The Amazon is losing its vast expanse of green, bit by bit. By 2013, the Amazonia — originally spread over nearly six million square kilometers — lost 12 percent of its forest cover. Such wide-scale forest loss is not only knocking down Amazon’s overall tree numbers, but is also driving individual tree species towards extinction.

In fact, more than half of Amazon’s immensely diverse 15,000 tree species could qualify as globally threatened under the IUCN Red List of threatened species criteria, an international team of 158 researchers conclude in a new study published today in the journal Science Advances.

“Our results suggest that the total number of globally threatened species listed by the IUCN should be at least a fifth higher—and that’s just accounting for the Amazon,” co-author William Laurance of James Cook University in Australia, told Mongabay.

Conservation status of trees in the Amazon remain relatively little-understood. To fill the gaps and see how forest loss is affecting populations of individual Amazonian tree species, the research team correlated known distributions of over 15,000 tree species with historical and projected patterns of forest loss in the Amazon.

While not the first study of Its kind, “it’s the most ambitious and, I think, the best in terms of the quality and quantity of data,” Laurance said.

On analyzing the data, researchers found that as a result of historical and ongoing deforestation in the Amazon, 36 to 57 percent of all Amazonian tree species —both common and rare—have either already lost, or will lose, more than 30 percent of their original populations, or have fewer than 1,000 individuals left in the wild, qualifying them as threatened under the IUCN Red List criteria. These include some iconic Amazonian species such as Brazil nut (Bertholletia excelsa) and wild populations of cacao (Theobroma cacao), the team found.

“Our estimates of the threat status of all Amazonian tree species constitute the largest threat assessment ever carried out,” researchers write in the paper. “In fact, the number of species assessed in our analyses (15,200) is nearly as large as the number of all plant species evaluated by the IUCN over its 50-year history (19,738).”

The researchers found that populations of tree species are most threatened where deforestation is the highest. And this includes southern and eastern Amazonia, also referred to as the “Arc of Deforestation.”

It is not all doom, though.

“We aren’t saying that the situation in the Amazon has suddenly gotten worse for tree species,” co-author Nigel Pitman of The Field Museum in Chicago, USA, said in a statement. “We’re just offering a new estimate of how tree species have been affected by historical deforestation, and how they’ll be affected by forest loss in the future.”

The researchers found, for instance, that under an “improved governance scenario” (IGS) in the future, the average loss of tree species could be less severe than that under a business-as-usual scenario.

While the latter scenario assumes that recent deforestation trends will continue, the IGS is an ambitious scenario which assumes, “that there will be strict enforcement of mandatory forest reserves on private properties, careful zoning of land uses based on ecological and agricultural criteria, and expansion of the current protected-areas network,” Laurance said.  “It’s not quite ‘pie in the sky’ but let’s just say that it’s a best-case scenario based on a lot of things going right for the Amazon environment.”

The researchers estimate that given the trends of species loss in the Amazon, most tree species in other tropical forests around the world would also likely qualify as globally threatened under IUCN Red List criteria.

For the Amazon, however, there is a ray of hope. The present network of protected areas and indigenous territories covers over 50 percent of the Amazon, researchers write.

“I had thought the situation was much worse,” lead author Hans ter Steege of Naturalis Biodiversity Center in the Netherlands, told Mongabay. “The good news is that over 80% of the Amazon forest is not deforested… and around half of that is in some form of conservation area.”

On correlating species distributions with the network of protected areas, the team found that all the common Amazonian tree species, and around half of all the rare tree species, are protected to some degrees by the network of protected areas and indigenous territories in the Amazon.

“Our findings underscore the very real importance of ensuring the integrity of the current network of protected and indigenous lands,” Laurance said. “If these lands are well protected, then a much smaller fraction of the Amazonian tree flora will be in trouble.”

Moreover, the spatial models used in the study can be used to “highlight gaps in the current protected-area system (that includes indigenous lands, in our analysis),” Laurance added.  “These would be places where there’s lots of species that are poorly represented in some kind of protected or indigenous land.”

However, the team cautions that the results are still preliminary.

“Red-listing these species will require case-by-case assessments by the IUCN/Species Survival Commission Global Tree Specialist Group and country-level teams, taking into account other data sources and threat criteria,” the researchers write. “What we show here are the size, urgency, and feasibility of this task.”

Citation:

• Hans ter Steege et al. (2015) Estimating the global conservation status of more than 15,000 Amazonian tree species. Science Advances. DOI:10.1126/sciadv.1500936

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Shreya Dasgupta Editor

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AgricultureDeforestationEnvironmentExtinctionForest LossForestsHabitat DegradationHabitat LossRainforestsThreats To RainforestsTropical ForestsAmazonSouth AmericaInternational Union for Conservation of Nature (IUCN)

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