Lonny Miasma

Hello, I am owning a huge share of group. One member contributes land too 3.072 sqm. I dont know if she comes back - health issues - it might even happen that credit card expires. So what can I do? Can I just raise my contribution? what would happen then? Will the other contributions go down? Or will Linden take some land if the credit card expires or the membership? I have no idea. If anybody would know I would be grateful for advice. Lonny