> is it really more important to preserve it as a landmark than for the land to go to use

The Amazon has 10% of the worlds biodiversity, I wouldn't exactly call it a landmark, this isn't historic preservation - and the land is already "in use". Also I'm not sure that "the people of the country" are buying and farming cattle on large chunks of the Amazon, I'd assume the economic gains are highly concentrated amongst a few companies (this is conjecture). Either way, lowering demand for cattle raised in the Amazon would be one way to make this less common.