Lima has desert not just dessert

I had many misconceptions coming to Peru – that there were not any large modern cities, that llama and alpaca were two names for the same animal, and that the entire country was either coastline or highlands. I was completely unaware of the huge desert and lack of rain that permeate so much of the country, including Lima. When I began to consider what I should discuss in my first blog post, I thought to what questions baffle me the most. While not a particularly sexy question, I had never seen a coastal desert and wondered how that was possible given what I knew about the forming of normal deserts. Furthermore, I was always intrigued by how these huge cities and civilizations developed when a large part of the area received no rain and why. 

The first question was answered by our first tour guide Ronaldo as we travelled throughout Lima. The waters of the Pacific off the coast of Peru are an intersection point for two currents, one of them being the Humboldt. This current is unique due to the influx of cold water it brings right off the coast, which has the effect of sucking moisture out of the surrounding land instead of providing it with rain, creating a coastal desert.

The second question proved to be less straightforward and more subject to interpretation, but also far more interesting. Ancient cultures in the South American deserts, from the Sechura to the Atacama, used different techniques for acquiring and storing water for the dry seasons. Lima relies on glacial runoff and other means to get its water, but another method was via lomas, oasis-like pockets of vegetation that emerge during July and November. These acted as life lines for animals and populations by the trapping of fog created by the same Humboldt current that creates the coastal deserts in the first place. These lomas have been declining recently due to deforestation and global warming, causing people to turn back to other techniques, some ancient in nature. One plan involves refurnish old structures called amunas originally constructed by the Wari people, which allows rainwater to sink into the ground and highlands instead of flowing all downstream, creating a store of water that resurfaces during the dry season.