INTRODUCTION

            The migration of the Germanic tribes is a well-known and documented occurrence, first referred to as the Völkerwanderung or “people movements” in the 1700s (Goffart, 1980) .  The region east of the river Rhine and north of the river Danube was never fully conquered by the Roman Empire (Figure 1.2).  This region, generally called “Germania” for the Germanic tribes who inhabited this region was comprised of many heterogeneous clan-based groups (Figure 1.3).  For some reason these tribes began to move and attack the Roman Empire, eventually destroying the autonomy of Rome.  Rome lost control of much of its Empire in the third century AD partially due to these tribes, but recovered much of the Empire starting in AD 275 (Figure 1.4).  There have been many theories postulating the reasons these tribes began and continued to move.   However, almost all of these theories have neglected the role of climate change and some have disputed it altogether (Wolfram, 1997, Wells, 1999) .  This is understandable because the tools necessary to reconstruct the climate during this period were not available to the early historians.  The early theories that formulated the climate-migration argument in the early 20^th century had to rely on theory only without any empirical data (Huntington, 1907) .

Advances in paleoclimatology over the last few decades has allowed for the reconstruction of climate in historic and prehistoric times (Bradley, 1999) .  Depending on the proxy, climate indicators can reveal changes in the earth’s climate for the past few thousand years.  One of these proxies, dendroclimatology, has allowed for a detailed reconstruction of paleoclimate (Douglass, 1937, Glock and Pearson, 1937, Huber, 1943) .  Dendroclimatology, or the study of annual changes in tree-ring growth, has allowed paleoclimatologists to accurately determine small changes in temperature and precipitation to the year.  The process of crossdating allows for the “bridging” of live trees to both dead and fossil trees, which has extended the tree ring chronologies in Europe to about the Older Dryas, about 18,000 YBP (years before present) (Pilcher et al., 1984, Becker, 1993, Spurk et al., 1998) (Figure 1.5).  Trees in the same region that live or lived in similar climatic conditions theoretically produce similar ring patterns.  If two trees germinated at different times, but overlap in time, theoretically their rings can be crossdated.  This method of crossdating living and dead trees allows for a continuous reconstruction of annual changes in tree-ring growth into the distant past, far beyond the lifespan of an individual tree.  These variations in tree rings can reflect past climates.  These chronologies offer the paleoclimatologists and historian a new tool for evaluating climate change and historical events.

These two components, our current historical understanding of the Völkerwanderung and new data allowing for annual paleoclimatological reconstruction, allow the question: did climate change cause or influence the migration of the Germanic tribes?  Firstly, it is in order to describe the study area, geographically, to determine if there is evidence in this region having record of a sustained climate change that could have affected the inhabitants?  It is also necessary in a study such as this to address the issue of causation and correlation or even coincidence.  How can a change in climate and subsequent migration or movement of a peoples be connected?

The second chapter will ask: if there is a way to get around or limit the random correlation between movements of peoples and climate change, how can this gap be bridged?  What steps can be taken to reduce the possibility that events that coincide are merely a correlation and have no causal connection whatsoever?  There is a possibility that climate changes in AD 214 – 232 and 364 – 383 may have affected the indigenous tribes in Germania, but these hypotheses have been disputed and even rejected by many scholars.  Chapter three will address these theories and the climate data that was not available to them.

Chapters four and five address the question of correlation from both the evidence that climate did change and that migrations did occur.  While chapter six will address the relationship between these climate changes and migrations that are seemingly coincidental.  It will also address the specifics of how these data could be interpreted and finally the implications of climate change and the migration of the Germanic tribes.  Through this series of steps the question, Did extreme climate conditions stimulate the migrations of the Germanic tribes in the 3^rd and 4^th centuries AD?, will be addressed.