Amazon rainforest seeing slower growth due to animal extinction

Deforestation has led to the extinction of large mammals across the Amazon rainforest, which is now having a marked impact on the growth rates of new trees, according to scientists.

Scientists from Oxford University have revealed that the absence of large animals, such as the five-tonne sloth, has caused the Amazon rainforest to grow far more slowly than it did previously, due in part to the waste produced by the animals acting as fertiliser for the trees.

Carrying out a programme of research into how soil nutrients are spread throughout the Amazon basin has revealed that there is a distinct lack of certain minerals such as phosphorus, because animals produce less waste as they are now smaller, due to deforestation killing off many of the larger ones.

Christopher Doughty, the author behind the study which was published in Nature Geoscience, confirmed that the shortage of minerals was having a major effect on the face of the rainforest today.

He told The Independent newspaper: “The Eastern Amazon in particular is phosphorus-limited which means that if you added phosphorus to the region the trees there would grow faster.

“When you had big animals roaming more than 12,000 years ago, there would have been wider dispersal of minerals such as phosphorus and the trees there would have been growing faster than they are today,” he added.

The study found that around 98 per cent of nutrient-dispersal has disappeared since the large animals died out. The spreading of minerals across the forest has slowed so much as they now tend to collect in muddy soil located in the flood plains, rather than get spread around.

Tens of thousands of years ago, when large wildlife did roam the forests, the minerals were spread through their manure, dispersing the essential minerals needed for plant growth to higher ground. Their dead bodies also provided forest food, Dr Doughty confirmed.

“Most of the planet’s large animals have already gone extinct, thereby severing the arteries that carried nutrients far beyond the rivers into infertile areas,” he added.

Fertilisers used by farmers on the rainforest land is also cutting the dispersal of minerals in the region, as well as the act of keeping wildlife in pens and not allowing them to roam free to spread minerals in their manure.