Green Mountain on Ascension Island transformed from barren land to a lush forest through 19th-century tree-planting, but nature's own recovery may outperform human efforts.
Volcanic island's misty forest
Green Mountain, the highest point on the island of Ascension, now has a forest of mist that did not exist in nature. This volcanic island in the South Atlantic rises 859 meters above sea level and covers about 91 square kilometers.Historical planting efforts
Starting in 1850, the British Navy and the Kew Botanical Gardens introduced vegetation from Europe, South Africa, and Argentina to the summit of Green Mountain. When Charles Darwin visited the island in 1836, he described a barren landscape without trees. The British did not establish a garrison there until 1815, and at that time, sailors cultivated a vegetable garden on Green Mountain to feed themselves.Vision for greening the island
Joseph Hooker, a friend of Darwin, visited the island in 1843 and proposed making it greener by planting trees from around the world. In 1847, he advised the Royal Navy to launch a long-term planting plan with Kew's help, hoping the trees would capture mist and provide enough fresh water to eliminate the need for importing drinking water. Between 1847 and 1850, over 300 trees were sent from Kew to Ascension and planted on the highest peak.Transformation of the landscape
By the end of the 1870s, Norfolk pines, eucalyptus, bamboo, and banana trees were growing abundantly on Green Mountain. By 1870, an additional 5,000 trees had been planted. What was once a gardener's experiment had become a mountain-scale construction site.Ecological transformation
Biologist David Wilkinson of Liverpool John Moores University describes how the island's ecosystem changed from species-poor slopes dominated by ferns to a species-rich cloud forest in about 150 years. Soil fertility even recovered in less than a decade.Natural regeneration vs. planting
A meta-analysis of 133 studies found that natural regeneration outperforms active restoration for plants, birds, and invertebrates by 34 to 56 percent in ecological richness. Natural regeneration can recover 80 percent of a tropical forest's fertility and diversity in 20 years without human intervention.Mixed results and concerns
While accounts of increased rainfall lack reliable measurements, the botanical results are impressive. Hooker, now elderly, expressed regrets about the project and predicted its effects a century later. Ecologists note that natural regeneration surpasses active restoration, and Ascension remains an exception.Global reforestation efforts
The Bonn Challenge, aiming to restore 350 million hectares by 2030, has spent billions on reforestation. However, 80 percent of its commitments involve monocultures or non-native species, with limited effects on carbon dioxide storage and negative impacts on biodiversity.Choosing between planting and regeneration
The choice between planting and assisted natural regeneration depends on the type of plot and the history of the forest to be restored. In France and Europe, the challenge is forest degradation, not deforestation. Planting projects face higher tree mortality risks than assisted regeneration projects, and the two approaches can be combined on the same plot.Ongoing efforts on Ascension
On Ascension, the story continues. The removal of invasive species on Green Mountain has created a restoration site where endemic species are reintroduced. The euphorbia Euphorbia origanoides, the only low-altitude endemic plant on the island, is now confined to the most remote desert areas. A conservationist cited by National Geographic extends Hooker's forest, the trees that intercept the mist, to provide ferns with a shelter where they can survive.
