What if there was no attempt at conservation at all, and humans in the first half of the twentieth century just kept slaughtering wild animals until none were left by 1950, just domesticated beasts and insects?
I just found out today that the elephant population in Africa fell from 20 million before the Berlin Conference, to 10 million by 1900, to 1 million by 1970, to 352,00 today. But the decrease did slow over time. That is alot of elephants killed in the nineteenth century. But the pace slackened, as some people tried to save the elephants. What effects would have happened if people just finished them off in the early twentieth century instead?
This falls on the borderline of chat but I think having no conservationist movement is a legitimate alternative course of history.