Terraforming Ascension Island

In the nearly 175 years since Charles Darwin made the first geological reconnaissance of Ascension Island (on his way home from the HMS Beagle voyage to the Galapagos), its peaks have been transformed from barren piles of ash to lush tropical oases. In the twenty three years since my first trip to the island, I have seen the dramatic changes firsthand.

The BBC ran a fascinating story the other day, describing the bringing of a vast array of plants from London's Kew Gardens so that "in effect, what Darwin, Hooker and the Royal Navy achieved was the world's first experiment in "terra-forming". They created a self-sustaining and self-reproducing ecosystem in order to make Ascension Island more habitable."

My first trip to Ascension was made in 1987 in the cargo hold of a US Air Force C141 transport. After an all-night flight from Patrick Air Force Base in Florida, we arrived just after dawn on a rocky barren pile of cinders and ash. The only serious vegetation grew on the upper slopes of Green Mountain [right, taken from Green Mtn, view of cinder cones to the north. My photo, 2003] , the central peak of the 34 square mile volcanic hot spot in the center of the South Atlantic.

I was part of a team from the University of Utah that was drilling deep exploratory wells looking for geothermal energy. The first well found temperatures of 480F but not enough flow rate to run a power plant. I was there to help site the second well - looking for active faults or fracture zones that might provide high water flows. [typo correction 9-6-10, 14:53]

In 2003 I made my 4th (out of 5 trips ultimately) trip to Ascension with Mike Valentine from the University of Puget Sound, to collect samples for paleomagnetic analysis. During my first trips in the 1980s I collected a number of oriented surface samples that went to Mike's paleomagnetic lab. What Mike and his students found was enough for NSF to fund a return trip to collect hundreds of paleomag cores for more precise measurements.

The most striking difference between 1989 and 2003 was the spread of vegetation across many of the low volcanic plains and flanks of cinder cones. The geothermal well site that was stark in 1989 was now almost inaccessible due to thick growths of what was locally called monkeypod trees. The seed pods from the tree were providing abundant food for the feral donkey population which had exploded over the same period [middle, my photo, 2003].

Meanwhile, a team had been systematically rounding up or killing the large population of feral cats that had roamed the island for centuries, devastating the once huge migratory bird population. The cats were let loose initially to kill the rats that went ashore from the British ships that provisioned the uninhabited island. The rats ate birds eggs but the cats went after the birds as well as the rats.

As the BBC notes, the evolution of Ascension Island [bottom, credit NASA] is taking place over the course of scores of years rather than over geologic time scales, and could serve as a real life laboratory for environmental change or perhaps for how we might terraform Mars for eventual human settlement.