Doughty and colleagues simulated the distribution of phosphorus, a nutrient that plants need to grow in the Amazon basin in South America.

Thousands of years after human hunters wiped out big land animals like giant ground sloths, the ecosystems they lived in are still feeling the effects.

Many ecosystems rely on big animals to supply them with nutrients, mostly from dung.

This area was once home to spectacularly large animals, including the elephant -- like gomphotheres and giant ground sloths.

It's not just humans that still feel the effects of a trauma many years later, ecosystems do too.

"If you remove the big animals from an ecosystem, you pretty much stop nutrients moving,"says Chris Doughty of the University of Oxford.

But 12500 years ago, around the time humans moved into South America, these huge animals all died out, hit by a double whammy of being hunted and a changing climate.

Nowadays the Amazon is still home to a huge diversity of animals.

"But these extinctions cut out all the big animals, "says Doughty.

In South America, the most phosphorus rich soils are found near the Andes mountain chain in the west.

Nutrients are released when rocks are eroded, and then get distribute onto floodplains by rivers.

If Doughty is right, the Amazon is still changing in response to the extinction.

He estimates the spread of nutrients will keep getting patchier for another 17 000 years, although the effect will likely be dwarfed by the impacts of deforestation and climate change in the short term.

It seems the mass extiction had a profound effect on how phosphorus is spread around the Amazon basin.