A Man-Made rainforest that should have taken millennia to evolve has baffled
scientists by springing up in just 150 years.
Rainforests should take millions of years to develop the highly complex,
interactive ecosystems for which they are famed, in which every species fills an
But the forest on Green Mountain, Ascension Island, in the mid-Atlantic sprung
up chaotically from a mixed bag of botanical scrap brought in by the Royal Navy
And the introduced species have thrived at a rate that has stunned experts and
could trigger a rethink of conventional ecological theory, New Scientist
magazine reports today.
When Charles Darwin stopped off at Ascension Island in 1836 on the home stretch
of his long journey on the Beagle, he described it then as "entirely destitute
of trees". Lying 1,200 miles from the nearest continent, the volcanic island was
almost barren because of its remoteness, with only about 20 plant species,
But in 1843, an ambitious British scheme for revitalising the island began, with
Royal Navy troops planting thousands of trees a year, using seedlings from
Argentina, South Africa, and the Royal Botanical Gardens at Kew.
Soon the bare white mountain was cloaked in vegetation and renamed Green
Mountain. By the early 20th century the mountain's slopes were covered in guava,
banana, wild ginger, the white-flowered Cleroden drum, Madagascan periwinkle and
eucalyptus from Australia. A thick bamboo forest crowned the summit.
Now Green Mountain is a thriving tropical forest, yet it grew from species
collected randomly. Conventional theory suggests complex ecosystems only emerge
through a slow evolution in which different organisms develop in tandem to fill
But Green Mountain suggests that natural rainforests may be constructed more by
chance than by evolution.
Dissident theorists call this "ecological fitting". It says species do not so
much evolve to create ecosystems as make the best of what they have.
"The Green Mountain system is a spectacular example of ecological fitting,"
David Wilkinson, from Liverpool John Moores University, told New Scientist. "It
is a man-made system that has produced a tropical rainforest without any
co-evolution between its constituent species."
But Alan Gray, an ecologist at the University of Edinburgh, argues that the few
surviving endemic species on Green Mountain would still be co-evolving and may
form the framework of the new ecosystem, meaning the newcomers may be
Even the new species may not be such a random collection.
"Many of the imports may have come from the same place, importing their
co-evolutionary relationships," said Gray.