With or without leather cattle and other livestock would be kept to provide meat and dairy products, and as draught animals. Hence last year the EU announced their Product Environmental Footprint Category Rules defining leather carbon footprints as starting at the abattoir rather than with livestock husbandry, which equates to 0.42%
Furthermore hides from the cattle types described in the article do not produce the attractive leather demanded by luxury brands who mostly prefer leather from European or United States hides. Currently demand for Brazilian beef has grown strongly because of the decimation of China’s pig population with African Swine Fever.
With leather being natural, long lasting and renewable for as long as society eats meat it is one of the most sustainable materials. Attacking it based in bad science only serves to push society towards fossil fuel based alternatives, while unwanted hides and skins end up becoming a cost of disposal to the abattoir - something which is already happening around the world.
Lucy Siegle should know the paper (2015) published by Rafael Silva from the University of Edinburgh recommending a 30% increase in beef production in order to reduce Brazil’s green house gas emissions, a plan adopted by the pre Bolsonaro Government. This concluded that the cattle population and deforestation had been decoupled and that more and better grazing was urgently needed to improve the existing extensive Savannah region, where the grass is in poor repair. Brazilian grass is exceptionally good at sequestering carbon dioxide only requiring improvement via appropriate livestock grazing for this to work via fertilising, grazing and treading.
Brazilian cattle are about beef rather than leather and to use the Amazon to fabricate an attack on leather is a distraction and unhelpful to everyone involved.