Life on Earth - it's all about Connections

Life is all about interdependence, and this has been the case for over 4.5 billion years of evolution on Earth.

This was the message of Dr Mary White in her Keynote Address to the Botanic Gardens Australia and New Zealand NSW (BGANZ NSW) conference run by Hunter Region Botanic Gardens. Mary’s talk was titled Major environmental issues on the significance and importance of equatorial forests and species conservation, but it can be distilled down to life being ‘symbiotic’ and if you change one setting you almost certainly effect the whole system.

Mary started by stressing the important role of botanic gardens in educating people, whether through talks, walks or horticultural displays. She sees botanic gardens as great places to talk about the interdependence of living things on earth, sometimes called Gaia. This is the green planet where all depends on photosynthesis and on each other.

The talk started (metaphorically) four billion years ago with first bacterium in near-boiling water…our ancestry. We are part of life’s continuum, said Mary.

Molten earth cooled until liquid water was present. Then the Earth’s crust started to crack into plates, with lots of volcanic activity producing new material at edges of crusts (Mary’s early training in Africa was as plate tectonics was given scientific credence).

From a chemical soup in primeval oceans, there has been four billion years of evolution of life. About 3.5 billion years ago photosynthesis begins in cyanobacteria. Then we get further microscopic single-celled life, which starts to alter the environment – ‘preparing it’ for future life forms. For first three billion years life was a bacterial and single-celled world [me: one could argue it still is but they have more and different places to live…]

To illustrate the connectivity between climate and life, Mary mentioned the role algae play in cloud formation when they rot and produce sulphides that rise from the oceans surface. This ‘albedo’ effect dates back at least two billion years. Mary quotes Lynn Margulis, that Earth is no more rock covered in life than we are a skeleton infested in cells.

Mary gives special mention to lichens (a very close symbiosis between algae and fungi) as early colonisers of the land. Life with more than one cell, ‘multicellular life’, comes late and relatively rapidly… 470 million years ago our back-boned ancestors, the fish, evolve.

The rest of the talk was a journey through the evolution of life, and Earth, to the present day where humans are having a major (negative) impact on the planet. Mary asked us to stop all clearing of forests, to restore forests where we can, avoid burning vegetation generally, and to reduce our (human) population. For botanic gardens staff she asked us to help restore Gaia.

Mary has been an observer and a participant in the discovery of this fascinating story. She has published a series of colourful and stimulating books starting with Greening of Gondwana in 1986. While working at the Australian Museum Mary described, for example, the fossil species Agathis jurassica, part of the ancestry of today’s kauris and our very own Wollemi Pine.

Images: Sign outside Hunter Region Botanic Gardens and Dr Mary White presenting the story of life on Earth.