Afforestation is planting trees on land that hasn’t had forest cover in a very long time, sometimes ever. Reforestation is restoring trees to land that was recently forested but lost its tree cover to logging, fire, or land clearing. Both aim to expand forest area, but they start from very different baselines, and that distinction shapes everything from how the soil responds to how much carbon the new forest can capture.
How They Differ
The dividing line comes down to land-use history. The IPCC defines afforestation as planting new forests on land that “historically has not contained forests.” Think of converting abandoned farmland, degraded grassland, or even former industrial sites into forest for the first time. Reforestation, by contrast, means bringing trees back to a place that had them recently, whether the forest was cleared for agriculture, destroyed by wildfire, or harvested for timber.
In practice, the boundary can be blurry. Some definitions set a specific number of years without tree cover as the cutoff; others use vaguer language like “historical time.” What matters practically is that reforestation sites typically still have forest soil, seed banks, and root systems that give new trees a head start. Afforestation sites often lack those advantages entirely, which makes establishing a healthy forest slower and more challenging.
Why Both Matter for Climate
Trees pull carbon dioxide from the air as they grow, locking it into wood, roots, leaves, and eventually the soil. How much carbon a new forest captures depends heavily on the climate, tree species, and growing conditions. U.S. Forest Service data illustrates the range: fast-growing pine plantations in the southeastern United States can store roughly 4.4 tonnes of carbon per hectare per year during their first decade. A hardwood forest of oaks and hickories in the Northeast captures about 0.55 tonnes per hectare annually over the same period. Cold-climate spruce and fir forests in the northern lake states manage only about 0.16 tonnes per hectare per year in those early years.
Tropical forests, with their year-round warmth and rainfall, generally capture carbon faster than any of these temperate examples. That’s one reason so much global restoration effort focuses on the tropics, even though those projects face their own serious challenges.
The Global Picture
The world is still losing more forest than it gains. According to the FAO’s 2025 Global Forest Resources Assessment, about 10.9 million hectares of forest were cleared annually between 2015 and 2025. The net loss, after accounting for new forest growth through afforestation and natural expansion, was 4.12 million hectares per year. That net loss actually increased compared to the previous period, not because deforestation sped up, but because the rate of new forest growth slowed down. Since 1990, roughly 489 million hectares of forest have been lost to deforestation worldwide.
International pledges aim to reverse this trend. The Bonn Challenge, launched in 2011, set a goal of restoring 150 million hectares by 2020 and 350 million hectares by 2030. So far, countries have pledged over 210 million hectares. Pledges and actual restoration are different things, though, and progress on the ground has lagged well behind commitments.
Planting vs. Letting Forests Grow Back
Not every restoration project involves people putting seedlings in the ground. Natural regeneration, sometimes called passive restoration, means stepping back and letting forests regrow on their own from remaining seeds, root systems, and surrounding forest. Active planting, by contrast, means choosing species, raising seedlings in nurseries, preparing the soil, and physically placing each tree.
A 2024 study in Nature Climate Change found these two approaches are remarkably close in cost-effectiveness for carbon removal. Across 138 low- and middle-income countries, natural regeneration was the cheaper option on about 46% of land suitable for reforestation, while plantations were cheaper on the remaining 54%. The median cost came out nearly identical: about $23.80 per tonne of CO₂ removed for natural regeneration versus $23.00 for plantations. Plantations gain a financial edge because they produce timber that can be sold, but if you strip out that revenue, they remove about 21% less CO₂ below a $50 per tonne threshold.
Naturally regenerated forests tend to support greater biodiversity, better water retention, and more erosion control. Plantations produce more wood products. The best approach for a given site depends on what’s available in the surrounding landscape, what the land was used for previously, and what the goals of the project are.
Why Many Planted Trees Don’t Survive
Large-scale tree planting sounds straightforward, but survival rates tell a more complicated story. Research from the UK Centre for Ecology and Hydrology found that about 18% of saplings planted in tropical and subtropical restoration projects die within the first year. After five years, roughly 44% have been lost. That means on average, nearly half of planted tropical trees don’t make it past their fifth birthday.
The reasons range from drought and poor species selection to competition with grasses, grazing by livestock, and lack of follow-up care after planting. A seedling placed in compacted, nutrient-poor soil with no shade or protection faces very different odds than one planted in rich forest soil with nearby mature trees providing shelter. This is one area where the distinction between afforestation and reforestation becomes practical: reforestation sites, with their remnant forest soils and closer proximity to seed sources, often give young trees a better chance.
How Restoration Projects Work in Practice
Professional reforestation follows a sequence that starts well before any tree goes into the ground. Site assessment comes first: teams evaluate the slope, soil type, moisture conditions, and what vegetation is already present. On steep or erosion-prone land, heavy machinery is avoided entirely, and seedlings are planted by hand to minimize soil disturbance. On flatter ground, mechanical site preparation can clear competing vegetation and loosen soil, but operators work along the contour of slopes to prevent water from carving channels downhill.
Species selection is critical. Choosing trees adapted to the local climate, soil chemistry, and rainfall patterns dramatically improves survival. Seedlings are typically ordered from nurseries months in advance, and planting is timed to coincide with the wet season or the period of least stress for young trees. After planting, seedlings are distributed evenly across the site to mimic natural spacing and reduce competition for light and water.
Risks of Getting It Wrong
Not all tree planting is ecologically beneficial. Planting the wrong species, particularly fast-growing non-native trees in monoculture plantations, can cause real damage. A systematic review published in PLOS One found that forest restoration projects frequently reduce local water availability. Trees increase evapotranspiration, pulling water from the soil and releasing it into the atmosphere. When non-native species are used, this water demand can be significantly higher than what native species would require, lowering groundwater levels and reducing stream flow.
In plantation forests, the problems can compound. Without natural understory vegetation, soil infiltration may never recover. Management activities like drainage construction, road building, and repeated harvesting cycles prevent the soil from developing the sponge-like structure that healthy forests depend on. The result can be a stand of trees that looks like a forest from the air but functions nothing like one ecologically, offering little habitat for wildlife and actively depleting local water resources.
Planting trees on ecosystems that are naturally treeless, like native grasslands, peatlands, or savannas, is another well-documented mistake. These landscapes store enormous amounts of carbon in their soils and support specialized species that disappear when shaded out by trees. Afforestation projects need careful assessment to ensure the target land genuinely benefits from tree cover rather than being a functioning ecosystem in its own right.