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Sci­en­tists esti­mate 16,000 tree species in the Amazon

pub­lished 20 Octo­ber 2013 | mod­i­fied 13 Sep­tem­ber 2014

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.

Canopy westamazonOf 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.

This is very valu­able infor­ma­tion for improv­ing preser­va­tion of Ama­zon­ian ecosys­tems and species
Hans ter Steege, lead author, Nat­u­ralis Bio­di­ver­sity Cen­ter and Utrecht Uni­ver­sity, the Netherlands »

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.”

Hyper-​dominant species
Virola surinamensis fruitWhy 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.

Rio negro panorama

(Source: Nat­u­ralis Bio­di­ver­sity Cen­ter press release, 17.10.2013)

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