An international team of scientists including from the University of Adelaide have discovered 467 million hectares of previously unreported forest – an area equivalent to 60% of the size of Australia, and increasing current estimates of global forest cover by 10%.
Published today in Science, the scientists say that not only will the new finding help dramatically improve the accuracy of global carbon modelling, it has also revealed the true potential in forest cover of the world’s drylands and may lead to new opportunities for mitigation of climate change through improved conservation and restoration in dryland habitats.
Led by the Food and Agriculture Organization of the United Nations (FAO), teams of scientists and students from 15 organisations around the world carried out an innovative new global analysis of the distribution of forests and woodlands across drylands. This class of forest and woodland has previously been difficult to measure globally using satellite imagery or other remote sensing because of the relative low density of trees.
A new photo-interpretation tool developed at FAO, called Collect Earth, overcomes the limitations of automatic and often inaccurate categorisation of forest types of satellite imagery by using a simple validation check for tree number and density. Data supplied by the Terrestrial Ecosystem Research Network (TERN) was crucial in providing the on-ground verification of the system.
“Just when we thought we knew the world, this project shows we are still improving our knowledge and description of natural systems,” says Professor Andrew Lowe, Chair of Plant Conservation Biology at the University of Adelaide’s Environment Institute.
“To ‘find’ an area of forest that represents 10% of the global forest cover is very very significant, with broad consequences for global carbon budgeting and dryland restoration and management.
“It shows that dryland regions have a greater capacity to support trees than previously perceived and understood. With its low opportunity costs, dryland could therefore provide a unique chance to mitigate climate change through large-scale conservation and afforestation actions. It also shows the potential for improved livelihoods of the people in these areas.”
The research teams analysed very high resolution satellite imagery of more than 210,000 dryland monitoring sites to calculate global forest cover and its change over time.
“The main reason for the underestimate of forest cover is that previous land type classifications have been based on older and lower resolution satellite imagery without any kind of ground validation,” says Associate Professor Ben Sparrow, leader of the TERN analysis team at the University of Adelaide.
“This new reassessment has been possible due to access to higher resolution satellite imagery, through Google Earth Engine, as well as the incorporation of ground validated information from TERN’s ecological plots.”
The study identified dryland forest across all inhabited continents, and concentrated to the south of the Sahara desert, around the Mediterranean, southern Africa, central India, coastal Australia, western South America, north-east Brazil, northern Colombia and Venezuela, and northern parts of the boreal forests in Canada and Russia. The differences in coverage estimates are most significant in Africa where the estimates have doubled.