The forests of Chaco Park, the most extensive forest region of Argentina, have been affected by cutting, burning and inappropriate management for centuries. In the last decades, however, exploitation of these forests progressed at such a high rate that the whole area is in danger of being transformed into a semi-desert unless measures of conservation and afforestation are taken. The area of the Chaco forests corresponds approximately to the area of Germany and is therefore not negligible. If the exploitation of forests continues at the present rate, world climate will suffer. For this reason, the authors attempted to characterize the trees still growing in the Chaco and to determine which adaptational strategies they use to survive in its semi-arid climate, with long periods of heat and drought, with occasional torrential rainfalls sweeping away valuable soils, and great differences in temperature ranging from +47°C to -7°C. The authors studied their dendrology, wood and bark properties, their radical system, their phaenology, as well as their economic uses. With this knowledge the authors suggest measures for the conservation and the afforestation of these precious woodlands. Proposals for a better management include suggestions as to which species would be most appropriate for afforestation.