Although Açaí palm, the Amazon region’s “Surfer Superfood,” is well known to food faddists around the world for the nutritious purple-black rind on its tiny coconut used to make a yoghurt-like drink, its equally edible first cousin the Jussara palm is hardly known outside the Atlantic Coastal forest that forms its habitat.
Rather than stepping out on the world stage as a new food trend, chances are that Euterpe edulis (as Jussara – or Juçara – is known), could be heading toward extinction.
The problem isn’t just that natural growths of Jussara are preyed upon by illegal harvesters for their valuable heart of palm, which necessitates cutting down the whole tree. The problem is the absence of wild birds and animals which – like the surfers hungry for Açai – would normally devour the choice fruits of the Jussara palm.
Jussara has also been identified as a “super-antioxidant” with huge potential for wellbeing remedies using plant extracts. Science for Brazil profiled initiatives to use Jussara as a commercial ingredient. You can read our story here.
Conservation of E. edulis is directly linked to the maintenance of biodiversity in the Atlantic Rainforest biome. More than 48 bird species and 20 mammals feed on its seeds and fruits. Toucans, guans, thrushes and bellbirds are the main seed-dispersal agents, while agoutis, tapirs, peccaries, squirrels and many other animals benefit from its seeds or fruits. The fruits attract many animals because they are rich in fat and anti-oxidants.
Climate change in the Atlantic Rainforest – which itself is far more threatened as an ecosystem than the Amazon – is bringing about profound habitat changes affecting the vectors of plant dispersal, that in turn may lead to the disappearance of this particular palm species in the wild.
That’s why Brazil’s National Flora Conservation Centre (CNCFlora) includes E. edulis in its Red List of endangered plant species.
And why the Ecology Department of São Paulo State University (UNESP) at Rio Claro (São Paulo State, Brazil), has been studying the plant. Biologist Mauro Galetti and his team have been studying how changes to climate, and the reduction in seed-eating birds, have adversely affected the Jussara.
They say they found that the Jussara palm’s genetic diversity has been reduced by both variations in climate during the last 10,000 years, which are part of a natural historical process, and defaunation, as human presence scares away frugivores (fruit-eating animals) and larger seed-eating birds such as the toucan.
Researchers at UNESP have found that the rapid decline in populations of seed-dispersing birds due to habitat fragmentation or destruction, as well as illegal trapping, is eroding the Jussara palm’s genetic variability. When a species loses genetic variability, it becomes more fragile and less capable of surviving challenges, such as climate change.
In a study published in the journal Conservation Genetics, researchers from UNESP, the Federal University of Goiás (UFG) and the University of Santa Cruz (UESC) conclude that the current pattern of genetic diversity in E. edulis in the Atlantic Rainforest is the result of a combination of climate variability over thousands of years and the impacts of more recent human activity, such as habitat destruction and the extinction of seed-dispersing bird species.
Research conducted in Galetti’s laboratory had already confirmed that there was a link between a decrease in the size of the palm’s seeds (which vary naturally from 8 mm to 14 mm in diameter) and local extinction of large seed-dispersing birds.
This is because seeds not eaten by birds do not germinate. In the case of E. edulis which has larger seeds, small birds cannot cope with the fruit and help its dispersal. This requires larger birds.
In other words, in Atlantic Rainforest areas where toucan, guan and bellbird populations have become locally extinct owing to hunting, the larger seeds were no longer dispersed because they were too large to be eaten by thrushes and other small frugivores, which can only swallow small seeds.
The study of the ecology of E. edulis occupies a central place in Galetti’s scientific career. “I began studying seed dispersal while I was an undergraduate in 1986, with a scholarship from FAPESP,” he said. “I investigated which birds dispersed and fed on jussara palm seeds. That was the basis for all our later studies. We have a solid natural history foundation on the interaction between frugivores and E. edulis and we can identify the best dispersers of its seeds with great confidence.”
“Without the Jussara palm the Atlantic Rainforest will become impoverished, because it feeds the main seed dispersers in the forest,” Galetti said. “When I delivered a presentation on this problem to farmers and people who produce seedlings of E. edulis in nurseries, they told me that from now on they’re going to select larger seeds and produce seedlings from them.”
A study published in the journal Science in 2013 described how the researchers investigated 22 areas of Atlantic Rainforest in Paraná, São Paulo State, Rio de Janeiro State, Minas Gerais and southern Bahia. They found that, in areas containing large frugivorous birds, such as toucans (Ramphastos spp.) and guans (Penelope spp. and Aburria jacutinga), the jussara palm’s seeds were larger, often exceeding 12 mm, whereas in areas where narrow-billed birds, such as thrushes (Turdus spp.), predominated, the seeds were never more than 9.5 mm in diameter.
This difference in seed size may seem negligible, but it is important to the conservation of the Jussara palm. “Smaller seeds more easily lose water because of their smaller surface area,” Galetti explained. “As a result, the palms are more sensitive to longer periods of drought, which will become more frequent owing to climate change.” The researchers found that, in forest areas near Rio Claro (São Paulo State) in which Jussara palms with small seeds predominated, the seeds simply failed to germinate after the severe drought in 2014.
You can find articles related to the research on the Jussara palm by clicking on these links:
“Climatic stability and contemporary human impacts affect the genetic diversity and conservation status of a tropical palm in the Atlantic Forest of Brazil” (doi: 10.1007/s10592-016-0921-7) by Carolina da Silva Carvalho, Liliana Ballesteros-Mejia, Milton Cezar Ribeiro, Marina Corrêa Côrtes, Alesandro Souza Santos and Rosane Garcia Collevatti: link.springer.com/article/10.1007/s10592-016-0921-7.
“Defaunation leads to microevolutionary changes in a tropical palm” (doi:10.1038/srep31957) by Carolina S. Carvalho, Mauro Galetti, Rosane G. Colevatti and Pedro Jordano: nature.com/articles/srep31957.
“Functional extinction of birds drives rapid evolutionary changes in seed size” (doi: 10.1126/science.1233774) by Mauro Galetti, Roger Guevara, Marina C. Côrtes, Rodrigo Fadini, Sandro Von Matter, Abraão B. Leite, Fábio Labecca, Thiago Ribeiro, Carolina S. Carvalho, Rosane G. Collevatti, Mathias M. Pires, Paulo R. Guimarães Jr., Pedro H. Brancalion, Milton C. Ribeiro and Pedro Jordano, 2013: science.sciencemag.org/content/340/6136/1086.
You can also read an article on this subject by Brazilian journalist Peter Moon by clicking here.