When the Past Lives On

I like to be reminded - and I think it's good for all of us - that we are here by merest chance at just this moment. Things could have been very different had we happened along even just a few thousands of years ago or hence. Such reminders abound in the rocks, including fossils such as the dinosaur footprints we talked about recently, or snapshots in stone of past conditions.

Fossil seashell, Morton National Park, New South Wales,
in a site that is now 50km inland and a couple of hundred metres above sea level.

Ripple marks laid down on ancient shoreline, Watarrka National Park, central Australia.

There are plenty of such stories to be told, but that's not my intent today. Rather I wanted to look at a couple of living examples, both from central Australia. 

I recently had the pleasure of finally getting to the renowned Palm Valley, 22km south of Hermannsburg community along a rough road, then a challenging creek bed. Here, along just two kilometres of creek bed grow the remarkable Red Cabbage Palms - remarkable because the nearest palms are some 1000km away, across country far too arid to support palms. 

Red Cabbage Palms Livistona mariae, Palm Valley.

It is 30,000 years at least since the great central salt lakes were permanently full and the inland rivers ran as the norm. We're not sure what the rest of the land looked like then - the rainforests were long gone - but it is quite plausible to suppose that palms survived in oases from an earlier even wetter time, and perhaps even the fruit were carried by people as food or trade items. 

Their survival  here is due to an unlikely combination of events. It seems to me that the sheet sandstone that makes vehicle access both possible and very rough is a key factor, acting as a basin for water running down through the porous sandstone of the surrounding hills. It is a remarkable, and remarkably beautiful, place, and one guaranteed to set any rational person thinking.

Sheet sandstone creek bed, Palm Valley.

(Some recent work suggests that the nearest relation is the Mataranka Palm L. rigida, 1000km to the north, from which it diverged only 17,000 years during the last arid glaciation, in which case human vectors seem the most likely explanation for its presence, rather than being remnant vegetation. The story is still to be resolved.)

Another ancient plant found in these inland ranges has a larger range than the palm, but this range still only represents a dot on the map of Australia. Cycads are far older, as a group, than the flowering plants (including palms); they evolved in lush forests and while some modern cycads have adapted to drier situations, they can't cope with deserts. Again, the sheltered gorges of the Macdonnell and George Gill Ranges have enabled them to survive long after their relatives disappeared for well over a thousand kilometres around - long enough for them too to have evolved into a distinct species. 

MacDonnell Ranges Cycad Macrozamia macdonnellii, Standley Chasm, West MacDonnell Ranges.

It is always something of a surprise - and delight - to come across them in the sheltered gorges and cooler east- and south-facing slopes. 

Another surprise is finding a fig, but Rock Figs too survive in the gorges, and even in the harsh world of the canyon edges. This one isn't limited to the centre, but is found in suitably sheltered situations from here north-west to the distant coast, though the centre represents its south-eastern limits. Its ancestors were rainforest inhabitants, as are most of its relations today.

Rock Fig Ficus brachypoda; Ellery Creek Big Hole, West MacDonnell Ranges (above);
Watarrka National Park, George Gill Range (below).

Time fascinates me, so doubtless we'll be exploring variations of this theme in times to come.

BACK ON TUESDAY