Today we took a holiday – doing fieldwork seven days each week blunts our enthusiasm for the forest. So we made a short journey to Culebra, a small island to the east of Puerto Rico.

Culebra is a very dry island, with a very different flora than our rainforest. It is so dry that there are no running streams or fresh bodies of water anywhere. This fact provides strong constraints on the types of organisms that can live here. The plants are short, a tangle of branches with small or thick leaves – adapted to salty, sunny, and hot conditions.

The size and climate of the island also constrains the activities of human settlers. Everything has to be imported from somewhere else. Plants and animals must immigrate, and all human supplies must be shipped in. Towns like the one below could not exist without this ongoing stream of imports. Oftentimes it is possible to learn something about the history of a place based on the things one finds there – for example, a lack of large mammals may indicate their inability to cross large bodies of water, or insufficient resources on an island, while very different species on an island compared to a mainland may indicate that speciation is occurring (think of Darwin and his finches).

Of course, human imports are also visible – here are the remains of a tank, brought here for amphibious landing exercises decades ago. The history of these islands is deeply intertwined with military usage and abuse.

For me, seeing this very small island highlights the amount of resources our lifestyle requires – everything we are accustomed to having, and to using, comes from somewhere. Only occasionally do we get to see that dependency so starkly.

We crossed the ocean by ferry at sunset. Back into the rain and clouds for more work and more thinking tomorrow.