(RELAXED MUSIC) (ANIMALS CALL)
JOSH: Once a showcase
of wildlife on public display,
the modern zoo has evolved.
These days, zoos play a key role in the conservation of wildlife.
The loss of natural habitat means that sometimes
zoos become the last refuge for the survival of a species.
Here at Perth Zoo,
work being done to save a critically endangered species
has led to the conservation of a resource
that we all use in our gardens.
Whether it's for drinking,
for cleaning and grooming
and even as habitat,
the population of the average zoo
needs a lot of water.
Alongside the irrigation that keeps the grounds presenting well
all year round,
part of Perth Zoo's remit
is to re-create the exotic habitats
that some of the residents originate from.
Yes, zoos can use a lot of water,
but often it's part of their critical mission
to support and conserve wildlife.
One of the things the team here at Perth Zoo have been doing
is finding ways to utilise water more than once,
and that involves plants.
This story starts with these little reptiles,
the western swamp tortoise.
MAN: It's critically endangered,
and for more than 50 years was presumed extinct.
Dr Peter Mawson oversees the breeding programs
of a number of native species here at Perth Zoo.
After a slow start, we've been very successful.
We've raised and released over 800 western swamp tortoises
into the wild
at a number of locations.
But everything that western swamp tortoises do in their life
takes a long time.
15-20 years to reach sexual maturity.
Small egg clutches.
And then fairly low survival of those very small hatchlings,
which only weigh four or five grams when they hatch.
It takes a long time before you see any great improvement
in the numbers of animals in the wild.
But we got down to a stage where there was only 20-30 adults left
in the wild, in the early '80s.
And we're now at somewhere... 125, 150 adults in the wild.
So that's a really significant improvement,
given that we're dealing with a species
that lives life in the slow lane.
Each of these pond areas seem quite curated.
It's almost like you're doing some gardening within them.
We are - we're trying to provide the plants
so that the females will have somewhere
to dig their egg nests next to.
But we don't want it so overcrowded with plants
and with roots from the plants
that the females can't dig into the loose soil
or that we can't then find those nests and dig them up.
But also, we don't want a lot of shade during the winter months
because when it's cold,
the animals like to come out and bask in the sun,
either on the edges of the brickwork or on the hot soil.
And so, by having a sparse planting,
we get the best of both worlds.
How important is the water quality to the animals?
We certainly looked at the prospect of a circulating system
where we would, you know, filter it and clean it
and put it back in.
But the risks of losing more than 50%
of the world's population of western swamp tortoises
to a new pathogen
that your filtration system wasn't designed to cope with
was just too great.
So that's why we use the one-way flow-through system.
How much water passes through the facility?
Varies between 30-50,000 litres a day,
depending on whether we're trying to keep the ponds warm
or whether we're trying to cater for evaporation.
So that's a lot of water to potentially capture and put to use.
It is, and that's why it was really important to be able to do something
other than just send it to the sewer.
From here, it goes to a sump.
And we have the options of either directing it
into two 100,000-litre water tanks,
which we can then use to irrigate the grounds of the zoo, downslope,
or now we have the option to direct it to the wetlands,
where the large volume of water helps dilute the nutrients
in that water body.
(GENTLE PIANO MUSIC)
The Australian Wetlands is one of Perth Zoo's cornerstone exhibits,
and being wetland habitat,
it requires a constant supply of water.
So, Josh, this is the Australian Wetland exhibit.
It contains native bird species here from Australia
and it also contains native sedges and the like
to demonstrate what the Swan Coastal Plain used to look like
with its wetlands prior to settlement.
So the planting scheme, the rushes and sedges,
are what you'd commonly find in the Greater Perth region?
Absolutely.
We're trying to create a natural habitat
just like the Australian wetland.
Where does the water come from to top up this wetland?
So it's a combination of sources.
It's both groundwater
and overflow from our western swamp tortoise facility
at the top of site.
The water comes down through a pipe, gravity-fed.
We're a sustainable zoo and we try to save energy where we can.
When the Australian Wetland overflows,
it previously went to sewer.
That's a big amount of water being wasted.
So Perth Zoo worked very hard
on finding a solution to save that water.
We now re-use that by sending it through to the Main Lake.
The Main Lake is something I'm super keen to check out,
as I worked on it with Greg and the Perth Zoo team
as a design project a couple of years back
and I want to see how it's performing.
These planted wetland beds are looking fantastic.
What role do they play in treating the water from the native wetland
and the Main Lake?
These wetland beds are critical to remove, firstly, nutrients
and secondly, the removal of sediments.
And how does the process work?
So the process is quite complex,
but once the water reaches these wetland beds,
it's allowed to trickle through the gravel beds underneath,
move into the main body of the Main Lake.
The water then circulates around,
is pumped up into the constructed wetland bed just behind us here.
And once again is allowed to flow back down into the main body.
That water movement is critical to oxygenate the water,
cool it down, allows more nutrient removal,
and keeps the water at the optimum level
for the health of our animals.
The water quality's improved tremendously.
Nutrient levels have really dropped in here.
We've seen such an improvement
in the species that exist in the water,
the macro invertebrates.
We've seen a jump in the number and range of bird species here,
and it's looking great.
The planting scheme around the Main Lake
is much more exotic compared to the native wetland.
What was the thinking behind this?
The Main Lake has been an exotic exhibit
with exotic species of plantings around it for many a year.
At the moment, we house two different species
of critically endangered gibbons on our islands.
But in the makeover of the Main Lake,
we have maintained that exotic feel.
We wanted it to look vibrant and lush for our visitors.
(GIBBONS CALL OUT)
Of course, the principles being demonstrated here
can be applied on a much smaller scale at home.
For example, a garden pond or even an aquarium.
And taking cues from big projects like this
for inspiration on water conservation or creating habitat
is really important,
no matter how small a way you decide to apply it.
Because, really, any positive difference
is a difference worth making.