Capturing the Diversity – The Green Oasis

High in the clouds above the rest of Ascension island is a lush oasis of vegetation.  From the west, Green Mountain looks like a sharply pointed peak, but in fact it is a heavily eroded ridge orientated west to east, with several fatter spurs coming out especially on its southern side.  It is battered by every type of weather, but that plays to its inhabitants advantage.  For Green Mountain’s topography  produces so many different elevations, aspects and niches that everything can thrive up there in its proper place.   There was one problem with this, and that was to get plant seeds and spores there in the first place for them to experiment, evolve and thrive.  Being so far from any other land made it so difficult for plants to colonise.

It is difficult to imagine what Green Mountain looked like 500 years ago.  Only a small number of higher plant species are known to have existed there. Most of these are the ferns, whose spores could have travelled hundreds of miles on the wind.  The spurge too might have reached by wind perchance, or more likely from being stuck in the gullet or foot of a migratory bird.  But not much else.  The only other plants which seemed to find their niches were the lower ones, called bryophytes.  Algae and moss, liverworts as well, had set up their stalls on rock faces and in crevasses and maybe in amongst the rocks themselves. Maybe those people searching for life on Mars could learn a few hiding places by searching the lava flows of Ascension Island.

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The natural vegetation types

So why is Green Mountain and the surrounding area coated in grasses, shrubs and trees?  Quite simply, it was a huge experiment.  Various settlers and scientists, the most famous being Joseph Dalton Hooker of Kew Gardens,  used the slopes to see how you might be able to colonise a pristine environment with species from other places.  Seeds of all types, shapes, sizes and from a variety of climates were brought, and the mountainside was literally planted up.  Some were a complete failure, others you have to search hard for examples, like coffee beans or tea plants, but some relished the lack of competition and went rampant.

It was part experiment, but also was a way of trying to humanize the island.  As one of the first visitors to the island, the explorer Dampier, discovered, if you wanted to live on the island long term, you needed to get food, water and shelter.  The lack of vegetation made a lot of that very difficult – and so planting up timber forests not only supplied you with building materials, but help capture moisture, stabilise slopes and temper the climate.

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Lush Green Mountain Vegetation

So in came pine trees, eucalyptus, the casuarina tree.  Also came fruiting shrubs like raspberries, guava, bananas.  The guava in particular loved the climate and has spread far and wide over the south eastern portion of the island.  In theory they could be sizeable shrubs, but the winds of the south eastern corner of the island often stunt their growth down to barely a few inches off the surface of the rocks.   Look closely though, and you might find specimens that are several metres long, but their trunks and branches are flattened against the ground.

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Horizontal Tree

Flax, bamboo and other grasses have gone unbridled on some slopes.  Ginger too has expanded, it knots itself in amongst other vegetation and is a devil to remove.

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Flax and other plants on the roof of the island

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