The success of woody plant removal depends on encroachment stage and plant traits

Woody plants (shrubs and trees) are encroaching across the globe, affecting livestock production and terrestrial ecosystem functioning. Despite the widespread practice, there has been no quantitative global assessment of whether removal of encroaching woody plants will re-instate productive grasslands and open savanna. Here we compiled a global database of 12,198 records from 524 studies on the ecosystem responses of both the encroachment and removal of woody plants, and show that removal fails to reverse encroachment impacts. Removing woody plants only reversed less than half of the reductions in herbaceous structure induced by encroachment, and woody expansion actually enhanced ecosystem functions (+8%). The effectiveness of removal varied with encroachment stage (that is, time since treatment) and the functional traits (for example, deciduousness and resprouting) of the focal woody species, and waned in drier regions. Our results suggest that assessment of woody plant communities before removal is critical to assess the likelihood of successful ecosystem recovery.

Automated summary

Woody plants are spreading globally, causing negative impacts on livestock production and terrestrial ecosystems. A global assessment was conducted to determine if removing these plants can restore productive grasslands and open savannas. However, the results show that removal is not effective in reversing the encroachment impacts, with only partial recovery of herbaceous structure and an overall enhancement of ecosystem functions. The success of removal varies with the encroachment stage and functional traits of the woody species, and is influenced by regional aridity.