Unfortunately that's probably not true (and I say that as someone who has some much-loved merino clothes). The problem with animals like sheep is that they tak

Unfortunately that's probably not true (and I say that as someone who has some much-loved merino clothes). The problem with animals like sheep is that they take up a huge amount of land, both directly grazing and for any additional feed that they require. The more intensively you farm them, the more ecosystem damage they do, but of course less intensive grazing either requires more land or reduces production and increases prices. I couldn't quickly find any numbers to compare to other materials like cotton, but at least for food production, grazing animals are an order of magnitude worse on this metric than any plant-based crops (e.g. [1]). The reason that land usage is bad is because it's zero sum: land that's being used for farming is likely to be less good at trapping carbon than other possible uses of the same land (e.g. reforestation), and is typically not very good habitat for wildlife (sheep in particular selectively graze on the tastiest plants and so tend to leave behind a monoculture of rough grasses which are their least favourite food). If you have to buy new clothes today, I don't really know what the best option is. Plastic-based fibres obviously require oil (although many are based on recycled plastics) and end up creating microplastic pollution and waste products that won't biodegrade. Cotton is very land intensive to produce, but I suspect wool is even worse. Maybe destroying land in the tropics is worse for biodiversity than grazing sheep in temperate regions (similar to palm oil being land efficient, but damaging to rainforests in particular)? In any case I don't know of a simple way to weigh these tradeoffs. The only thing that seems unambiguously like a win is buying fewer clothes and making them last longer. [1] https://ourworldindata.org/grapher/land-use-per-kg-poore https://ourworldindata.org/grapher/land-use-per-kg-poore