How man has wreaked havoc on the Brazilian rainforest: Scientists find large birds have been driven out and seeds have evolved to become SMALLER due to deforestation



Deforestation of Brazilian rainforest has caused the seeds of palm trees to shrink - because birds like toucans and cotingas have been driven out

Disappearance means palm trees can't distribute their bigger seeds

Researchers say evolutionary process has been sped up 100 times



Deforestation of the Brazilian rainforest has caused the seeds of palm trees to become smaller - because large, fruit-eating birds have been driven out, researchers have found.



The disappearance of toucans and cotingas, which were once abundant in the rainforest and spread seeds through their droppings, means that palm trees have no way to distribute their bigger seeds, the Brazilian researchers said.



They believe the changes could be disastrous to the palm trees that once thrived in the forests.



Deforestation of the Brazilian rainforest has caused the seeds of palm trees to become smaller - because large, fruit-eating birds - such as the channel billed toucan - have been driven out

Toucanets also play a fundamental role in the forest as seed dispersers of large seeds

In general, researchers estimate that human activity, such as deforestation, drives species to extinction about 100 times faster than natural evolutionary processes.



However, few studies have successfully documented such rapid evolutionary changes in ecosystems that have been modified by human activity.

Galetti and his colleagues used patches of rainforest that had been fragmented by coffee and sugar cane development during the 1800's to set up their natural experiment.

They collected more than 9,000 seeds from 22 different palm tree populations and found that in patches of forests deserted by large birds such as toucans and large cotingas - because of deforestation - palms produced significantly smaller seeds.



'Small seeds are more vulnerable to desiccation and cannot withstand projected climate change,' explained Galetti.



But, smaller birds such as thrushes that populate the fragmented patches of forest are unable to swallow and disperse large seeds.



As a result of this, palm regeneration became less successful in the area, with less-vigorous seedlings germinating from smaller seeds.

In undisturbed patches of forest, large-gaped birds - whose beaks are 12mm wide or more - still make their homes and palms continue to produce large seeds, successfully dispersed by the birds through their droppings, the researchers found.



Only large-gaped birds, such as toucans and cotingas, can disperse large seeds

They then determined that the absence of large, seed-dispersing birds in the area was the main reason for the palm seeds shrinking in size - and this shrinkage could have taken place within 100 years of an initial disturbance.



They say their findings provide evidence that human activity can trigger fast-paced evolutionary changes in natural populations.

THE INCREDIBLE BEAK OF THE TOUCAN

Recent research has found that toucans regulate body temperature by adjusting the flow of blood to their beak.

More blood flow means more heat is released. When toucans sleep, they tuck their beak under their feathers to keep them warm. Toco toucans also use their beaks to pluck and peel fruit, their main source of food.

In addition, the beak houses a flat tongue of the same length, which helps the toucan catch insects, frogs, and reptiles.

'Unfortunately, the effect we document in our work is probably not an isolated case,' said Galetti.

He is also concerned that small seeds are 'more vulnerable to desiccation and cannot withstand projected climate change'.

Long periods of drought and increasingly warmer climate (as predicted by climate model projections for South America) could be particularly harmful to tropical tree populations that depend on animals to disperse their seeds.

'Habitat loss and species extinction is causing drastic changes in the composition and structure of ecosystems, because critical ecological interactions are being lost,' said Galetti.



'This involves the loss of key ecosystem functions that can determine evolutionary changes much faster than we anticipated.



'Our work highlights the importance of identifying these key functions to quickly diagnose the functional collapse of ecosystems.'

The study is published in the journal Science.



