2nd century AD mosaic from the House of the Laberii at Uthina, a Roman colony in the valley of the Miliana, Tunisia. It shows the various activities of a 'mixed economy' estate, including oxen ploughing the wheatfield (the main source of its income), a shepherd with a flock of sheep, a herdsman with goats, partridges being driven into a keep, a pole-and-bucket well with a horse drinking nearby, olive trees, dogs, horses and a mule. Hunting is also shown, including a figure spearing a wild boar. Although this part of north-west Africa was the major producer and exporter of wheat to Rome and the Roman Empire, by the end of the 1st century AD, soil exhaustion and erosion plus the increased demand from Rome for olive oil and wine, meant the producers were encouraged by the State to bring into cultivation the more marginal land on which they planted olive groves and vines.