overlay 3

{
    "type": "region_overlay",
    "id": "field_contents",
    "regions": [ "all" ],
    "field_coverage": {
      "percent_coverage": 20,
      "default_ter": "t_shrub",
      "other": {
        "t_tree_young": 0.2
      },
      "boost_chance": 0.833,
      "boosted_percent_coverage": 2.5,
      "boosted_other": {
        "f_dandelion": 5.0
      },
      "boosted_other_percent": 50.0
    }
  },