Cropland encroachment on global protected areas and its national-level drivers.

Cropland encroachment on protected areas (PAs) impedes the achievement of global biodiversity conservation goals. However, the extent and expansion of cropland in PAs as well as regional and protection level differences on timescale, and national drivers thereof remains unassessed. We analyzed the land cover composition of global PAs to identify cropland changes from 1985 to 2020 and visualized cropland encroachment degree of PA patches by calculating cropland grid density (CGD) which is defined as the amount of cropland grids per square kilometer. We further identified nations' economic and agricultural development indicators as the primary drivers of cropland encroachment through correlation analysis and GLM method. The results indicate that cropland encroachment on PAs occurs worldwide with significant different level at both regional and protection levels. In western Europe, southern Latin America, central Africa, and southern Asia, a proportion of PA patches have high CGDs. CGDs of Asia and Pacific, Europe and Latin America, and Caribbean PA patches declined, whereas the indices increased in Africa and West Asia. CGDs of PAs with high protection levels are lower than that of PAs with low protection levels. At the national scale, economic development, agricultural development level, and cropland encroachment degree show negative correlations, whereas positively correlated with poverty stress and rural population percentage. The optimal model suggests the GDP per capita, arable land and permanent cropland percentage are significant factors influencing cropland encroachment on PAs. This study highlights the challenges to balance agricultural development and ecological protection and call for a stricter protection on PAs.