We’re often told that nature is a kindly thing, a spiritual force that keeps the world in harmony, in balance and all that nice touchy-feely stuff.

The truth is that nature is a vicious beast. I remember thinking of this when I lived in the Tanzanian bush, listening to hyenas at my door and the sound of insects eating my house. There were odd slithering sounds from the far corner of the room most nights, and I had to be careful of the black mambas under the house, with that appalli...