How extinction of five-tonne sloths slows up growth along the Amazon

Region now lacking the fertilising effect provided by South America's distinctive 'mega-fauna' - which has led to a serious imbalance of soil minerals

Vast regions of the Amazon are growing more slowly than they were several thousand years ago because they lack the fertilising effect provided by South America’s distinctive “mega-fauna” – the very large mammals that went extinct soon after the arrival of humans.

A study of how soil nutrients are distributed within the Amazon basin has revealed there is a dearth of vital minerals such as phosphorus because large mammals no longer roam the region to fertilise the soil with their dung.

Scientists believe that the extinction of large herbivores, such as five-tonne ground sloths and armadillo-like glyptodonts the size of small cars, led to a serious imbalance of soil minerals which is still having an impact today.

“It is having a big effect. The Eastern Amazon in particular is phosphorus-limited which means that if you added phosphorus to the region the trees there would grow faster,” said Christopher Doughty of the University of Oxford, the lead author of the study.

“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,” Dr Doughty said.

Minerals are continually washed down from the high Andes by the Amazon and its tributaries, but the elements tend to remain within the muddy soil of the flood plains rather than being dispersed more widely.

This was not the case for tens of thousands of years previously when generation after generation of the mega-fauna fed on the plants and trees growing in the flood plains before roaming to higher ground where they fertilised the soil with their dung and dead bodies, the scientists said.

The study, published in Nature Geoscience, calculated 98 per cent of nutrient-dispersal has been lost since the extinction of the mega-fauna, which happened around the same time that humans first colonised South America from the north.

“While 12,000 years may be a timescale that is beyond most people’s understanding, through this model we show that extinctions back then still affect the health of the planet to this day,” Dr Doughty said. “Put simply, the bigger the animal, the bigger its role in distributing nutrients that enrich the environment.

“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 said.

Deforestation of the Amazon is hindering the dispersal even more because although human activity leads to increased fertilisers being added to the land, these become concentrated as a result of farming practices such as the fencing-in of livestock.

Wild mega-fauna that roamed freely acted in the same way as the arteries of the human body by distributing nutrients further and further from the source, the scientists said.

Start your day with The Independent, sign up for daily news emails
ebooks
ebooksAn introduction to the ground rules of British democracy
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
SPONSORED FEATURES
Independent Dating
and  

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

Recruitment Genius: Technical Author / Multimedia Writer

Negotiable: Recruitment Genius: This recognized leader in providing software s...

Recruitment Genius: Clinical Lead / RGN

£40000 - £42000 per annum: Recruitment Genius: This is an exciting opportunity...

Recruitment Genius: IT Sales Consultant

£35000 - £40000 per annum: Recruitment Genius: This IT support company has a n...

Recruitment Genius: Works Engineer

Negotiable: Recruitment Genius: A works engineer is required in a progressive ...

Day In a Page

Isis profits from destruction of antiquities by selling relics to dealers - and then blowing up the buildings they come from to conceal the evidence of looting

How Isis profits from destruction of antiquities

Robert Fisk on the terrorist group's manipulation of the market to increase the price of artefacts
Labour leadership: Andy Burnham urges Jeremy Corbyn voters to think again in last-minute plea

'If we lose touch we’ll end up with two decades of the Tories'

In an exclusive interview, Andy Burnham urges Jeremy Corbyn voters to think again in last-minute plea
Tunisia fears its Arab Spring could be reversed as the new regime becomes as intolerant of dissent as its predecessor

The Arab Spring reversed

Tunisian protesters fear that a new law will whitewash corrupt businessmen and officials, but they are finding that the new regime is becoming as intolerant of dissent as its predecessor
King Arthur: Legendary figure was real and lived most of his life in Strathclyde, academic claims

Academic claims King Arthur was real - and reveals where he lived

Dr Andrew Breeze says the legendary figure did exist – but was a general, not a king
Who is Oliver Bonas and how has he captured middle-class hearts?

Who is Oliver Bonas?

It's the first high-street store to pay its staff the living wage, and it saw out the recession in style
Earth has 'lost more than half its trees' since humans first started cutting them down

Axe-wielding Man fells half the world’s trees – leaving us just 422 each

However, the number of trees may be eight times higher than previously thought
60 years of Scalextric: Model cars are now stuffed with as much tech as real ones

60 years of Scalextric

Model cars are now stuffed with as much tech as real ones
Theme parks continue to draw in thrill-seekers despite the risks - so why are we so addicted?

Why are we addicted to theme parks?

Now that Banksy has unveiled his own dystopian version, Christopher Beanland considers the ups and downs of our endless quest for amusement
Tourism in Iran: The country will soon be opening up again after years of isolation

Iran is opening up again to tourists

After years of isolation, Iran is reopening its embassies abroad. Soon, there'll be the chance for the adventurous to holiday there
10 best PS4 games

10 best PS4 games

Can’t wait for the new round of blockbusters due out this autumn? We played through last year’s offering
Transfer window: Ten things we learnt

Ten things we learnt from the transfer window

Record-breaking spending shows FFP restraint no longer applies
Migrant crisis: UN official Philippe Douste-Blazy reveals the harrowing sights he encountered among refugees arriving on Lampedusa

‘Can we really just turn away?’

Dead bodies, men drowning, women miscarrying – a senior UN figure on the horrors he has witnessed among migrants arriving on Lampedusa, and urges politicians not to underestimate our caring nature
Nine of Syria and Iraq's 10 world heritage sites are in danger as Isis ravages centuries of history

Nine of Syria and Iraq's 10 world heritage sites are in danger...

... and not just because of Isis vandalism
Girl on a Plane: An exclusive extract of the novelisation inspired by the 1970 Palestinian fighters hijack

Girl on a Plane

An exclusive extract of the novelisation inspired by the 1970 Palestinian fighters hijack
Why Frederick Forsyth's spying days could spell disaster for today's journalists

Why Frederick Forsyth's spying days could spell disaster for today's journalists

The author of 'The Day of the Jackal' has revealed he spied for MI6 while a foreign correspondent