The Torres and Banks Islands, two small archipelagos of northern Vanuatu, are home to 9400 inhabitants and to 17 distinct languages. With an average of 550 speakers per language, this region constitutes an extreme case of the linguistic fragmentation which is typically observed throughout Melanesia. This study presents the linguistic diversity of that area, examines its social underpinnings and outlines its historical dynamics. These islands form an integrated network where a variety of social forces interact, sometimes in conflicting ways. A long lasting bias toward cultural differentiation of local communities has led historically to the linguistic mosaic observable today. This traditional fostering of diversity was correlated with a principle of egalitarian multilingualism. But while these ancient social attitudes have survived to this day, the linguistic diversity of northern Vanuatu has already begun to erode, due to various recent social changes. These changes have reshaped the language ecology of the region and already resulted in the partial loss of earlier linguistic diversity. While northern Vanuatu is still linguistically diverse today, the increased imbalance of power among languages potentially makes the weaker varieties vulnerable in the decades to come.