Planting trillions of trees won’t replace the 10 million hectares of forest ecosystems lost each year, but documenting them could prevent further losses
2 March 2022
SINCE the 13th century, forests have been managed as sources of trees that can be processed into timber. More recently, with mounting concerns over climate change, they are often studied as potential carbon sinks because trees are capable of sequestering greenhouse gas emissions. But what remains largely unknown is the true relationship between a forest and the trees that make it up. While there is an international commitment to protecting biodiversity, a lack of knowledge about forests poses a huge obstacle to making effective conservation decisions.
With global attention drawn to increasing the number of trees as a means of climate change mitigation, highly publicised strategies such as the Million Tree Initiative, the Plant a Billion Trees scheme and the Trillion Tree Campaign have emerged. Overshadowed by these commendable feats is the degradation and deforestation of 10 million hectares of forests worldwide each year.
Many of the trees we are losing are in primary forests – a type of pristine ecosystem that offers irreplaceable ecological and socio-economic benefits, such as harbouring threatened flora and fauna, as well as underpinning the unique cultures and customs of Indigenous communities. Some have survived earthquakes, hurricanes, fires and other natural disasters over thousands of years, but have been wiped off the face of the Earth in a short space of time due to adverse human impacts. Perhaps we can plant millions, billions or even trillions of trees, but those we are putting in the ground today can hardly make up for the forests we are losing, and very few of these trees will ever grow into a primary forest.
When a forest is regarded as simply a collection of trees, we miss the holistic value of its biodiversity. From uniform alpine and circumpolar forests to tropical rainforests that host a plethora of species, they are the most important global repository of terrestrial biodiversity. When a forest is cut down, we also lose other living organisms from which we can draw new materials, processes, designs and inspiration to confront environmental, medical and engineering challenges in a world full of crises. For instance, in 2019, scientists discovered a new antibiotic in a Mexican tropical forest; hundreds of other potential pharmaceuticals are still waiting to be found.
To address the lack of knowledge about tree populations, my colleagues and I compiled a unique, ground-sourced forest database through the Global Forest Biodiversity Initiative. Underpinned by complete tree-level survey records from more than 1 million sample plots across 110 countries and territories, it is a snapshot of forest ecosystems and allows us to estimate important attributes of forest biodiversity at a global level. One such attribute is the total number of tree species worldwide. According to our estimate, there are approximately 73,000 tree species on Earth, and more than 12 per cent of them haven’t been documented yet. These findings remind us how little we understand our own planet.
What is still unknown is the number of tree species at a local level and how evenly trees are distributed among these species. Mapping them across the global forest range is vital for prioritising global conservation and detecting, monitoring and assessing the rate of extinction, as well as its impact on ecosystem functionality and human well-being.
To effectively protect forests, international communities must work together to address the disproportionate share of responsibilities between richer and poorer countries, since more than 90 per cent of the most diverse forests are in low-income nations. Together, we can truly begin to see the forest for the trees.
Jingjing Liang is a co-founder of the Global Forest Biodiversity Initiative
More on these topics: