The rest have been irretrievably lost, mainly due to deforestation for pastureland, according to estimates by scientists from Tropi-Dry, a research network sponsored by Inter-American Institute for Global Change Research (IAI).
Using modelling techniques and remote sensing, they monitored changes in land use in the tropical dry forest areas of Brazil, Mexico and across Central America since 2005.
Unlike rainforests, tropical dry forests exist in areas with long dry seasons. The two most extensive contiguous areas that remain intact are located in northeastern Brazil (Caatinga) and across southeastern Bolivia, Paraguay and northern Argentina. In most other areas, these forests are fragmented.
“With the exception of Costa Rica, all the other tropical dry forests are quickly vanishing.”
Arturo Sanchez-Azofeifa, University of Alberta in Canada
“With the exception of Costa Rica, all the other tropical dry forests are quickly vanishing”, says Arturo Sanchez-Azofeifa, a professor at the University of Alberta in Canada, and Tropi-Dry’s lead researcher, in an interview with SciDev.Net.
He adds that the study’s results raise concerns over how these forests might respond to climate change — a concern that is even more pressing because they have received little attention from scientists over the last century.
For every 300 scientific papers on tropical rainforests published since the turn of the 20th century, just one was related to tropical dry forests, according to the research.
In the neotropical region of the American continent — which includes almost all of South America, Central America, Antilles, parts of the United States and Mexico — dry forests host at least 66 per cent of water reservoirs.
In addition to being an important source of firewood, medicinal plants and hunting animals, they provide important ecosystem services that regulate the water cycle and protect the soil from erosion.
“Dry forests were [until recently] believed to be ecosystems with low biological diversity”, biochemistry Antonio Salatino, from the University of Sao Paulo’s Bioscience Institute (IB-USP), tells SciDev.Net. Because of the harsh conditions in areas of dry and semi-arid climate, it was assumed these forests were incapable of sustaining a high diversity of animal and plant life”, he explains.
Salatino has been researching Caatinga’s biodiversity for at least two decades, funded by FAPESP. He believes tropical dry forests have been overlooked because the long dry seasons mean that many plant species lose chlorophyll, making the landscape look grey and desolate. “Taking their high biodiversity value into account, tropical dry forests should be given as high a priority for conservation as the Amazon rainforest”, Sanchez-Azofeifa points out.
Conserving these forests would also benefit terrestrial vertebrate species, such as the reptiles. In a study recently published in Nature Ecology & Evolution, an international group of researchers mapped the distribution of over 10,000 species of terrestrial reptiles.
The mapping revealed unexpected patterns, and high biodiversity in areas not considered a priority for conservation — including Caatinga, which is the world’s largest dry forest and takes up nearly 10 per cent of Brazil’s land area.
"Most of the lizards are distributed across open or semi-arid areas, such as the Caatinga, and there are several endemic species in these regions”, says ecologist Cristiano Nogueira, from the IB-USP, and one of the study’s authors.
IAI and FAPESP are both SciDev.Net’s donors
This article was produced by SciDev.Net’s Latin American & Caribbean desk.