Saving Bibra Lake

An aerial view of Bibra Lake on a sunny day

Cradled in the swales of the ancient dunes of the Swan Coastal Plain, and spanning over 384 hectares are the Beeliar Wetlands! They are bustling with stunning biodiversity, that include some of the most unique and fragile lifeforms on earth. Here, the calm, placid Bibra Lake stands as a timeless testament to our heritage and cultural values.

Historically, North Lake – Coolbellup and Bibra Lake – Walliabup, have served as important locations for the Aboriginal Nyoongar people. They are associated with the mythology of the ‘Waugal‘– the rainbow serpent, and Dreamtime tales of the ‘Spirit Children’.  Numerous Aboriginal campsites have been documented adjacent to the lakes. The Beeliar mob had semi-permanent camps on the land, caring for the boodja (country), precisely where the controversial Roe 8 tollway was proposed.

While we closely evaded that disaster, there are still a number of factors that continue to impact our precious wetlands. Over 90% of Perth’s once ample and abundant wetlands have been lost to agricultural pursuits, urbanisation, and development & infill. Bibra Lake and the surrounds are a reminder of what we’ve lost and what we stand to lose unless we take strong action. Together.

 

Changing wetlands in a changing climate

Our wetlands are dynamic in nature and they transform with changing seasons. Water levels in the wetlands, such as Bibra Lake, rise and fall with rainfall and the seasonal movement of groundwater. Bibra Lake experiences this seasonal flooding and drying, and oftentimes, this leads to alterations in the depth and area of the body of the lake. The transient wetlands are designed to cope, redistributing their animal and plant life in accordance with these changes.

However, with a decrease in rainfall and an increase in human activity surrounding our wetlands, the natural variations are becoming exaggerated. Causing alarming fluctuations in the wetland zonation. Introducing irreversible expansions and contractions of the wetland area.

 

Comparisson of flooded zones of Bibra Lake from 1995 to 2005
Figures depicting altered wetland zonation for Bibra Lake

Looking back, we remember the water levels of Bibra Lake during the 1980’s and 1990’s to be much higher than they are now. Many of us believe that those water levels were “proper”. However, the higher water levels of Bibra Lake at the time were actually an aberration caused by the removal of vegetative cover for the development of surrounding suburbs.

On the other hand, we also see prolonged drying of the wetlands in some years. The reduced rainfall has impacted the recharging of groundwater. And since the groundwater is also our source of drinking water for the Perth metropolitan area, this has caused a further shrinkage of the precious resource.

Bibra Lake has suffered adverse impacts. Usually, maximum water levels were seen around October and minimum levels during April. However, Bibra Lake and North Lake are now breaching these standards. This has significant implications for planting and weed control.

 

Two pictures comparing seasonal water levels of Bibra Lake
Snapshots comparing maximum and minimum seasonal water levels in Bibra Lake

A thorough understanding of these circumstances is essential towards developing a successful restoration program for Bibra Lake. We need to take the variations and on-ground conditions into account, adjusting when and where we weed and plant as we maintain and restore the lake and its surrounds.  The focus as we move forward must be on adaptive management.

We must also accept that we are moving into a period of some uncertainty, with climate change and global/local weather events becoming unpredictable. We may not get this 100% right 100% of the time. But every failure is a learning and a step forward.

 

Weeds and invasive species

Weeds are one of the most pressing problems we face at Bibra Lake, and weed control is an ongoing initiative. Often, the removal of one weed creates space for another. In some cases, it even allows the overgrowth of opportunistic native plants which can pose additional challenges. We see this most starkly in the constant balancing act of Typha control on our lakes. But that is a story for another day…

A combination of manual and chemical control along with mulching and saturation planting has been the most effective method in combating weeds. (Saturation planting is when native vegetation is planted densely and in large numbers so as to saturate and give little scope for invasive species to spread.)

At Bibra Lake, the following have been our findings:

  • Weeds must be actively growing before initiating weed control.
  • The revegetation plan should be in place prior to weed management to make the best use of the weed control efforts.
  • A monthly weed control commitment is required with a plan for the whole year.
  • At The Wetlands Centre, we have developed Seed Production Areas (SPAs) and refined propagation techniques to grow plants in our nursery.
  • The weed biomass in the seasonal zone degrades during one flooding and receding event. Slashing is sometimes required to make the area suitable for planting.
  • Mulching of the lower damp to upper seasonal zone (the weediest zone) with Typha mulch reduced the frequency of weed control.

 

Satelite images of Bibra Lake from 1953 to 2018 showing vegetation cover
Satellite images showing revegetation of Bibra Lake by The Wetlands Centre Cockburn over the years

Invasive species such as feral bees, foxes and cats are also detrimental to our wetlands. The feral cats and foxes prey on vulnerable native animals. Foxes are an introduced species and our lizards, turtles and quenda are especially susceptible since they have not developed any specific defences to stay protected.

 

Runoff and Algal Blooms

Human activity is primarily responsible for the degradation of our wetlands. Our urban developments are placed closer and closer to the wetlands, with little or no buffer. Roads and tracks crisscross the perimeter. And our wetlands are losing their lush cover, that helps protect wildlife from noise, light and other forms of pollution. All this further challenges their survival, exposing our species to danger and disease, and putting them at a risk of endangerment.

This also means that there is a greater impact on how nutrients, sediments and pollutants are naturally filtered by the wetland. The degraded quality of some of the fringing and upland vegetation around Bibra Lake is causing alterations in the water-quality of the catchment. However, Bibra Lake still fairs better than other heavily impacted lakes within the Beeliar Wetlands.

Runoff, whether it is the chemical runoff from roads or the phosphorus, potassium and nitrogen from fertilizers that we use in our gardens, leads to a nutrient explosion, and subsequently, algal blooms. The algae reduce temperature and light penetration in the catchments, suffocating and dominating over aquatic life. The algae also spread rapidly and give off an unpleasant odour as they break down. There is a direct link between the excessive use of garden and horticulture fertilizers and algal blooms in our waterways.

Reducing the use of chemicals in our gardens, keeping our storm drains clear of unwanted litter, conserving water and using it judiciously, and using landscaping practices that benefit wildlife and their habitats – every little step you take can lead to positive outcomes for our lake.

 

Join The Wetlands Centre Cockburn

At ‘The Wetlands Centre Cockburn’, we are fortunate to be located adjacent to the resplendent Bibra Lake, within the Beeliar Regional Park. This places us in an ideal position to lead by example in the care of our natural surroundings. We recognize that we bear a great responsibility to inspire, reinforce and connect, and to work with the community to safeguard and protect this amazing area.

The issues we have highlighted in this article are very real. They are threatening the health of our wonderful lake and its bountiful surrounds. We are working hard to understand and combat these issues while spreading awareness of core problems. Our team of volunteers and staff are dedicated and ever-vigilant.

In working with the land and connecting with its nurturing ways, we have come to cherish it deeply. And we want to share this connection with the greater community. Come, get involved with us. Learn. Plant. Protect. Conserve. And spread the joy.

 

This article is adapted from and based on notes and insights shared by Denise Crosbie, Wetlands Officer, The Wetlands Centre Cockburn.

A Wetland Habitat For Our Amazing Turtles

A close-up shot of an oblong turtle with an inset of one swimming in the wetlands

Turtles are remarkable and resilient creatures that inhabit our wonderous wetland worlds. They are widely celebrated in both popular culture and folklore as totems of balance, beauty and prosperity. In Aboriginal culture too, turtles are seen as symbols of longevity, endurance, and the continuation of life (especially in the face of great hardship and struggle).

We have much to learn from our endearing turtles. However, the avenues are limited as turtles are also inherently shy creatures. They seldom venture out, staying confined to the comfort of their wetland habitat and sanctuary for long stretches of time. And their rituals of mating, nesting, feeding and living, remain largely undocumented and mysterious.

Hidden in the grassy underbrush and marshy swamps, they thrive. Feeding on bugs, snails, worms, fish, crustaceans, plants and animals, scavenging and flourishing, they play a crucial role in the wetland ecosystem. They are vital indicators of wetland health. This is why their ever-dwindling numbers, impacted habitats and disrupted food-webs demand our most serious consideration.

 

Come, Meet Our Oblong Turtle

The oblong turtle or, the long-necked turtle, is a native species that is only found in this part of the world – in a small pocket at the southwestern tip of the state of Western Australia. And we are fortunate for their presence here!

The oblong turtles owe their name to the oblong shape of their carapace (upper shell) and snake-like long neck. Dark brown or muddy black in colour, these turtles are found in waterways across Perth and throughout the south-west. They occur in permanent and seasonal freshwater habitats, including rivers, swamps, lakes, damp lands, and natural as well as artificial wetlands.

Adult turtles can grow large and measure about 30-50cms from the tip of their tails to the end of their beaks. The young hatchlings are tiny as they begin their journey though, with a carapace merely the size of a 20-cent coin!

A long neck turtle walking through the wetlands
Image by Sharon Mcarthur

The Turtle Nesting Period is On!

September to January is a special season indeed. At this time of year, you can witness turtles leaving their watery homes in search of suitable nesting sites. They are known to travel up to a kilometre in search of the perfect site with soft sandy soils where they can lay their leathery eggs.

Unfortunately, a turtle out of water is a turtle at risk! Turtles get run-over by cars as they cross busy roads and pavements, oftentimes distracted by loud sounds and noise from moving traffic. Turtles are also exposed to birds and other predators that prey on them as they find their way. Dehydration and tiredness from the long journey and the added confusion of a changed or disturbed site can cause the turtle to feel lost and ultimately perish from fatigue.

If you are lucky to site a turtle that is on its way, help it cross the road by halting incoming traffic till it crosses. If this is too risky, you could lift it across the road (make sure that you take it in the direction it is headed and not back!) and ensure that there are no other threats around. If you have the time, you could also follow the turtle (at a safe distance) to and from the nesting site. Protecting our exposed and vulnerable turtles can go a long way in ensuring the survival of the species.

 

Threats to The Oblong Turtle

We lose a number of turtles to road accidents each year. In fact, in the period leading from September to January when turtles nest, and from June to July when hatchlings make their way back home to the wetlands, our turtles are at their most vulnerable.

A baby oblong turtle peeks above the water surface to breathe.Feral animals including birds of prey, cats, dogs and foxes are a significant threat to our oblong turtles. Feral animals are known to attack the turtles as well as their nests, feeding on eggs. Poaching and removing turtles from their wild habitat to keep as domestic pets is also a major threat. Although catching and keeping turtles as pets is illegal and punishable by law, it still happens.

And finally, it is the increasing urban sprawl, especially in the vicinity of the wetlands, that is leading to fewer and more disjointed habitats for our turtles. The compromised water quality and enhanced pollution levels are impacting their numbers, even as safe and suitable habitats become threateningly scarce.

 

Turtles on Your Property?

If your home happens to be popular with the turtles and you see a great number on your property, chances are that you are on a nesting site! Turtles are known to follow the same pattern year-on-year and are likely to end up in the same favourite spot for nesting. If you are a turtle buff, this can be an incredible opportunity for you to witness something magical!

Allow the turtle to nest and observe at a safe distance. Ensure that your pets are on a leash and away from the turtle. Make sure that there are no other threats that could harm the turtle. The female turtle will take anywhere between 15-30 mins to lay her leathery eggs, using her plastron (lower shell) and legs to dig and later cover-up the hole.

The turtle will be tired from her strenuous journey and vigorous nesting activity. If you find her at risk, you could help her get back to the wetlands safely, but not unless you are sure that’s the direction she is headed in. Keep the nest undisturbed while the mum is away. Turtle hatchlings will emerge after a period of incubation, and you can help them get back to the water too.

Here are some handy instructions if you are required to move a nesting site or handle a turtle anytime. Please remember that our turtles are wild creatures, and it is not encouraged to interfere with their movement unless they are at risk. That is please do not pick up hatchlings or adults unless absolutely necessary!

An illustration showing the right way to hold a long neck turtle.

Handling a Turtle: When handling a turtle prepare for them to resist and squirm strongly. They do not bite; however, they are known to scratch and struggle. Take care to keep a strong hold and not to drop them when this happens. Wrapping a small damp towel around the turtle can help you get a good grip. Always use both your hands and keep the turtle away from your own body.

Moving a Nest: If you are required to move a nest for any reason, or if you come across a compromised nest and want to help relocate it, here is what you do: Make sure you dig around with gentle hands and get all the eggs in the nest. Mark the position the eggs were in exactly and ensure you put them into the relocated site as they were found. The fresh hole you dig should be at the same depth and with similar conditions of dampness or dryness. Remember turtle eggs that are rotated will not hatch! If the temperatures are too cold too, the eggs won’t hatch!

 

Facts You May Not Know About Our Turtles

Here are some quick oblong turtle facts that may surprise and wow you!

  1. Freshwater turtles, such as our oblong turtles, can drop their body temperature, slow their pulse rate and use their stored body fat in place of fresh food to survive severe hot and dry conditions. This ability, known as aestivation, is the reason our hardy turtles can cope with the roughest Western Australian weather.
  2. Turtles are the only creatures with an exterior shell that is all bone and attached to their spine. The turtle shell is living material, much like our own fingernails. And they can sense pain, touch and temperature through it!
  3. It is a common misconception that our oblong turtles can protect themselves by retracting into their shells. Oblong turtles cannot retract into their shell!
  4. Our oblong turtles can live a long life of over 60 years when the conditions are right. They need to live long because they have very low recruitment rates (few surviving offsprings). In fact, on average only 1% of turtle eggs go on to hatch and survive until adulthood.
  5. Turtles are known to feed on the dead and decaying organic matter and debris. Turtles help keep the waterways clean and aid in wetland function.

 

Help Us Turtle Watch!

Sighting a turtle is a beautiful and moving experience! Be sure to share your lucky sighting at climatewatch.org.au. You can log your sighting using their app. Or call us at The Wetlands Centre Cockburn at our Turtle Watch Helpline.

Keeping a lookout on the migration patterns and movements of our native turtles helps us identify important habitats and nesting grounds. It also helps us create safer homes for these amazing wetland creatures!