Biological hazard: Soil on sea freight loaded with invasive species

Invasive species are often brought into new regions unintentionally through human activities, posing a threat to native wildlife. If they become established, invasive species can outcompete, prey on, or bring diseases to native species, which might lead to their decline or even extinction. This disrupts the balance of the ecosystem.

The cost of controlling invasive species, and the economic losses they create, can be immense. Some invasive species carry diseases that affect human health. 

It is important to understand how these species are introduced, and why they establish in new places, in order to help prevent their destructive impacts. However, there remains a lack of research in this domain, and many questions remain. 

Biological hazards 

In a collaboration between AgResearch and Better Border Biosecurity (B3), researchers set out to investigate the biological hazards presented by soil found on the external surfaces of sea freight. These included shipping containers and machinery at New Zealand’s sea ports.

The goal was not only to understand this potential biosecurity threat but also to fine-tune measures to prevent the entry and spread of invasive organisms.

What the researchers learned 

The study revealed that soil was present on almost all sea freight, regardless of its origin. This is troubling because soil is a potential carrier of harmful microbes including plant pathogens.

The average amount of soil detected on a single sea container was 5.3 kg, whereas the overall mean weight was 417g. Surprisingly, the majority of this soil was located on the underside of the sea freight.

Invasive organisms 

Mark McNeill of AgResearch, who led the study, noted that while the presence of soil is perhaps not surprising, the presence of live bacteria, fungi, worms, seeds and insects associated with the soil was of greater concern. 

“Various regulated biosecurity organisms were recovered from the samples, including plant-parasitic worms, seeds, insects and spiders that were not recorded as being present in New Zealand.”

Study implications 

“Not only does the spread of exotic species through these networks represent significant environmental, economic and social costs to natural and agricultural environments if invasive alien species were to establish, a loss of biodiversity is also an expected consequence of invasive alien species establishment,” wrote the researchers.

“For islands, the implications can be significant, as they have high levels of endemism and invasive alien species establishment can lead to extinction of species as well as biodiversity declines.”

An interesting comparison was made to a prior study examining soil contamination on footwear carried by international airline passengers. The comparison revealed that soil on sea freight, although less diverse, still presents a tangible biosecurity threat.

The study highlights the importance of sea freight as a notable entry route for invasive species. Preventative measures, such as pre-departure container cleaning and thorough border inspections are recommended to curb the potential spread of these harmful organisms.

The study is published in the journal NeoBiota.

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