The Help of Satellite Maps
The geographic information software, Grazgrad, was developed by Pickup to manipulate this data, aggregate it by distance from water and plot cover against distance from the water. By plotting the vegetative cover against the distance from water he gets a curve – a grazing gradient – that rises and flattens. Close to the water more animals graze, leaving little vegetation. But as you go further away fewer graze per unit area. Ideally, the curve would be flat, if water were available everywhere and grazing evenly spread.
The difference between the flat and the curve gives the effect of grazing. In healthy areas, after rain, all the plants eaten should regrow. However, in a damaged system, after rain, there is still a curve – it cannot recover fully. Pickup and his team have done this for target rainfalls, when a full recovery is expected, and have been able to assess the effect of livestock in degradation.
This occurs in two ways – a reduction in vegetative cover due to damage to the soil and a change in the nature of that cover due to grazing. The plant species change – so that as a paddock is grazed out only the poor species are left which are unpalatable for the animals. The result is a collection of satellite mapes of the grazing gradients showing reduction in cover and giving a measure of land degradation.
