- That the introduction of bee hives to nature reserves is a potential threat to natural pollinators as a result of inter-specific competition.
- That the volumes of nectar available from particular nectar sources are so vast that there will be no effect on wild bees; and that natural pollinator numbers are so low that there is a need for bee hives to facilitate the necessary pollination services.
Monday, 26 March 2018
Have honeybees obscured the real environmental pollinator dilemma?
A thread on the BWARS Facebook group yesterday brought the issue of honeybees on nature reserves sharply into focus. There seem to be two schools of thought (with permutations):
Needless to say, I sit in the first camp! But I only do so after careful thought (I am naturally quite pragmatic and aware of political sensitivities).
In past threads I have voiced concern about the potential for competition between honeybees and solitary/wild colonial bees. But, I have also been less than certain that there was detrimental competition between honeybees and other pollinators such as hoverflies. My rationale was that whilst there is a direct link between pollen/nectar resources and wild bee brood success, other insects may not be as reliant upon nectar and pollen to ensure breeding success. Upon reflection, I think I may have under-estimated the importance of nectar to allow females to live as long as possible and to lay eggs in as many places as possible; and also the importance of pollen to facilitate egg maturation. Slap on the wrists for me! Nevertheless, there remains a dichotomy and it would be instructive to determine how vital nectar and pollen sources are to breeding success of individual species of flies (for example).
Yesterday’s thread brought my thinking far more into focus and I am now thoroughly convinced that on all counts there is no case for allowing honeybee hives to be placed on nature reserves. Unfortunately, as is also the case for wildfowling (where flight ponds sometimes ring wildfowl reserves), there is nothing to stop hives being placed in close proximity to nature reserves and for beekeepers to exploit the nectar and pollen resource that should be available for the natural pollinators.
We know that wild pollinators have declined massively (across all taxa) but the reasons for decline are less certain. The chances are that there is no single factor (as I have written previously). Habitat loss and degradation are undoubtedly significant, as are the use of pesticides and herbicides. Others in the mix must also include atmospheric nitrification and climate change. We might also have to consider the impact of bee-borne pathogens spread by honeybees. Recent research suggests that pathogen levels in honeybees are pretty high, but are also high in some wild bees and have even been detected in some hoverflies.
There could easily be negative effects from honeybee farming. For example, I was amazed by the vast trucks of bee hives imported into the Lime woods of Serbia at flowering time. They must have stripped the trees bare of nectar! Yet, I have also seen/heard the same frenetic activity by bumblebees where honeybees were not dominant. One fantastic example was a Sycamore in Scotland that at 9pm literally hummed with bumblebee activity. I’ll bet a couple of beehives would put paid to that local population!
So, although there is scope for various avenues of research into inter-specific competition between hive bees and wild bees as well as other nectar and pollen-dependent taxa, there is a strong precautionary case for excluding bee hives both from nature reserves and from a zone around such reserves.
I felt that the real worry about the honeybee debate was the suggestion that without honeybees wild plants on nature reserves would not get pollinated. This seems to me to be a spurious argument because honeybees make up just part of the range of pollinators. Furthermore, it is equally possible that honeybee numbers are suppressing productivity amongst wild pollinators and if the competition was removed then there would be scope for wild pollinator numbers to expand (assuming this competition is part of the problem). I would have thought it should be possible to investigate this interaction and the response of natural pollinators to reduction of competition.
The debate went further, with the implied suggestion that habitat creation would not be successful without pollinators, and that this by necessity was honeybees. Again, there is scope for research but the theory I would advance is that in the absence of honeybees there would be sufficient natural pollinators to facilitate plant development. Early successional stages should also mean that there would be bare ground, so beloved by solitary bees as nesting habitat. Aphid numbers are likely to be good amongst plants that do not require insect pollination (e.g. grasses) and as a result there should be plenty of hoverfly pollinators. It might take time for numbers to build up, but then that is what succession is about! Granted, some plants require long-tongued pollinators, but it is difficult to envisage a total absence of such insects in the timescales needed for habitat creation.
We know that replicates of natural grasslands can take many decades to acquire a representative flora, so there is time for the pollinator assemblage to evolve. Far more critically, where will the seeds come from and are the soil conditions right for specialist species? Soil chemistry, hydrology, bacteriology and mycology are probably far more critical factors underlying potential success of habitat creation schemes. Deep ploughing and herbicide/pesticide application have effectively destroyed most soils that might be used for habitat creation. In common with maintaining wildlife, nature reserves are critical natural soil assets.
So, if we want to safeguard pollinators per se, we must think about the impediments to their population growth. Honeybees have a place in the mix, but in a natural system there would be checks and balances on them too. It is therefore inappropriate to argue that because honeybees are a native species they should be the focus of attention to the detriment of wild species. I therefore think the research debate needs to shift towards the potential negative effects of importing honeybees into localised environments either on a permanent or temporary basis. In the meantime, the precautionary principle should apply because there are sufficient potential connections to construct a case for a detrimental effect.