All lIchens need is water, sunlight and Carbon Dioxide! The Tree lichen essentially uses the tree bark to align itself with the sun! The bark may provide a good pH too which attracts it and amy even provide some anti-amicrobial prptection for the Lichen!
Canada geese are primarily vegetarian – roots, grass, leaves (not a fan of large leaves though), water plants, seeds and grain. Geese will eat the occasional insect too.
Canada geese eat a lot of grass, some claim three geese can eat the same amount of grass as one sheep. The partiality to grain can be problem for farmers at geese eat crops. The eating of large quantities of grass can damage local habitats.
And while geese like bread, it’s not particularly good for them – it isn’t nutritious enough.