As I begin to write this post rain is pattering against the windows with increasing frequency and a brisk wind stirs the browning horse chestnut leaves that overhang the garden from a neighbouring property. Autumn is here. It’s a chilly Sunday morning and beside me is a large cup of good coffee, hot, black, and bitter, warming and stimulating in equal measure. It’s our first Sunday at home for a fortnight as last weekend was taken up by a speaking engagement in Hereford at a large bee keeping convention where coffee featured highly, as I’ll explain.
The Hereford convention wasn’t the kind of academic research conference that I’d normally attend, but I thought it would be fun to go with Karin, and I’d learn more about bee keeping (both proved to be true). For this broad audience of amateur and professional bee keepers I presented a version of my professorial inaugural lecture from earlier this year entitled “How many bees does it take to wake up in the morning? The importance of biotic pollination in a changing world”. It’s a title with multiple layers of meaning, referring to bees as ecosystem service providers, my enjoyment of my work which gets me out of bed every day, and the energising effects of a strong cup of fresh coffee first thing.
As part of that lecture I present some back-of-the-envelope calculations that are meant to put coffee production into a biodiversity perspective, rather than being a rigorous analysis, but which are nonetheless worth considering. They go like this.
Global coffee consumption in 2010 (the most recent year for which I could find figures) amounted to 93 million export bags, each weighing on average 60kg (there are larger and smaller bags used in different parts of the world, so we’ll use this figure). The export value of this crop was estimated at US$15 billion for the (largely tropical) countries that produced it. That’s the value before it’s processed and sold, which is much more difficult to calculate, though coffee retailing is clearly big business. For example, Starbucks’ total revenue for the same year was US$10.7 billion and it supports over 150,000 full time employees. So it’s lucky for us that it pays its taxes.
Although coffee is partly self pollinating, it relies on insect pollination to produce large crops, mainly involving bees of various types. I tracked down a number of studies by researchers such as Alexandra-Maria Klein and Taylor Ricketts which showed that managed honey bees are responsible for anywhere between zero and over 90% of flower visits, depending on the diversity and abundance of local wild bees (over 40 species of which are known to pollinate coffee in Costa Rica alone). At this point I throw out a question to the audience: how well do we understand this globally important agricultural ecosystem service? Do we have any idea of how many individual insects are required to support this industry? Some more calculations:
Each coffee bean is the product of a single fertilisation event following the deposition of at least one pollen grain on a flower’s stigma. The mean weight of a single coffee bean is 0.103g (I weighed a sample in preparation for the lecture) which means there are approximately 582,524 beans in a 60kg bag. Total number of coffee beans produced in 2010 is therefore 93 million bags multiplied by 582,524 beans per bag, which equals 54,174,757,281,553. In words, that’s more than 54 trillion coffee beans. As coffee is 50% self pollinating we can half that figure: coffee production requires at least 27,087,378,640,777 (over 27 trillion) pollinator visits.
But here I confess to the audience that it’s impossible to go further and answer the questions I posed above: we really have no idea how many bees are supporting the coffee industry. The problem is that there are big gaps in our knowledge of some basic aspects of the natural history of these bees and their interactions with coffee flowers. For example, how many flowers does an individual bee visit in its lifetime? How effective are different bees at pollinating the flowers? What is the minimum population size for these bees, below which they would go locally extinct? All that we can say with certainty is that the global coffee industry (and the individual productivity of many workers) is supported by a LOT of bees. Many billions is my best guestimate. Perhaps we don’t need to know the number: perhaps it’s enough to know that if we provide sufficient good quality habitat for these bees, they will provide the service. But at least it illustrates our reliance on these insects and is something to consider when you’re enjoying the first cup of the day.
Bees are not the only animals that we have to thank for coffee production as a recently published study has shown: birds in Costa Rica help to reduce the impact of an important pest of coffee. As Jana Vamosi, from whom I shamelessly stole the title of this posting, commented when I posted this link on Facebook: any friend of coffee is a friend of mine!
