Tropical Dry Forest out of the shadow; let’s shine a light
When one thinks of tropical forests, often the first thing that comes to mind is the exuberant and lush rainforests that served as inspiration for the adventures of Tarzan and Mowgli in the Jungle Book. These forests, which hold about 50% of all the planet’s biodiversity, have been an attraction for thousands of scientists, in the social and natural sciences, who have presented evidence of the importance of these forest for the regulation of the cycles of the planet. The importance of conserving this ecosystem is inherent to the continuation of life on earth, and many NGOs, academic institutions, and governments are making significant efforts to preserve them.
However, other tropical forests exist that have lived in the shadow of their megadiverse brother. These forgotten forests are the Tropical Dry Forests, which owe their name because they only receive rain for three to five months a year. They endure prolonged months of drought, causing the trees to shed all their leaves to order to prevent the loss of water. Contrary to the rainforests, the dry forests are found in the Neotropics, and they are distributed in patches throughout Central and South America (Fig. 1). Some hypotheses suggest that historically, they had covered a considerably larger area, but now they have been isolated for more than hundreds of thousands of years. This isolation has generated many kinds of flora and fauna that is exclusive to these forests, leading to the highest rates of endemic species not found in any other forest in the world.
For example, the total number of all species of birds present in all dry forests in the Neotropics (635 species) barely exceeds the amount found in just one single site in Manu National Park in the Peruvian Amazon. However, there are no two regions of tropical dry forests in the Neotropics that share more than half of their species, while adjacent rainforests can share up to 85% of their species. In an article published in Science in 2016, the team from Latin America and Caribbean Seasonally Dry Tropical Forest Floristic Network (DryFlor), found that in an inter-Andean dry forest of
northern Peru, almost 40% of the woody plants that grew there cannot be found anywhere else in the world. These two examples illustrate the unique composition of birds and plants that are restricted to dry forests, with populations that are concentrated in small spaces. This isolation makes the various species vulnerable and reflect a need to be conserved.
Despite providing invaluable ecosystem services and supporting the livelihoods of many of the world’s poorest people, dry forests are among the most threatened and under-researched ecosystems in the world. With less than 10% of its original cover remaining in many countries (Fig. 2)., the square acreage of dry forests and their species richness is smaller than rainforests, these dry forests are being largely ignored by the scientific community. The tropical rainforests have captured much of the public’s attention, despite the critical conservation significance of tropical dry forests.
- Chidumayo, E. N., & Gumbo, D. J. (2010). The dry forests and woodlands of Africa: managing for products and services. Earthscan.
- Dryflor, Banda, K., Delgado-Salinas, A., Dexter, K. G., Linares-Palomino, R., Oliveira-Filho, A., Prado, D., … & Weintritt, J. (2016). Plant diversity patterns in neotropical dry forests and their conservation implications. Science, 353(6306), 1383-1387.
- Janzen, D. H. (1988). Tropical dry forests. Biodiversity, 538.
- Stotz, D. F., Fitzpatrick, J. W., Parker III, T. A., & Moskovits, D. K. Neotropical Birds: Ecology and Conservation. (1996). University of Chicago.
- Azhar, E. I. et al. Evidence for camel-to-human transmission of MERS coronavirus. N. Engl. J. Med. 370, 2499–2505 (2014).Waeber P, Ramesh B, Parthasarathy N, Pulla S & Garcia C. (2012). Seasonally Dry Tropical Forests in South Asia: A Research Agenda. Prepared for “Key Issues for the Global Dry Forests” workshop organized by CIFOR/ ForDev, Zurich, 28–30 October.