An unusual climate along the northern coast of Peru and southern coast of Ecuador is responsible for the extraordinary deciduous dry forests. Even though these forests lie on the equator, they find themselves in the rain shadow of the mighty Andes, the world’s longest mountain range. And for seven to eight months of the year they get little moisture from the ocean because it’s cooled by the Humboldt Current flowing north from Antarctica.
Deciduous dry forests are rare and highly endangered. Because of human activity, less than 5% of the original ecosystem remains.
These forests occur in regions with heavy rainfall for part of the year followed by a long dry season. The trees are well adapted to this climatological reality of almost no rain for up to seven months. They are dense with greenery during the wet summers, but become a starkly different landscape during the dry winters when most trees shed their leaves to avoid transpiring their stored water into the air. Because of these dramatic conditions, these ecosystems have many endemic species adapted to the area’s extremes.
The deciduous forests are are home to one of the highest concentrations of endemic bird species in South America, making them a top conservation priority.
These forests, often known as the Tumbesian ecosystem, are unique and precious. They rank as one of the world’s highest biodiversity priorities for two reasons: First, they are home to one of the highest concentrations of endemic species in all of South America. And second, the degree of threat is grave because the climate is good for farming of export crops like corn, bananas and rice. Making matters more dire, the Tumbesian region has been farmed for 500 years, since the Spanish conquistadors first landed here in search of gold. Presently, only 5% of the original dry forests remain standing.
“The tropical deciduous forests rank among the most threatened on Earth in terms of biological extinction as a result of human activities.”
Priority conservation designations covering the region include the Tumbes Endemic Bird Area, identified on the basis of 55 species, of which 19 are globally threatened and 45 are endemic to the region. The Tumbesian region stands out among such areas as holding one of the largest numbers of restricted-range species (fourth in the world). This is especially unusual given its proportionally small area.
The deciduous forests extend into North America and the northernmost are found in Sonora, Mexico. Sometimes called tropical savanna, this ecosystem once reached continuously from northern Mexico over a thousand miles into Central America, but now only 15% remains and only 1% is in protected status. The Sonoran forests support a high diversity of birds with approximately 330 species and is a critical region for birds migrating from the Rockies. Additionally, the deciduous forests of Sonora hold five species of wild cats including the jaguar, puma, bobcat, and ocelot, and 79 species of amphibians and reptiles.
Much is still to be learned about the deciduous dry forests. Nature & Culture operates a field station in our Laipuna Reserve in southern Ecuador dedicated to biological research to uncover and protect endangered populations of endemic birds such as the blackish-headed spinetail, the henna-hooded foliage-gleaner, and the rufous-necked foliage-gleaner. It has also discovered the presence of white necked peccaries, white-tailed deer, and pumas.