The paper uses data from excavations and field surveys of Roman ironmaking sites in the Weald of south-eastern Britain to assess the effect on an ancient landscape, in terms of deforestation to provide charcoal as fuel for smelting, and of ore mining. It is calculated that operations on six of the largest sites would have resulted in the clearance in a little over one century of 300-500 km² of forest, and ore exploitation over an equivalent area. Data from experiments in reconstructed Roman furnaces and from modern primitive ironmaking are used to assess the probable manning requirements of individual furnaces, settlements, and the entire military operation in this part of the Weald.