What does it take to make a native plant or animal or fungus abandon its companionable habits to carve a path of destruction across the landscape?

Over the past few years, I have been looking into the complexities of this debate and I can tell you only one thing with confidence: it’s a huge, vigorous muddle.

In the final few miles we began to come across the bodies of dead birds: guillemots – first one and then another, and another, and another – feathers water-logged and bedraggled.