Rainforest Revelations

In no small part, pristine, old-growth Daintree Rainforest owes its integrity to the magnificent design of the Fan Palm (Licuala ramsayi).  Spectacularly long-living, densely-packed and growing to two-thirds rainforest height, the large round leaves are organised to provide an excellent funnel that captures strangler seeds dropped by over-flying birds and fruit-bats.  Fan Palms are less susceptible to the effects of ‘strangulation’ that upper-canopy giants suffer.  Once established, the Fan Palm stranglers connect the upper network of vines that tie rainforest crowns into a single structural inter-connectedness, through a vertical integration into the root-mat at the forest-floor.

Rainforest with a predominance of mature fan palms contain noticeably low populations of seedling numbers giving the impression of a low recruitment of successors.  This could well be caused by the competitive requirements of long-living parents with such an obstructive influence to available sunlight, implying seedling recruitment is at its richest on the edges of dominant fan palm communities or where disturbances are rendered through natural collapses from the upper-canopy.However, there is another disturbing variance that is stripping those few juveniles of any chance of succession, through the rapacious foraging of feral pigs (Sus scrofa).  Fan palms have an inner, growing core or ‘heart of palm’, that feral pigs find irresistible.  Harvesting this food-source causes the plant’s death.

As pigs were released into Australia around 224-years ago, chances are they found the fan palm’s crown shortly thereafter.  Two centuries of harvesting would account for a significnt reduction on seedling population size, despite any pre-existing natural trend in favour of mature populations.

What would it mean for the ancient rainforests of the Daintree, if Fan Palms were no longer able to ascend to their rightful position in the secondary canopy?  How would the rainforest cope, in terms of its structural integrity, if Fan Palms were no longer part of the arsenal of assets that stand up to the successive natural impacts of cyclones?

How fortunate were the pigs to be introduced into an area with delicious fan palms and large juicy earthworms that have enabled them to thrive to an estimated 60,000 in the World Heritage Area, protected from hunting and shooting by government regulations!  Their adaptability and omnivorous competitive advantages have guaranteed their survival, but at the expense of the integrity of the rainforest and loss of cassowary habitat and food.