For the first time ever the number of trees per species in the Amazon have been estimated. Scientists have calculated that half of all of 400 billion trees in the Amazon are made up of just 227 species.
Of the nearly four hundred billion trees of the Amazon, half are made up of just 227 hyperdominant species. This is just 1,4% of the total number of 16,000 species estimated. Researchers, taxonomists, and students from 120 institutions around the world have provided new answers to two simple but long-standing questions about Amazonian diversity: How many trees are there in the Amazon, and how many tree species occur there? The study is published on 17 October 2013 in Science.
“The most common species now have a name”
Surprisingly little is known of the Amazon Basin, the area with the richest plant biodiversity on earth. The vast extent and difficult terrain of the Amazon Basin (including parts of Brazil, Peru, Columbia) and the Guiana Shield (Guiana, Suriname, and French Guiana) has historically restricted the study of its extraordinarily diverse tree communities to local and regional scales.
Now, however, over 120 experts on the Amazon, led by Hans ter Steege of Naturalis Biodiversity Center and Utrecht University, the Netherlands, have contributed data from 1,170 forestry surveys in all major forest types in the Amazon. They generated the first basin-wide estimates of the abundance, frequency and spatial distribution of thousands of Amazonian trees. “Because over 120 researchers have pooled their data, we were now able to make a collective analysis and provide a first picture of the whole”, says first author Ter Steege. “Not only do the most common species now have a number, they also have a name. This is very valuable information for improving preservation of Amazonian ecosystems and species”.
A small number of species produce half of the ecosystem services
The lack of basic information about the Amazonian flora on a basin-wide scale has hindered Amazonian science and conservation efforts. “In essence, this means that the largest pool of tropical carbon on Earth has been a black box for ecologists, and conservationists don’t know which Amazonian tree species face the most severe threats of extinction”, says Nigel Pitman, Robert O. Bass Visiting Scientist at The Field Museum in Chicago, and co-author on the study.
The study suggests that hyper-dominants — just 1.4 percent of all Amazonian tree species — account for roughly half of all carbon and ecosystem services in the Amazon, such as water, carbon and nutrients. This is important information for governments and conservation organisations.
The World Wide Fund (WWF) calls the research “cutting edge”. WWF Netherlands director Johan van de Gronden: “It is the first time that so many data from the entire Amazon are available in one study. A conservation organisation such as WWF, can now determine much more accurately which areas hold the richest, most diverse nature, and in which regions potentially endangered species are found. For the future of the Amazon this is of great importance.”
Why is it that just 227 species are so successful? It is a fact that these “hyper-dominant” species, as the authors termed them, are found across large surfaces and in large numbers. They must be able to deal with parasites and fungi very well, because these affect mostly common species. At the same time, almost none of the 227 hyper-dominant species are consistently common across the Amazon. Instead, most dominate a region or forest type, such as swamps or upland forests. Eschweilera coreacea (a species from the Brazil nut family) is the only species dominant in all regions. Why these species are so dominant is still open to debate, the authors say.
Among other possible explanations, the authors suggest that hyper-dominant trees may be common because pre-1492 — when Columbus discovered the New World — indigenous groups cultivated them, though this is a topic of debate. “Fact is that several hyper-dominants are of enormous value to local people”, says Tinde van Andel, ethnobotanic at Naturalis Biodiversity Center and one of the co-authors. “Açai palm (Euterpe oleracea) grows in enormous numbers in Amazonian swamps. Thousands of families in Brazil, Surinam and Guyana make a livelihood harvesting and selling fruits and palm hearts of this species.”
36% of the species are rare and unknown
The study also offers insights into the rarest tree species in the Amazon. According to the mathematical model used in the study, roughly 6,000 tree species in the Amazon have populations of fewer than 1,000 individuals, which automatically qualifies them for inclusion in the International Union for Conservation of Nature (IUCN) Red List of Threatened Species™. The problem, say the authors, is that these species are so rare that scientists may never find them. Ecologist Miles Silman of Wake Forest University, another co-author of the paper, calls the phenomenon “dark biodiversity”, akin to “dark matter” in cosmology. “We know it is important, but it is devilishly hard to detect”, says Silman.
(Source: Naturalis Biodiversity Center press release, 17.10.2013)