Natural vegetation and biocontrol in southern Africa

In this post Dominic Henri discusses his recent paper ‘Natural vegetation benefits synergistic control of the three main insect and pathogen pests of a fruit crop in southern Africa‘ You can also find a poster ‘Distance-dependent natural vegetation benefits to the biocontrol of multiple pests and pathogens in South Africa mango farms’ associated with the paper here.

It is a widely held view among the scientific community that ecosystem services are important to the productivity of modern agriculture. It is further thought that the presence of local natural vegetation is essential for the ‘health’ of these services. However, while these thoughts are justified in the main, the relationship between local natural vegetation and ecosystem service provision is highly variable across geographic regions, seasonal patterns and the crop, pest, enemy or pollinator in question. Furthermore, the vast majority of our understanding of these processes comes from regions that, in the global scheme of things, retain little of their biodiversity or natural habitat. Studies in Western Europe or the USA occur in areas that retain at most 20% of their natural habitat, while undeveloped nations with large agricultural industries can retain upwards of 55%. Without a mechanistic understanding of the key factors responsible for the differences in ecosystem service provision between studies, it is not possible to scientifically extrapolate across studies or provide general recommendations to agricultural practitioners.

Our study is the first, in what we hope will be a long-line of studies that considers the impact of local natural vegetation on multiple pests and their natural enemies within the same system, in a comparatively undeveloped region. We find strong evidence for beneficial pest-control ecosystem services provided by local natural habitat; however, these benefits decline dramatically with distance into the agricultural estate.

Our results contradict previous theory regarding the relationship between habitat diversity and the efficacy of management practices (intermediate complexity hypothesis), as we suggest that management practices can still promote ecosystem service provision in high diversity areas. Particularly, in these regions we suggest that practices aimed at improving natural enemy movement into the agricultural habitat, via natural habitat corridors, may mitigate distance limitation. Furthermore, our results support the broader literature suggesting that pest and enemy trophic generalism and movement capability may be responsible for the variation discussed above.


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