evidence: One of the fastest growing areas in the quest for next generation materials is vegan leather. Although these alternative leathers – whether they are plastic or plant-based or both – are marketed as a sustainable alternative to real leather, the jury is still out on their long-term impacts. [...] Angela Winkle, the chief sustainability officer at boot maker R.M. Williams – which is exploring vegan leather alternatives through an investment in startup Natural Fiber Welding – says: "We need to know whether leather alternatives can actually improve over time, in the way that leather does." [...] The first vegan leathers on the market were made from variations of two types of plastic: PU and PVC . Interchangeably described as leatherette, pleather and vinyl, both PVC and PU are derived from fossil fuels. While they don’t rely on animal products, their impact on the environment should give animal lovers pause.