Long-term environmental change and human impact have been reconstructed at fine spatial and temporal resolutions in an archaeologically rich, and floristically interesting, part of southwestern Ireland, namely the Beara peninsula, County Cork. Detailed pollen and macrofossil analyses, and radiocarbon dating have been carried out on several short peat monoliths, and on a peat core and a lake core from small basins. Landscape evolution, vegetation dynamics, and farming activity from the end of the Neolithic (c. 2500 B.C.) to the present day, i.e., the period of greatest human impact in southwestern Ireland, have been reconstructed. While significant opening-up of the landscape began relatively early in the Bronze Age (between c. 2400–2100 B.C.), the main woodland clearances took place in the later Bronze Age (beginning c. 1400 B.C. and continuing into the Iron Age, i.e., to c. 400 B.C.). In the mid- and later Iron Age, there was considerable fine-scale spatial variation, with activity being concentrated mainly in the uplands (at c. 200 m asl) and at lower elevations. Radiocarbon dating and pollen evidence show that the linear stone-wall system, now partly obscured by shallow peat, was laid out towards the end of the Iron Age (c. A.D. 400) in the context of a largely open landscape. While the initial foci of bog growth appear to relate to the late Neolithic/beginning of the Bronze Age, widespread development of blanket bog was essentially a phenomenon of the late 1^st/early 2^nd millennium A.D. It was probably favoured by wetter and cooler conditions during the Little Ice Age. Detailed records are presented for the filmy ferns, Hymenophyllum tunbrigense, H. wilsonii, and Trichomanes speciosum, and also Myrica and Ulex, both shrubs with pronounced, oceanic distribution patterns.