Repeal Bill Environment amendments

The Government has made repeatedly clear that all EU legislation will be converted into UK law at the point of the UK's departure from the EU. This will provide continuity and certainty for individuals in the UK and in the EU. Parliament has the power to amend or repeal any laws that it wishes and it will, of course, be able to modify retained EU law in the future.
The environmental principles that you mention have had an important influence on the creation of EU environmental legislation which is itself being transferred into UK law. The EU (Withdrawal) Bill will ensure that, wherever practical, the same rules apply in this country after we leave as they did before.
Although the jurisdiction of the European Court of Justice will end, the Government will ensure that strong and effective governance arrangements are in place after the UK's exit from the EU. No decisions have yet been taken on the UK's future relationship with EU agencies including with the European Environment Agency. This is a matter for the negotiations.