2. If the world is poorer, it will be able to afford to protect the environment less, not more. The wealthier a nation, or a neighbourhood is, the more it cares about protecting its local environment. For example, as China gets wealthier, it cares more about having cleaner air.
3. Wealth concentration in the right hands is not necessarily a bad thing. Increasing taxation is just concentrating more wealth in the hands of parliaments/governments, which they are unlikely to spend too effectively given that they are spending someone else's money, but yet which still results in some great outcomes (scientific advancements, until recently space flight etc.). Wealth concentration means that great leaps forward can happen in areas that at first are going to be very expensive (medical/longevity research, grand projects like SpaceX, even originally mobile phones etc.)
If you want to tax anything, it is probably better to tax (frivolous) consumption, i.e. wealth destruction, instead of wealth creation.
