Tree diversity in temperate and dry forests should not be overlooked

Researchers at the University of Exeter have discovered that temperate and dry forests are home to the same level of biodiversity as tropical rainforests. 

Conservation efforts are widely focused on rainforests because they contain so many unique tree species.

However, the study shows that nearly 30% of tree evolutionary diversity is found in temperate or tropical dry forests, as opposed to just 26 percent in rainforests.

“Our findings show that temperate forests and dry forests have a unique evolutionary history that merits far greater conservation attention,” said Professor Toby Pennington.

“Protecting rainforests is obviously vital for many reasons, but we shouldn’t ignore the unique tree biodiversity of temperate and dry forests.”

The study was focused on data from more than 10,000 forest and savanna sites across the Americas. The researchers pinpointed special tree biodiversity.

“The temperate forests in Chile and further north in the Andes, and scattered and isolated tropical dry forests across the Americas, are highlighted as particularly unique, threatened and in need of conservation action,” said study first author Ricardo Segovia.

Temperate forests like those found in Chile and the United States are positioned between the tropics and the cold boreal regions. 

The study revealed that temperate forests have distinctive tree lineages that include members of the oak and elm families. Among the dry forests, unique tree lines include members of the pea and cacti families.

“What is unique about this study is that it uses DNA sequence information from thousands of tree species right across the Americas to give completely new insights into the countries and habitats where the major branches of the tree of life are found,” explained Dr. Kyle Dexter.

The researchers investigated the main factors that prevent species from expanding into new areas and environments. The “fundamental divide” was found to be the presence or absence of freezing temperatures, which some plants cannot tolerate.

The team also identified an evolutionary split between trees that dwell in rainforests versus dry tropical forests.

“This is a really important paper in terms of our view of what has controlled the global distribution of plant biodiversity through history,” said Dr. Dexter.

The study is published in the journal Science Advances.

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By Chrissy Sexton, Earth.com Staff Writer