Forest Gardeners

I’ve been thinking that the developers at Ella Bay should perhaps think about advertising for a special type of gardener if their proposed 450 hectare urban development/resort actually gets approval from the Federal Government.

Their advertisement could go a bit like this:

Wanted: skilled rainforest seed collectors/planters/gardeners (at least 7 positions available)

Qualifications:

• Must be able to run through rainforest at speeds approaching 50 km/hr
• Good swimmer (able to swim wide rivers confidently)
• Ability to jump 1.5 metres high with ease (needed for seed collection)
• Ability to distribute thousands of fertile seed seeds up to 5km from parent trees
• Willingness to work 7 days a week 12 hours per day
• Must be frugivore willing to subsist on rainforest fruits (often toxic)
• Prepared to endure extreme risks from traffic and wild/domestic dogs
• No accommodation available will have to camp out in one of Australia’s wettest regions
• Applicants required to work alone and unassisted
• No financial remuneration available, no superannuation and no health care of course

Just quietly I don’t think there would be a rush of applicants for these jobs!

Want the good news… there’s already a great team at Ella Bay doing this job perfectly.

Indeed they and their ancestors have been performing this task for so long that plant species have co-evolved with these birds to make good use of their seed dispersal methods.

Of course I am talking about the endangered Southern Cassowary Casuarius casuarius johnsonii. There are scores of reasons for humans to work hard to ensure this endangered bird is saved from the extinction it now faces. Today I just want to focus on its role as a seed dispersal agent.

Southern Cassowary Dad and his chicks, photographed by Liz Gallie

As I mentioned cassowaries have been around for a long time and they appear to have evolved from a group of large flightless birds called the emuarius. The emuarius existed about 20 to 30 million years ago. The Australian fossil records show Cassowaries in Pliocene fossils (3 million to 7 million years old). That’s plenty of time for the co-evolution of both rainforest plants and cassowaries. These birds are one of the few animals capable of distributing the seed contained in large rainforest fruits.

Adult Cassowary, photographed by Liz Gallie

The long term survival of large fruited rainforest trees is strongly linked to the presence of viable populations of seed dispersing cassowaries. During the time the seed spends in the cassowary’s gut the bird may travel distances exceeding 5km from the parent tree. Without these birds they have no way of maintaining their population spread.

Why are cassowaries so good at distributing rainforest seeds?

Good question I’m glad you asked! Cassowaries have been observed eating over 200 species of rainforest seeds. They have a relatively short gut and don’t grind seed in a gizzard like a lot of birds. This means the seed goes in one end of the bird wrapped in a nice fruity parcel and about 10 hours later it pops out the other end of the bird cleaned of the fruit and deposited with a nice fertiliser package… thank you very much! Cassowary droppings have also been shown to repel seed eating animals ensuring the excreted seed has a reduced chance of destruction prior to germination.

Cassowary pooh

Often fruits around seeds contain germination inhibiters so by digesting this coating the cassowary starts the germination clock ticking. During their studies, B.L.Weber and I.E.Woodrow found that passing through a cassowary gut improved germination rates for the rare rainforest tree Ryparosa. They recorded 92% germination with cassowary and 4% germination without, pretty strong evidence of the benefits of this avian seed disperser!

I wish to quote our Federal Environment Minister Peter Garrett AM MP. This was taken from the media release Decisive Action Taken To Protect Mission Beach Cassowaries dated 28 July 2008 (PDF file). Minister Garrett said “The southern cassowary is a case study of how native species contribute to the overall resilience of an ecosystem. The southern cassowary eats rainforest fruits like native laurels, lilipillies and palms, and disperses the seeds in their droppings. So their survival was central to the regeneration of the area and long-term viability of rainforest communities”.

Well that’s the good news now here’s the bad, southern cassowaries are on the way out yep that’s right they are facing extinction. Why? Well the biggest factor has been habitat loss and fragmentation.

Kofron and Chapman assessed the decline of the species in 2006 and found only 20 to 25 percent of their original habitat remains. Remaining habitat is fragmented which genetically isolates cassowary populations and exposes them to their second major threat which is vehicle strike. Kofron and Chapman Studied 140 cases of cassowary mortality and 55% were from vehicle strikes (followed by 18% from dog attacks). Between 1989 and 1998 Mission Beach recorded approximately 40 cassowary deaths in vehicle strikes alone. If you check out the Queensland Parks and Wildlife 2006-2007 State of the Wet Tropics Report it documents 31 Cassowary deaths in the wake of Cyclone Larry in 2007.

Southern Cassowary Dad and his chicks, photographed by Liz Gallie

Considering the Australian southern cassowary has a population of about 1200 to possibly 1500 animals these mortality figures are frightening. There are more pandas in China than cassowaries in Australia that’s why I’m sitting here taking hours to punch this out with 2 fingers!

But stop! The situation is not hopeless, however our government needs to take firm and decisive action to protect this species while a genetically viable population exists to work with. Habitat preservation should be the number 1 item on their list.

Cassowary tracks at Ella Bay beach (Photo by Ellie Bock)

Returning to the situation at Ella Bay the construction of a 450 hectare urban development/resort with a forecast population of 5000 people in an area that contains endangered cassowaries and recorded endangered cassowary habitat is simply unacceptable. Places like Mission Beach have already proven that cassowaries and large human populations cannot coexist without unacceptable and unsustainable losses to fragile cassowary populations.

Ella Bay has a cassowary population that needs our Federal Government’s intervention. If Federal Environment Minister Peter Garrett AM MP overlooks the gravity of the future threats facing Ella Bays cassowaries we may all be reading advertisements like the one I have suggested and I doubt any of us will be laughing.

Extinction is forever.