Recent decades have seen a significant increase in vegetation across the globe, a phenomenon called “global greening.” This surge in plant growth has been tracked by satellites, which provide data on leaf area. This data reveals that from a quarter to half of Earth’s vegetated lands have become greener over the last 35 years. This increase in foliage is equivalent to adding new vegetation covering an area twice the size of the mainland United States.
Primary Drivers of Global Greening
The primary factor behind global greening is the increasing concentration of atmospheric carbon dioxide, responsible for about 70% of the effect. Elevated CO2 acts as an airborne fertilizer for plants. During photosynthesis, plants use CO2 from the air, water, and nutrients to produce sugars for growth. With more CO2 available, plants can photosynthesize more efficiently, which spurs their growth and leads to an increase in leaf cover.
While CO2 fertilization is the dominant driver, other factors contribute. Land-use changes, such as large-scale tree planting and intensified agriculture in China and India, play a substantial role. Climate change is another contributor, as warming temperatures in northern latitudes are extending the growing season. Additionally, nitrogen deposition from industrial and agricultural activities can act as a fertilizer, boosting plant growth in some regions.
Global Hotspots of Greening
The greening of the planet is not uniform, with satellite data revealing specific regions where the trend is most pronounced. China and India are major contributors, accounting for a third of the global greening effect despite having only 9% of the world’s vegetated land. This impact is the result of programs to conserve and expand forests, alongside a large increase in agricultural cultivation.
Another hotspot for greening is the high latitudes of the Northern Hemisphere. In Arctic and boreal regions, rising temperatures are a dominant factor, extending the growing seasons. This has led to a “greening of the Arctic,” where shrubs and other vegetation are expanding their range into tundra areas that were previously too cold to support them.
Ecological Consequences of a Greener Planet
The increase in global vegetation carries a complex set of ecological consequences:
- Enhanced Carbon Sink: With more plants growing, more CO2 is absorbed from the atmosphere through photosynthesis. This process stores carbon in leaves, stems, and soil, acting as a partial brake on the pace of climate change.
- Altered Water Cycles: An increase in vegetation leads to higher rates of transpiration, the process where plants release water vapor. This can alter regional weather patterns and increase water stress in ecosystems, as denser vegetation strains water resources in arid regions.
- Changes in Surface Albedo: The expansion of vegetation alters the Earth’s surface albedo, which is the amount of solar radiation reflected into space. As darker forests expand, particularly over reflective snow in the Arctic, the land absorbs more heat, creating a warming feedback loop.
- Impacts on Biodiversity: These shifts in vegetation drive changes in ecosystem structure. The encroachment of woody shrubs into Arctic tundra, for example, alters the habitat for native species like caribou that rely on low-lying plants, which can displace native flora and change the food web.
The Greening Earth and Climate Change Context
It is important to place global greening within the broader context of climate change. While the increased absorption of CO2 by plants is a benefit, it does not counteract the full scale of human-caused emissions. The amount of CO2 absorbed by this new vegetation is far less than the volume of greenhouse gases being released from burning fossil fuels. The greening effect is a response to, not a solution for, climate change.
The primary driver of the greening trend—increased atmospheric CO2—is also the principal cause of negative climate change impacts. These impacts include rising global temperatures, the melting of glaciers, sea-level rise, and an increase in extreme weather events. The benefits of more vigorous plant growth do not negate the consequences of a warming planet.
Therefore, the greening of the Earth should be understood as a complex symptom of global environmental change, not a sign of planetary health. It demonstrates the influence human activities now have on Earth’s systems. The fact that the planet is becoming greener does not diminish the need to reduce greenhouse gas emissions, as the negative consequences of elevated CO2 far outweigh any benefits from increased plant growth.