LIFE ZONES

Unlike most equatorial regions, the Galapagos are not hot and humid. They lie instead in a dry zone of the Pacific, where temperatures are kept abnormally low by the cool upwelling in the sea. The cold Humboldt Current sweeps northward from the Antarctic and at the northern tip of Peru it is pushed toward Galapagos by southeast tradewinds. The mass of cold water cools the air and an inversion layer is formed which upsets the usual weather pattern associated with the tropics. This results in peak daytime temperatures during the warmer months, January to May, averaging 27°C (80°F) and in August the average upper limit falls to 22°C (70°F). Periods of rain are brief and water drains quickly through the porous volcanic soils. While the lowlands are experiencing drought, the highlands receive moisture in the form of mist precipitation locally known as "garua." Between these two extremes, the dry lowlands and lush highlands, there are six and in some places seven vegetation zones that can be recognized, which are grouped into four different life zones.

• Desert Tropical thicket (Littoral zone): an area between sea level and 35 feet of altitude, occupied by the ocean on high tides. The dominant species are the mangrove and occasional small-sized plants, covering only small areas of the beach. The temperature is on average 70° F, but on some months it somewhat rises or lowers, depending on the behavior of cold Humboldt Current and warm El Niño Current that year.
• Thorny Tropical thicket (Miconia and Arid zones): this life zone is located between 35 and 400 ft above sea level. It covers the area of all small islands and most of the bigger ones, the vegetation it supports becoming the characteristic type of Galapagos Islands. This vegetation, mostly different types of cactus, such as the endemic prickly pear cactus, has adapted to resist draughts and to dominate rocky areas. The usual temperature is 70° F.
• Thorny Pre-Montane thicket (Transition zone): this area within the range of 400 to 600 ft of altitude, serves as a transition between a very arid lowland and a slightly more humid highland. The trees have greater heights than lower life zones and there are some epiphytes, ferns and grasses already present. The temperature is between 60 and 70° F on average.
• Dry Tropical forest (Humid, Pampa and Brown zones): a life zone in all areas above 600 ft of altitude, more humid than the rest of the park. There is a dense forest of epiphytes, vines, ferns, fungi, mosses and lichens. The pampa vegetation zone is characterized by an abundance of ferns, graminaceous plants and orchids. The temperature ranges from 60 to 70° F normally.