"We only have 100 / 60 / 30 harvests left" often hits the headlines. It's a myth. No scientific basis to it.

In fact, soil erosion rates span five orders of magnitude. Some are eroding quickly, some very little, and others are actually thickening.


First global assessment of soil lifespans by @DanEvansol & colleagues shows:

→ lifespans cross five orders of magnitude
→ 16% had < 100 years
→ 50% had > 1000 years
→ One-third had > 5000 years
→ some soils are thickening

So the "60 harvests left" claim is overblown. But it shouldn't detract from the fact that soil erosion *is* a problem.

Thankfully there are things we can do:
→ cover cropping
→ minimal or no-till
→ contour cultivation

These soils showed longer lifespans in the study.

Once again: you cannot reduce all of the world's soils to a single figure.

This study used 'net erosion rates of the topsoil layer' as a best proxy. Even using this single metric, differences spanned orders of magnitude.

Many thanks to @DanEvansol & colleagues for their research on this.

Their work should get much more media attention than the bold claims that are not backed up by the science.

• • •

Missing some Tweet in this thread? You can try to force a refresh

Keep Current with Hannah Ritchie

Hannah Ritchie Profile picture

Stay in touch and get notified when new unrolls are available from this author!

Read all threads

This Thread may be Removed Anytime!


Twitter may remove this content at anytime! Save it as PDF for later use!

Try unrolling a thread yourself!

how to unroll video
  1. Follow @ThreadReaderApp to mention us!

  2. From a Twitter thread mention us with a keyword "unroll"
@threadreaderapp unroll

Practice here first or read more on our help page!

More from @_HannahRitchie

16 Oct 20
It's #WorldFoodDay

Much of our work at @OurWorldInData covers food & agriculture – it's central to many of the world's largest problems

Feeding everyone a nutritious diet in a sustainable way is one of our biggest challenges this century

Thread of some of our work on this 👇
No one in the world should go hungry.

Global hunger has declined massively over the long-term, but more than 1-in-10 (> 820M people) are undernourished.

This is unacceptable in a world where we produce more than enough for everyone.

Our work on hunger:
Despite rapid population growth over the last century, famines have become much more rare.

Today they are largely the result of sociopolitical instability, war and inequality vs. a lack of food on aggregate.

@JoeHasell and @MaxCRoser's work on Famines: ourworldindata.org/famines
Read 13 tweets
25 Sep 20
"China uses more cement in 3 years than the US did in the entire 20th century".

I see this claim a lot & was curious if it stacked up against data on CO₂ emissions from cement.

So, some more back-of-the-envelope fact-checking below ↓↓

Spoiler: yes, seems to stack up Image
I'm using annual data on CO₂ from cement prod from @gcarbonproject & CDIAC. You can explore, compare countries, download from our CO₂ data explorer here: rb.gy/szuwvo Image
My calcs:

CO₂ from cement in USA for entire 20th century = 1838 million tonnes

Annual CO₂ from cement in China (2018) = 781 million tonnes

China emits same in 2.4 years as US in 20th century.
Read 5 tweets
21 Sep 20
Important new paper published in @NatureFoodJnl. Looks at the impact of rising temperatures on 18 staple crops across the world.

A couple of interesting findings below ↓↓

Yields tend to show inverse-U response to temp. Different countries lie on different parts of curve.

As expected, for most crops it's lower-lat, warmer countries that see negative response to temp rise.

Maps show response to 1°C rise (red = yield decline; blue = increase).

Some higher-latitude countries see yield increases across many crops.

Most crops show a yield decline globally. But there are a few exceptions: soybeans, sorghum, potatoes show yield increase nearly everywhere.

Useful to know for crop selection.

Read 4 tweets
16 Sep 20
A popular claim that our soils "only have 40/50/60 harvests left" gets repeated over & over.

Many have tried and failed to find a credible source for this.

A new paper sheds some light on quality of our soils [no, we do not only have 60 years left]

iopscience.iop.org/article/10.108… Image
The study highlights a few key points:
– most of our soils have a 'lifespan' much greater than this.
– poor soil quality is still a problem in some areas
– we can increase this soil quality with proper management practices.

This is one of the key paragraphs 👇 Image
Many have tried to find a credible source for the "only 60 years of harvest left" claim, and struggled to find one.

@Botanygeek previously wrote about this in the New Scientist: newscientist.com/article/mg2423…
Read 4 tweets
8 Sep 20
When we look at the carbon footprint of diets we often overlook the 'opportunity cost' of how we could use the land if not for food production.

A new paper in @naturesustainab tries to quantify the 'opportunity cost' of producing meat and dairy.

Half of the world's habitable land is used for agriculture. Three-quarters for livestock.

The paper looks at how much carbon we could sequester if everyone adopted the EAT-Lancet diet (which has some meat & dairy, but much less than the current Western diet) or a vegan diet. Image
It estimates that through ecosystem restoration we could sequester the equivalent of 9 years of fossil fuel emissions by 2050 on the EAT-Lancet diet.

Or 16 years of fossil emissions on the vegan diet.
Read 4 tweets
31 Aug 20
The new @exemplarshealth platform tries to learn from success stories across a range of health challenges.

In my latest @OurWorldInData post I apply this approach to identify countries that have been most successful in preventing maternal deaths.

The motivation for this stems from the fact that despite GDP being a very strong predictor of social and health outcomes, we also see a lot of variation at each level of income.

@MaxCRoser looked at this in his latest post: ourworldindata.org/exemplars-in-g… Image
This is also true for maternal mortality.

There can be at a 35-fold difference (!) in maternal mortality rates for countries with the same average income level.

Clearly there are successful approaches and interventions that countries can learn from one another. Image
Read 4 tweets

Did Thread Reader help you today?

Support us! We are indie developers!

This site is made by just two indie developers on a laptop doing marketing, support and development! Read more about the story.

Become a Premium Member ($3/month or $30/year) and get exclusive features!

Become Premium

Too expensive? Make a small donation by buying us coffee ($5) or help with server cost ($10)

Donate via Paypal Become our Patreon

Thank you for your support!

Follow Us on Twitter!