Hacker News Reader

Comment by debacle | Hacker News Reader

I respect the right of Africa to try and reforest, but logically the most likely outcome is that the Amazon will start to die from the lack of the 30 million tons of dust and sand that fall on the Amazon each year from the Sahara.

Should Africa's desert be preserved to feed the Amazon? That's a question humanity seems ill equipped to answer.

View on HN

> logically the most likely outcome is that the Amazon will start to die

This seems like a very large leap of reasoning to "logically" make.

My understanding is that Saharan dust clouds carry phosphorus across the Atlantic, which nourish the Amazon.

It doesn't follow that Africa stopping the expansion of the Sahara will kill this cycle. The Sahel has historically been used for agriculture (with periods of massive drought in between) and preventing the Sahara from expanding into it does not mean erasing the rest of the Sahara.

> I respect the right of Africa to try and reforest, but logically the most likely outcome is that the Amazon will start to die from the lack of the 30 million tons of dust and sand that fall on the Amazon each year from the Sahara.

Math. Stopping the Sahara from expanding doesn't change how much dust and sand are going over to the Amazon, it just caps it at the current amount.

The Sahara desert is 3.5 million square miles. That will never be re-forested.

Never is a pretty long time. One of my favorite authors: Doris Lessing, wrote a book called: "Mara and Dan" which has a very interesting take on climate change. I would recommend all of her books to anyone who wants to stretch their perception of our world.

Okay, sure, if you look at geologic timescales then eventually Africa will move and the region of northern Africa will cease to be desert.

Within a human timescale, I think "never" is an acceptable term.

Atmospheric circulation means that the latitude of the Sahara is blasted with cool dry air from the upper atmosphere. Humans planting trees might slow the spread of the desert, but will not vanquish it.

To disrupt the effects of atmospheric circulation (ie Hadley cells) creating deserts at those latitudes, you'd need mountain ranges and oceans.

https://en.m.wikipedia.org/wiki/Hadley_cell

"For several hundred thousand years, the Sahara has alternated between desert and savanna grassland in a 20,000-year cycle caused by the precession of Earth's axis (about 26,000 years) as it rotates around the Sun, which changes the location of the North African monsoon."

https://en.wikipedia.org/wiki/Sahara#:~:text=For%20several%2....

Why are we working in human timescales? It's like saying the sun will never burn out because humans won't be around to see it happen.

To me, that's a pretty bold and naive claim.

Because this project is about humans and the environment's impact on them, and what they can do to improve it. So naturally human timescales are the measure on which we judge it. What happens in 10 million years is not something we can even pretend to comprehend or influence in a meaningful way. But what happens in the next 100 is.

It is cultural human hubris to bother, in any way whatsoever, to be worried about the sun burning out. It’s an interesting curiosity but we your life, if you lived to be 2000 years old (you won’t), you will have moved yourself 0.0000571428% closer to the time when that will happen. We DO need to actually be worried about our planet overheating, our agricultural spaces becoming despoiled, and other things that can actually happen in our lives. One of these things is not like the other.

Not with that attitude.

Found the Shai-Hulud.

The green wall isn’t in the Sahara. It’s across sub-Saharan Africa, trying to keep the Sahara from spreading, not cover it with trees.

There is plenty of evidence that the Amazon was largely a geo-engineering project, seems like that one worked out.

Reply on news.ycombinator.com