There is a place in the world where all the forces of nature converge and create an environment so unique that there are more animals than anywhere else on the planet. Volcanoes covered in tropical jungles rise above an ocean full of coral reefs and ecosystems intertwine to create unparalleled biodiversity. It is Insulindia, the Malay archipelago, the land of 25,000 islands that, between 1854 and 1862, Alfred Russel Wallace explored and where he made some of the most important scientific discoveries of his time.
Wallace traveled in a tireless desire to demonstrate how geography affects the distribution areas of species, conditions their origins and multiplies their diversity. Meanwhile, from his home in Downe, another naturalist, Charles Darwin, compiled the countless evidence and arguments that would support the publication in 1859 of
On the Origin of Species
, the book that conceptually disrupted the world. Whenever he embarked on an expedition, Darwin carried with him a copy of John Milton's
Paradise Lost
.
It was in the Galapagos Islands that Darwin's nemesis occurred, the shift from a timorous religious mentality to an openly heterodox one in which biological inheritance replaced the hand of the divine watchmaker. Galapagos, a paradise lost in the middle of the Pacific that, in the eyes of the young naturalist, appeared as a laboratory of evolution. Although the
Beagle
spent only five weeks in the Galapagos on its five-year journey
, approximately a quarter of Darwin's notes and field book are dedicated to this place. He had found one of the primeval paradises of evolution, and there he began to throw Milton's creationist cargo overboard. Keeping in mind the amazement that Wallace and Darwin felt in their respective island paradises, it is better to understand what the naturalists who have just described a new paradise of sealess islands must have experienced.
South East Africa Montane Archipelago
(SEAMA), this is its name. The landscape of the new ecoregion is dominated by 30 granite hills, some of which exceed 3,000 meters in altitude. They are
inselberg
or “island mountains”, isolated hills that dominate the plain, batholiths formed between 600 and 125 million years ago. Today, the largest (Mount Mabu) and smallest (Mount Lico) evergreen montane rainforests in southern Africa survive in the 30 hills. Further up the hill, above these primeval forests, biologically unique subalpine meadows thrive.
In Africa, mountains often house relict forests (last refuge of species), remains of a wide forest belt from the Tertiary. Before the elevation and progressive increase in aridity of the eastern plateaus, the forest extended over most of the continent.
During the early Oligocene, as the global climate cooled, Pan-African rainforests began to fragment. This caused a significant reduction in forests throughout the Miocene. Forest fragmentation produced the “islands in the sky” that host the unique biodiversity we see today. Much of the original forest in East Africa was confined to these isolated mountain patches that persisted thanks to orographic rainfall.
Immersed in these small, confined forests, limited by their low dispersal capacity, some species were trapped in highland refuges. There the trade winds, loaded with humidity, maintained a relatively stable climate.
Subsequent climatic fluctuations, throughout the late Cenozoic, hindered gene flow, the migration of genes, between individuals of the same species that were in adjacent mountains. So each of these rock islands became an evolutionary center that favored allopatric speciation (caused by the presence of a geographic barrier). Thus, until establishing the unique habitats, rich in endemic species: reptiles, amphibians, mammals, crabs and butterflies that now characterize African montane systems.
The wealth of paradise
The 3.3 square kilometers over which this small ecoregion extends are home to 30 species of strictly endemic butterflies, which only exist in the Montane Archipelago; six species of freshwater crabs; 11 species of amphibians; 22 new reptile species, including a tiny new pygmy chameleon (
Rhampholeon maspictus
); four new species of mammals and 117 species of strictly endemic plants. This is a remarkably high number for such a limited geographical area, and will most likely increase when sampling of some groups of cryptogams (seedless vegetables) and invertebrates that require analysis by groups of specialized taxonomists is incorporated.
The endemic component as a whole is a consequence of the isolation of the hills, separated since the Tertiary from the rest of the Pan-African forests by the immense plains covered with savannas, a sea of grass whose seasonal aridity prevents the development of forest biomes.
But not all are good news. Despite being of global importance for biodiversity and the efforts of the governments of Malawi and Mozambique, the ecoregion is seriously threatened. Since scientists began their studies 20 years ago, the mountains, buckling under the pressure of slash-and-burn agriculture, hunting and demand for fuel and timber, have lost a fifth of their rainforest extent, almost half in some cases, one of the highest deforestation rates in Africa. If the trend does not change, the new ecoregion, an Eden of biodiversity, can become, like Milton's, another lost paradise. Races condemned to millions of years of solitude do not have a second chance on Earth.
Manuel Peinado Lorca
is Professor Emeritus and Director of the Royal Botanical Garden of the University of Alcalá.
This article was previously published on The Conversation.
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