Improve forest restoration initiatives to meet Sustainable Development Goal 15

As one of the 17 Sustainable Development Goals (SDGs), Goal 15 (‘Life on Land’) stipulates that the protection and restoration of forest ecosystems is a critical challenge for countries around the world. According to the 2015 Global Forest Resources Assessment (FRA), forests occupy 30.6% of the Earth’s terrestrial surface area, but they have been severely degraded due to a combination of factors, both anthropogenic and natural. From 1990 to 2000, the annual net area loss of natural forests was 0.18%, though it was more severe in tropical and subtropical regions. In the twenty-first century, large-scale forest protection and restoration projects began to be implemented globally, and these have played a key role in slowing down net rates of forest loss. Satellite observations over the last two decades have revealed an ‘Earth greening’ phenomenon across terrestrial ecosystems worldwide, especially in Asia and Europe. However, according to the FRA data, the real crisis is that both the global forest and natural forest areas are still declining, and the only increase occurring is the area of planted forests, which has failed to slow or reverse biodiversity loss.

The research pointed out that current international restoration initiatives lead to preference for monoculture plantation. For example, under the Bonn Challenge Initiative, 45% of countries committed to restore their forest coverage via monoculture plantations. It is true that monoculture plantations have brought huge benefits to the local environment. Yet, several ecological crises have also emerged. Compared with natural forests with complex structures, monoculture plantations have begun to exhibit low biodiversity and productivity, less carbon stocks, poor soil stability and high vulnerability to pests and diseases. This research calls upon policymakers to focus on forest area and biodiversity restoration in combination rather than treating them separately，it also stressed that the structure of current monoculture plantation also need to be improved to avoid potential ecological crisis.

This research also analyze socioeconomic factors that may constrain the implementation of monoculture plantation reconstruction, then provide 4 specific suggestions: 1) improve biodiversity monitoring and assessment mechanisms of forest restoration projects；2）set up top-down restoration policies that encourage bottom-up behavior in local people to promote biodiversity in monoculture plantations；3）it is important to acknowledge that countries may need to designate certain areas as monoculture plantations for commercial purposes；4）developing evidence-based research is crucial for guiding the restoration of biodiversity in monoculture plantations.

These recommendations will not be equally important to countries that have less planted forests, such as the neotropical regions; however, even in these there may be a trend towards more monoculture plantation with the potential for critical ecosystem degradation2,21. Hence, our recommendations not only provide remedial measures for regions that rely too much on monoculture forest restoration, but also serve as a warning for other countries.