During the Devonian, continental ecosystems underwent major transformations including increases in primary and secondary production and in trophic differentiation and specialization. These are consequent on adaptations in vascular plants which increased resource acquisition and assimilation and reduced the effects of disturbance. The adaptations were probably initiated in relatively stable, rich, low disturbance habitats; their development involved a positive feedback with habitat characteristics so that improvements in utilization of resources and regulation of disturbance actually added to the availability of resources and moderated disturbance. Progressive development of this feedback system produced significant changes in the physical characteristics of continental habitats through the course of the Devonian. In particular, by late Devonian, the rate of chemical weathering must have been higher, and the rates of runoff, throughflow, and sheet and rill erosion lower with a concomitant reduction in variations in stream discharge. These changes would have had major consequences for alluvio-deltaic sedimentation, especially for determination of channel regimes and of depositional and early diagenetic patterns in overbank environments. Detailed studies of Catskill sediments can help to elucidate the extent of ecosystem changes.