Experts urge fresh thinking on tree protection

Efforts to protect Earth’s most vulnerable natural habitats should focus on temperate and tropical dry forests as much as rainforests, research suggests.

These vast woodlands – found mostly in drier areas north and south of the tropical rainforest belt - are home to thousands of tree species unique to those regions, a study shows.

Scientists say their findings overturn conventional wisdom on conservation, which has traditionally centred on rainforests, partly because they contain so many plant species.

An international team of researchers, led by the Universities of Edinburgh and Exeter, examined data from more than 10,000 forest and savanna sites across the Americas.

Our findings show that temperate forests and dry forests have unique evolutionary history that merits far greater conservation attention.

Professor Toby PenningtonGlobal Systems Institute, University of Exeter

Evolutionary diversity

They concluded that nearly 30 per cent of tree species’ evolutionary diversity is found only in temperate and tropical dry forests, compared with a figure of 26 per cent for tropical rainforests is.

The study found that temperate forests – such as those of Chile and the US – hold unique genetic lines of trees including members of the oak and elm families.

Unique lineages in dry forests – such as the Caatinga of Brazil and the Chiquitania of Bolivia – include members of the pea and cacti families.

The DNA sequence information offers completely new insights into the countries and habitats where the major branches of the tree of life are found.

Dr  Kyle DexterSenior Lecturer, School of GeoSciences, University of Edinburgh

Main factors

By examining the evolutionary make-up of tree communities, the researchers tried to discover the main factors that prevent species expanding into new areas and environments.

The determining factor was found to be the presence, or absence, of freezing temperatures – which some plants cannot tolerate.

An evolutionary split also developed between trees that exist in moist and dry forests in the tropics, the team says.

New understanding

The researchers say their study can help to reshape our understanding of what has controlled the global distribution of plant biodiversity through history.

The team included researchers from the University of Leeds and the Royal Botanic Garden Edinburgh. Also taking part were teams from universities in Brazil, Chile and the US.

The paper, “Freezing and water availability structure the evolutionary diversity of trees across the Americas”, is published in the journal Science Advances.

Related links

Journal paper

School of GeoSciences

Global Systems Institute, University of Exeter

Institute of Ecology and Biodiversity, Chile