This post is written by Jeff Ollerton, Visiting Professor of Biodiversity at the University of Northampton, and Visiting Professor at Kunming Institute of Botany. 

Coffee is something that we frequently take for granted as just a beverage that gives us a little kick first thing in the morning. But it’s so much more. In this edited extract from his forthcoming book, "Pollinators & Pollination: Nature and Society" (Pelagic Publishing, 2021), Dr. Jeff Ollerton (Visiting Professor of Biodiversity at the University of Northampton in the UK) explains why it’s such an important crop for small-scale farmers in the tropics, and the role that bees play in supporting a multibillion dollar global industry. 

How many bees does it take to wake up in the morning?

In the diary that Charles Darwin kept during his time aboard HMS Beagle, an entry written on a farm near Rio de Janeiro, where he stayed in April 1832, notes:

“On this [farm] are cultivated the various products of the country: Coffee is the most profitable: the brother of our host has 100,000 trees, producing on an average 2 lb. per tree, many however singly will bear 8 lb. or even more.”

Like many academics, I drink quite a lot of coffee and it’s my go-to drink first thing in the morning. It’s also a hugely valuable commodity that is traded internationally. Charles Darwin seems to have been interested in the crop too, though doesn’t appear to have appreciated the importance of pollinators to its production.

Coffee is represented in the global commodities market by different varieties of two species (Coffea arabica and C. robusta) in the family Rubiaceae. The flowers are pollinated by a variety of insects, predominantly wild bees and managed honey bees (Ngo et al., 2011). Because of its huge economic value (estimated to be in excess of US$80 billion per year), it supports millions of subsistence farmers throughout the tropics. It also supports a vast supply chain — and not a small number of baristas — in the developed world.

One sometimes reads statements about coffee being "the second most valuable global commodity after oil," and in fact, I repeated this notion in a recent review paper (Ollerton 2017). However, even careful scientists get things wrong sometimes, and I later discovered that this is a myth (Greenberg 2017). Nonetheless, regardless of its ranking, it is hugely valuable. In 2018/19, coffee production worldwide amounted to 170.937 million standard hessian coffee bags, each weighing 60 kilograms (International Coffee Organization, 2020). One coffee seed (what we refer to as a ‘bean’) results from a single fertilization event following the deposition of pollen on a coffee flower’s stigma, and there are two ovules per flower to be fertilized. The weight of a single coffee bean is about 0.1 grams on average (I know because I spent an hour in the lab weighing a sample a few years ago), so there are approximately 582,524 beans in one of those standard 60-kilogram export bags. The total coffee bean production in 2018/19 was therefore 170.937 million bags multiplied by 582,524 beans per bag, which equals 99,574,752,191,955.

Put into words, that is over 99 trillion coffee beans. That’s a lot of coffee.

However, coffee is on average 50 percent self-pollinating, though outcrossed coffee is better quality (Klein et al., 2003; Classen et al., 2014), and one visit to a flower by a bee might result in the fertilization of both ovules. Therefore, we can divide our bean total by four to give us the minimum number of pollinator visits to flowers required to sustain global coffee production: almost 25 trillion visits.

Think about that figure for a minute: at this very moment, somewhere in the world, billions of bees are going about their business, collecting nectar from coffee flowers and providing the basis for an industry that spans the world, generates jobs and prosperity for producers and the employees of coffee companies, and fuels a good deal of the intellectual output of universities.

The importance of the global coffee industry, and therefore of the pollinators it relies on, has risen by orders of magnitude since Darwin’s day. Thanks to the availability of historical data, it is possible to show how the role of bees in sustaining coffee production has increased exponentially over the past 170 years or so (Figure 1).

We can’t directly answer the question posed in the title of this blog post, as we simply don’t know enough about tropical bee ecology or the number of visits each bee makes to coffee flowers in its lifetime. At the very least, we would need to know the number of individual bees found in coffee plantations of different sizes. But what is clear is that billions of bees support the livelihoods of the farmers and other workers in the coffee supply chain. These bees in turn require semi-natural habitats to survive, as they have to find forage other than what is available within the coffee flowers, as well as places to nest and other resources. That’s why conservation efforts must include local small-scale farmers in their activities.

So, the next time you pour yourself a strong cup of Joe, give a thought to the bees who helped you to wake up in the morning.

FIGURE 1: The historical increase in the number of bee flower visits required to pollinate the world’s coffee crop, based on data of total production of coffee (one trillion = 1012). Pre-1990 data are averages per decade; post-1990 data are per year. The grey line is an exponential fitted trend. Data pre-1990 are from Bacha (1992); those from 1990 onwards are from the International Coffee Organization (2020). Inset images show a coffee bush with a ripe fruit and opening flowers (top left) and a selection of standard 60 kg hessian coffee bags.