Far North Queensland, the Superlative Wet Tropics & Heritage Listing – Series 1.3 Biological Evolution

Welcome to the third of our series of articles about the World Heritage Listing of the Wet Tropics. The Wet Tropics is not only inscribed by UNESCO for its superlative natural beauty and its wide variety of endangered species but it also displays much about the history of the natural world.  This is where we begin the discussion over the next two articles, here we will look at the history of nature in regards to the flora and it’s evolution. This is Criteria IX for World Heritage Listing, the Wet Tropics shows “outstanding examples representing significant on-going ecological and biological processes in the evolution and development of terrestrial, fresh water, coastal and marine ecosystems and communities of plants and animals”.

Series 3 of 4 – Biological Evolution – UNESCO World Heritage Listed

Diversity is one of the absolute highlights of the Wet Tropics and it is definitely seen in the plant life throughout the region. The rainforests are believed to be the oldest in the world, dating back over 100 million years, and has many remnants of the past with a brilliant display of the evolution of the worlds flora and the fauna. In the last article we spoke of the crocodile and how it lived through the times of the dinosaurs. Well, the plant life throughout the rainforest even predates the crocodile. The fauna in the rainforest has the oldest relics in the world, and shows a beautiful timeline of the biological evolution throughout time.

By exploring even one hectare of the rainforest you are likely to see examples from the many evolutionary stages of flora on the planet. When taking a hike through Wooroonooran NP or the Daintree you will notice plants dating back 470 million years within your first few steps. These are the first of the land based plants, the mosses. Moss was the first of the flora to become land bound and is one of the simplest of plants, they are non vascular and have an extremely shallow root system. Mosses are synonymous with rainforests and give the lush green feel to the environ, covering rocks along many pathways and water systems, they are the carpet of the rainforest. Mosses began the process of making the world inhabitable for humans. Due to their arrival atmospheric CO2 drastically reduced and the amount of oxygen in the atmosphere skyrocketed. Ahh, the beginning of a new evolution. These mosses caused major changes in the variety of soils enabling new habitats for animals and fungi. Not only that, but the shallow root systems allowed for sediment stability to help influence the formation of many natural landscapes including many of the worlds river systems. There are thought to be around 400 different types of mosses in the Wet Tropics region.

The next significant change in the biological world of plants was the formation of a vascular system meaning flora adapted to circulate water internally. This is commonly known as the age of the pteridophyte (don’t worry we can’t pronounce it either). This change occurred about 360 million years ago. Most of these are varieties of ferns, and ferns like to grow in wet or moist shady areas, so they are found in abundance around our rainforests. Pteridophytes have no seeds, reproduction is via spores relying a lot on the surrounding environment and weather conditions for dispersal. There are at least 40 types of ferns endemic to the Wet Tropics. The most famous and the largest of the ferns is known as a King Fern and there are some huge specimens in the tropics. The leaves of the fern can extend out about 6m which makes them look like a large palm. They are easily spotted throughout Wooroonooran NP, Cape Tribulation and in the Gondwanan Rainforest Walk in the Botanical Garden in Cairns . Ask our guides to point them out to you. The King Fern is not endemic to the Wet Tropics but there are about 40 other varieties of fern found only in the Wet Tropics.

The age of the Ferns began about 400 million years ago, and the next major adaption took millions of years. The next major stage of biological evolution began approximately 350 to 300 million years ago and was the development of seeded plants but still no flowers (gymnosperms). Seedless plants needed moisture, and wind for dispersal, and spores had a short life cycle once separated from their plant. The dry climate of land made it difficult for spore bearing plants to reproduce and survive. Seeded plants changed all this, seeds contain not only an embryo but also food supply and a durable coating. This means it can survive for longer before germination and allows for better dispersal, allowing these new types of plants to survive and thrive much easier. One of my favourite plants is a Cycad, the most beautiful of all gymnosperms. The Wet Tropics is the only place in the world that has all three families of cycads and contains 21% of Australia’s Cycad species. Many of those cycads are endemic to the region including the Hopes Cycad. These grow very slowly and are the tallest of all the cycads, growing up to 20m. These are seen as an endangered species and protected under the 1992 Conservation Act.

Ahh, the beauty of flowers, the next major stage in evolution. We all love the beauty of flowers and take them for granted. Angiosperms, or flowering plants, began to evolve about 140 million years ago and changed the face of the world, what a brighter and more colourful place it became. Humans are not the only animal attracted to the vibrance of flowers, different colours attract different insects and animals to help with the spread of their seed. These plants no longer relied on the wind to increase their habitat and reproduce. Even though flowering plants are found all around the world, the angiosperms found in the Wet Tropics include 16 of the 28 primitive species remaining on the planet. Some even think angiosperms developed in this region of the world as we have so many primitive varieties. The variety might also be due to the fact that about 70 million years ago there were mass extinctions around the globe and around 70% of living species were lost. Luckily it did not effect the southern hemisphere as badly and we are left with many of these primitive plants in the rainforests of the region. The most recognisable ancient angiosperms found here would have to be the pepper tree, a Queensland nutmeg tree and of course the ever beautiful orchids around the region.

Taking a walk through the Wet Tropics is like taking a walk through the timelines of history. There is so much to appreciate and it would take multiple lifetimes to truly learn about the full significance of the region. Every walk through the rainforest will uncover something new and hopefully you can discover some of this barefoot.

NB. Dates used in this article may not be exact. Throughout the research there are many discrepancies and these are best estimates from numerous sources.