A paper just out in the Journal of Applied Ecology is a really great illustration of the interactions among different components of agrobiodiversity that we’re always on about here. ((TADEY, MARIANA & FARJI-BRENER, ALEJANDRO G. Indirect effects of exotic grazers: livestock decreases the nutrient content of refuse dumps of leaf-cutting ants through vegetation impoverishment. Journal of Applied Ecology 44:1209-1218.)) The Argentinian researchers found that putting more cattle to graze on the steppe vegetation of the Monte Desert in Patagonia resulted in a progressive decrease in plant cover and species diversity. So what, right? Well, this affected the diet of leaf-cutting ants. And that meant that the ants’ refuse dumps were less rich in nutrients. Which meant lower soil nutrient avalability. And perhaps eventually less healthy and productive cows. As well as further changes in the vegetation. It just takes a slight reduction in stocking rate (the number of cows per hectare) to restore the ants’ diet and the fertility of the soil.