Threats to the Wet Tropics of Queensland (Wet Tropics) are detailed in the IUCN World Heritage Outlook Assessment reports from 2014, 2017, and 2020. These reports were published every three years but now come out every five years. The next one is scheduled for 2025. The Wet Tropics Management Authority also releases an annual State of the Wet Tropics report, which tracks threats and major issues affecting the region.
Invasive plants
Several weed species found in the Wet Tropics are of extreme management concern:
- miconia (Miconia calvescens, M. racemosa and M. nervosa)
- mikania (Mikania micrantha)
- limnocharis (Limnocharis flava)
- Koster’s curse (Clidemia hirta)
- Siam weed (Chromolaena odorata).
The Queensland Department of Primary Industries’ National tropical weeds eradication program targets limnocharis, miconia, and mikania vine.
Hundreds of other weed species are already established in the Wet Tropics World Heritage Area, with new weeds arriving each year.
Invasive plants:
- smother native vegetation
- remove food and habitat for native animals
- disrupt the ecosystem
- destabilise banks and slopes
- fuel fires.
Disease
In the Wet Tropics World Heritage Area, disease is a significant threat.
- The soil-borne water mould (Phytophthora cinnamomi) threatens hundreds of endemic species.
- The introduced fungus myrtle rust has spread widely. It threatens hundreds of native plant species, including the iconic eucalypts and the ecologically important lilly pillies (Syzygium spp.), among many others.
- Chytrid fungus (Batrachochytrium dendrobatidis) has caused severe population declines in eight frog species.
Three locally endemic, rainforest stream-dwelling upland frog species, once found widely and in high numbers throughout the Wet Tropics, have vanished from altitudes above 300 metres and are presumed extinct.
Ants
The yellow crazy ant (Anoplolepis gracilipes) has become established in several locations in the Wet Tropics World Heritage Area and immediately adjacent.
Yellow crazy ants:
- are omnivorous feeders with versatile nesting habits
- can monopolise food and nesting sites in areas that they invade
- can build to high densities, form super colonies, and become the most common consumer over large ground and forest canopy areas.
In areas of dense ant invasion, the ants disrupt and transform ecosystems and drive out or eliminate native invertebrates and other small animals. The Wet Tropics Management Authority manages the Yellow Crazy Ant Eradication Program.
Current projects suggest that local eradication can be achieved if resourcing is maintained.
The electric ant (Wasmannia auropunctata) was detected in Cairns, Queensland, in 2006. Since then, it has been the subject of an eradication program managed through Biosecurity Queensland. The electric ant has become established in several locations in the Wet Tropics and immediately adjacent areas.
Electric ants:
- are omnivorous feeders with versatile nesting habits
- are tiny and difficult to see but have a painful venomous sting
- can build to high densities, form super colonies, and rapidly become the most common animal over large areas on the ground and in the forest canopy
- are classified as Category 1 prohibited biosecurity matter under Queensland law.
In areas of dense ant invasion, the ants disrupt and transform ecosystems and kill or drive out other invertebrates and small animals.
Invasive animals
Vertebrate pests, such as pigs (Sus scrofa), continue to significantly impact the Wet Tropics’ soil, vegetation, sensitive habitats, and aquatic values. They also pose biosecurity risks as evidence suggests they may transmit pathogens, such as cinnamon fungus.
Other invasive animals, such as tilapia, are invading rivers and water bodies.
Challenges
Biological invasions can be synergistic, i.e. one invasive species may facilitate invasions of others.
Biosecurity programs are notoriously resource-intensive and require a rapid and flexible response, making them logistically and financially challenging, particularly under sporadic and project-based or intermittent funding agreements.
Despite these challenges, the success of the Wet Tropics Management Authority’s Yellow Crazy Ant Eradication Program demonstrates that great results can be achieved through coordinated efforts by government, community and researchers with adequate resourcing. Their program provides a model for other responses.
Assessment of State and Trend of World Heritage Values, IUCN World Heritage Outlook Assessment reports
Threat | 2014 Status | 2014 Location | 2017 Status | 2017 Location | 2020 Status | 2020 Location |
|---|---|---|---|---|---|---|
Invasive weeds and disease (terrestrial and freshwater) | Very high threat | Inside side Outside site | Very high threat | Inside site, throughout (>50%) Outside site | Very high threat | Inside site, widespread(>50%) Outside site |
Invasive pests (Yellow crazy ants) | Very high threat | Inside site, extent of threat not known Outside site | High threat | Inside site, extent of threat not known Outside site | ||
Invasive pests (Pigs) | High threat | Inside site, Outside site | ||||
Other – Insecticide application | Low threat | Inside site, Localised (<5%) Outside site |
