Well, the waterways that carry our freshwater through the landscape…
Queensland’s waterways are incredibly precious! Our huge state has always been a dry place, but with future predicted climate scenarios, water may become even more scarce than before. Waterways throughout Queensland come in an array of sizes and forms: from small ephemeral wetlands, overland flow paths and spring-fed seeps, to enormous salt-lake depressions, mighty rivers and coastal lagoons, estuaries and swamps. The ecosystems that form around these amazing places number over 800 distinct types in Queensland with Cooper Creek being the state’s longest and largest system.
But what about closer to home? Brisbane has always been regarded as a river city. From its early settlement by Europeans, the city was famed for its wide river access and northern positioning giving boats a convenient port of call heading to and from Asia. But how has the ever-growing city changed and impacted our waterways and our fresh water?
Waterways under threat…
One of the most significant impacts has been that of weeds. Weeds are a funny thing, many people visiting Australia, or even those residents who have not spent much time in the bush, often look at a patch of green vegetation and think, “wow, luscious nature!”. Well, the sad truth is, that much of what we see on a day-to-day basis in Brisbane is at best semi-natural, and many of the plants are exotic weeds brought here through years and years of development.
One of the waterways most affected by these changes is Bulimba Creek in the city’s south-east. The creek begins its life in Mount Gravatt’s Toohey Forest and flows north-east and south at a fork from Yimbun Park in the suburb of Macgregor. The northern arm then flows through 11 more suburbs before it joins the Brisbane River. The creek is an important and relatively large waterway, but sadly over the decades, it has become choked with weeds. Camphor Laurel (Cinnamomum camphora), Chinese Elm (Celtis sinensis) and Leucaena (Leucaena leucocephala) have overtaken and dominated the canopy, while shrubs like Castor Oil Plant (Ricinis communis) and Lantana (Lantana camara) choke out the mid-storey layers. Vines like the notorious Madeira Vine (Anredera cordifolia), Balloon Vine (Cardiospermum grandiflorum), Glycine (Neonotonia wightii) and Corky Passionflower (Passiflora suberosa) swamp the structure of the forest in cloaks of heavy foliage, and the ground-layer becomes a swarm of Singapore Daisy (Sphagneticola trilobata), Asparagus-fern (Asparagus africanus) and Blue Billygoat-weed (Ageratum houstonianum).
These plants together, over time, have left parts of Bulimba Creek impenetrable by any native plants and much of the native fauna has disappeared as well. Water-dwelling mammals and birds like platypus, rakali, rails and crakes, need native flora in order to find suitable forage, habitat and nesting material. The decline of koala food trees such as native eucalypts has also meant the Koala (Phascolarctos cinereus) has disappeared locally. Declining butterflies like Four-barred Swordtails (Protographium leosthenes) which rely on native zig-zag vines for their larval foodplant disappear as their foodplants fail to cope with the onslaught on invaders.
What can we do?
So what can be done about this? Well, since early 2020, Natura Pacific have been working with Brisbane City Council to design and implement a holistic Rehabilitation Management Plan for a section of Bulimba Creek in Mansfield; approximately 2km of the tributary. Here, our team have combed the whole creek to determine what treatments need to be carried out in order to reinstate native structure, function and composition of the original regional ecosystems and install monitoring points to determine how well things change over time.
We will be working closely with the Council over the coming years to undertake special BioCondition assessments of the area to see how vegetation changes, resilience increases, and habitat becomes more abundant through the treatments, which will include weed removal, tree planting, habitat augmentation and pest management, among others. We hope to be able to create real change here, to bring back some of the original character and more importantly, biodiversity value, of the creek and to reunite Brisbane with one of its old waterways looking in top condition once more.
Here’s to a more bountiful Bulimba!