I always enjoyed that moment. The aircraft rolled slowly towards the terminal and somewhere close to parking, depressurization of the cabin had occurred. You could tell when this happened. The warm humid air was thoughtless and intrusive. It was mere seconds between the near cold, dry air-conditioning and the lush tropical sauna.
Exiting the aircraft, I watched my parents and sister suddenly slump – the thick air of the lower latitudes hit them with all its force – however, the feeling was the opposite for me. It was as though gravity had faded and the breath of the tropical greenery filled me with an unusual giddiness. I suppose not everyone is made for Far North Queensland, but it had always felt like home to me.
Sixteen years old – nearly half my life time ago now – and unaware that circumstance would mean for this to be my last visit for at least another one and a half decades. In fact, I was pretty much unaware of everything that existed outside of this holiday. My visits to Cairns and the surrounding region were all too brief moments of lucidity, like waking for just a moment from a deep sleep, and I did my best to soak them up.
The memories that stay with me the longest, and in incredible detail, are those that highlight the abundance of life of northern Australia. Back home on the southern coast, throughout the warmer months, you would hear but a handful of bird species calling out lazily in the afternoon. The Mediterranean climate of Adelaide is beautiful, but comparatively sparse. Here, along this band of vegetation against the east coast, you couldn’t escape the call of life.
Invisible millions of cicadas kept a persistent tone that would render tinnitus the mildest of burdens and if you tried to plunge into the waters of the reef to escape from this forest sound, all you find is that the ringing has been replaced by an omnipresent crackling of endless parrot fish scrapping at coral.
Then there’s the life that physically surrounds you.
On our way to the Atherton Tablelands, a male cassowary stood in the middle of the road, bringing our hire car to a halt on the dirt track. Once the vehicle was stationary, the giant bird took its time, leisurely looking into the cabin at the giggling occupants. Once he had contented himself with his investigation, he walked away from us, nearly reaching the understory to the right of the car. Seconds later, a number of hidden chicks burst out from the vegetation in front of the vehicle, darted through their father’s legs, before disappearing again in the vegetation to the left.
The striking adult bird was in no hurry to follow his offspring back into the forest. He kept a casual eye on us as he slowly walked away. He clearly knew that he was boss.
Or there were turtles that nudge around you as you paddle beneath the almost too perfect Millaa Millaa Falls (Image 3).
And who, after swimming along the Outer Reef could ever forget that dizzying spell that follows immersing into the vibrantly coloured ocean metropolitan?
Even back in Cairns, I have a whole host of memories surrounded by wildlife – some enjoyable; such as the endless hoards of geckos that scurry across any given wall, and some less so; such as the spider, larger than my hand, that had made a resting platform of my folded bath towel, or the giant cricket that kicked my father’s hand, causing an impressive gash.
In every possible regard, the tropics saturate your awareness with life.
Indeed, when western settlers moved into such regions, they were struck silly with the richness of life of the tropics. Surely, agriculture could to do no better in any other region than it could on rainforest land.
It seemed logical enough and for the first few years, the yield spoke for itself. However, the yield suddenly declined after three or four years.
The soil wasn’t rich and fertile as the monstrous trees seemed to have suggested, but were old and depleted of most nutrients and useful minerals. By cutting and removing much of the vegetation, the settlers had effectively removed most of the available nutrients of the tropical system. Burning what remained after clearing, bought the farmer some time – by fertilising the plot – but this was only temporary.
The turnover rate of available nutrients is so rapid that the soil plays only a minor role in many tropical rainforests. Effectively, the living, breathing biota of the rainforest holds up the wealth and fertility of the region, almost in worship of the hot tropical sun. It was an alien environment to those from temperate Europe and shows, to this day, through the continuous extra effort placed in tropical agriculture compared to that of higher latitudes (see more here).
Not only has farming in the region removed much of the wealth before agriculture even began, but, with the assistance of other landscape use changes, it has introduced the potential of phosphorus fertilisation . As much as this is beneficial in higher latitudes, in phosphorus-limited rainforests, this has the potential to be disruptive to the carbon cycle – even leading the environment from a net carbon sink to one where carbon is lost from the environment in the form of CO2 emissions via increased respiration .
As tropical forests are responsible for at least a third of the global organic carbon storage and exchange of CO2 between the biosphere and atmosphere, phosphorus fertilisation has great potential for disrupting this valuable service in controlling CO2 atmospheric concentrations .
Another point that should be made is that the life found in such forests are amazing demonstrations of adaption. For example, tropical insects live far closer to their optimal temperature and are likely to be more susceptible to temperature changes than their temperate counterparts . Insects provide many valuable services to rainforests, such as pollination, aeration of soil, rapid breakdown of organic litter and providing a direct and indirect food supply to other species. Living so near to their optimal temperature zone leaves two options with the changing climate – adaption and / or migration – both of which have the potential to be disruptive to the services provided by these species . Clearly, the tropics are weird and wonderful place and work on very different principles to those westerners understood.
I hadn’t realised it at the time, but the forest on either side of the dirt track was likely to be maybe a couple kilometres wide. The adult cassowary was probably used to vehicles; being a large animal with young, he probably had to cross the road regularly simply to find enough food in the thin strip of remnant forest.
From landscape use changes (largely deforestation / wood harvest, agriculture and urbanisation), to pollution and climate change, rainforests are at risk and not only by hectare loss – but also by services loss at a species level.
A loss of a pollinator could mean the difference between abundance and local extinction of a plant species, which in turn could affect other species dependant on that plant. A loss of specialised recyclers of litter could lead to material being locked in waste or greatly increase in conversation time before it is returned as useful material – depleting nutrient and mineral availability even further.
Tropical forests may hold their wealth of fertility up high, but unwittingly, we’re cutting these ecosystems down at the knees, which has the potential of causing a dominoes effect. These highly productive regions are of great importance to human life for many of the ecological services that they provide. Are we effectively pulling the plug on a major life support system?
 Cleveland, C. C., and Townsendm A. R. 2006. Nutrient additions to a tropical rain forest drive substantial soil carbon dioxide losses to the atmosphere. PNAS. 103:27. 10316-10321.
 Deutsch, C. A., Tewksbury, J. J., Huey, R. B., Sheldon, K. S., Ghalambor, C. K., Haak, D. C., and Martin, P. R. 2008. Impacts of climate warming on terrestrial ectotherms across latitude. PNAS. 105:18. 6668-6672.