Pollinators in general and bees in particular have declined catastrophically, except in favoured districts that have escaped modern, intensive agriculture. However, in recent years much has been done to research and publicise this decline, with the result that even the Government seems to be about to take it seriously.
One problem amongst many is the widespread thinning out of wild flowers that sustain base-level populations of pollinators. Or, turning it round, one way of trying to reverse the decline is to restore the diversity of wild plants in the countryside. But, how? What are the priorities?
A recent research article (Journal of Applied Ecology, 2017, 54, 1856-1864) gives some guidance. Ecologists kept a systematic watch on the bee species visiting wild flowers in the farmland of the central Swiss plateau. After a long summer watching the 69 bee species in the region, they had recorded 2277 visits by honeybees to 56 plant species and 925 visits by wild bee species to 64 plant species. The plant species that each group preferred (and the strength of their preference) is given in this table. They visited other plant species, but showed no special preference for them. Likewise, honey bees, for example, visited Red clover, but showed no species preference.
| Preferred* plant species | Honey bees | Wild crop pollinators | Rare bees |
|---|---|---|---|
| Achillea millefolium, Yarrow | xxxx | x | xx |
| Centaurea scabiosa, Greater knapweed | x | ||
| Centuarea jacea, Brown knapweed** | xxxx | xxxx | |
| Cirsium arvense, Creeping thistle | x | ||
| Crepis capillaris, Smooth hawk’s-beard | xx | ||
| Echium vulgare, Vipers bugloss | x | x | |
| Epilobium hirsutum, Hairy willowherb | x | ||
| Hypericum perforatum, Perforate St-John’s-wort | xx | ||
| Knautia arvensis, Field scabious | xxx | xx | |
| Lotus corniculatus, Bird’s-foot trefoil | xxxx | ||
| Malva neglecta, Dwarf mallow | x | ||
| Medicago sativa, Lucerne | x | x | |
| Melilotus albus, White melilot | xxxx | ||
| Origanum vulgare, Wild marjoram | xxx | xx | x |
| Tanacetum vulgare, Tansy | x | ||
| Trifolium pratense, Red clover | xxxx | xxxxx | |
| Trifolium repens, White clover | xxx |
** the Continental equivalent of our Common knapweed.
For readers who come within the ambit of the PGP and who would like to do something for pollinators, I think the main lessons are:
- that a wide variety of wild flowers is needed to cater for all classes of pollinator, and
- some plant species are more widely useful than others. Yarrow, Knapweed and Red clover seem to be the most generally useful; and Bird’s-foot trefoil is particularly favoured by wild bees in general. Also,
- if we want to look after any rare bee species that might be hereabouts, Red clover is a lot more useful that White clover.