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Livestock units are all very well but what about human impact units?

Livestock has a unit of impact, which could also be applied to humans depending on how they use the land — but pity the poor Staffie owners, says Alasdair Mitchell

hiker on footpath

Should we assess human impact units as well?

The concept of a piece of land’s carrying capacity for livestock or wildlife is long established. Parts of my farm are subject to stocking rates laid down by Natural England. Different types of livestock are accorded different scores, which add up to livestock units, and various fields are allowed different numbers of livestock units per hectare per year. The idea is to allow the farmer to make a living without overgrazing the land and thereby reducing its environmental value.

The base level of one livestock unit, or LU, equates to an adult dairy cow — which munches a heck of a lot of grass. A beef animal scores 0.75 LU. A hill sheep is 0.06, while its heftier lowland cousin is 0.08. A farmed red deer hind is 0.3, a horse is 1.0 and a pony is 0.8.

The system gets more complicated when young animals at various stages of growth are included. The overall stocking rate per hectare is worked out using these figures and the proportion of a year that the animals will spend on the relevant land parcels.

Livestock units and human impact units?

Could something like this system be used to design countryside schemes for humans using rights of public access? (Read more on public access here.)  It occurs to me that different types of landscape can host varying numbers of people. Woodland, for example, can probably accept more people than a more open piece of land, where the visual intrusion and loss of tranquillity is more apparent. Car parks, dog walking, camping — all these things have an impact on land.

How are they best managed? Working out some human impact unit (HIU) scores might be a start. Certain fieldsports such as fishing, deerstalking and rough shooting might have very low HIU scores. So might a solitary walker — let’s say an HIU of 1.0. You could get more sophisticated about this; a person walking a labrador might be 1.5 HIU, or 90 HIUs if the dog is, say, a Staffordshire bull terrier… It’s well worth thinking about such matters because fieldsports themselves have varying levels of impact and those of us who participate in them risk being squeezed out — even on private land — if we fail to ensure that our own activities are seen in perspective.

I recall having to present an annual activity report on wildfowling to a group of interested parties, including local residents, birdwatchers, conservation officials and so forth. Whenever the subject of disturbance came up, I would point out that we had plentiful facts and figures about wildfowling itself — but what about all the unregulated activities?


It seems obvious that a few wildfowlers tucked away unseen in creeks on the foreshore, firing the odd shot at ducks that are already in flight, would have less impact than a garrulous gaggle of brightly clad ramblers wandering along the top of the sea wall. But guess which of these two activities is the more closely monitored and restricted?