GEOSCIENCE MEETS GENEALOGY: AN INTERDISCIPLINARY ANALYSIS OF INUNDATION, LAND USE CHANGES, AND ANCESTRAL TRIBAL LAND OWNERSHIP IN SOUTHERN LOUISIANA

Louisiana’s coastal delta plain is under threat. Land loss affects millions, including the Grand Caillou/Dulac Band of Biloxi-Chitimacha-Choctaw (GCDBCC). This state-recognized tribe seeks federal recognition, but to succeed they must satisfy the Bureau of Indian Affairs’ “Community” criterion 83.11(c), showing that “More than 50 percent of the members reside in a geographical area exclusively or almost exclusively composed of members of the entity”. This is complicated because although many GCDBCC members live in Dulac and along Bayou Grand Caillou, the tribe is spread out across the area and nearby towns. However, this is for reasons beyond the tribe’s control. First, GCDBCC homelands are converting to open water at a rate of 0.7% per year, more than double the coastal plain average (Parfait and Cox 2020); second, the area has been a centre for oil and gas extraction since the mid-20^th century. Oral tribal histories indicate that Natives were coerced or forced off their land by oil companies. We used geoscience tools to gather evidence that these factors drove individuals to relocate, contributing to today’s somewhat decentralised tribal distribution.

We built a database of ancestors from GCDBCC genealogies, cross-referenced with the Bureau of Land Management’s records of land patents issued in the 19^th century. We located those landholdings on contemporaneous survey plats, digitised their outlines in Google Earth Engine, and overlaid them on modern maps. We imported a database of ~57,000 oil and gas wells, and mapped canal networks to establish the impacts of hydrocarbon extraction. We found that GCDBCC ancestors lived primarily to the east and north pf the current homeland area, in areas where few still reside.

The ancestral landholdings fall into two categories: areas that are now largely inundated, and areas now occupied by hydrocarbon infrastructure or underlain by oil and gas wells. We also found legal documents confirming cases in which ancestors had been unwillingly removed from such lands. We infer that GCDBCC ancestors were forced from their landholdings by a combination of land loss (partially extraction-induced) and manipulative land-transfer processes. These results illustrate that the current distribution of tribe members is a culmination of outside pressures, despite which they still retain cultural community structure and close family ties.