Protecting existing Amazon rainforest from fire and logging may deliver greater biodiversity and carbon benefits than planting new trees, according to a study that compared different conservation strategies across millions of hectares in Brazil’s Pará state.
Researchers examined land-use changes across about 3 million hectares in Pará between 2010 and 2020. They modelled what the landscape could have looked like if different forms of forest damage had been prevented, comparing forest protection, avoided deforestation and restoration.
The analysis found that preventing fire and logging in standing forests could have avoided 68.5% of the biodiversity loss recorded in the study area. Preventing deforestation could have avoided 28% of biodiversity losses.
For carbon however, the pattern was different. Preventing deforestation accounted for 60.8% of the avoided carbon losses in the model, compared with 46.8% for preventing fire and logging.
During the decade studied, fire and logging damaged about 273,558 hectares of old growth forest, while approximately 158,980 hectares of forest were cleared. Researchers noted that more forest was damaged through degradation than outright clearing.
Restoration performed less strongly when considered as a standalone strategy. The researchers modelled restoration to bring properties into compliance with Brazilian legal requirements for protected vegetation along waterways and minimum forest cover. This would have resulted in about 80,705 hectares of additional forest.
The model estimated that restoration alone could compensate for 6.5% of biodiversity losses and 14.7% of carbon losses. It was also the most expensive of the three strategies examined.
However, the researchers found that the relative benefits of restoration changed significantly in areas where forest cover had already fallen to low levels.
On properties with less than roughly 43% forest cover, planting trees provided greater biodiversity benefits than simply avoiding further deforestation. The crossover point for carbon was approximately 41% forest cover.
This suggests that conservation strategies may need to differ according to the amount of forest remaining in a landscape. Protecting intact or relatively well-preserved forests can be particularly important where substantial forest cover remains, while restoration becomes increasingly important in heavily cleared areas.
Combining the three approaches produced substantially larger benefits. The model found that preventing deforestation and avoiding forest degradation together could have increased biodiversity by about 12% and carbon by 18% compared with the landscape’s 2010 condition. Adding restoration increased the modelled gains to 22% for biodiversity and 42% for carbon.
Researchers also found that the strategies could reinforce one another. Newly restored forest located next to older forest can reduce edge effects, while protecting existing forest from clearing only delivers long-term carbon benefits if the forest is also protected from subsequent fire and degradation.
The study also highlights the limitations of satellite-based assessments. Some forms of disturbance, including hunting, low-intensity fires beneath the forest canopy and small-scale cutting, may not be detected effectively. This means the actual ecological impact of forest degradation could be greater than the estimates captured by the model.
The researchers also noted that the analysis covered only a 10-year period and did not account for every possible land-management option available to property owners. For example, some landowners can meet legal forest requirements by acquiring or leasing forest elsewhere rather than restoring vegetation on their own properties.
Fire remains a major concern for restoration as well. In the study regions, 63.1% of young forest that regenerated between 2010 and 2020 subsequently burned, highlighting the vulnerability of newly restored areas to wildfire.
The researchers cautioned that the relative effectiveness and cost of different conservation strategies may vary across the Amazon. Timber values, fire conditions, land-use patterns and ecological characteristics differ between regions, meaning the findings should not automatically be applied everywhere.
The study, published in Science, highlights the importance of combining forest protection, deforestation prevention and restoration rather than relying on tree planting alone. The researchers argue that conservation planning should account for both the amount of forest remaining and the different threats affecting standing forests.