Whether the Earth has more trees now than in the past is a complex question without a simple answer. While some regions are experiencing forest expansion, others face substantial tree loss. Understanding these dynamics requires examining global trends, the factors driving changes, and the methods scientists use to track these shifts. The overall picture of the world’s trees is one of continuous change, influenced by both human activities and natural processes.
The Global Tree Count: Are We Gaining or Losing?
Globally, the total forest area has seen a net decrease over recent decades. The world lost 178 million hectares of forest between 1990 and 2020, an area roughly the size of Libya. While the rate of net forest loss has decreased, it continues due to ongoing deforestation, despite increases in other areas from planting and natural expansion.
In the most recent five-year period from 2015 to 2020, the annual rate of deforestation was estimated at 10 million hectares, a reduction from 12 million hectares in 2010-2015. The world has a total forest area of 4.06 billion hectares, covering 31 percent of the total land area. This global figure translates to approximately 0.52 hectares of forest per person, though distribution is uneven across the world.
While there is a net loss, the world also experienced 130.9 million hectares of tree cover gain between 2000 and 2020, an area comparable to Peru. However, this gain did not offset the total loss, resulting in a net reduction of over 100 million hectares during the same period.
What Shapes Our Forests: Factors of Change
Changes in tree populations are driven by a variety of factors, encompassing both human activities and natural events. Agricultural expansion stands as a primary cause of tree loss, particularly in tropical regions, with large-scale agriculture responsible for over 70% of global deforestation. The growing demand for commodities such as soybeans and beef fuels much of this clearing. Logging and wood extraction, including for timber and charcoal, also contribute significantly to forest reduction. Urbanization and infrastructure development, such as road building and expanding cities, further lead to forest conversion.
Beyond direct human impacts, natural disturbances play a role. Wildfires, often exacerbated by climate change, destroy millions of hectares of forest annually. Droughts, pests, and diseases also weaken and eliminate trees, making forests more susceptible to damage.
Conversely, various efforts contribute to tree gain. Reforestation involves restoring previously forested areas through tree planting or natural regeneration. Afforestation refers to establishing new forests on land that was not previously forested. Natural regeneration, where forests regrow from existing seeds or surviving trees, accounts for a significant portion of new tree cover, often supplemented by human intervention. Improved forest management practices, including selective cutting and sustainable harvesting, also help maintain and enhance forest health and density.
How We Measure Earth’s Trees
Scientists employ a combination of advanced technologies and traditional methods to monitor Earth’s tree populations. Satellite imagery and remote sensing are fundamental tools, providing consistent coverage over vast areas. Satellites like Landsat have been in operation since the 1970s, capturing optical multispectral images that help detect deforestation, track canopy conditions, and assess forest health. High-cadence imagery from commercial satellites allows for near real-time monitoring of changes in forest cover, including illegal logging and fire damage.
Ground-based surveys, or forest inventories, complement satellite data by providing detailed, on-site information. These surveys involve physically measuring tree characteristics such as species composition, number of trees, diameter, height, and overall health within specific plots. This direct measurement helps to calibrate and validate the data collected from remote sensing.
The integration of artificial intelligence (AI) and machine learning (ML) has significantly enhanced the analysis of forest data. AI algorithms process vast amounts of information from satellite images, drone surveys, and ground-based data to identify patterns, classify tree species, detect early signs of tree stress, and predict future changes. These technologies improve the accuracy and efficiency of forest monitoring, supporting better management and conservation decisions.
Local Stories, Global Impact: A Look Ahead
Global tree trends often obscure diverse regional experiences, with some areas facing significant losses while others achieve gains. Tropical regions, such as the Amazon Rainforest, continue to experience substantial tree loss primarily due to agricultural expansion, illegal mining, and logging. In the United States, states like California, Oregon, and Colorado have seen considerable tree cover loss, largely attributed to wildfires, droughts, and pests.
Conversely, some regions and countries have demonstrated notable increases in tree cover. Europe, as a continent, experienced a net increase of 6 million hectares of tree cover between 2000 and 2020. Countries such as Ireland, Poland, Denmark, and the Netherlands have shown some of the largest increases. In Asia, countries like Tajikistan, Kyrgyzstan, Bangladesh, India, and Pakistan have also contributed to net gains.
Looking ahead, sustainable forest management, conservation, and restoration efforts are necessary for the future of global tree cover. These actions include protecting existing forests, promoting natural regeneration, and actively planting trees in degraded areas. Addressing the underlying causes of deforestation, such as unsustainable agricultural practices, is also part of a comprehensive approach to maintaining healthy forest ecosystems globally.