UPDATE: On Twitter, Andrew Hubbard kindly drew my attention to the short article from 1919 at the bottom of this post in which it was estimated that British bee stocks at the time were as low as 32,500 hives. As Andrew pointed out, this means that the estimate by Bailey and Perry of 800,000 hives in the 1920s cannot be correct.
In one of the chapters of the book that I’m currently completing I deal with the question of the evidence for changes in the abundance and diversity of pollinators over time, both in Britain and globally. Are we really in danger of losing most of our pollinator species? Have honey bee numbers plummeted? Has pollination of wild and crop plants been affected? The evidence is mixed and too complex to deal with in a short blog post: you’ll have to read the book 🙂 However I want to present some data that I’ve collated on changes in honey bee hives in Britain to gauge opinions on what has gone on. I’m not a specialist in bee keeping by any means, others are far more knowledgeable, so as always I’d be interested in peoples’ thoughts on this.
The graph above has been pieced together from data presented in various sources – see below. From a post-WW2 peak of about 450,000 hives, numbers dropped to about 150,000 hives in the 1970s. That seems very clear. Numbers remained fairly stable until the early 1990s and then….what? There are two possibilities: either numbers of hives crashed to fewer than 100,000 by 2008; or they increased hugely to more than 250,000. Both scenarios cannot be correct!
There are huge uncertainties about the data during this period, however the most recent data from Defra is fairly solid, though it does require beekeepers to register their hives on BeeBase. Given the wide range of the low and high estimates, the fact that bee keeping has become more popular over the past decade, and that the recent data sit more-or-less within this range (at least initially), I wonder whether honey bee numbers have actually remained quite stable over the past 25 years or so, and indeed have hovered around the 150,000 hives or so since the 1970s.
Of course an alternative scenario is that the varroa mite (which arrived in Britain in 1992) led to that huge collapse in bee numbers. But I wonder if there’s really any evidence for that? Were whole apiaries wiped out by varroa? It’s notable that the decline in this period started much earlier than the arrival of varroa, in 1985. Why was that?
The earliest data available are those in Bailey & Perry (1982 – Bulletin of Entomological Research 72: 655-662) that span 1946-1982. This should be fairly accurate for England and Wales, though their estimate of 800,000 hives in the 1920s needs to be treated with caution as they make a number of assumptions in their regression-based analysis that may be incorrect; I’ve therefore not included that data point on the graph. Unfortunately the UK stopped returning official numbers of hives to the United Nations’ Food and Agriculture Organisation (UN-FAO) in 1977, and their data up to 1987 is an unofficial estimate (http://www.fao.org/faostat/en/#home). From 2003 the UK had to report bee hive numbers to the European Union to claim money for the National Apiculture Programme (https://ec.europa.eu/agriculture/sites/agriculture/files/honey/programmes/programmes_en.pdf), but the figures were rather suspiciously constant between years. More recently beekeepers have been encouraged to register their hives with BeeBase (http://www.nationalbeeunit.com/) and hopefully these estimates are more realistic.
Data for part of this period were also presented in Potts, S.G. et al. (2010) Declines of managed honeybees and beekeepers in Europe? J. Apic. Res. 49, 15–22 Thanks to Prof. Simon Potts for sharing the data from that study.