The rainforest canopy has been described as the ‘Last Frontier’ of biological research, a hidden world that has only been explored by a small number of scientists. The most common organism to inhabit these rainforest canopies are epiphytes, plants which grow on other plants for support and access to light. Vascular epiphytes, higher order plant species such as orchids and ferns, represent approximately 9% of the world’s plant diversity. Australia is home to around 380 vascular epiphyte species, with the vast majority confined to a very small proportion of the continent: the tropical and subtropical regions in the north-east.
Having no direct contact with the ground, epiphytes rely on regular moisture inputs from fog and rainfall. As a consequence, they are highly sensitive to small changes in precipitation and will be greatly affected by climate change. Many plausible climate models predict a reduction in humid cloud forests, where epiphyte diversity is greatest, leading to a loss in habitat for many epiphyte species. The loss of epiphytes from the forest ecosystem would greatly affect the nutrient balance, water storage capacity and habitat characteristics of the ecosystem.
Considering the importance of epiphytes to the functioning of rainforest ecosystems, very little research on epiphytes has been conducted within Australia. This is extremely surprising as the Wet Tropics region of north-eastern Australia has a high abundance of epiphytes and is home to approximately 165 epiphytic orchid species. Bryophytes (the group consisting of mosses, liverworts and hornworts) also remain understudied throughout Australia.
Below is a write up for WILD magazine
“It is not going to be easy” Jennifer Sanger the lead researcher said as we talked through the project. “It’s a rainforest. It will be cold, wet and you will be hanging in your harness all day everyday.” Not much of a sales pitch I will admit, however, the rainforest canopy is equivalent to the deep sea as one of the natural worlds last true frontiers. Its undiscovered epiphytic inhabitants, the sole reason for us being there, have been living their lives for countless generations free from prying eyes, invisible from the forest floor, until now.
Known as the Gondwanan Rainforest, the Border Ranges National Park is an extensive area of subtropical rainforest that covers 3,665 square km in northern New South Wales, adjacent to the Queensland border. The park was our home for 2 months as we surveyed 50 trees over 5 altitudinal plots ranging from 300m to 1100m above sea level. The goals of the project were two fold. Firstly, to record and sample all epiphytes like orchids, ferns and mosses and secondly, to create a highly detailed distribution dataset so that the future impact of climate change on these species could be projected.
Getting into the canopy of a 50m high rainforest tree in order to survey its upper branches where most epiphytes grow is quite an operation. Especially when you have to beat your way through the undergrowth to the base of the tree carrying bags of equipment. The real challenge is getting a line into the lower canopy using what’s known in the industry as a ‘Big Shot’, which is essentially a 2.5 meter high slingshot. The big shot would launch a bag with a line attached 30m into the tree, over a branch and then back down the ground so a climbing line could be pulled into the tree. On a good day it might only take 2-3 tries to hit your mark, but on a bad day you could still be shooting, detangling and retrieving throw line most of the day.
However with a climbing line in the tree and safely secured the real fun and thrill of climbing could begin. Petzel ascenders were our primary device for getting to the base of the canopy from there we used the double rope technique to move around the branches and make the final climb to the upper limits of the canopy research area. Moving about the canopy was a time consuming task with its throwing, retrieving, tying off and clipping onto the next line but it did grant us both many hours of unforgettable experiences.
The one experience that stands out the most does not include any of the exotic brightly coloured birds or the fantastically varied epiphytes we were lucky to meet. This experience was a day of thick clouds that moved through the forest almost completely obscuring the other trees and the ground from view. Many minutes passed as I hung there in complete silence. It felt as if the tree and I were the only beings on the planet. As the moment continued I could hear through the muffled atmosphere a sound like a waterfall gaining intensity and within a few short seconds a strong wind was upon me. A flurry of panic passed over me as the branches and greater tree began to sway more than any other time before but it quickly settled. The tree had moved metres from side to side as it flexed in the wind and regained its equilibrium between gusts, it was like being on a ship rocking in an ocean except this was a living breathing entity
The real work began afterwards, and it still continues, with Jennifer working full time at the Queensland Herbarium analysing, identifying and cataloguing. More than 400 moss samples. 13 species of orchid and 14 species of fern were taken throughout the project and they will all require many hours of dedicated microscope work to correctly identify. As I ask about her progress she seems overwhelmed by the sheer amount of unidentified species of moss and what exactly to do with them. It is quite possible that dozens on new species of moss will be classified by the end of her time at the herbarium but as yet the work continues.
Looking forward to next year we are both set to undertake another 2 month season of field work for this project in the Wet Tropics of North East Queensland. It is said that the Wet Tropics is the epiphyte hotspot of Australia which means we will both be in for a busy season of climbing and recording.