09/07/18

Diversity as opportunity

For the last two years, the fall armyworm has been on the march through the fields of Africa, not only decimating harvests but triggering a general discussion on how to deal with invasive species.

The more diverse a landscape, biotope or garden, the easier it is for a habitat to respond to problems. We can see this from the following example: Wasps may well be valuable for nature but they can also spoil our enjoyment when eating outdoors. However, if we surround the eating area with fruit trees and berries, the number of wasps is far less because the shrubs and trees are also home to various wasp predators.

Free rein to invasive pests

It is exactly the same with agro-ecological systems. Monocultures are a paradise for pests; food in abundance and no predators to be seen. In order to avoid the total destruction of harvests, farmers often resort to artificial insecticides. Even more devastating is what happens when an alien species from a different country or continent is brought in. Its new habitat has none of the natural competitors it had at home. This allows invasive species to spread unimpeded.

Belated realisation

Shocked by the invasion of the fall armyworm, experts from 27 countries met in Nairobi in February 2018 in order to plan the next steps in the fight against the pest. The conference agreed to draw up a range of possible scenarios for Africa designed to identify potential trouble spots and the transport routes used by the invasive species. Ideally, the invaders would be captured before reaching land but if new pests do arrive in Africa, countries need action plans that allow them to respond quickly and so prevent the pests spreading further. Admittedly, farmers will still be left to their own devices until effective monitoring and response mechanisms can be put in place.

Spreading throughout Africa – larvae of the fall armyworm.

Ecological cultivation systems are more robust

For smallholders and their families, the additional pressure from an invasive species can be the last straw as they are already having to cope with drought and flooding. In order to control the pests, smallholders are adopting agro-ecological systems that increase diversity and so are more flexible and resilient to such invasions. For example, the mixed-cropping systems like the Push-Pull method supported for many years by Biovision or the building of terraced banks planted with shrubs or fruit trees provide important habitats for a large number of beneficial insects. Such methods make a valuable contribution to food security in rural areas.