tm_shape(predictors) +
    tm_polygons(c('precipitation', 'temperature', 'footprint', 'cropland'), 
                fill_alpha = 0.9,
                col='grey45', col_alpha = 0.2, lwd = 0.25,
                fill.scale = list(
                    tm_scale_intervals(n = 6, style = 'pretty', 
                                       midpoint = 0,
                                       values = 'brewer.pu_bu',
                                       value.na = 'grey80'),
                    tm_scale_intervals(n = 6, style = 'pretty', 
                                       midpoint = 0,
                                       values = 'brewer.yl_or_rd',
                                       value.na = 'grey80'),
                    tm_scale_intervals(n = 6, style = 'pretty', 
                                       midpoint = 0,
                                       values = 'brewer.purples',
                                       value.na = 'grey80'),
                    tm_scale_intervals(n = 6, style = 'pretty', 
                                       midpoint = 0,
                                       values = 'brewer.pu_bu_gn',
                                       value.na = 'grey80')),
                fill.legend = tm_legend(#title='',
                    item.space = 0,
                    reverse=T,
                    frame=F,
                    frame.lwd = 0.1,
                    bg.color = 'white',
                    position = tm_pos_out()) 
    ) +
    tm_layout(panel.show = FALSE) + 
    tm_crs(crs=st_crs(4326)) + 
    tm_options(component.autoscale=F)