Many solitary wasps and 70% of wild bees nest below ground and require protection during this long and crucial period of their lifecycle. However, the Food and Agriculture Organisation, since 2002 assigned to safeguard soil biodiversity, excludes ground-nesting pollinators by focusing on species directly providing four ecosystem services contributing to soil quality and functions. Recent research has demonstrated the extent of threats to which ground-nesting pollinators are exposed, namely chemicals, deep tillage and soil compaction. Ground-nesting pollinators contribute indirectly to soil quality and functions as 87% of all flowering plants require pollinators. Without pollinators, soil would lose all ecosystem services provided by these flowering plants e.g., litter, shadow, roots for habitats and erosion control. Above- and below-ground biota are in constant interaction. Therefore, the key-stakeholder, the Food and Agriculture Organization should protect ground-nesting pollinators explicitly within soil biodiversity conservation.
Photo above: Dasypoda maura dig nests up to 80 cm deep – and this is the soil they have to transport above ground. Read more about this fascinating species here: El Abdouni I, Lhomme P, Hamroud L, Wood T, Christmann S, Rasmont P, Michez, D. 2021. Comparative ecology of two sympatric specialist bees: Dasypoda visnaga and Dasypoda maura, Journal of Hymenoptera Research, 81, 10-126, doi: 10.8937/jhr81.60528
The new article in Ecological Applications highlights the lack of system-wide protection by main stakeholders like FAO and EU. The Convention on Biological Diversity (CBD) defines soil biodiversity as “the variety of life below ground, from genes and species to the communities they form, as well as the ecological complexes to which they contribute and to which they belong, from soil microhabitats to landscapes” and charged FAO with global conservation of soil biodiversity and with the International Pollinator Initiative to promote synergies. However, FAO excludes ground-nesting pollinators by focusing on soil organisms directly providing four ecosystem services contributing to soil quality and functions: nutrient cycling; regulation of water flow and storage; soil structure maintenance and erosion control; carbon storage and regulation of atmospheric composition, thus on organisms like moles, beetles, ants, termites, earthworms, millipedes, woodlice, tardigrades, mites, nematodes, fungi, bacteria, protozoans etc.
This has negative impacts on ground-nesting pollinators and on soil organisms as well, on the latter notably because soil organisms like worms and mycorrhizal fungi are extremely dependent on stable vegetation above ground due to their low mobility. Soil bacteria and protists, for example, can move actively around 0.000001m only, nematodes 0.01m and arbuscular mycorrhizal fungi 0.005m per day. Therefore, they depend on pollinators promoting regeneration of 87% of flowering plants. The article demonstrates this dependence of soil organisms but also of humans by striking examples, e.g. the common pollinator-dependent mangrove Avicennia germinans.
The value of pollinators for soil biodiversity and soil functions has never been assessed. Also, the impact of soil compaction on ground-nesting pollinators has not been analyzed. Research on the impacts of tillage is rare. Pesticide risk assessments are conducted on honeybees (having support of beekeepers and nest in the hive), but rarely include the most exposed groups, ground-nesting pollinators or aquatic syrphid species.
Protection of ground-nesting pollinators within soil biodiversity requires revision of insufficient definitions and practically
D. Susan Willis Chan, University of Guelph