The first records of aquatic weeds in the Wet Tropics show that they began to arrive in the 1800s. Most of the ones we are dealing with today were introduced through the aquarium trade, as culinary plants or released for agriculture. The internet has made it worse by causing an explosion in food plants being imported from other parts of the world, especially south-east Asia.

In other parts of Australia, weeds die back during the dry months but because we have so much water all year round, weeds continue to spread. They can choke and smother our rivers, alter their flow and change the water chemistry, which create the perfect conditions for pest species like tilapia to thrive. Weeds also have a negative impact on the productivity of our farms.

Some of the species that are affecting our waterways currently are Amazon frogbit, pond apple, water hyacinth, water lettuce, limnocharis, hymenachne and paragrass.

Surveys show that the Murray and Herbert catchments are most impacted by invasive weeds in the Wet Tropics. The Barron River has been impacted by an infestation of floating macrophyte Amazon frogbit (an aquarium plant), which has spread through several tributaries within the basin.

Tips for aquarium lovers:
• Know the legislation and which plants are on the ‘naughty’ list.
• Buy aquarium plants from reputable suppliers.
• Look for local alternatives.

What has been done so far?

Unfortunately, aquatic weeds are almost impossible to eradicate. The best we can do is control infestations as they crop up by removing weeds manually or with the use of herbicides. Community groups, rangers and parks services are among those involved in weed control programs. We can all help by making sure we don’t inadvertently transfer weeds to other areas on machinery and boats.