Manzano et al. 2023

Challenges for the balanced attribution of livestock’s environmental impacts: the art of conveying simple messages around complex realities

The article is soft so I think we should probably not be too hard. They're arguing for nuance but the scale of animal agriculture and meat consumption is to vast that nuance probably doesn't matter at this point.

Overall I think this article is too vaguely worded and not focussed enough to have any meaningful impact on the debate. If we have limited words to refute the DubDec we could probably get away with ignoring this entirely or dismissing it by pointing out that it mostly fails to provide concrete, direct evidence or even reason to suspect that the impact of ruminants on agriculture is less than expected.

It finishes with "triggering a casca de of social effects with unpredictable consequences.". Basically the paper is trying to sow doubt by complexifying the issues and making vague warnings that 'we don't know what will happen' if we rapidly reduce livestock numbers. While we don't know for sure what the effects of reducing livestock will be, we do know that the rapid increase of livestock across the world has had disastrous impacts on our ecosystems. Our default assumption should be that things will go back to the state they were in before animal ag exploded.

They start by arguing that while methane is 28 times worse than carbon dioxide when assessed by 100 year impacts (GWP100), if calculated under a 20-year timeframe (GWP20), a CH4 (non-fossil) is considered to have a GWP 80.8 times more potent than CO2, whilst over 500 years (GWP 500), it is 7.3 times more potent than CO 2. Given that many consider climate change to be an immediate threat, if anything this highlights that the effects of methane are worse than we thought.

They then argue that we don't fully understand how regional differences in hydroxyl (OH-) radical levels, which react with Methane to produce CO2. We certainly acknowledge the complexity of these atmospheric processes, and agree that climate change efforts would benefit from improved climate models. However, what Manzano et al don't make clear is why we should think any of these things would substantially reduce the large impacts of ruminants on the environment

They argue that green water (water in an area that I believe comes from rainfall) is often erroneously thought to be used by livestock, when in reality it feeds blue water sources elsewhere which humans can use. They do not provide any references or even calculations about how this might impact things, so it is not clear how this would show livestock in a more favourable light.