A maple in my sister's garden has a fungus growing out of it, and bark has peeled off all the way from the fungus to the ground, and about halfway around the tree at ground level. We tried to remove the visible fungi, but i suspect that the visible part is only a small part of it and that the tree might be hollow. It has been visible for quite some time and the leaves on the tree has been getting autumn colors quite early the last 3-4 years. She is wondering if anything can be done to save the tree.
Yes, hollow, and potentially a dangerous tree. Best have it examined on site for a safety report by a professional arboricultural consultant.
Getting an expert to come and look at it here would be quite expensive, is there anyway we can check if its in danger of falling over ourselves? There is lots of children playing in the area around the tree and in the tree. If there is a real danger of it falling over she wants to cut it down.
In that case, just remove it, if you can do so legally. For removing a tree that size, I'd strongly advise employing a professional to do it - decaying trees may fall very unpredictably when cut; if cut by an amateur, you have a high risk of getting a dead amateur as well as a dead tree.