Sahara - Amazon rainforest connection

[jety89]

Hi

I am being told in "PBS NOVA 2013 Earth from space" that the Amason rainforest is being fed continously with phosphites from the Sahara desert where an ancient lakebed releases diatomites into the atmosphere.
All good and well - you might think. But wait! The same program, as well as other sources claim the Sahara desert to be 6000 years old only. So how did the rainforest in South America survived for millions of years, or otherwise -- just how strong Is the dependence of the vegetation in the Amasonas basin on the Sahara nutrients?
Are there any studies of this, or has this question never been asked before?
Why is this connection being quoted so many times? Is it that important of a discovery?

 

[Andre]

I guess we could trace sources like this and this confirming the narration.

To my knowledge that question has not popped up anywhere. Also , looking at the totally different paleoclimate situation compared to today, I could imagine that there may be/have been other sources for the mineral requirements for the Amazon rain forest.

 

[jety89]

Thanks for the sources

The article in the IOPScience journal suggests that

*the makers are also interested in these questions:
"Answers to these questions are needed to understand the nature of the emissions in the past, and the future capability of the Bodélé to fertilize the Amazon."

*they list all, or most of the relevant sources available.

*they are dedicated to answering these questions.

*But there is no anser yet to them.

Therefore, I think it is satisfactory to evaluate our current state of knowledge on the question about the importance of the Bodélé depression as a phosphate source to the amazon.
Still, it would be interesting to know, if there are other "hidden", or less interesting sources of phosfate available to the rainforest. I would imagine that those sorts of minerals could come from the Andes, transported using the river system. The Amason rainforest seems to have existed for millions and millions of years, without ever becoming a "wet desert". In fact, I don't really know of any good example of a wet desert in existence today. Any suggestions?

 

[pumila]

There appears to be a school of thought that the Amazon rainforest is a closed system, not requiring any input other than sun and water. The soil is generally impoverished except in certain localities where people built villages and towns and recycled body waste to build up a black soil for crops. Although rainforests are sometimes known as the lungs of the planet they do not seem to have any useful oxygen surplus.

Storms in the Sahara sometimes dump loads of sand in the UK, most of it on my car;-) 100s of thousands of tons at a time, apparently.

 

[Andre]

It's customary to make statements like that supported by evidence. There have been instances like the Younger Dryas that things were a bit different. But that's to keep science awake and non-complacent.

 

[pumila]

Sorry, I should have put in some references. In common with many readers of these forums, I have a limited access to real scientific papers. But everyone should be able to get to these...The fertility of the Amazon rainforest soil is dealt with indirectly in this Wikipedia page. Useful references are at the bottom of the page:-

http://en.wikipedia.org/wiki/Terra_preta

On the "lungs of the planet" we have...
http://wiki.answers.com/Q/Rainforest_are_sometimes_called_the_lung_of_the_earth_what_does_it_mean

...and...

http://www.agairupdate.com/article_detail.php?_kp_serial=00000571

And finally, on UK sand from Sahara...
http://metofficenews.wordpress.com/2012/06/28/dust-storm-brings-saharan-sand-to-the-uk/
(If you look at the dust on your car after these events under a microscope you can see classic wind-born sand - sand in a low energy environment tends to be silicate with rounded grains, unlike the high-energy environment of the sea)

Hope this is useful

 

[jety89]

Very mouch so, thank you