Which bee to keep?

Hairy-footed Flower Bee Anthophora plumipes ©Natural England/Allan Drewit

Hairy-footed Flower Bee
Anthophora plumipes
©Natural England/Allan Drewit

Bees often hit the headlines. Where birds once ruled supreme, the bee is the rising star of the conservation movement. The beneficent, busy bees make our world work for us by pollinating our crops and some provide us with honey.

During a recent visit to a firm in the City, I was scanning the surrounding buildings and picked out two bee hives set up on a ledge in the vertiginous face of a nearby building. Defra has a bee hive on its roof and our little friends busily exploit the nectar in the nearby London planes around Westminster. In spite of the sting in its tail, we have embraced the bee.

A lot of information passes by me on a daily basis but occasionally something jumps out at me. Recently, it was the juxtaposition of a scientific paper published in Nature Communications and a draft report that I had to review. The paper was about pollination with information about species loss from Britain.

The paper reported the remarkable discovery that about 80 per cent of crop pollination was provided by only two per cent of bee species. Meanwhile, the report listed all the rare species that might disappear from Britain in the not too distant future.

Without seemingly realising it, the authors of the scientific paper recapitulated a rule of nature which says that abundance distributions tend to follow something called power laws.  They occur in a huge diversity of situations: the number of words in languages, the number of people in relation to their wealth, and the energy used by animals and plants in relation to their body size. Power laws are all over the place.  They apply to the distribution of values of cars on the roads of Britain – you see very few expensive Ferraris, but lots of cheap hatchbacks. A chap called Preston wrote a seminal paper in 1962 showing that species abundances tended to follow these power laws. There are lots of rare species and just a few abundant species.

So, why did this connect in my mind with the messages I picked up about species loss? Well the dilemma the pollinator paper highlights is that most of the rare species listed in the report possibly facing extinction in Britain are likely to be functionless. On what basis could I advise about which species to keep – just the two per cent of bees that provide 80 per cent of pollination; surely not?

The science of ecology has known for a long time that species come and go. Studies by luminaries MacArthur and Wilson in the late 1960s suggested that species that inhabit islands do so. Since the world is made up of islands of a sort, whether in a sea of water or of cereal fields, their conclusions have broad implications for how to interpret species presence, absence and extinction. The species in any one place are a combination of the long standing residents who have adapted to the local environment and the opportunists.

The two per cent of bee species that provide 80 per cent of the pollination are likely to be such opportunists who have coped with the changing landscapes mainly brought about by agriculture. Those listed in the report as under threat of extinction from Britain, although not necessarily from elsewhere, are the losers in this game.

So does this new knowledge guide us towards a more informed kind of conservation? It defines the difference between two doctrines; one of species protection and another of functional importance. This is a spectrum and our individual values place us somewhere between its two extremes. I like species that are unusual and I also see a need to have productive, functional landscapes. Can the two be compatible?

The doctrine of function is played out most strongly through the lens of economics. A growing school of thought attempts to place a formal valuation on assets like species. By those criteria, the 98 per cent of species that contribute only 20 per cent of the pollination services have relatively little utility. Some environmental campaign groups quote the eye-watering large financial value placed on them by economists to support the case for conserving pollinators, but this has a different perspective if it applies to a few per cent of all species. Those who adhere to the doctrine of species protection will say that the same two per cent of important species today might not be the same two per cent needed in future. Maybe we need to protect them all just in case? The low-value 98 per cent of bees that don’t help much towards the pollination of our crops might have other roles we don’t yet see.

These views sit at either end of the spectrum. Of course we don’t want to lose rare species, but we may also need to take species utility into account. We could compromise by defining better ways to construct our landscapes but that will mean some hard choices. Whatever choices we make will favour some species over others and building a rational basis for those choices, as for example the current work on natural capital is tending to do, will be important. Science has a lot more to do to make the case for those we don’t want to lose and those we need to keep.

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