Northern Australia has a reputation for retaining large areas of relatively weed-free natural environment in comparison with more developed regions.  However, in many ways weeds are hidden from the eyes of human observers. For example, people may not have sufficient familiarity with natural environments to distinguish between weeds and native flora, or they may be entirely ignorant of the impacts of weeds on native biodiversity and human livelihoods. Large areas at risk (or invaded) are in sparsely settled areas and may not be easily accessible. Humans are often reluctant to accept the notion that some plants that they like or have in their control may be potential weeds; yet it is people who are the principle vector of weed spread and the source of new introductions.

To further complicate matters, the notion of what is or isn’t a weed is not always agreed upon. Some invasive plants also have economic uses which can result in conflicts of purpose between different sectors of society. Many introduced plants are not truly invasive but may persist (even reproduce) in the environment and not cause significant impact. Science does not deal in absolutes but in terms of risk and probability, and the evidence that it relies upon can require interpretation and contextualisation. In a world where resources are limited, it is the human perception of the problem which has become the battleground, and the Top End is at serious risk of being further impacted by invasive plants over coming decades.

Louis Elliott is based in Darwin and has been working on topics related to Top End plants for the past 7 years. He has been Weed Scientist at the NT Weed Management Branch for the past 3 ½ years. His duties include administration of the NT Weed Risk Management System, and the evaluation of the impact of biological control agents of Mimosa pigra, a serious weed of the Top End.