Do you ever wonder, in your bleaker moments, whether the world would be better off without you? Well, I don't mean to depress you, but the answer is 'yes'. It would. Without all of us. I've been reading The World Without Us, which is sort of the book precursor to that History Channel show I mentioned a while back.

The book considers the question of how long it would take for our impact on the planet to fade if we all disappeared today. And it alternates with a similar hypothetical enquiry: what if humans had never existed? But the author seems a little fidgety about sticking to the 'world without us' premise and often goes for many pages at a time without a nod towards the linking theme of the book. Instead he's busy listing all the awful things we've been getting up to.

Even so, it's fascinating - if depressing - stuff. For a start we've created rather a lot of compounds which can't be degraded by any bug, worm, mould or form of erosion in Mother Nature's arsenal - more so than I realised. The sea is increasingly full of minuscule pellets of plastic, the ground-down remnants of bags and bottles which get smaller and smaller but never dissolve or decompose. Imagine that: oceans full of microscopic plastic sediment which gets in everywhere (including inside living creatures) and might never go away. Even bio-degradable plastics don't necessarily break down in the ocean depths.

But the book also charts our history of battering the planet, and the charge sheet goes back so much further than I realised. There's a mass extinction that's much more recent than the death of the dinosaurs and it coincides with Homo Sapiens getting the hang of hunting in packs. That's the timeframe within which all but a handful of large animals were wiped off the face of the planet. America, Europe and Australia all had their equivalents of Africa's megafauna - and Africa had a lot more of it. Monstrous giant slothes, impossibly huge mammoths, and gigantic big cats were all wiped out on a timescale which leaves our early ancestors the likeliest culprit. And like the TV program, the only melancholic comfort we can take from this history of devastation comes from observing the way in which wildlife is proliferating at Chernobyl or in the mine-strewn DMZ between North and South Korea. Ecosystems bounce back with amazing speed if humans can be removed from the picture. So if you fancy a nicely written and authoritative total downer, might I recommend The World Without Us by Alan Weisman.