This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Labor-intensive harvesting and complex processing make macadamias among the most expensive nuts in the world. This makes it all the more important to protect the trees from pests.
An international research team led by the University of Göttingen investigated how natural vegetation in and around macadamia plantations affects pest infestation, paying particular attention to bird and bat populations. The researchers demonstrated that the higher the level of bat activity, the lower the incidence of pest infestation. At the same time, yields increased in landscapes with a higher proportion of natural vegetation.
The findings are published in the journal Agriculture, Ecosystems and Environment. The team studied 10 intensively managed macadamia plantations in South Africa. At each site, the researchers compared trees at the edge of the plantation with those in the center to analyze the influence of the surrounding vegetation.
They recorded 111 bird species through observation and 16 bat species via their echolocation calls. Bat activity reduced insect damage, particularly in plantations that contained less natural habitat or were surrounded by it. Natural habitat in this context includes, for example, native forests, bushland or scrubland.
In contrast, so-called exclusion trials showed a significant effect on nut quality: When birds and bats were kept away from the trees by nets, the proportion of nuts damaged by insects rose from 6.2% to 10.7%—an increase of around 70%. However, no direct influence of bird numbers on pest infestation could be demonstrated. Not only did the number of bats increase as the proportion of natural habitats rose, but so did their diversity.
The yield from the macadamia trees was also linked to this proportion, reaching its highest level when natural habitats accounted for around 60%. At the same time, bird communities differed between the edges and the center of the plantations: Species that prefer dense and woody vegetation were more common at the edges, while species of open habitats predominated in the center. "Natural habitats are valuable refuges and support beneficial organisms that provide pollination and pest control, which in turn is good for agricultural production and for farmers.
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