A 21-year study in Denmark has highlighted a trade-off between rapid carbon accumulation and biodiversity recovery in forests established on former agricultural land, suggesting that future restoration projects may need to balance climate and ecological objectives, The Times of India reported.
Researchers from the University of Copenhagen compared areas where trees were deliberately planted with farmland that was abandoned and allowed to regenerate naturally. The long-term comparison found that planted forests accumulated tree biomass and stored carbon much faster, while naturally regenerated forests developed greater plant diversity and more varied ecological structures.
The study, titled Passive versus active afforestation of agricultural land: Two decades of impacts on tree biomass and ecosystem carbon storage, examined how the two approaches developed over approximately two decades. The researchers also compared the younger forests with mature, actively managed forests to provide a longer-term reference.
The planted forests had accumulated substantially more tree biomass than naturally colonised areas. According to the study, they contained about 16 times more above-ground woody biomass after roughly 20 years.
Researchers attributed the faster biomass accumulation to deliberate tree planting, which allowed forests to develop more quickly than areas dependent on natural succession. The higher biomass accumulation also resulted in faster carbon storage in trees during the early stages of forest development.
However, the researchers noted that rapid biomass growth does not necessarily mean that a plantation develops all the ecological characteristics associated with a mature forest.
Naturally regenerated forests followed a different trajectory. Without predetermined planting, vegetation developed through ecological succession, allowing different plant species and structures to establish over time. Although this process was slower, the resulting forests showed greater diversity and ecological variation than the plantations.
The findings do not suggest that plantations have no biodiversity value. Rather, the study indicates that their structure and species composition can differ substantially from forests that develop through natural regeneration.
The research suggests that forest restoration cannot be assessed solely by the amount of carbon stored or the number of trees planted. Where rapid carbon sequestration is the primary objective, plantations can provide an advantage by accelerating biomass accumulation. Natural regeneration, meanwhile, can support greater ecological diversity as forests develop.
The researchers therefore present afforestation as a more complex process in which restoration strategies may need to balance rapid carbon capture with biodiversity and the development of ecological complexity.
