"Without them you would have quite a silent and sterile environment. But if you bring animals in, which going back thousands of years would have been totally normal, immediately the whole place begins to burst into life.
"We know that given time this land will end up with gorse, birch, heather, native grasses and wildflowers, then eventually successional oak will come through and bramble.
"But the important difference is, because of the animals, it won't just be a woodland, it will be a mosaic. That is the key word. You don't want it to be just one thing, you want a whole host of different things, and you want it at all stages of a lifecycle."