Thread by @DaveGoulson

On cows and carbon sequestration.
There is a lot of confusion on Twitter about the role of ruminants in producing greenhouse gases (bad) versus helping to sequester (store) carbon in soil (good). I thought a short summary of the state of knowledge might help:

Ruminants produce a lot of methane, a highly potent greenhouse gas (although there is some evidence that they may produce less on an herb-rich diet). Even so, this is bad, especially given that there are 1.5 billion cows on the planet.

Also, rangelands are often overgrazed, leading to soil erosion and yet more greenhouse gas emissions.
On the other hand, at low density, grazing animals can promote biodiversity (e.g. Knepp estate). Managed well (e.g. mob grazing), they can help to increase soil organic matter,

...particularly if the soil was previously degraded. Increasing soil organic matter locks up carbon – this is sequestration. However, this can only happen for a finite period of time – after a decade or two the soil will reach equilibrium.

At this point it will be rich in carbon but it cannot keep storing more and more carbon indefinitely (unless it is a peat bog). So however well managed, sequestration can only happen for a fixed period. After that the cows are still producing methane but not locking up any carbon

[On a related matter, it is a popular misconception that long-established forests such as the Amazon sequester carbon – they do not, but they are large stores of carbon]

Overall, there is no doubt at all that we need to reduce numbers of livestock globally, if we are to tackle climate change. On average, we need to eat less meat, and entirely avoid grain-fed, intensively-reared beef. This is NOT saying everyone has to go vegan...

...or that we should get rid of all cows, but every vegan is helping to reduce global meat consumption, and should be applauded, not mocked and derided. Note, I am not a vegan. For more info, this article is good: fcrn.org.uk/sites/default/…