"Increasing CO2 has driven global greening: over the last 40 years, half of the world’s vegetated area has undergone greening, of which 70% is attributed to elevated CO2 (Zhu et al. 2016)"
Right, but the study is titled "ENVIRONMENTAL DRIVERS OF AGRICULTURAL PRODUCTIVITY GROWTH" and the OP comment included the word "agriculture" right before quoting the study.
Seems this whole thing got rather confused.