Where does the plastic in the ocean come from?

A new study published in @ScienceAdvances updates our understanding.

My latest @OurWorldInData article looks at the global picture of plastic pollution: ourworldindata.org/ocean-plastics

Thread of key points 👇
Previous studies suggested a small number of big rivers accounted for most of ocean plastics.

But higher-resolution data suggests many more small rivers play a big role.

To cover 80% of plastic inputs you need to tackle > 1,000 rivers.

1/
Factors that matter a lot for a river's plastic inputs:
– waste management practices
– distance to coast
– cities nearby
– precipitation rates
– slope of terrain

Here are the top 10 rivers 👇
(most are small rivers in the Philippines)

2/
Previous modelling did not have such high-resolution data on topography, terrain, climate etc.

Therefore put more emphasis on the *size* of the river basin. So it assumed: large river basin = lots of plastic inputs.

That's why the latest results are markedly different

3/
The regional distribution of plastic inputs is similar to previous studies.

Most plastic inputs come from rivers in Asia (81%).

4/
But some of the smaller countries in Asia play a larger role.

One-third comes from the Phillippines. It has a lot of small rivers with cities close to the coast.

5/
What people often get wrong about plastic pollution:

They underestimate how important waste management is.

It's not the case that using more plastic use = more pollution.

Most rich countries contribute very little because they manage the waste.

6/
Improving waste management is not a sexy solution. Most people find it boring.

But if you're serious about tackling plastic pollution, this is where to put your focus and investment.

7/
This recent paper is from @LourensWater & colleagues in @ScienceAdvances.

You can check it out here: advances.sciencemag.org/content/7/18/e…

8/
And @TheOceanCleanup has a beautiful high-resolution map with all the rivers that I recommend you check out: theoceancleanup.com/rivers/

/end

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More from @_HannahRitchie

4 Mar
Half of world's ice- and desert-free land is used for agriculture. Most for meat & dairy.

Dietary changes could reduce this by as much as 75%.

But you don't have to go vegan: massive reductions by simply switching to chicken, eggs, fish.

Latest article: ourworldindata.org/land-use-diets
A point that comes up often: "grazing land is not suitable for growing crops".

True. Two-thirds of grazing land is not great for crops.

But that's okay: more plant-based diets tend to need *less* cropland, not more.

How can this be true? 👇

2/
It's because so much of our cropland is used to produce feed for animals.

Less than half of the world's cereals go directly to human food.

3/
Read 6 tweets
14 Jan
"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.

1/

ourworldindata.org/soil-lifespans
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

2/
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.

3/
Read 5 tweets
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:
ourworldindata.org/hunger-and-und…
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 ↓↓

nature.com/articles/s4301…
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

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