Recently, I was honoured to be invited by the Green Anglicans Movement, Africa, to present on the topic of indigenous versus alien trees. My research for this presentation was truly eye-opening, as it highlighted the critical importance of selecting the appropriate tree species for an ecosystem to maintain biodiversity. While preparing, I learned that although ecosystems rely on the trees we plant, this doesn’t mean we should abandon alien tree species entirely, because many of us plant these trees for their fruits, like mangoes and guava, as well as for wood and aesthetic purposes.

Watch the recording of this presentation on Green Anglicans Movement, Africa’s Facebook page minute 43 – 1:08:01 

Indigenous trees, often synonymous with native species, possess a deeper cultural significance for the indigenous communities where they grow. These trees hold traditional importance, such as the Murewa tree among the Shona people of Zimbabwe. In contrast, alien trees are those that originate from foreign regions and have been introduced to new environments.

So, when do alien species become invasive?

This is the crucial question to consider when thinking about planting alien trees. While they can offer benefits like food and timber, species like eucalyptus, pine, and acacia mearnsii can also pose significant risks. Their rapid growth, prolific seed production, and lack of natural enemies often enable them to outcompete native plants and disrupt ecosystems. 

Which brings us to the moral dilemma

While indigenous species often offer ecological and cultural benefits, alien trees can also provide valuable resources. However, the introduction of alien species can pose significant risks, as evidenced by the invasive nature of some. To navigate this dilemma, our tree-growing initiatives must prioritize careful species selection, appropriate planting locations, and consistent monitoring. By avoiding the introduction of invasive alien species and promoting the cultivation of native trees, we can ensure a balanced approach that safeguards ecosystems and biodiversity.