Abstract
Large urban trees have many benefits. However, falling branches pose a serious hazard to both people and infrastructure. In several tree species, aerial roots grow down from branches to the ground. These roots are capable of thickening to support the branches, lessening the risk of tree failure. Unfortunately, in urban environments most aerial roots die before reaching the ground. Here, we report a new method for encouraging aerial roots to reach the ground, developed by the second-year botany class at UNSW Sydney. Our class tested three experimental treatments on aerial roots of Ficus rubiginosa Desf. ex Vent. (Port Jackson Fig)—PVC pipes filled with sphagnum moss, PVC pipes filled with potting mix, and PVC pipes filled with sphagnum moss and topped with funnels to catch extra rainwater. All three treatments significantly improved aerial root growth, with 26 of the 30 (87%) treatment roots reaching the ground after one year compared to 0 of the 10 control roots. Our method was successful for roots up to 3 m above the ground, suggesting the potential growth rate of aerial roots is substantial when conditions are favourable. Our novel approach is an attractive and cost-effective alternative to slings and other artificial supports. This project is an example of using undergraduate practical classes to teach science while simultaneously addressing important real-world problems.
Highlights
Falling tree branches are a serious hazard, in heavily populated areas such as city streets, university campuses and schools [1]
Facilitating aerial root growth of urban Ficus rubiginosa worldwide, and falling branches are responsible for many deaths each year
11% of all outdoor education-related deaths in Australia are caused by falling trees or tree branches [2]
Summary
Falling tree branches are a serious hazard, in heavily populated areas such as city streets, university campuses and schools [1]. Tree failures cause substantial damage to property. Facilitating aerial root growth of urban Ficus rubiginosa worldwide, and falling branches are responsible for many deaths each year. 11% of all outdoor education-related deaths in Australia are caused by falling trees or tree branches [2]. Deaths from tree failures are common during tropical cyclones and high winds [3, 4]. As extreme climate events like cyclones are predicted to increase in frequency and intensity [5], the damage caused by falling branches is likely to rise in the coming decades. The problems caused by falling trees are not restricted to Australia, but apply in urban environments around the world
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