Here’s an edited version of the talk, which covers a bit of my fieldwork in the past two years:
Of all the people i know, I’m on the naive and optimistic end of the spectrum, but even i cant look at this image without dying a little inside.
Because this is the exact opposite of what we’re doing.
The current global food system is overrun with problems. Our growing population and growing demand for protein are fuelling widespread environmental degradation and species extinction, public health epidemics such as malnutrition, obesity and heart disease, and exacerbating economic inequality between producers and consumers.
So how does conservation fit into this context? We want food - and we want to save wild species. How can we best do this?
There are many ideas out there, but the one that inspired me to do this research was that of edible insects. Insects, we’re told, have a low environmental footprint, are nutrient rich, and are a highly valued resource currently controlled by some of the world’s poorest people.
Some edible insects are wild-harvested, some are farmed. Yet others are present in existing agricultural systems - and are harvested as a by product.
I felt like these by-product insects were particularly interesting - we’ve sort of been semi farming them for thousands of years, because we’ve been propagating their food source across large areas of land. We’re living in an era of accelerating agricultural intensification and the disintegration of traditional food cultures - what does this mean for semi-farmed edible insects?
So, the agricultural system in southwestern Burkina Faso can be most accurately described as maize- and shea-dominant agroforestry.
African edible caterpillars are delicious, fascinating creatures. Many of them are highly seasonal, but very abundant when in season. However, the vast majority are only found in forest environments. This was the first time i’d ever heard of an agricultural system that had edible caterpillars. Looking into it, i found papers that referred to the caterpillar as a ‘pest’ of shea. i had endless unanswered questions, and decided a pilot trip would be necessary to try and understand which of my questions would be most relevant to those living in the region.
Farmer interviews & consultations
In 2016 I spent a couple of weeks visiting villages and interviewing men and women whose primary income source was smallholder farming. I consulted them about their priorities, and it was clear that one of the most important questions to people here was: what are effects of defoliation by caterpillars on yields of shea and maize?
I decided to ask this as the driving research question for one of the chapters of my thesis.
Following pilot interviews, I randomly selected a sample of 45 households, stratified by household size, all of whom owned at least 1ha of maize. I selected three shea trees in each field - also stratified by size. I did approx 14 months of fieldwork in 2016-17.
Field data collection
In 2016 I collected observational data on shea tree defoliation and the growth of maize plants under and outside of tree canopies. In 2017 I repeated this data collection and also collected data on the abundance of shea nuts and the weight of maize cobs relative to plant height.
In 2017, in collaboration with two farmers, I conducted a field experiment: we planted two rows of maize (30 plants each row) and applied caterpillar faeces as fertiliser to one of the rows. We then measured the growth of each plant and weighed the eventual harvested cobs.
The results of observations and experiments have been surprising, and as ever, I wish I had another year or so to collect more data!
I can’t publish the graphs that accompanied here because they’re being submitted for peer review, but here’s a summary of my results:
- There was no significant relationship between the extent of shea defoliation and the abundance of shea nuts on trees the following year. Given the extent of defoliation, this is really surprising.
- in 2016 there was less difference in maize height underneath trees with more defoliation, suggesting that defoliation does help crop growth. However, the same trend was not observed in 2017.
- Plants that are fertilised with caterpillar faeces grow taller - there's a significant height difference from Day 50 onwards - but there was no significant difference in maize cob weight.
What does this mean?
Overall, my first conclusion is that caterpillars aren’t a ‘pest’ in the conventional sense – and what I mean by this is that there is no evidence that they cause any harm to yields of either shea or maize.
Secondly, it looks like defoliation by caterpillars may assist maize growth, probably due to light and/or fertilization of the soil by caterpillar faeces - but more data is needed to verify this. 2016 may have been a false positive; 2017 may have been a false negative.
Finally, the field experiment results do suggest that there may be a positive impact of caterpillar faeces on maize productivity – but again, more data is needed.
So, let’s return to the first image, & the problem that made me start this study.
I think I can say something new about this now, for what it's worth:
In West Africa, edible caterpillars aren’t a pest insect.
They might even help fertilize the soil that produces the staple crop.
In order to build a more sustainable food system we need to do more research, and when we do so, we need to listen to the farmers to whom this matters most.
Thank you for reading! And thanks to those who made this study possible: