ABSTRACT. The synthesis of the contributions in this special issue about the tropical city of San Juan has resulted in five themes. First, the city is subject to multiple vulnerabilities, but socioeconomic factors and education level affect the perception of citizens to those vulnerabilities, even in the face of imminent threat. Second, in light of the social-ecological conditions of the city, how its citizens and institutions deal with knowledge to respond to vulnerabilities becomes critical to the adaptive capacity of the city. Third, the relationship between socioeconomic factors and green cover, which in 2002 covered 42% of the city, is not what has been reported for other temperate zone cities. In San Juan, neighborhoods with households of high socioeconomic level were not necessarily associated with greater green cover. However, in adjacent neighborhoods within the densely populated zones of the city, households of high socioeconomic level did preserve green cover better than households in lower socioeconomic-level neighborhoods. Fourth, tropical conditions such as climate may explain some of the unique aspects of the social-ecological system of San Juan. The most obvious is the exuberance of tropical biota in the city that not only forms novel species assemblages but also provides many ecological services, including food production for up to 60% of the members of particular neighborhoods. Ecosystem resilience is particularly high in aquatic and terrestrial ecological systems in San Juan. Fifth, it appears that the emergence of novel systems in the city represent adaptive responses to the social end ecological conditions in the city. We conclude that the study of a tropical city provides contrast to the prevailing literature on temperate and boreal cities and expands the suite of behaviors of urban social-ecological systems, thus advancing the dialogue on the functioning of cities in light of environmental change.

Puerto Rico is an unincorporated territory of the United States of America. As part of the political-economic arrangement between both political entities, Puerto Rico does not control the local price of oil because it does not have domestic sources of oil, and it does not control its monetary policy, as that is a right reserved by the U.S. Federal Reserve System.  This paper investigates the impacts of exogenous shocks of oil price and monetary policy on the Economic Activity Index, Puerto Rico Consumer Price Index, total non-farm employment, electricity consumption, gasoline consumption, and cement sales. Impulse response functions are used to study the oil price and monetary policy shocks. The oil price shock had a more significant effect on gasoline consumption than on electricity consumption. Monetary policy shocks had a higher magnitude on electricity consumption than on gasoline consumption. The monetary policy and oil price shock had minimal effect on the aggregated endogenous variables, Economic Activity Index, and Puerto Rico Consumer Price Index. This study suggests that individuals in Puerto Rico are vulnerable to a volatile oil market. Also, both exogenous variable shocks had minimal impact on employment. As for future steps, it would be prudent to investigate the effect of both exogenous variables on individual employment sectors, not aggregated. Besides, the government of Puerto Rico should develop policies to minimize the effect of oil price shocks.