First-of-its-kind estimate of the total number of tree species


One person can’t measure all the trees in the world, but when many people come together, a global view becomes possible. A worldwide collaboration of scientists has produced the first ground-sourced data estimate of the total number of tree species on Earth and found that more than 9,000 species have yet to be discovered.

Although around 64,000 tree species have been documented, the total global number of tree species – both documented and undocumented – remained unknown. The international team’s work, which is detailed in a paper in the Proceedings of the National Academy of Sciences, reveals an answer. It estimates there are approximately 73,300 tree species in the world today.

Liang in front of electronics

Jingjing Liang (Purdue University Photo/Tom Campbell)

This project is co-led by Jingjing Liang, a professor of quantitative forest ecology in Purdue’s Department of Forestry and Natural Resources, and Peter B. Reich, a professor of forest ecology at both the University of Minnesota and the University of Michigan. A YouTube video is available online.

“Tree species diversity is the key to maintaining healthy, productive forests, and it is important to the economy and environment,” said Liang, who is the founder of the Global Forest Biodiversity Initiative (GFBI), and part of the Purdue’s Next Moves’ digital forestry initiative.

Reich, the co-corresponding author of the paper, said, “These results highlight the vulnerability of global forest biodiversity to anthropogenic changes, particularly land use and climate, because the survival of rare taxa is disproportionately threatened by these pressures.”https://www.youtube.com/embed/h7rJXZu4Gyo

The researchers estimate that one-third of the undiscovered species are rare with small numbers of trees and likely exist in tropical or subtropical areas like the Amazon Rain Forest.

“For instance, South America contains roughly 43% of the planet’s tree species and the highest number of rare species,” Liang said. “It is very possible we could lose undiscovered tree species to extinction before we even find them.”

Bryan Pijanowski, professor of landscape and soundscape ecology in the Department of Forestry and Natural Resources, who participated in the project, said the analysis is a critical step for environmental protection.

“As scientists assess how global biodiversity is changing, we need to know how many species currently exist and where global hot spots are for us to begin to reverse the disturbing trends that we are now witnessing on planet Earth,” he said.

The number of tree species and individuals per continent in the GFBI database. (Purdue University image/courtesy of Jingjing Liang)

The number of tree species and individuals per continent in the GFBI database. (Purdue University image/courtesy of Jingjing Liang)

The global initiative GFBI has steadily grown over the past five years, and its efforts to understand the world’s tree population are bearing fruit. The global tree species estimate follows development of the first global map of tree symbioses, published in the journal Nature, and discovery that forest biodiversity benefits the economy by more than five times the cost of conservation efforts, published in the journal Science.

“We combined individual datasets into one massive global dataset of tree-level data,” Liang said. “Each set comes from someone going out to a forest stand and measuring every single tree — collecting information about the tree species, sizes and other characteristics. Counting the number of tree species worldwide is like a puzzle with pieces spreading all over the world. We solved it together as a team, each sharing our own piece.”

Liang originated the idea for the initiative while he was a junior faculty member in Alaska working on forest growth models.

“I literally found a rich forest inventory dataset in someone’s drawer,” he said. “I realized people would want that information, but it had never been published. Scientists would share their data on a project or request basis, but there was no central repository for the valuable data people were collecting.”

“It sparked a personal mission, and I began collecting more datasets. Over the next few years it evolved, with the help of many others, into this global, grassroots effort.”

The global dataset is the largest known to date, Liang said. It currently includes more than 38 million trees, spanning 90 countries and 100 territories.

“Through this vast amount of data, we have a good picture of tree species diversity for different biomes and at the continental level, which is what we used to make this estimate” said Liang, who also is co-director of Purdue’s Lab of Forest Advanced Computing and Artificial Intelligence (FACAI). “Our database includes 64,100 confirmed tree species. Our estimate of the total global number of tree species fits with existing scientific knowledge and is in line with numbers theorized in earlier studies.”

To improve the accuracy of their estimate, the team members also used in their analyses an independent occurrence-based sample data of more than 6 million trees across all continents. Because the overall dataset was so large, the team used Purdue’s high-performance computing facilities to assess the data, Liang said.

“It is difficult to manage or conserve resources without a good understanding of what exists,” said Douglass F. Jacobs, Purdue’s Fred M van Eck Professor of Forest Biology and associate head of Extension, who was part of the project team. “The GFBI has allowed us to leap forward in developing more accurate estimates through unparalleled collaborative global data sets and advanced computing technologies.”

FACAI Lab postdoctoral research associate Roberto Cazzolla Gatti, who is now an associate professor at the University of Bologna (Italy), was a team member and first author of the paper.

Ascending rope by tree

(Courtesy of Global Forest Biodiversity Initiative)

“Extensive knowledge of tree richness and diversity is key to preserving the stability and functionality of ecosystems,” Gatti said.

Mo Zhou, associate professor of forest economics and management in the Department of Forestry of Natural Resources at Purdue and co-director of FACAI, contributed HPC resources to this study.

“An accurate estimation of the number of tree species globally is a great piece of knowledge,” Zhou said, “No matter what will happen in future, our children and their children will know the Earth harbors approximately 70,000 tree species in the dawn of the 21st century.”

This work is supported in part by the USDA National Institute of Food and Agriculture McIntire Stennis projects 1017711; and New Faculty Start-Up Grant, Department of Forestry and Natural Resources, Purdue University

Link to the PNAS publication: https://www.pnas.org/content/119/6/e2115329119

Pandemic Lessons: Open Data for Forest and Climate Action

A recent article is featured on FAO REDD homepage: http://www.fao.org/redd/en/and under the News section: www.fao.org/redd/news/detail/en/c/1303779/

The article is authored by four members of the National Forest Monitoring (NFM) Team from the Forestry Division of the Food and Agriculture Organization of the UN (FAO) – Javier García Pérez (Gamarra) (javier.garciaperez@fao.org), Rocío D. Cóndor-Golec (rocio.condor@fao.org), Rebecca Tavani (rebecca.tavani@fao.org), and Julian Fox (julian.fox@fao.org) – and Jingjing Liang, Assistant Professor of Quantitative Forest Ecology and GFBI coordinator, Department of Forestry and Natural Resources, Purdue University, US (jjliang@purdue.edu).

The article can be shared through the following links:

Nature paper offers global map to understand changing forests

An international collaboration of hundreds of scientists – led in part by the Forest Advanced Computing and Artificial Intelligence(FACAI) Laboratory in Purdue’s Department of Forestry and Natural Resources – has developed the world’s first global map of tree symbioses. The map is key to understanding how forests are changing and the role climate plays in these shifts.

The findings, reported today in the journal Nature, come from the Global Forest Biodiversity Initiative (GFBI), a consortium of forest scientists and practitioners of which the FACAI Lab is a key hub and global center. Jingjing Liang, a Purdue University assistant professor of quantitative forest ecology, is co-supervisor of the FACAI Lab, coordinator and co-founder of the GFBI and co-lead author of the paper. Mo Zhou, a Purdue assistant professor of forest economics and management, is a senior author of the paper, co-supervisor of the FACAI lab and lead economist of the GFBI.

Purdue’s FACAI lab employs artificial intelligence and machine learning to study global, regional and local forest resource management and biodiversity conservation. For this research, FACAI compiled species abundance data from 55 million tree records in 1.2 million forest sample plots spanning 110 countries. The organization of the data was integral to developing the global map.

“The map and underlying global forest inventory database will serve as the foundation for research on the environmental impacts of forest changes, biological conservation and forest management,” Liang said.

The map identifies the types of mycorrhizal fungi associated with trees in a particular forest. These fungi attach to tree roots, extending a tree’s ability to reach water and nutrients while the tree provides carbon necessary for the fungi’s survival. The two most common types of mycorrhizae are arbuscular, which grow inside the tissues of tree roots and are associated with tree species such as maple, ash and yellow poplar, and ectomycorrhizal, which live on the outside of roots and are associated with tree species such as pine, oak, hickory and beech.

Those associations are important because the mycorrhizae affects the trees’ ability to access nutrients, sequester carbon and withstand the effects of climate change.

“Managing forests for climate change mitigation and sustainable development, therefore, should go well beyond managing only trees,” Zhou said. 

The authors found that climate is the most significant factor affecting the distribution of mycorrhizae. A warming climate is reducing the abundance of ectomycorrhizal tree species by as much as 10 percent. That change is altering forests’ ecological and economic footprints, especially along the boreal-temperate ecotone, the border areas between colder and warmer forest. Losses to ectomycorrhizal species have implications for climate change since these fungi increase the amount of carbon stored in soil.

“Knowing the species composition in the forested area across the world is an important start,” Liang said. “There are many fundamental and socioeconomic questions we can answer now with GFBI data and cutting-edge machine learning techniques.”

The FACAI lab is currently developing collaborations to explore questions about ecology and economics, including self-learning forest models, innovative approaches to biodiversity valuation, locating unknown forest resources and space exploration.

The work aligns with Purdue’s Giant Leaps celebration, acknowledging the university’s global advancements made in health, space, artificial intelligence and sustainability as part of Purdue’s 150th anniversary. Those are the four themes of the yearlong celebration’s Ideas Festival, designed to showcase Purdue as an intellectual center solving real-world issues.

Brian S. Steidinger, a postdoctoral research fellow at Stanford University, and Thomas Ward Crowther, an assistant professor at ETH Zurich, are co-lead authors of the Nature paper with Liang. Sergio de Miguel, an assistant profession and principal investigator of the GFBI Hub at University of Lleida, Spain, and Xiuhai Zhao and Chunyu Zhang, professors at Beijing Forestry University, are among the senior collaborators of this paper.

Data from this research can be downloaded at https://ag.purdue.edu/facai/data/

For full details of this paper, visit here.

Writer: Brian Wallheimer, 765-532-0233, bwallhei@purdue.edu

Sources: Jingjing Liang, 765-496-0254, liang292@purdue.edu

Mo Zhou, 765-494-3098, mozhou@purdue.edu

Forest Scholars Worldwide Team Up For Biodiversity Research

Loss of biodiversity has long been recognized as detrimental for nature, for nature’s sake. Now a team of scholars from 90 institutions in 44 countries show that it also provides enormous economic benefits. The team, formally known as the Global Forest Biodiversity Initiative (GFBI), consolidated field-based forest inventory data from 777,126 permanent plots across the world, and discovered that for forests in every part of the world, those with many tree species are more productive than nearby forests with few. 

The team then estimated that the economic value of biodiversity in maintaining commercial forest productivity alone is worth USD$166–490 billion per year. This benefit- only one of many such benefits of biodiversity- is more than 20 times greater that what is spent each year on global conservation. This finding highlights the need for a worldwide re-assessment of biodiversity values, forest management strategies, and conservation priorities. 

The research, published in the Oct. 14, 2016 issue of Science, marks the first major accomplishment of FACAI and GFBI team.