Boosting food security through biodiversity
So often preserving the planet’s rich diversity of animals, plants and insects is talked about in terms of conservation alone. But this ignores the big picture and the many benefits that the Earth’s biodiversity provides humans. A new paper, by the ESPA ASSETS project in Malawi, demonstrates that biodiversity can mean the difference between a good harvest and bad one, affecting the lives of millions of people in one of the world’s poorest and most food insecure regions.
The abundance and types of animals and insects present can have a big impact on crop health and yields. For example pollinators, such as bees, boost crop yields and improve fruit and seed health whilst ‘pests’, such as rodents, consume crops and are accountable for 14% of agricultural losses annually. Yet even pests have their enemies and snakes, for example, act as natural pest controllers by controlling rodent populations. To add to the complexity other species, such as ants, can play all three roles acting as a pest, pollinator and pest control. Untangling the likely impact on crop yields involves gaining a thorough understanding of the number and types of pest, pollinators and pest controllers and their interactions. Yet most research to date has only examined the role of pollinators or pest controllers in isolation. This is the first study of its kind to look at the big picture by creating a model which analyses the effect of all three on crop yields.
The study focused on four rural villages in Malawi and analysed existing literature and data to create a model predicting the number and types of animals present. Sub-Saharan Africa is a data deficient region so testing the accuracy of the model was essential. To tackle this the researchers asked local communities to contribute their knowledge of the region’s biodiversity, in a process called Participatory Rural Appraisal (PRA), to help fill the gaps in the data and check the accuracy of their results. The results revealed that bees, bats, other flying insects and ground insects boosted crop yields. On the other hand rodents, large herbivores and monkeys were damaging to crop yields. Despite this biodiversity had an overall positive impact on crop health and yields, as the positive effects of the pollinators and pest controllers outweighed the losses due to pests.
The researchers’ analysis also revealed some of the limitations and biases in the existing scientific literature. For example much of the existing literature examines whether the effect of different animal species is positive or negative yet few quantify this. There is also a bias in the literature which focuses predominantly on species which lead to crop loss, with limited data quantifying the effect of species that boost crop yields. Some species are the focus of much more attention than others, for example studies examining pollination often focus on bees, ignoring the many other species that are equally as beneficial to pollination.
Interestingly the PRA process also revealed some unique insights into the local communities’ perceptions of biodiversity. Much like the bias of existing scientific literature towards crop loss, local communities often perceived that animals had a negative effect on their crops. There was often limited or no knowledge of pollinators and pest controllers. This is not surprising as the subtle benefits that certain smaller species provide are difficult to observe compared to the obvious destruction that other, larger species have on crop yields. In fact some crop pests such as monkeys are viewed positively, providing ‘cultural services’ by providing entertainment and being aesthetically pleasing. On the other hand the communities often kill snakes which are perceived as dangerous despite the fact that they provide a valuable pest control service by hunting rats.
Working in data deficient regions such as sub-Saharan Africa is challenging and the analysis took into account the limitations of using PRA, recognising that perceptions can be inaccurate, certain species are difficult to count and that subtle positive impacts can be missed. Long term field studies could help in checking the accuracy of this data and it is often these regions, which are the poorest and most food insecure, that could benefit most from robust data. However the model developed proved useful for broadly predicting the number and types of animals in the region. By revealing and quantifying the overall positive effect that biodiversity has on crop yields it challenges existing scientific and community biases and perceptions. It is this more comprehensive understanding which could lead to important insights on how to increase crop yields and boost food security.