With its mainly deciduous cover, Guanacaste’s tropical dry forest, created by the combination of a Pacific lowland topography and arid conditions, looks startlingly different depending upon the time of year. In the height of the dry season, almost no rain falls on lowland Guanacaste, the trees are bare, having shed their leaves in an effort to conserve water, and the landscape takes on a melancholy, burnt-sienna hue. In April or May, when the rains come, the whole of Guanacaste perks up and begins to look comparatively green, although the dry forest never takes on the lush look of the rainforest.
The story of the demise of the tropical dry forests in Mesoamerica is one of nearly wholesale destruction. In all, only about two percent of the region’s pre-Columbian dry forest survives, and what was once a carpet stretching the length of the Pacific side of the isthmus from southern Mexico to Panamá now exists only in besieged pockets. Today, dry forests cover just 518 square kilometres of Costa Rica, almost all in Guanacaste, concentrated around the Río Tempisque and, more significantly, north in the Parque Nacional Santa Rosa. Due to deforestation and climatic change, tropical dry forests are considered a rare life-zone. Their relative dryness means they are easily overrun by field fires, which ranchers light in order to burn off old pasture. Hardy grasses spring up in their wake, such as the imported African jaragua, which gives much of Guanacaste its African savannah-like appearance.
Along with the leafy trees, tropical dry forest features palms and even a few evergreens. At the very top of a good thick patch of dry forest you see the umbrella form of canopy trees, although these are much shorter than in the tropical rainforest. Dry forest is a far less complex ecosystem than the humid rainforest, which has about three or four layers of vegetation. Like temperate-zone deciduous forests, the tropical dry forest has only two strata. The ground shrub layer is fleshed out by thorn bushes and tree ferns, primitive plants that have been with us since the time of the dinosaurs. Unlike rainforest, dry forest has very few epiphytes (plants growing on the trees), except for bromeliads (the ones that look something like upside-down pineapple leaves). The most biologically diverse examples of tropical dry forest are in the lower elevations of Parque Nacional Santa Rosa, where the canopy trees are a good height, with many different species of deciduous trees. There are also some pockets of mangroves and even a few evergreens in the wetter parts of the park.
Tropical dry forests can support a large variety of mammal life, as in the Parque Nacional Santa Rosa–Parque Nacional Guanacaste corridor. Deer and smaller mammals, such as the coati and paca, are most common, along with large cats, from the jaguar to the ocelot, provided they have enough room to hunt. You may see the endangered scarlet macaw, which likes to feed on the seeds of the sandbox tree, in a few remaining pockets of Pacific dry forest, including Lomas Barbudal and, further south, around Río Tarcoles and Parque Nacional Carara, itself a transition zone between the dry forests of the north and the wetter tropical cover of the southern Pacific coast. In addition, the staggering number and diversity of insects are of great interest to biologists and entomologists: there are more than two hundred types of bee in Lomas Barbudal, for example, and a large number of butterflies and moths in Parque Nacional Santa Rosa.