PATTERNS OF LAND-PLANT DIVERSITY, CLIMATE AND GEOGRAPHY IN THE PALEOZOIC AND MESOZOIC

It is tempting to link broad-scale patterns of vegetation change observed through the Phanerozoic to concomitant changes in the marine realm, and to then invoke globally catastrophic events. However, such changes are typically subtle and can often be better understood by analyzing them in the context of gradual climatic and geographic changes. To illustrate this, ‘raw’ patterns of land-plant diversity (i.e. without considering climate and geography) are shown for the Paleozoic and Mesozoic of Europe and North America. Next, climate-sensitive sediments (e.g. coals, eolian sands and evaporites) introduce a somewhat independent means of determining broad scale patterns of climate change in terms of the precipitation/evaporation ratio. Finally, these patterns are assessed in the context of changing paleogeography and latitudinal motion, and reveal a more complex scenario of vegetation and climate change. Results are derived from analyses of data in the NCEAS Paleobiology and Paleogeographic Atlas Project (University of Chicago) databases, and the Paleomap Project. The available evidence shows that precipitation and plant diversity were highest in the low latitude ‘tropical’ regions during the Carboniferous and Early Permian, but were highest in the mid latitude ‘temperate’ regions during the Late Permian and Mesozoic. This change corresponds to the well-documented icehouse-hothouse transition, and raises the question of whether it also affected distribution patterns of shallow marine organisms. Such broad geoscience questions can be addressed by ensuring the interoperability of databases, an approach advocated by GEON (The Geosciences Network).