The biotic response to global change: a summary

INTRODUCTION What comes over so clearly in the contributions to this volume is that the nature and rates of biotic response to global change have been very variable. While many biotic groups show a marked response to the physical variables of global change considered in Chapters 2 and 3, in others the main changes over the last 145 Ma have been driven primarily by intrinsic or extrinsic biological factors. Furthermore, any organisms that contributed substantially to carbon burial (e.g. trees, corals, nannofossils) helped to drive global change. In this chapter we bring together some of the common strands that have emerged from the preceding chapters. ENVIRONMENTAL CONSIDERATIONS AND BIOTIC RESPONSE Climate change, itself a product of other components of global change, is a key forcing mechanism for global biotic change. The time interval embraced by this volume witnessed a major change in Earth's climatic history, from a very warm ‘greenhouse’ state in the Cretaceous through a long, but far from monotonic, decline through much of the Cenozoic to the present-day icehouse world. During the ‘green-house’ phase, climate varied but apparently changed only slowly over many thousand to several million years. But as global climate cooled a clearly marked cyclicity developed, driven by Milankovitch and sub-Milankovitch scale cycles.