Increasing atmospheric concentrations of greenhouse gases (GHGs) are having irreversible consequences for the future of the Earth. However, the general pattern of the impacts of ecological restoration on the three major GHGs on a global scale has not yet been analyzed.

Land-use change and ecosystem degradation have caused massive anthropogenic emissions of GHG, such as carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O), leading to irreversible consequences for the future of the Earth.

According to a new study published in Nature Communications, researchers from the Wuhan Botanical Garden (WBG) of the Chinese Academy of Sciences (CAS) have found that restoration of forests, grasslands and wetlands can enhance carbon sink, reduce the global warming potentials, and serve as strategies to mitigate GHG emissions.

This study is a meta-analysis of a global dataset of 253 peer-reviewed articles. The results provide valuable insights for policy makers to select effective ecological restoration measures.

Forests, grasslands, and wetlands are the three major ecosystems that are critical to the global GHG budget, but there are multiple factors (restoration types, methods and age, etc.) that affect GHG. "Although many studies have investigated the effects of ecological restoration on the emission of one or a few GHGs at the plot or regional level, the general pattern of the impacts of ecological restoration on the three major GHGs at the global scale has not yet been analyzed," said Prof. ZHANG Kerong of WNG.

To gain a global perspective, the researchers analyzed data from 235 studies to quantify the impact of ecological restoration on GHG emissions.

They found that forest and grassland restoration significantly increased CH₄ uptake by 90% and 30.8%, respectively, while, wetland restoration significantly increased CH₄ emissions by 544.4%. Forest and grassland restoration had no clear effect on N₂O emissions, while wetland restoration significantly reduced N₂O emissions by 68.6%.

"This study highlights the importance of restoration age in regulating GHG emissions in restored ecosystems," said Dr. HE Tiehu of WBG.

Net ecosystem CO₂ exchange (NEE) in wetlands was exponentially and negatively correlated with restoration age, and the transition time from net CO₂ sources to net CO₂ sinks was estimated to be about four years. The NEE of the restored forests decreased with the age of afforestation and reforestation, and the estimated switchover time from CO₂ sources to net sinks was about three to five years, and about six years for the clear-cut sites and 13 years for the post-fire sites.

Taken together, the study suggests that forest, grassland and wetland restoration could serve as an effective strategy for mitigating GHG emissions and reducing global warming potential.

This study was supported by the National Natural Science Foundation of China and the Youth Innovation Promotion Association of CAS.

Relationships of the response ratios of CH₄ and N₂O fluxes, and the annual CO₂ fluxes with restoration age. (Image by WBG)