Without question it's the river/rainforest. It's one of the most biodiverse regions in the world, with over 16,000 species in an area of 7,000,000km².

Can't recall where I saw it but someone created a visual comparison of volume / time (ie, throughput) of the Amazon River vs Amazon.com's delivery of physical goods. The river won by a lot, but they were on the same scale.

Edit: of course, it was xkcd: https://www.xkcd.com/1165/

Does it matter in this case?