Researchers have linked dietary data from over 55,000 individuals with data on the environmental impacts of the foods they eat. The team, from the Livestock, Environment and People (LEAP) project at the University of Oxford, found that the dietary impacts of vegans were around a third of those of high meat eaters. They also saw a 30% difference between high- and low-meat diets for most of the measures of environmental harm.
Not really. Protein is not something particularly difficult in a reasonably balanced vegan diet, for most people. There are plenty of dietary sources of protein in vegan cooking.
Anybody requiring particularly high levels of protein is probably already supplementing it. Usually with vegan sources anyway.
Of all the possible deficiencies in a vegan diet, protein is by far the least of people’s, already small, worries.