text: Intermediate 
  Apart from volcanoes, hurricanes and earthquakes, there are two key things that can make a city disintegrate or even totally disappear  water and sand. 
  A century ago, Venice  one of the most beautiful and low-lying cities in the world  used to  ood around ten times a year. Nowadays, its lowest point, Piazza San Marco (only three feet above sea level) is inundated with water approximately 100 times a year.
  But rising sea levels are not the only cause. In many parts of the world, the land is also sinking. In Venice, subsoil compaction (a result of industrial exploitation of the surrounding area) lowered the city by 20cm between 1950 and 1970. Ho Chi Minh City in Vietnam is also sinking by about 2cm a year  but thats nothing compared to Jakarta, which is dropping 10 to 20cm each year. In the past three decades, the city has sunk roughly four metres. 
  Unfortunately for the Indonesian capital, it has pumped out so much groundwater to support its population that the land above is drying out and compacting  this has created a bowl. Rivers that used to  ow through the city down to the sea have had to be diverted because they cannot drain uphill.
  While there are many plans to save Venice  and Ho Chi Minh City and Jakarta are taking the problem seriously  the same cannot be said for Miami, where politicians refuse to admit the city has a serious environmental problem.
  There are three problems in Miami. It is less than ten feet above sea level; an increasing number of tropical storms are inundating the city; and it is built on porous rock, which is absorbing the rising seawater. This water then  lls the citys foundations and comes up through drains and pipes, forcing sewage upwards and polluting its fresh water. It is possible that Miami may one day become uninhabitable.
  In the Maldives, the populations of whole islands are now considering abandoning their homes. The capital, Male_, population 153,379 and only four feet above sea level, has built a ten-foot sea wall at a cost of $63 million  but, long term, only a stabilization of rising sea levels will save it and the rest of the islands.
  In Africa, deserti cation is causing the Sahara to spread south at a rate of 30 miles per year, threatening settlements in northern Mauritania. Over the past 20 years, for example, the desert has grown by more than 260 acres around the trading and religious centre of Chinguetti, where the population has declined from 20,000 people in the mid-twentieth century to just a few thousand now. Trading has almost completely stopped as sand piles up in the streets. 
  Likewise, the Californian resort of Rancho Mirage, near Palm Springs, may have to be abandoned in the next decade. This city is just one example of a problem caused not so much by global warming as human over-expansion. Californias dream of farming the desert made sense while its total population remained around half a million (in 1870)  but now the state is home to 38 million people, who own 32 million vehicles.
  The daily water use in Rancho Mirage is more than 200 gallons per person, which is causing a man-made drought. A 25% cut in water use has been implemented but this is unlikely to stabilize the resort, which is surrounded by sand and dust. The long-term answer in Californias desert is likely to be the abandonment of some cities.
  Fire is a growing threat to urban settlements in America  in fact, forest  res cause the most damage after severe storms, with 800 major  re disasters there between 1953 and 2014. A new report by the USDA Forest Service maps the increasing number of urban locations that are particularly vulnerable to wild re.
  Similarly in Australia, some of Victorias resorts and several Melbourne suburbs have been placed on a list of the states 52 most vulnerable bush re spots because long-term droughts are making trees highly combustible. Its unlikely that a forest  re will ever destroy an entire city but a succession of  res could make it uninhabitable. 
  Many cities are  ghting a losing battle against nature but is it possible to identify the worlds most vulnerable city? Natural events are very dif cult to predict  but Males future looks particularly bad because, even if its new sea wall continues to be effective, the islands around the Maldives capital are going to disappear before too long. And, if they disappear, Males raison detre disappears, too.