Without grazing animals, the scrub emerging from our post-agricultural fields would soon turn into closed-canopy woodland, which is a poor habitat for most wildlife. Disturbance from grazing, browsing, rootling, rubbing and trampling, provides a check on galloping scrub; and the battle between these two processes – animal disturbance v vegetation succession – creates all sorts of vegetation structures which contribute to a dynamic, ever-shifting mosaic of valuable habitats.
Involving a suite of different animals in a project such as this increases complexity and biodiversity, in ways that often complement each other. A particular function that grazing animals would have performed in the past, is the transference of nutrients across the landscape, often over enormous distances. Eating in one place, then dunging, and even dying, in another, moves trace elements across different soil types. Seed dispersal, via the gut, hooves and hair, is another important role of herbivores. Each animal has different plant associations.
The key to establishing and maintaining this rich mosaic of habitats is to ensure that there are neither too many, nor too few, grazing animals. Too many and the land becomes entirely grassland; too few and it reverts to closed canopy woods. Keeping the populations within these parameters allows us to take animals off the land to process into meat. We sell 75 tonnes (live-weight) of free-roaming, pasture-fed organic meat every year – an important income stream for the estate. In reality, we are still farming, but on a very extensive scale and with very low carbon inputs - much like ranching.
Conspicuously absent from our rewilding project, of course, are large predators like the wolf, wolverine, bear and lynx. These would have played an important role in our ecology in the past. While predators do not, as is commonly believed, directly regulate herbivore populations through predation (essentially, food resources do this), they do clearly affect the behaviour of grazing animals. How much influence they bring to bear is still hotly debated by ecologists. Some insist that in a ‘landscape of fear’ grazing animals would be constantly under stress and on the run, seeking the more inaccessible and possibly less fertile areas to live and breed, and this would have a huge impact on vegetation succession. Others suggest that predators only affect their prey in this way when they are on the hunt.
Whatever the impact of predators, there is clearly no such landscape of fear at Knepp, and our grazing animals wander in loose herds, sometimes scattered over large areas, going wherever they please.
‘Large herbivores in the wildwood and in modern naturalistic grazing systems’. English Nature report no. 648. (2005) http://publications.naturalengland.org.uk/publication/50016