Before the arrival of the Spanish in the early 16th century, dry forests blanketed the Pacific coastal lowlands from Panamá to Mexico. Fires set by the Spanish and by generations of farmers and ranchers thereafter spread savannas across the province. Three decades ago, the dry forests had dwindled to some 2 percent of their former range—a mere 520 square kilometers of Costa Rica in scattered patches centered on the lower Río Tempisque of Guanacaste. Far rarer than rainforests, they are significantly more endangered, especially by fires, which eviscerate whole forest patches, opening holes in which weeds and other ecological opportunists rush in. Eventually savanna comes to replace the forest. (The fate of even the preserved dry-forest parcels hinges on the success of two ambitious conservation projects that are exemplars of forest restoration: one focusing on educating children and former farmers about the value of the dry forest, one studying and promoting the scarlet macaw, vital to the survival of the sandbox tree.)

Unlike Costa Rica’s rainforests, the rare tropical dry forest is relatively sparsely vegetated, with far fewer tree species and only two strata. Canopy trees have short, stout trunks with large, flat-topped crowns, rarely more than 15 meters above the ground. Beneath is an understory with small, open-top crowns, and a layer of shrubs with vicious spines and thorns. Missing are the great profusion of epiphytes and the year-round lush evergreens of the rainforest.

From November through March, no rain relieves the parching heat. Then, the deciduous dry forests undergo a dramatic seasonal transformation, the purple jacaranda, pink-and-white meadow oak, yellow corteza amarilla, scarlet poró, and the bright orange flame-of-the-forest exploding in Monet colors in the midst of drought.