Two or three thoughts about the current crisis.

When there is a major climate disaster in the US, people move. Since the US is big and has large gaps in population, it looks different than when a disaster happens in some other places. Five million (or more) Syrians leaving the Levant left a major mark across the globe. A half million leaving the Katrina hit zone was barely noticed on a global, or even national, scale, not just because it was one tenth the amount, but because of our size and space as well.

Something close to half the 400K or so displaced by Katrina (over half of them from NOLA) have returned to the vicinity they formerly lived in, and only a third to the same original location. The others are all over the place, distributed with a rapidly decreasing distance decay function. So these displacements, in the US, tend to be very long term and can thus affect demography and politics far afield.

An exodus from Puerto Rico will likely have a different decay function than seen for Katrina because it is, and apparently few people know this, an Island! But anyway, it is likely that there will be an exodus from Puerto Rico and it is starting to look like it will be sufficient to make Florida less Purple and more Blue, and specifically, more anti-Trump.

Note that in the past, New York was the most likely destination for a person from Puerto Rico to move, which is funny given Trump’s statements about all his Puerto Rican friends. For those not from that region, Puerto Ricans have long been hated by white supremacists in the greater NY metro area. But I digress. Anyway, over recent years, Florida has become a growing center of the US Mainland Puerto Rican community.

For context: There are about 3.5 million people living in Puerto Rico who identify as Puerto Rican, and about 5.3 million self identified Puerto Ricans in the lower 48. Currently there is somewhat under one million in Florida, somewhat over in NY, but Puerto Ricans are everywhere in the US, with the fewest in the upper plains and the most in the greater NY area (as far out as Penn) and Florida.

We are concerned that cholera will spread in Puerto Rico. You may remember the ca 2011 epidemic that mainly struck Haiti (see chart above). There was another ten years earlier. There is some interesting research out there linking cholera to climate change. The pathogen, Vibrio cholerae, lives in coastal waters where it has a keystone commensal relationship with copepods and other microinvertebrates. We think of cholera as a highly contagious pathogen among humans, but it starts from its natural reservoirs in water. In some areas of South Asia, cholera was significantly attenuated by the discovery that simply passing well water through common cotton cloth filtered out the disease enough to make a difference, at least in some contexts.

For historical context, there was a huge cholera epidemic in the Caribbean in the 19th century, and I understand this event, which killed something like 30,000 in Puerto Rico alone, is still a traumatic memory in the region. From a 2011 summary of the historic epidemic, written I suspect in response to the re-emergence of the problem about six years ago:

The Caribbean region experienced cholera in 3 major waves… The 3 periods of cholera in the Caribbean that we have identified are 1833–1834 (with, according to Kiple [6], possible lingering cholera in outlying areas until late 1837 or early 1838) in Cuba; 1850–1856 in Jamaica, Cuba, Puerto Rico, St. Thomas, St. Lucia, St. Kitts, Nevis, Trinidad, the Bahamas, St. Vincent, Granada, Anguilla, St. John, Tortola, the Turks and Caicos, the Grenadines (Carriacou and Petite Martinique), and possibly Antigua; and 1865–1872 in Guadeloupe, Cuba, St. Thomas, the Dominican Republic, Dominica, Martinique, and Marie Galante.

It is thought that Cholera is more likely to be abundant and to spread into human populations with warmer waters, and possibly the range over which cholera is a lingering constant threat in coastal waters is likely increasing. Also, increased air temperatures and rainfall can increase growth or spread of cholera in the wild. This is a relationship first identified in the 1990s, and that has been demonstrated through several studies. The next few weeks and months in Puerto Rico are an accidental and potentially horrific experimental laboratory to test the science that has been percolating along over the last 20 years.