Size matters: food for thought and our future
Millions of years ago, our rugged land was covered in lush, rich and dense rainforest. Now, only tiny ecosystem pockets remain and in the World Heritage listed Nightcap National Park in northern NSW, several native trees face extinction because they can no longer spread their seeds.
Many Australian rainforest trees produce large fleshy fruits, which drop to the floor when they’re ripe and ready to be eaten by animals. However, in the rainforest - size matters. Only a few native rainforest animals that can ingest fruits larger than 3cm in diameter remain, and unfortunately in NSW, we don't have the Cassowary to do the job.
Dr Rossetto said past ice ages have resulted in the repeated reduction and fragmentation of rainforests in Australia and while some plant species have survived this, many large-fruit dispersers were lost in the process.
"The animals that can feed on the big rainforest fruits and move their seed around are fairly limited in Australia compared to South America, Asia, and Africa, which have rhinoceroses, monkeys, squirrels and all sorts of birds to do this,” Dr Rossetto said.
“While we don't have the Cassowary in NSW, we still have animals such as the wampoo fruit dove and bats, which are capable of eating and dispersing the smaller fruits such as figs and lilly pillies,” Dr Rossetto said.
Many rainforest species in Queensland, such as the larger fruited trees from the same family as the avocado (sometimes known as native walnuts), are now solely reliant on the Southern Cassowary to spread their seeds.
“They scoop up the big fleshy fruits that rainforest trees have dropped beneath them, swallow them in one gulp, digest the pulp and pass out the seeds unharmed all over the rainforest in large piles of poop,” Dr Rossetto said.
“It’s starting to become a ‘chicken and egg’ situation. As the rainforest disappears, so does a vital resource of food, protection and habitat for a huge percentage of Australia’s wildlife,” Dr Rossetto said.