How it began
Ascension Island is part of the territory of Saint Helena, Ascension and Tristan da Cunha. Charles Darwin visited in 1836 and lamented that the island was destitute of trees. The botanist Joseph Hooker visited in 1843 and proposed a plan to increase vegetation on the highest peak. In 1847 he persuaded the Royal Navy to ship trees and bushes from Kew Gardens, where his father was director, and plants began to arrive in 1850 from Europe, Argentina and South Africa.
Before it existed
Visitors in the early 19th century described Ascension as exceptionally barren. Only a handful of species, mostly ferns, mosses and some grasses, grew on the higher slopes of the mountain. Royal Marines had established a garden there to supply vegetables and fruit for the garrison, but crops were limited by the lack of fresh water on the dry island, and a water catchment was the main supply.
How it works
The strategy of Hooker was to plant trees to increase rainfall, to put vegetation on steep slopes to prevent soil erosion, and to introduce a wide variety of crops. The idea was that forests on the mountain would trap moisture and enrich soil that would hold fresh water. Organized forests, shrublands and pasture were planted with over 220 exotic plant species. Kew sent over 330 plant specimens. Only the fittest of the introduced species survived.
Who pushed back
The Ascension Island Government notes that the project can also be seen as a man-made biological invasion that degraded a previously pristine island environment. Most native and endemic plants of Ascension are now severely out-competed by the introduced ones, and several endemic ferns are critically endangered.
What changed first
By the late 1870s the plantings were flourishing. Above about 600 meters the mountain became a misty cloud forest of ferns, eucalyptus, bamboo and other trees, along with food crops such as bananas, ginger and coffee. The mountaintop is about 7 degrees Celsius cooler than the coast, and the old water catchment is no longer needed.
Where it stands today
Green Mountain was designated a National Park in 2005. The conservation directorate of the island works to balance native and endemic flora with the introduced plants, some of which help native species: bamboo gives endemic ferns a place to grow. Kew continues to be involved. Scientists interested in terraforming cite the mountain as evidence that people can assemble a functioning ecosystem within decades.
