Vulnerability assessment for supporting sustainable coastal city development: a case study of La Paz, Mexico

Coastal zones and adjacent land areas support 60% of the human population and eight of the top-10 largest cities in the world. These regions are exposed to natural hazards and climate-change-induced stresses, which requires continuous assessments of their vulnerability in many coastal regions around the world. Evaluations and monitoring of vulnerability models in coastal areas will assist in formulating environmental policies and guiding decision-makers to address the central tenets for the sustainable development of coastal cities. Baja California Sur (BCS) is the Mexican state with the longest coastline in the nation, and its capital city of La Paz is the most crowded city and without a vulnerability assessment. In this context, La Paz was regionalized based on biotic, natural landscape and socio-economic factors within geographic information systems, obtaining 74 environmental units (EnvUs). Assessment of each unit with a coastal vulnerability model involved physical, environmental and socio-economic indicators and composed indices which considered three main elements: (1) a fixed component defined by Coastal Vulnerability Index; (2) a Pressure Index and (3) a Fragility Index. Nearly 38% of EnvU and over 60% of total area showed high and very high fragility, including the capital city. Only 7% of EnvU and 14% of all the area of interest presented high and very high pressure. Nearly a third of EnvU had high and very high vulnerability, mainly in La Paz and southwest of the study area without actual human pressure, especially due to the presence of lower slopes and high-energy streams. Results allow focusing efforts on environmental policy instruments to implement adaptation measures for sustainable development in the BCS region.