Investigating the Urban Response to Border Closure in a Transnational Metropolitan System. The case of the Gibraltar/Algeciras Bay

Border regions tend to be the cradle of dense metropolitan areas shaped by the (socio- eco- nomic, governance, and planning) differentials intrinsic to borders. However, the border permeability variations have historically exposed such systems’ fragility. The paper aims to investigate the spatial repercussions of border closures in cross-border metropolitan re- gions characterised by strong socio-spatial inequalities. It takes the Bay of Gibraltar/Algeciras cross-border area as an analytical framework, focusing on two instances of abrupt border closure. The first is historical (1969-85) and was caused by the Francoist dictatorship’s expan- sionist policies, while the second is recent, caused by the overlap of the Brexit process and the Covid-19 pandemic. These crises shed light on the vulnerability of strongly asymmetrical cross-border urban agglomerations. They act as cautionary tales and testing grounds, proving the necessity of a robust endogenous collaboration on the local cross-border level to create a more resilient, equitable, and polycentric socio-spatial development.