Brazil's Northeast Atlantic Forest At RiskWASHINGTON, Mar. 1 (IPS) -- Brazilian researchers estimate that about one-third of tree species will shortly become extinct in the biologically rich tropical forests along the Atlantic coast of northeast Brazil, according to a study published today in the scientific journal Nature.
If current trends in habitat loss and the extinction of key bird and animal species -- responsible for tree pollination and seed dispersal -- continue, about 34 percent of tree species will become extinct in the region, warn Jose Maria Cardoso da Silva and Marcelo Tabarelli, researchers at the Federal University of Pernambuco in the northeastern city of Recife, Brazil.
"Because northeast Brazil is the most threatened sector of South American Atlantic forest, our results highlight the need to change the current conservation paradigm in this region," they say.
Because of its wealth of species and since its habitat is rapidly disappearing, Brazil's entire Atlantic forest has been labeled an ecological "hotspot" by Conservation International (CI).
According to the Washington-based environmental organization, Brazil's Atlantic forest contains some of the most diverse and distinct animal and plants species in the world.
Biologists estimate that 54 percent of the region's trees, 80 percent of its primates and more than half the country's other mammals live nowhere else but in the Atlantic forest. Among the unique and threatened species are the golden lion tamarin, the maned sloth, the thin-spined porcupine and the red-tailed parrot.
But the northeast region -- located north of Brazil's Sao Francisco River -- is very distinct from other sections of the Atlantic forest, because its flora and fauna is influenced by the nearby Amazonian rainforest basin, according to the study.
Like the Amazon, while the Atlantic forests of northeastern Brazil are some of the world's most biologically rich, they are also the most threatened tropical forests because, like many tropical forests, they are highly fragmented.
Most of the region's forests have been converted into agricultural land, with only two percent of the original forest remaining, according to the study. The remaining small patches of forest are surrounded by open fields.
Threats to the Atlantic forest come from deforestation due to coastal development, as well as uncontrolled logging, agriculture and charcoal production, according to CI.
"Protected areas in this region are mostly small, isolated and badly managed," says the study.
Besides directly impacting tree species, this loss of habitat also threatens the survival of many tree species indirectly by negatively impacting bird and mammal species that disperse or pollinate seeds, a process necessary for many trees to reproduce, say the study's researchers.
"Pollination and seed dispersal are critical because they directly affect the reproductive success of plants, and in tropical species they usually involve direct interaction with animals," the report says.
The researchers recorded 427 tree species in the region. A total of 305, or 71 percent, of these species disperse their seeds with the help of birds and mammals.
Of the several possible scenarios or models, the researchers focus on two different issues impacting these tree species and the birds that disperse their seeds.
The first takes into account that fruit-eating birds, such as large cotingas and trogons, that disperse seeds are sensitive to habitat disturbance and will disappear following forest fragmentation, says the study.
Where mammal species that originally dispersed seeds have been wiped out, seed flow of several types of trees throughout the region is very limited.
Uncontrolled hunting of bird species that disperse and pollinate seeds further threatens the survival of tree species. Birds currently threatened by hunting in northeast Brazil include all large fruit-eaters, such as guans, chchalacas, toucans and aracaris.
The second model in the study accounts for the fact that most forest bird species are unable to cross more than 100 to 200 meters of open space. Even mammals are unable to travel long distances in inhospitable habitats, according to the study.
"Thus seed dispersal will be highly limited and several tree species with large fruits will become locally extinct," state the researchers.
These findings, they argue, make a strong case for the implementation of a region-wide reserve that would ensure the survival of these bird species. Currently, conservation policies focus on the creation of isolated reserves in remnant areas of forest.
"Unfortunately, most of them contain no large fragment that, if isolated, would be able to sustain a viable population of large fruit-eating vertebrates," says the study.
The largest forest remnant in northeast Brazil is about 2,000 hectares.
Throughout the Brazilian Atlantic forest, reserves are very small and are therefore insufficient to maintain key biological processes, says the study. Of the 239 existing reserves, more than 53 percent are smaller than 500 hectares.
"We suggest that a new paradigm for Atlantic forest conservation is urgently needed," says the study.
It should not be focused on or restricted to transforming the last medium-to-large size forest fragments into reserves, it says.
"A bioregional planning approach is required," say the researchers.
This would involve the protection of landscapes composed of archipelagos of fragments, connected by corridors of original or restored vegetation and representing several thousand hectares of forest, say the researchers.
"We believe that if area requirements for large fruit-eating birds are reached, there is a good chance of preserving other essential...relationships that affect both plants and animals," they argue.