There, a mix of agricultural plants and grasses bees like are added. Bumblebees take to agricultural legumes, while sunflowers are also good for bees.
In a recent project, Carvell said ecologists tested a few different options. In land where were there simply crops, there was no value for bees. In areas without pesticides, there was only a limited response. Where the “natural generation of plant communities” was allowed, there was also only a limited response. She said the key is creating sites with pollen and nectar, a diverse seed mix, which resulted in a “significant response” from the bees.
But one seed mix, no matter how diverse, will “not have sustained benefits.” There is a seasonal component; some plants die off. Flowering plants that offer nectar need to be re-sown every 3-4 years. Diverse plant mixes must include perennials.
Former Mining Sites Can Provide Habitat
Former mining sites litter the globe. Given all the untapped land, there are lots of opportunities to restore them as habitat for bees. But how good are these sites?, asked Karen Goodell, an ecology professor at Ohio State University.
The answer: reclaimed mines “can aid bee conservation,” but they will not be as good as remnant (untouched) habitat. It’s difficult to restore plant communities that existed in mining areas before. Forests can be re-created, but the full ecosystem is another story. While “floral diversity and abundance will positively affect bee recruitment,” bees will be less diverse in these mining sites than in remnant habitats.
In an observational study of 24 sites at The Wilds, a leading conservation site in Ohio, Goodell netted bee species, counted floral resources, and assessed nest habitat. She looked at sites that “vary in proximity to natural habitat.” A few experimental sites had “augmented nest sites;” another set only got “nest blocks” in the second year.
Looking specifically at Megachilid bees, which are more solitary than honey bees and nest on or in the ground, she found that “the abundance of floral resources wasn’t really important, restoring nesting substrate was far more critical.” Nesting “subtrate” includes stem wood and bare soil. She added that “adding additional artificial nest substrate didn’t help.” To that end, she said it’s important habitats, whether they are restored or not, have ample hollow stem wood lying around, shrubs, dead wood, and bare ground, if you want to attract Megachilids.
Challenges with Ecosystem Restoration
For Neal Williams, University of California – Davis, the transformation of wild areas into agricultural areas is the primary reason for bee habitat loss. Near the Sacramento River in California, a group of farmers and other interests are restoring an 80-kilometer swath along the river corridor from Red Bluff to Chico. Williams’ study there is looking at the community of pollinators in the restored fragments in comparison with the remnant riparian forests. His interest is what factors contribute to the “persistent differences” between the two areas.
Williams said the sites were actually restored. A mono-cultural landscape filled with Walnut orchards was turned back into a forest, but now there is no understory. The issue then was that “species richness was restored, but not composition.”
Lastly, Rufus Isaacs, Michigan State University, discussed bee habitat restoration in managed lands in Michigan. He said there’s a “great diversity of fruit and vegetable production in the area and farmers are very interested in the health of bees.” Hopefully, more will actually do something about setting aside land for bees, given so much of America’s farm produce relies on pollinators.
Image credits: Bee Habitat / Honeybee Conservancy