By mass fishing, off shore drilling, and population.
La Ramblas is the central boulevard in Barcelona, and it is also the one main tourist's attraction in the city. It is approximately 1.2 kilometers long with Port Vell at the Southernmost end and Placa Catalunya at the Northernmost end. It can also be divided into seedy and non-seedy areas. Attraction in Ramblas includes live performances, human statue art, an artist that draw your portrait or caricature and the Erotica Museum.
Freezing and thawing,Plant growth and Abrasion
Lack of economic development!!! i hope that helps you