Ecuador’s Rio Los Cedros is a source of insight for Robert MacfarlaneMurray Cooper/Minden Pictures/Alamy Is a River Alive? Robert Macfarlane (Penguin Books (UK) W. W. Norton (US, 20 May)) Early on in this often beautiful, wild and wildly provocative book, Robert Macfarlane recounts telling his son the title of his project. The boy exclaims that of course a river is alive, so this is going to be a very short book. Macfarlane isn’t so sure, and nor am I. It has been a long time since I have felt so torn over a new piece of writing. No…